Water reclamation and reuse

4. Water Reclamation and Reuse

4.1 What is Water Reclamation and Reuse

Water reuse encompasses both the direct use of STP effluent for beneficial purposes without further treatment, and the use of reclaimed water. For the purposes of this report, water reclamation refers to the beneficial use of effluent from municipal sewage treatment works after further treatment to meet more demanding quality requirements.

The main barrier to reuse programs is usually the lack of community support, which can be mitigated by the use of good communication of the reuse program to potential consumers and residents (Mackie et al., 2009). Currently, water reuse is practised in Canada on a relatively small scale in mostly isolated cases (Exall, 2004). Examples of reuse schemes in Canada include agricultural irrigation (British Columbia, Alberta, Saskatchewan and Manitoba), golf course and landscape irrigation (Ontario, British Columbia and Alberta) and for residential toilet flushing and irrigation on a trial basis (Ontario, British Columbia and Nova Scotia) (CCME, 2002).

Effluent from municipal sewage treatment works can be used in a number of different ways, some of which will require further treatment (i.e., reclamation). Treatment requirements for the production of reclaimed water may be extensive for some options. Information in this section is on options for using effluent from sewage treatment works externally (i.e., water reuse applications outside of the sewage treatment works). Information on the options for using reclaimed water at the sewage treatment works itself is provided in Section 3.1.4.

4.2 Challenges of Using Reclaimed Water

4.2.1 Health Concerns

Without the use of advanced treatment technologies, there are risks to human health associated with the microbiological and/or chemical constituents in treated sewage. The greatest health concern with water reclamation and reuse is the potential transmission of infectious diseases by pathogenic microorganisms. Microorganisms can transmit waterborne diseases to humans through ingestion, inhalation or skin contact of the infective agents, or indirectly by contact with individuals previously infected (U.S. EPA, 2004). The pathogenic microorganisms that are present in municipal wastewater are largely from faeces of infected humans and are mainly transmitted by consumption through the direct ingestion of contaminated water or by human exposure through the use of contaminated water in agriculture and food processing (U.S. EPA, 2004).

Disease-causing microorganisms can be found in any potable water source contaminated by human or animal wastes. Microorganisms that can cause waterborne diseases include bacteria, viruses, helminths and protozoa. The foremost bacteria of concern include Salmonella species, Shigella species, Campylobacter jejuni and Escherichia coli. There are over 100 types of enteric viruses that can be potentially shed in faeces, their presence in wastewater being a function of circulating viruses in the community. Common viruses found in wastewaters include enteroviruses (poliovirus, coxsackie, echovirus), adenovirus, norovirus (Norwalk agent), rotavirus and hepatitis A virus (Exall et al., 2004; Metcalf & Eddy and AECOM, 2007). Helminthic species such as Taenia species (tape worm) and Ascaris lumbercoides (round worm) are common intestinal parasites. Also of concern in wastewater are the ova of helminths and the cysts and oocysts of protozoa which can remain viable outside of their host for an extended period of time, e.g. Giardia lamblia and Cryptosporidium parvum (Exall et al., 2004). A large proportion of microorganisms excreted in the faeces are non-pathogenic, i.e., they are part of the normal flora of the intestines of humans and warm-blooded animals. Testing for indicator organisms, e.g. fecal coliforms, fecal streptococci, E. coli, Enterococcus,is conducted to indicate if there is fecal contamination and a risk that pathogenic protozoa, bacteria or viruses may be present that can cause waterborne diseases when consumed (Metcalf & Eddy and AECOM, 2007). However, bacterial indicator levels may not correlate with those of specific pathogens, particularly viruses and protozoa.

As well as exposure by ingestion, viruses and pathogenic bacteria can be transmitted to humans through inhalation of aerosols. Aerosols are particles less than 50 µm in diameter that are suspended in air (U.S. EPA, 2004). Aerosols could be a concern in a number of areas where reclaimed water is used, including spray irrigation in landscaping and agricultural areas, areas that use cooling water and any other application where there is a risk of human exposure. Measures to reduce the human exposure to bioaerosols should be considered, including the use of enclosed systems (e.g. CIP), proper disinfection and storage.

Although risks typically associated with water reuse and reclamation focus on microbiological parameters, chemical constituents may also limit suitability for some reuse applications. Chemical constituents of potential concern for water reuse include inorganics, organics, nutrients and heavy metals that may affect the suitability of the reuse/reclaimed water for the intended use. Research is ongoing into the health and environmental impacts of chemical constituents that may be found in reclaimed water, but these impacts are relatively unknown at this time (Metcalf & Eddy and AECOM, 2007).

In recent years, some concern has developed with contaminants of emerging concern such as endocrine disruptors, pharmaceuticals and chemicals used in personal care products entering groundwater through the application of reclaimed water in irrigation practices (Exall et al., 2004). A 1996 American National Research Council Report on the use of treated municipal wastewater stated that the immediate or long- term threat from organic chemicals to humans consuming food crops irrigated with reclaimed water is negligible, since many toxic organics are removed during wastewater treatment, volatilize or degrade when the water is added to the soil, and are therefore not taken up by the crops (Exall, 2004).

In industrial and agricultural applications there is some concern of the health impacts from the use of reclaimed water on worker health. A concern to workers applying reclaimed water is the inhalation of aerosols containing volatile and organic compounds, as well as microbiological contaminants (Exall et al., 2004).

Treatment processes are available that can reduce the contaminants of concern to public health. The type of treatment required is dependent on the effluent quality, the contaminant(s) of concern and the degree of removal required for the particular reuse application. Typically, the higher the level of treatment required, the more costly is the reclamation option. Further information on treatment for reclaimed water use is provided in Section 4.5.

4.2.2 Environmental Concerns

Ecosystems can be affected by constituents in treated sewage; therefore, the effects of water reclamation and reuse on the environment should be considered. Effluent constituents that can have an adverse effect on an ecosystem include biodegradable organics, recalcitrant organics, nutrients, heavy metals, residual chlorine and total suspended solids.

Leaching of biodegradable organic matter into a body of freshwater can result in low dissolved oxygen (DO) levels as a result of naturally-occurring bacteria that will degrade this material, a process which consumes oxygen. Low DO levels can result in fish kills, and if it occurs over a long period of time will change the biology of the ecosystem to one more tolerant to low DO conditions. Recalcitrant organic compounds can potentially be toxic to fish and invertebrates.

Nitrogen, phosphorus and potassium are nutrients required for plant growth and thereby enhance the benefits of water reuse for agricultural irrigation. However, these nutrients may contribute to eutrophication when the reuse/reclaimed water enters water courses. There is also the potential for groundwater contamination associated with irrigation with STP effluent.

An accumulation of heavy metals in the environment can be toxic to plants and animals. Residual chlorine is toxic to many aquatic organisms and must be removed prior to discharge to receiving waters. Chlorine can also be toxic to plants. Research is currently being carried out on the uptake and accumulation of contaminants of emerging concern, and at this time, the potential impacts of these compounds on plants and animals ingesting crops grown using reclaimed water are unknown.

Soil productivity may be reduced if reuse/reclaimed water with high levels of dissolved solids is applied to land over extended periods of time (Exall et al., 2004). Irrigation with reuse/reclaimed water may cause salt accumulation in soil leading to an increase in osmotic potential of the soil solution, which interferes with water extraction by the plants.

There are measures which can be adapted to mitigate negative impacts of reuse/reclaimed water on the surrounding environment. In irrigation systems, a buffer zone should be provided between the irrigated field and adjacent properties, occupied dwellings, watercourses, and surface water bodies. In addition, treatment of effluent can be used to reduce or eliminate contaminants of concern, which is discussed further in Section 4.5.

The impact of removing water from a watershed as a result of a reuse scheme should be considered. This has the potential to adversely affect river flows if a significant fraction of flow of a receiving river is from effluent discharged from a municipal sewage treatment works.

4.2.3 Public Perception

The public acceptance of a water reuse or reclamation scheme is critical to its success. To a great extent, acceptance of a scheme will be dependent on the application, whereby the higher the degree of potential contact with the reclaimed water, the lower is the chance of public acceptance (Metcalf & Eddy and AECOM, 2007). This is due to concerns over potential public health and/or environmental risks, which should be addressed as part of a comprehensive public consultation and education process.

4.2.4 Impact of Wastewater Sources on Water Reclamation and Reuse

The influent to municipal sewage treatment works contains wastewater from domestic uses such as toilet flushing, dishwasher and washing machine water and bathing water. It may also contain discharges from industry. In areas where industrial waste streams contribute to the municipal sewer system, there may be high levels of constituents that are toxic to plants and animals if they are not removed at source or at the municipal sewage treatment works. Wastewater treatment facilities receiving substantial amounts of industrial high-strength waste may be limited in the number and type of suitable reuse applications unless further treatment of effluent is carried out before reclaimed water is used (U.S. EPA, 2004).

4.2.5 Impact of Treatment Plant Size and Location on Water Reclamation and Reuse

The size and location of a municipal sewage treatment works can impact water reuse and reclamation projects. Large, centralized facilities will have a larger volume of effluent available for use, which may result in a lower cost per volume for reuse schemes compared with smaller facilities as a result of economies of scale. The location of the wastewater treatment facility in relation to the location of the end user(s) is also important. Centralized facilities are typically in more urban areas, where reuse/reclamationschemes will typically involve industrial, agricultural and residential users.

Smaller, local sewage treatment works can be used in developed metropolitan areas for producing recycled water for toilet flushing in apartment and office complexes or for local irrigation projects such as a city park (Metcalf & Eddy and AECOM, 2007). The use of such satellite systems can lessen hydraulic loads on existing centralized treatment systems.

Smaller, decentralized sewage treatment plants are most commonly used in semi- urban, rural and remote areas where economic, technical, environmental or political (e.g. municipal planning or sustainability policies) factors do not allow for a centralized facility. The infrastructure needs are reduced for decentralized systems, as managing wastewater locally reduces the size and cost of the reuse water distribution systems. For decentralized facilities, viable reuse schemes will generally be limited to irrigation.

One of the benefits of decentralized systems compared to centralized systems is that they generally receive wastewater from a well-defined source, typically with little or no industrial wastewater discharges that can contain problematic constituents such as metals, salts and hazardous trace organic constituents. In addition, decentralized systems cover a small application area when compared to centralized systems, so that problems with the reclaimed water treatment system at a decentralized system will affect a lower number of users of the reclaimed water.

There are disadvantages of decentralized systems compared to centralized sewage treatment works, which include a high variability in flow rate and influent concentration that can affect effluent quality, as well as lack of redundant systems and long periods of time between maintenance activities (Metcalf & Eddy and AECOM, 2007). These factors may adversely affect the quality of reclaimed water.

4.3 Options for Using Reuse/Reclaimed Water

There are a number of options for using reclaimed water, which are described in the following subsections. Viable options for specific sewage treatment works are dependent on a number of factors, including effluent volume and quality, location of the sewage treatment works in relation to prospective reuse areas, acceptance by potential users, and costs associated with treatment and distribution of reuse water. In many parts of the world, water scarcity will dictate the reclaimed water use and in these cases high level of treatment for demanding reuse applications may be economically feasible. Disinfection of effluent, and in some cases supplemental disinfection, is a requirement for most water reuse options due to the potential for human exposure to effluent microbes. Table 4.1 presents a comparison of the level of treatment and economic, social and environmental factors for various water reuse options.

4.3.1 Agricultural

Given the large water demands associated with agricultural irrigation, significant opportunities exist for water reuse to reduce the reliance on freshwater sources. Another benefit of water reuse for irrigation is enhancement of crop production (B.C. MELP, 2001). The use of treated sewage represents a valuable source of water and nutrients for irrigation systems. Treated sewage contains nutrients that can be used by agricultural crops, although the levels may be too low to meet all nutrient needs.

It is estimated that irrigation represents as much as 75 percent of total global water usage (U.S. EPA, 2004). Not surprisingly, agricultural irrigation makes up a significant portion of existing water reuse systems. Irrigation with reuse/reclaimed water is widely practised in water-scarce areas such as the Middle East and the Mediterranean and is also increasing in other countries. In many European countries, reclaimed water is mainly used for irrigation purposes (Mackie et al., 2009). In some parts of the world, untreated municipal wastewater is still directly applied to irrigate crops; however, due to adverse health and environmental impacts secondary treatment and disinfection is required in almost all irrigation applications in the United States (Metcalf & Eddy and AECOM, 2007).

Typically, treated sewage contains higher concentrations of organic material and in some cases, higher sodium and salt levels when compared to "high quality irrigation water sources" (Alberta Environment, 2000). As well, there is a need for pathogen reduction in water reuse irrigation systems to minimize the risk of spreading infectious diseases, including the exposure of agricultural workers.

Agricultural water quantity requirements warrant consideration during development of a water reuse scheme. Demand for irrigation water is typically calculated as the sum of the water required to fulfil crop needs plus water required to overcome irrigation system losses. The latter includes losses due to percolation, surface runoff, transmission and distribution system losses, evaporation, and losses resulting from wind drift. Irrigation system losses can range from 2 to 60 percent; however, actual losses are site specific and can be difficult to determine.

With the exception of greenhouses, the growing of agricultural crops in Ontario is seasonal. As a result, the demand for reuse water for irrigation is limited to the growing season and alternative options for STP effluent are required at other times, either through other reuse methods, storage or discharge to the environment. The local climate will affect the amount of water needed for irrigation, whereby less is needed during wet seasons versus periods of low rainfall. Therefore, alternative options for the reclaimed water may be needed for years when less water is needed for irrigation due to higher rainfall amounts.

Uses of reclaimed water from a STP for agricultural irrigation include direct application to food crops, greenhouses, silviculture, crop cooling during the hot part of summer and frost protection in the spring and fall (B.C. MELP, 2001; Exall, 2004). Crop type and rooting depth, infiltration capability and water storage capacity of the soil, and climate should be taken into account when determining irrigation requirements. Other design considerations include the application system used, which can be categorized into three types: sprinklers or rotors, spray heads and drip.

Sprinkler (or rotor) systems are commonly used for irrigation. The size of the rotor depends on the field size, type of crop, water supply and pressure availability (B.C. MELP, 2001). Spray head systems are typically used in small, narrow turf and landscaped areas spraying water up to 6 meters. These systems have a high application rate and to prevent runoff they should be operated for short durations (15 minutes or less) (B.C. MELP, 2001). Drip systems are point-source or spray-emitter systems. Such drip/trickle-type systems use emitters to directly apply water to the plant rooting area at a low flow rate. They are used frequently; usually daily to replenish the area irrigated (B.C. MELP, 2001). Drip systems are buried below the soil surface to increase the volume of soil wetted by an emitter, which improves the crop yield and quality, reduces disease transfer and reduces weed growth (B.C. MELP, 2001).

Excessive irrigation with reuse water should be avoided to reduce runoff to nearby watercourses, which could result in negative impacts on the irrigated land as well as the receiving watercourse (B.C. MELP, 2001 and Exall, 2004).

4.3.2 Landscape Irrigation

Reclaimed water can be applied to landscaped areas such as school yards, playgrounds, golf courses, sports fields, cemeteries, individual and multi-family residential lawns, highway medians and shoulders, public parks and landscaped areas surrounding commercial, office and industrial developments (U.S. EPA, 2004). Landscape irrigation makes up the second largest use of reclaimed water in the United States with the largest use occurring in Florida and California (Metcalf & Eddy and AECOM, 2007). The water demand for landscape irrigation varies with geographic location, season and type of vegetation. Landscape irrigation requires many of the same controls and considerations as agricultural irrigation.

Since this particular use of reuse/reclaimed water is typically in public areas, there is the potential for more public exposure to the reclaimed water, and therefore a higher water quality level is usually required in terms of TSS and microorganism levels when compared to agricultural applications (Metcalf & Eddy and AECOM, 2007). Typically, tertiary or an equivalent level of treatment and disinfection is required for irrigation of landscaped areas with the exception of subsurface irrigation systems, which do not pose as high a risk to public health.

The water quality requirements for reuse/reclaimed water used in irrigation of landscapes will also depend on the type of vegetation. Constituents in the water and the tolerance of plants to these constituents need to be considered. Constituents that should be monitored include sodium, chloride and boron, as well as the effects of salinity and sodicity (i.e., high sodium content) on irrigated land and landscape plants. Nutrients are considered beneficial and may create significant savings in fertilizers costs; however, excessive loading may cause biofilm growth in the reclaimed water distribution system as well as having a long term adverse effect on the land. Leaching and drainage of the area should be considered when developing a water irrigation system (Metcalf & Eddy and AECOM, 2007). Similar to agricultural irrigation, landscape irrigation with reclaimed water should benefit the plants or grass areas and excessive runoff should be minimized to protect the surrounding environment.

When designing reuse/reclaimed water landscape irrigation systems, existing systems can be retrofitted or new landscape areas can be established using reuse/reclaimed water. Landscape irrigation can be categorized into three types of systems, namely sprinkler or rotor, spray heads and drip, as described in Section 4.3.1.

4.3.3 Environmental and Recreational

Environmental use of reclaimed water includes wetland enhancement and restoration, stream augmentation, and enhancement of wildlife habitat and refuges (U.S. EPA, 2004). Recreational uses include landscape impoundments, water hazards on golf courses, full-scale development of water-based recreational impoundments, incidental contact (fishing and boating), and full body contact (swimming and wading) (U.S. EPA, 2004).

The primary intent of reuse/reclaimed water wetland projects is to provide additional treatment of effluent prior to discharge from the wetland. Wetlands provide many positive functions such as flood attenuation, enhancement of wildlife and water fowl habitat, support of food chains, aquifer recharge, water quality enhancement and water conservation by regulating the rate of evapotranspiration (U.S. EPA, 2004).

Stream augmentation is used to maintain desired stream flows, enhance aquatic and wildlife habitats and maintain the aesthetic value of water courses. The quality of water required will depend on the designated use of the stream and desired aesthetic appearance (U.S. EPA, 2004). The reuse/reclaimed water should be non-toxic to aquatic life and should not adversely affect downstream uses or users. Nutrient control may be required to prevent eutrophication, algal blooms and odour problems in the receiving waterbody.

Recreational and aesthetic impoundments may serve a variety of functions from aesthetic, non-contact uses, to boating, fishing and swimming. The required level of treatment will vary with the intended use; generally, if there is human contact (swimming, boating) the level of treatment required increases. Nutrient control may also need to be incorporated into the system to avoid eutrophication, algal blooms and odour issues (U.S. EPA, 2004).

Reclaimed water impoundments can be easily incorporated into urban development as ornamental landscape uses and decorative water features, such as fountains, reflecting pools and waterfalls. The reclaimed water should be clear and odourless (U.S. EPA, 2004).

4.3.4 Domestic

Domestic use of reclaimed water includes toilet flushing and irrigation. Toilet flushing accounts for approximately 30 percent of in-home water usage, and significant amounts of water can be used for residential landscape irrigation during the summer. The use of reclaimed water for residential toilet flushing and irrigation can make significant contributions to reducing potable water use (B.C. MELP, 2001). In addition to residential properties, toilet and urinal flushing can be implemented in institutional, commercial and industrial buildings (U.S. EPA, 2004).

4.3.5 Commercial

Commercial uses of reuse/reclaimed water include toilet and urinal flushing in commercial and industrial buildings, dust suppression, soil compaction, and vehicle and street washing.

Over 80 percent of the water used in commercial buildings is for toilet and urinal flushing and air conditioning. Since commercial buildings typically have toilet facilities located centrally on each floor, a common water reclamation piping system can be easily installed (B.C. MELP, 2001).

In the construction industry reclaimed water can be applied for dust suppression and soil compaction by using a tank mounted on a moving truck. The reuse water should be applied to the target area only, and runoff should be minimized to ensure that there are no adverse impacts. The vehicle used to transport water should be dedicated to this purpose only and contain proper signage stating that it contains reclaimed water (B.C. MELP, 2001).

Reclaimed water of a high enough standard that allows public contact can be used for commercial vehicle, driveway and street washing. Other uses include window washing and mixing water for pesticides, herbicides and liquid fertilizer (U.S. EPA, 2004).

Reclaimed water may be used indirectly as a heat source or sink for heating and air conditioning systems. Snow melting is another indirect use, where treated sewage is diverted to a centralized basin from where it is pumped through pipes below the surface where snow melting is required. The rate of snow melting will depend on the effluent flow rate and the temperature, density and specific heat capacity of the water and snow (Exall, 2004).

4.3.6 Industrial

Water reuse for industrial applications can provide a more sustainable solution for the use of reclaimed water than other applications that are more seasonal in nature (e.g. irrigation, snow melting). Typical industrial applications include the use of reclaimed water for boiler feed, in cooling towers, and for process water, depending on the industry. For example, reclaimed water is often used as process water in power plants and oil refineries.

According to the U.S. EPA, cooling water is the largest use of reclaimed water by industry. Once-through systems and recirculating evaporative systems are the two basic types of cooling water systems where reclaimed water can be used. As water evaporates, constituents in the recirculating water become more concentrated than the original make-up water and must be removed or treated to prevent build-up, which can impair the operation of the cooling towers and ancillary equipment. Water quality problems associated with cooling water systems include corrosion, biological growth, and scaling (U.S. EPA, 2004).

Use of reclaimed water as boiler feed water usually requires extensive additional treatment. This is because the quality of boiler feed water is typically equivalent to or better than that of potable water. Special attention should be paid to iron, copper, silica and total dissolved solids concentrations in boiler feed water. The specific water quality requirements depend on the pressure under which the boiler is operating – the higher the pressure, the higher the quality of water needed. Another requirement when using reclaimed water for boiler feed water, and also when used in cooling towers, is to have a low hardness level to minimize scaling. The concentrations of calcium, magnesium, aluminum and silica in the boiler feed and cooling tower water need to be reduced in order to prevent scaling. In addition, high alkalinity levels in boiler feed can contribute to foaming, which in turn can result in deposits in the superheater, reheater or turbines (U.S. EPA, 2004). The need for high quality water and the small quantities generally required mean that reclaimed water is not a primary source of boiler feed water.

When using reclaimed water in evaporative cooling towers, care should be taken to control the growth of Legionella sp. through the use of adequate disinfection. Preventing scale formation through control of the hardness level will also help to prevent the growth of Legionella sp. In British Columbia, reclaimed water is not approved for use in evaporative cooling towers in residential or commercial areas due to the potential for pathogen build-up over extended periods of time (B.C. MELP, 2001).

Water quality requirements for specific industries vary greatly, according to production needs and use of the water. Reclaimed water can be used as process water, depending on quality requirements as well as other considerations such as occupational health. Exposure to aerosols that contain microbiological constituents or potentially toxic chemical contaminants (such as volatile organic substances) often restricts the use of reclaimed water for industrial processes. In some jurisdictions, the use of reclaimed water is excluded from processes that could result in contact with food, pharmaceuticals, or in cosmetics manufacturing. Potential industrial process water users include pulp and paper, chemical, textile, petroleum, and coal industries (U.S. EPA, 2004).

4.3.7 Indirect Potable Use

The introduction of reclaimed water into a raw water supply, such as a raw water reservoir or a groundwater aquifer, is referred to as indirect potable reuse. The treatment achieved in the environment may eliminate the need for costly advanced wastewater treatment processes.

Indirect potable reuse through surface water augmentation involves the blending of reclaimed water in a water course or in a raw water supply reservoir. The intent is for natural processes in the environment to improve the water quality (U.S. EPA, 2004), which could be determined by comparing the concentration of water quality parameters before and after blending.

Soils can provide additional in situ treatment of reclaimed water applied for groundwater recharge through natural biodegradation and filtration. Aquifers provide a natural mechanism for storage and subsurface transmission of reclaimed water. There is the risk of metals leaching into groundwater systems through aquifer recharge, and this should be taken into account when considering this option. Groundwater recharge can be accomplished by surface spreading, vadose zone injection wells or direct injection. The use of reclaimed water for irrigation practices may indirectly contribute to groundwater recharge (U.S. EPA, 2004).

4.3.8 Direct Potable Use

Direct potable use refers to the introduction of highly treated and disinfected reclaimed water either directly into the potable water supply distribution system downstream of a water treatment plant, or into the raw water intake system immediately upstream of a water treatment plant. Direct potable reuse is not commonly practised because of negative public perception (U.S. EPA, 2004) and, in fact, is only currently practiced in Namibia, where highly treated effluent is blended with conventionally treated surface water (Metcalf & Eddy and AECOM, 2007).

4.3.9 Other Urban Uses

Other uses of reclaimed water include fire fighting, and snow or ice making. Areas that use reclaimed water should be adequately marked (i.e., reclaimed water fire hydrants, ski areas and snowmaking equipment).

Reclaimed water may be used for both indoor and outdoor fire fighting. However, this requires additional efforts when designing the water reclamation system since urban potable water distribution systems are sized on fire flow requirements. For outdoor use, fire protection through reclaimed water fire hydrants can be used (U.S. EPA, 2004). Typically in fire protection, reclaimed water provides an additional source while potable supplies are the primary source. Reclaimed water should not contain any pathogens as the reclaimed water will be used in public areas or areas where the public is present (B.C. MELP, 2001).

Reclaimed water can be used for snow making to supplement natural snowfall. The use of reclaimed water can supplement the fresh water used in snow-making machines prior to the operating season for skiing and snowboarding to create a good snow base for the season. The water used for this process should be of a sufficiently high standard as the public will be in contact with these areas, and to ensure the surrounding soil and water courses are not negatively impacted (B.C. MELP, 2001).

4.4 Reuse Water Quality

4.4.1 Requirements in Ontario

There are currently no provincial policies or regulations governing water reclamation and reuse in Ontario. Some guidelines exist on the design of sewage treatment works from which treated effluent is intended to be land applied, such as by spray irrigation (MOE, 2008). The approval of any water reuse or reclamation project that involves discharging reclaimed water to a waterbody, even if indirectly and strictly for environmental reuse purposes (e.g. wetland enhancement), or onto the surface of the ground or into the ground subsurface falls under MOE’s jurisdiction. Furthermore, any municipal sewage treatment works with a design capacity of greater than 10,000 litres per day supplying reuse water for any beneficial use application requires a CofA under Section 53 of the Ontario Water Resources Act (OWRA). The MOE's decision to approve water reuse or reclamation for any application proposed by proponents is made on a case-by-case basis, from the perspective of protecting the environment (water, soil, plant and other species), as well as risk to human health. The procedure that a proponent is required to follow includes consulting with the local District Office and Regional Office of the MOE to establish the site-specific effluent quality criteria, requirements for treatment, monitoring and reporting, and contingency measures. The complete application process will be similar to that required for the approval of municipal and private sewage works (MOE, 2000a).

For land application of treated effluent, there is also a requirement to carry out an assessment of potential groundwater impacts under the MOE's policy document "Reasonable Use Concept in Groundwater Management" (MOE, 1994).

4.4.2 Regulations and Guidelines in Various Jurisdictions

There is no universal quality standard for reuse/reclaimed water due to the differing environmental conditions between and within national jurisdictions that have implemented water reuse, and the number of options available for water reuse. Information is provided in this section on regulations and guidelines for a number of jurisdictions, which are provided for example purpose only and are not endorsed by the MOE. The specific requirements associated with prospective water reuse/reclamation applications in Ontario would need to be determined on a case-by-case basis.

Currently in Canada there are no national guidelines or regulations for water reclamation and reuse, with the exception of the "Canadian Guidelines for Domestic Reclaimed Water for Use in Toilet and Urinal Flushing" (Health Canada, 2009). The latter guidelines were developed to promote on-site household reclaimed water use as a means of reducing potable water consumption. The document provides guidelines for reclaimed water quality, guidance on management of on-site reclaimed water systems, an overview of the scientific and technical basis for the guidelines and design and installation requirements for such non-potable water systems.

Alberta and British Columbia have developed guidelines related to water reuse. In 2000, Alberta Environment published the "Guidelines for Municipal Wastewater Irrigation" with the objective of providing assistance with the approval process to wastewater system owners and consultants. The guidelines emphasize the importance of using treated sewage for irrigation only when it is environmentally acceptable and agriculturally beneficial. In British Columbia, a water reuse document for a much broader range of applications entitled "Code of Practise for the Use of Reclaimed Water: A Companion Document to the Municipal Sewage Regulation" was developed in May 2001. This document provides guidance on the use of reclaimed water and information on supporting regulatory requirements in the province of British Columbia. The B.C. Reg. 129/99 in British Columbia covers numerous reuse applications and specifies requirements for water quality, associated levels of treatment and monitoring.

In 2006, the WHO revised and published the "Guidelines for the Safe Use of Wastewater, Excreta and Greywater" to maximize public health benefits and the beneficial use of scarce water resources in agriculture and aquaculture. The guidelines are designed to protect the health of farmers and their families, local communities and product consumers (WHO, 2006).

In the United States, legislation for water reuse applications is the responsibility of the individual states and this varies considerably from state to state. Arizona, California, Colorado, Florida, Georgia, Hawaii, Massachusetts, Nevada, New Jersey, New Mexico, North Carolina, Ohio, Oregon, Texas, Utah, Washington and Wyoming have developed regulations or guidelines that strongly encourage water reuse (U.S. EPA, 2004).

Although there is no federal regulation, the U.S. EPA in 2004 published the revised "Guidelines for Water Reuse" document to provide greater detail about the wide range of reuse applications and introduce new health considerations and sewage treatment technologies. The document includes suggested guidelines for various applications of water reuse, including urban reuse, restricted access area irrigation, agricultural irrigation for food and non-food crops, recreational and landscape impoundments, industrial reuse, groundwater recharge and indirect potable reuse. There are no guidelines for direct potable reuse in the U.S. EPA document. As well as specifying reclaimed water quality guidelines, the document recommends guidelines for wastewater treatment processes and monitoring (Exall, 2004). Generally, the U.S. EPA Guidelines for Water Reuse are accepted to be more stringent than the WHO guidelines (Radcliffe, 2004).

The State of California has a relatively long history of water reuse. California developed a set of Public Health laws related to reclaimed water that are summarized from the Health and Safety Code, the Water Code, and Titles 22 and 17 of the California Code of Regulations in a publication known as "The Purple Book". The requirements for contaminant concentrations and how those requirements are to be achieved are contained in California’s "Title 22 Regulation". These standards have been used to form the basis of standards and regulations developed by other countries and U.S. states (Radcliffe, 2004).

Israel uses reclaimed water for irrigation. Approximately 70 percent of municipal effluent collected is used for this purpose (U.S. EPA, 2004). Israel developed a nationwide integrated water management system to manage water reuse, which involves storing effluent during the winter in underground reservoirs for use as irrigation water in the summer. The Ministry of Health regulates the level of total coliforms, BOD, TSS, chlorine and DO in reclaimed water. Municipal effluent used as reclaimed water is typically taken from wastewater treatment facilities for medium and large cities (U.S. EPA, 2004).

In Australia, the majority of water reuse applications are located in New South Wales, Victoria and Queensland. In 2000, the document "Guidelines for Sewerage Systems – Reclaimed Water" was developed to set out the reclaimed water quality and monitoring requirements for various potential uses (Radcliffe, 2004). In 2006, the Australian government published the "Australian Guidelines for Water Recycling: Managing Health and Environmental Risks". This document, which is the first phase of a 2-phase project on water reuse, provides information on water reuse for a range of options, including residential, irrigation, fire protection and industrial applications. The second phase is currently under development and will cover water reuse for augmentation of potable water supplies and aquifer recharge.

There are currently four facilities in Singapore that treat municipal wastewater effluent for use in various applications, one of which is as an indirect potable water source. The Ministry of Environment and Water Resources in Singapore has set water quality and other requirements for these facilities for all reuse applications.

To date, no European regulation of water reuse exists; however, several individual European countries have adopted water reuse. Water reuse applications are typically in Southern Europe and countries with water shortages. Guidelines and regulations vary from country to country. Those for Spain, Austria and Italy are discussed below as examples.

The Spanish Ministry of Public Works, Transportation and Environment proposed reclaimed water quality standards for various applications similar to those contained in California’s Title 22 Regulation (U.S. EPA, 2004). In Austria, although there is an abundance of water, source control of water pollution is a high priority. Due to the Water Act, Austria has a very strong precautionary principle for ground and surface water protection and water reuse is relevant only when it contributes to reduce pollution and/or costs (Angelakis and Bontoux, 2004). In Italy, legislative constraints have restricted the use of reclaimed water to discharges onto soil for agricultural purposes, and only if wastewater addition can increase crop production (Radcliffe, 2004).

The following sections provide a summary of existing regulations and guidelines on water quality and quantity for use of reclaimed water in various applications.

4.4.3 Agricultural Applications

Human health and the impact of reuse water on crop and soil quality should be considered for agricultural applications. Water quality should be sufficient to ensure there is no danger to human health from the consumption of food produced when reclaimed water is used for irrigation. The health of agricultural workers also needs to be taken into account if they are exposed to the reuse water during the irrigation process.

A guiding principle adopted by health agencies in many jurisdictions is the restriction that only sewage that has been subjected to tertiary treatment and microbial disinfection can be applied to food crops that are eaten raw. Wastewater that has received a lower level of treatment is often allowed to be used on crops that are cooked before being consumed.

In addition to considering the impacts on human health, there is a need to consider the potential impacts of reuse water on crop growth and soil conditions. In particular, attention should be paid to:

• evapotranspiration, which can lead to high salt or metals accumulation in soils, which in turn can result in crop damage
• the potential for toxicity resulting from elevated concentrations of boron, chloride, and sodium in the soil, which can reduce crop yields.

According to the U.S. EPA, salinity is the single most important parameter in determining the suitability of reclaimed water for use in irrigation. Conductivity and/or total dissolved solids (TDS) are used to estimate the salt content of reclaimed water. Crop tolerance to salt varies widely. Recommended limits for TDS for water reuse in irrigation applications range from 500 to 2,000 mg/L. At concentrations less than 500 mg/L, no detrimental effects are usually found. When TDS exceeds 2,000 mg/L, reclaimed water should only be used to irrigate salt-tolerant crops on permeable soils. A common salinity mitigation strategy is to over-irrigate crops in order to promote the leaching of water and salt downward and away from the crop root zone. The location of the water table can impact the effectiveness of this mitigation strategy; a high water table may result in the upflow of water into the crop root zone. Care should be taken to ensure that groundwater used as a potable water source is not contaminated using this mitigation method.

In North America and other jurisdictions, five-day biochemical oxygen demand (BOD₅) and TSS are parameters that are typically used to monitor and regulate discharges from sewage treatment plants. Chlorine residual and turbidity are sometimes used as well. Because these general parameters are already monitored in treated sewage, jurisdictions that have implemented water reuse schemes often set criteria for these parameters to assure the quality of the reclaimed water meets that required for the intended end use, as presented in Table 4.2. Water quality criteria for other contaminant parameters are provided in Tables 4.3 and 4.4.

Reclaimed water typically contains higher levels of nutrients, such as nitrogen and phosphorus, than potable water. As a result, reclaimed water used for irrigation provides a source of nutrients and can reduce reliance on synthetic fertilizers. At the same time, care should be taken to ensure nutrient application rates do not exceed crop needs. Of particular significance is nitrogen, both in terms of the concentration and form. Nitrogen stimulates crop growth, but too much nitrogen applied in the latter part of the growing season can cause excessive growth, delayed maturity, and/or poor crop quality. Furthermore, excessive nitrate in forage that is used as the primary feed for livestock can cause a nutrient imbalance in grazing animals.

Uptake and accumulation of organic and inorganic contaminants in foods, including from fruit trees, destined for human consumption should be considered. Table 4.3 presents limits, published by various agencies, for inorganic constituents in reclaimed water used for irrigation.

The control of microbiological contaminants for water reuse is directed mainly at the health aspects of agricultural irrigation. As stated above, there are no universal quality standards for reclaimed water, including microbiological quality. One reason for the lack of universal microbiological standards is that there are no epidemiological data demonstrating a direct link between the quality of water applied to crops and the rate of disease transmission or infection.

Notwithstanding the lack of epidemiological data, most jurisdictions that practice water reuse have relied on the precautionary principle and have adopted microbiological criteria that are intended to safeguard health. Coliforms (total, fecal and E. coli) are the surrogate parameters most frequently used to measure the suitability of reclaimed water for different agricultural uses. In some jurisdictions, limits are also published for Salmonella species, Cryptosporidium, helminths and nematodes. The end use of the crop often dictates the upper limit for specific microbiological contaminants. Table 4.4 presents fecal coliform criteria for reuse water in a number of jurisdictions, for a range of crop uses.

Typically, if reclaimed water discharging to the environment contains a free chlorine residual greater than 1.0 mg/L, de-chlorination is likely necessary. Free chlorine residuals at concentrations less than 1 mg/L usually pose no problems to plants; however, concentrations greater than 5 mg/L will cause severe problems to plants (U.S. EPA, 2004).

One of the main advantages of using reclaimed water for irrigation is that it can often enhance fertility of the land to which it is applied. However, excessive irrigation can inhibit plant growth and potentially contaminate groundwater.

4.4.4 Industrial Applications

Reclaimed water quality required for industrial applications depends on the industry and the specific reuse application. The most common use of reclaimed water by industry is as cooling water. Table 4.5 presents examples of reclaimed water quality requirements for cooling water applications in various jurisdictions.

Table 4.6 presents industrial process water quality requirements for different industries. The information in Table 4.6 is illustrative only, since individual companies and operations may have their own unique requirements.

4.4.5 Indirect Potable Applications

The U.S. State of Florida has regulations governing groundwater recharge and augmentation of surface water supplies. Singapore also has regulations on indirect potable reuse. A summary of the regulations for these two jurisdictions is presented in Table 4.7.

4.4.6 Other Applications

The Alberta Environment Guidelines for Municipal Wastewater Irrigation establish a limit for total coliform of <1000 cfu/100 mL and fecal coliform of <200 cfu/100 mL for reclaimed water used to irrigate golf courses and parks (Alberta Environment, 2000). In British Columbia, B.C. Reg. 129/99 stipulates treatment and quality requirements for reuse water for a range of uses. Reuse options in B.C. include urban uses (e.g. non-agricultural irrigation, vehicle washing, toilet flushing, fire protection), recreational (e.g. snow making, stream augmentation, impoundments), construction (e.g. dust control, concrete making, equipment washdown) and environmental (wetlands). The reclaimed water quality requirements are dependent on whether there is restricted and non-restricted public access to areas where water is reused. Table 4.2 provides information on reuse water quality requirements for agricultural applications in terms of general chemical parameters in B.C. In addition, for various defined reuse applications, there is a requirement for fecal coliform levels to be ≤ 2.2 cfu/100 mL for unrestricted access and ≤ 200 cfu/100 mL where public access is restricted, based on the median value for the last seven samples taken. The maximum allowable number of fecal coliform for any sample taken is 14 cfu/100 mL and 800 cfu/100 mL for unrestricted and restricted public access, respectively. In addition, for restricted public access, the regulation in B.C. requires that the fecal coliform level be less than 14 cfu/100 mL where there is frequent worker contact with the reclaimed water.

Table 4.8 presents a summary of U.S. EPA suggested guidelines for water quality and level of treatment for various reuse applications.

Table 4.7 Water Quality Limits for Indirect Potable Reuse in Florida, U.S. and Singapore (Adapted from Metcalf & Eddy and AECOM, 2007)

4.5 Treatment Processes for Water Reclamation and Reuse

The type of treatment required for producing reclaimed water is dependent on the intended reuse application and the corresponding effluent quality requirements. Different technologies can be utilized either singly or in combination to achieve the desired water quality. Table 4.9 lists technologies used in water reclamation applications and the constituents removed.

The following subsections provide a summary of treatment technologies that can be used to reduce or remove specific constituents in municipal sewage for water reclamation.

4.5.1 Removal of Dissolved Organic Matter

Biological and chemical processes are used to remove the majority of organic matter through secondary treatment. Biological treatment processes include activated sludge, membrane bioreactors, trickling filters, hybrid processes (combination of suspended growth and attached growth systems), biological aerated filters and rotating biological contactors. These types of mechanical secondary treatment processes are capable of removal efficiencies of 85 to 95 percent of BOD₅. Lagoons can also be used to provide secondary equivalent level of treatment, with similar removal efficiency. Typically preliminary treatment (screening and grit removal) and primary sedimentation are used prior to mechanical secondary treatment. Final clarifiers are used to remove biological suspended solids from secondary effluent.

Although biological treatment removes significant amounts of suspended matter and nitrogen and phosphorus, its primary purpose is to remove dissolved organic matter. Table 4.10 describes the types of biological treatments and constituents removed, in addition to BOD₅.

Membrane bioreactors (MBR) can be used to treat wastewater for water reuse. This process combines biological treatment with an integrated microfiltration or ultrafiltration membrane system to remove organics and suspended solids. The process has a relatively small footprint as it eliminates the conventional treatment operations of clarification (e.g. sedimentation) and filtration. It typically results in lower concentrations of BOD₅, TSS and phosphorus compared with other biological treatment systems. However, the MBR process is more energy-intensive than other biological treatment systems.

As can be seen in Table 4.10, secondary treatment followed by disinfection will likely produce effluent that can be used for landscape irrigation, environmental, groundwater recharge and some agricultural purposes. Filtration (either as part of an MBR or separate filtration process) after secondary treatment, with or without advanced treatment may be required for other reuse options.

For systems that require a lower level of effluent dissolved organics after secondary treatment, granular activated carbon (GAC) is an effective method for removal of biodegradable as well as refractory organic constituents in sewage. GAC can reduce organic chemicals in an effluent by 75 to 85 percent, depending on the characteristics of the organic matter. According to the U.S. EPA, carbon adsorption preceded by conventional secondary treatment and filtration can reduce effluent BOD₅to 5 mg/L or less (U.S. EPA, 2004).

Table 4.10 Biological Treatment Technologies Commonly Used for Removal/Reduction of Dissolved Organic Matter (Adapted from Metcalf & Eddy and AECOM, 2007)

4.5.2 Removal of Dissolved Inorganic Matter

Wastewater contains dissolved inorganic matter such as salts which may cause scaling or corrosion in equipment and piping systems, especially in cooling towers. Sources that contribute to dissolved inorganics in wastewater include a high mineral content in the source water, accumulation of minerals through domestic water use, salt-based water softeners, commercial and industrial facility discharges to sewer, chemical addition during wastewater treatment (i.e., sodium hypochlorite and some coagulants), road salt runoff during the winter, and saline water intrusion in coastal areas (Metcalf & Eddy and AECOM, 2007).

If a higher quality of reclaimed water is required, the removal of dissolved inorganics may be necessary. The treatment technologies required are different from those typically used at sewage treatment works. Treatment processes that can be used to remove these constituents from wastewater include reverse osmosis (RO) or electrodialysis (Metcalf & Eddy and AECOM, 2007). Nanofiltration (NF) can also be used if the membrane porosity is relatively tight. All of these advanced treatment processes require a relatively high quality influent, and would typically be preceded by secondary treatment and filtration. In the case of RO and electrodialysis, upstream microfiltration (MF) or ultrafiltration (UF) will be used after or in lieu of conventional tertiary filtration to ensure operational stability.

NF and RO processes use a semi-permeable membrane to remove dissolved constituents. In these processes, water is separated from dissolved salts by using pressure-driven filtration. Substances are removed when water is diffused through a membrane from the higher concentration to the lower concentration side. In addition to dissolved inorganics, colloidal matter, bacteria and organic matter can also be removed from the wastewater with these treatment processes. NF and RO operate at significantly higher pressure compared to MF and UF systems owing to lower membrane permeability and porosity. RO systems have very high energy requirements as a result of the pumping pressure needed as a driving force for this type of treatment.

The typical operating ranges for particulate sizes retained by NF and RO systems are 0.001 to 0.01 µm and 0.0001 to 0.001 µm, respectively (Metcalf & Eddy, 2003). The water mixed with the constituents that do not pass through the membrane is referred to as the "reject", which varies in quantity with the type of membrane and wastewater strength. The rejected volume in an RO system can be between 10 and 50 percent of the influent flow and, if contaminant levels are high, may require special disposal procedures. When using these treatment processes, the disposal of the waste reject stream should be considered during the design phase. Disposal options can include discharge to the wastewater collection system, evaporation ponds, land application, and evaporation or crystallization or spray drying followed by landfilling (Metcalf & Eddy and AECOM, 2007).

Membranes are prone to fouling especially when organic material, calcium, magnesium, silica, sulphate, chloride and carbonates are present in the raw water. Fouling occurs in the form of scale, biofilms and colloidal material on the membrane surface which reduces the membrane throughput or flux (U.S. EPA, 2004). Membrane systems require backwashing and periodic cleaning to remove the accumulated solids on the membrane surface and restore its operating capacity. The quality of influent to NF and RO systems needs to be relatively high to ensure efficient and effective operation. As a result, upstream treatment typically includes MF or UF membranes, or an MBR treatment process.

Electrodialysis is an electrically driven process that removes dissolved inorganics and other species. Dissolved constituents are removed through an ion-selective membrane barrier from one solution to another under the driving force of direct electrical potential, leaving behind a dilute solution.

Each of these processes will have a waste stream, or reject, that needs to be disposed of. This waste stream can be recycled to the influent stream of the sewage treatment works or will need to be disposed of off-site.

Even though these advanced processes will remove some level of microbial contamination, for most reclamation/reuse applications disinfection is required as part of a multi-barrier approach to ensure system reliability and the microbial integrity of the product water and to prevent bacterial regrowth in storage and distribution systems (Metcalf & Eddy and AECOM, 2007).

4.5.3 Removal of Suspended Matter

Residual suspended matter can be found in effluent from secondary treatment as subcolloidal, colloidal, and particulate matter and may have to be removed by additional treatment processes depending on the intended use of the reclaimed water. The size and composition of the suspended matter will depend on the secondary treatment processes utilized.

Particulate matter contributes to turbidity and may be associated with undesirable chemical contaminants or pathogens in addition to interfering with disinfection. Suspended solids can reduce the effectiveness of disinfection by shielding microorganisms. Suspended solids can also clog sprinklers and drip irrigation tubes. Toxic constituents may also adsorb onto colloidal solids in the effluent, which could limit the reuse potential of reclaimed water.

The enhanced removal of suspended matter from secondary treatment effluent can be achieved by deep bed filtration, surface filtration, membrane filtration or dissolved air flotation (DAF). Removal efficiencies of suspended solids and turbidity for various technologies are shown in Table 4.11.

Table 4.11 Suspended Solids and Turbidity Reduction through Filtration and DAF (Source: Ortega and Iglesias, 2009)

In depth filtration, secondary effluent is passed through a filter bed containing granular or compressible media. The use of depth filtration allows more effective filtration, acts as a pretreatment step for carbon adsorption, membrane filtration or advanced treatment, and also removes chemically-precipitated phosphorus.

Surface (or sieve) filtration removes particulate matter from the influent by mechanical sieving. Surface filtration processes can be utilized as a substitute to depth filtration and as a pretreatment step for membrane filtration.

DAF removes particulates by separating chemically flocculated solids through the addition of fine air bubbles, which allow the solids to float and then be removed by skimming. This process, which usually relies on chemical additives, can be an alternative to sedimentation for water containing high levels of nutrients and algae and for low-alkalinity, coloured water. DAF can serve as a pretreatment step for depth or surface filtration or as a substitute for sedimentation, specifically if the water contains high levels of algae and low-density particulate matter.

Membrane filtration refers to a physical separation process driven by pressure in which contaminants are rejected by a permeable membrane. In the membrane system the particles are removed from the wastewater through surface filtration as the wastewater is passed through the membrane surface and the particles are mechanically sieved. Separation of particles occurs by driving the influent water through very small pores located on flat sheets, hollow tubes or hollow fibres, rejecting all constituents larger than the absolute pore size of the membrane. MF and UF are low-pressure membranes typically used in wastewater applications following biological treatment to remove particulate matter, organic matter and some nutrients. These two processes can be used to replace depth filtration to reduce turbidity, remove TSS, and also remove microorganisms. In some cases, depth filtration may be used prior to MF or UF to improve the efficiency and reduce the cleaning requirements of the latter treatment processes. The pore size ranges for MF and UF are 0.08 - 2 µm and 0.005 - 0.2 µm, respectively (Metcalf & Eddy, 2003). UF produces higher quality permeates than MF, due to the smaller pore size for UF. The effluent from membrane filtration processes can be used for reuse applications after disinfection or be further treated by NF or RO (Metcalf & Eddy and AECOM, 2007).

MF and UF membrane systems require backwashing and periodic cleaning to remove the accumulated solids on the membrane surface and restore its operating capacity, and produce a waste reject stream that requires disposal.

4.5.4 Removal of Nutrients

Nutrient removal may be required for reclaimed water that is used for environmental or indirect potable water applications. It can be achieved by integration of biological nutrient removal (BNR) processes into the main biological process, or by chemical addition. Secondary treatment processes will remove some nitrogen and phosphorus from wastewater, but the amount removed may be insufficient for certain water reuse options. The removal of nutrients such as nitrogen and phosphorus to low levels may be required when high quality water is necessary (e.g. discharges into recreational and sensitive water bodies, groundwater recharge).

To remove total nitrogen from wastewater, the sequential biological processes of nitrification (ammonia oxidation) and denitrification (nitrate reduction) are utilized. It can be achieved using a number of treatment processes, including variations of many common suspended growth and some attached growth treatment processes. Biological denitrification can yield residual nitrate concentrations of 2 to 12 mg/L using fixed film or suspended growth processes, assuming the proper microbial environment is created and maintained (U.S. EPA, 2004).

Phosphorus removal can be achieved by using enhanced biological treatment (e.g. biological nutrient removal processes) or chemical precipitation. The choice of method is dependent on the influent quality, existing treatment processes and the desired effluent quality.

Conventional secondary treatment will remove some phosphorus from wastewater, typically reducing the level in secondary effluent to around 4 to 6 mg/L, depending on the raw sewage strength. Lower levels of phosphorus can be achieved using the BNR variations of the activated sludge process. Biological nutrient removal processes typically produce effluent with total phosphorus concentrations of 0.5 to 1.0 mg/L, although lower levels can be achieved by the addition of a tertiary treatment process (i.e., by post-precipitation and clarification or filtration).

Chemical coagulants (e.g. metal salts such as alum, ferric sulphate or ferric chloride) can be added to precipitate phosphorus, which is then removed during the primary or secondary clarification stage, or can be removed to lower levels if tertiary filtration is used. Chemicals can be added at more than one location, depending on the degree of removal required (MOE, 2008). Effluent total phosphorus (TP) concentrations less than 1 mg/L can result from chemical precipitation without filtration. If tertiary filtration is used, TP levels as low as 0.10 mg/L can be achieved. Regardless of the method, the phosphorus is removed as a waste sludge that requires disposal (U.S. EPA, 2004).

4.5.5 Removal of Metals

Treatment processes for removal of metals from effluent include secondary treatment processes, adsorption and ion exchange. Metals removal may be required for agricultural, environmental and indirect potable reuse applications.

There will be some metals removal from municipal wastewater with conventional secondary treatment processes, which can be enhanced with the use of chemical precipitation and filtration. Chemically assisted sedimentation with lime can also be used as a separate process to remove metals from the reclaimed water stream (U.S. EPA, 2004).

Adsorption used in reclaimed water systems is typically a polishing step after biological treatment and tertiary filtration. Adsorption can remove organics as well as metals. It is a mass transfer operation which removes constituents from the wastewater by adsorbing the constituents from the liquid phase and accumulating them on the adsorbent material. The most common adsorbent used is GAC. Activated alumina and granular ferric hydroxide are other examples of adsorbents. Carbon adsorption can be used to remove metal ions such as cadmium, hexavalent chromium, silver, selenium, arsenic and antimony (U.S. EPA, 2004). As an alternative to GAC, powdered activated carbon can be added to the activated sludge process or be mixed with the reclaimed water stream before settling or filtration. Different types of carbon are available to remove different metals and it is recommended that testing be carried out to determine an appropriate carbon type for each application.

Ion exchange is a physical/chemical separation process by which an ion in a solid phase is exchanged with an ion in the feed water. The solid phase is typically a synthetic resin which has been chosen to adsorb the particular contaminant(s) of concern. A strong-acid anion exchange resin is used for removal of iron, magnesium, calcium, chromium and manganese while a strong-base anion exchange resin is used for arsenic removal (Crittenden et al., 2005). In water reclamation systems, ion exchange can be used for the removal of other ionic constituents such as Na⁺, Cl^-, SO₄^2-, NH₄^- and NO₃^-. It can also be used for water softening (i.e., the removal of Ca²⁺, Mg²⁺), and for the removal of other constituents such as barium, radium and perchlorate. Ion exchange typically requires a filtration pretreatment stage to reduce the solids loading to this process.

4.5.6 Removal of Pathogens

Disinfection is used to reduce the number of microorganisms in reclaimed water typically using chlorine, UV light, or ozone. In some reuse cases, a supplemental disinfection process may be required for the reclaimed water stream to reduce the number of microorganisms to a level suitable for reuse. Supplemental chlorination may also be required to prevent microbial regrowth in the distribution system.

The type of disinfection process best suited for water reuse is dependent on the quality of the effluent to be disinfected and the reuse application. Certain applications will require a significantly lower number of pathogenic microorganisms, e.g. irrigation of food crops or indirect potable reuse. The formation of disinfection byproducts (DBPs) may be an important factor when determining the disinfection method.

Table 4.12 presents a summary of destruction/inactivation effectiveness for different pathogens for the main disinfection processes used in reclaimed water systems.

The efficiency of chlorine disinfection is a function of water temperature, pH, degree of mixing, contact time, presence of interfering substances, concentration and form of chlorinating species, and the number and type of microorganisms in the water. Generally, bacteria are less resistant to chlorine than viruses. Interfering substances include organic constituents, particulate matter and ammonia. Chlorine is consumed by organic constituents reducing its effectiveness in the destruction of microorganisms. Particulate matter protects the microorganisms from the effects of the disinfectant, and ammonia reacts with the chlorine forming chloramine, which is a much less effective disinfectant than free chlorine. Residual chlorine can adversely affect ecosystems and therefore, dechlorination will likely be required if chlorination is used as the disinfectant and the reclaimed water is being discharged into a natural environment or is being used for irrigation. There is also the potential to form chlorination by-products that may be toxic to the natural environment and which may restrict the reuse application as a result (e.g. may make it unacceptable for environmental reuse). In some cases, a residual chlorine level may be desirable in the reclaimed water distribution system to minimize the risk of recontamination by microorganisms, e.g. if used for industrial process water.

UV irradiation destroys the ability of microorganisms to replicate and infect. The UV light inactivates pathogens by damaging their cellular structures and nucleic acid. Over the past decade, UV disinfection has gained prominence due to several advantages over other disinfection systems. These include the ability of UV to inactivate a wide variety of microorganisms, no formation of disinfection by-products (in contrast to chlorination or ozonation), minimal chemical usage for cleaning of lamps, compactness, overall low capital and operating costs and the elimination for the need for dechlorination prior to release of effluent to the environment (Gutierrez et al., 2009). Another benefit of UV is its effectiveness against Cryptosporidium and Giardia compared to chlorination (U.S. EPA, 2004). However, there is no residual disinfectant after treatment, which may be required for some reuse schemes. In addition, the energy required for this process is relatively high.

The use of ozone is most common for potable water treatment applications, and is uncommon for wastewater disinfection (Gutierrez et al., 2009). Ozone is a powerful, quick-acting disinfectant that must be generated on-site due to its instability. Ozone is a chemical oxidant in both organic and inorganic reactions (U.S. EPA, 2004) and therefore, the amount of ozone required for disinfection needs to take into account the impact of effluent residual organic and inorganic material on the ozonation process. Ozone destroys bacteria and viruses by rapid oxidation of the protein mass. Disadvantages of ozone include the relatively high cost and energy requirements for this process, greater operational and maintenance requirements than other disinfection processes, and the fact that there is no residual disinfectant after treatment, which may be required for some reuse schemes (U.S. EPA, 2004). There is the potential for the formation of DBPs, such as aldehydes that can affect the reuse application. Pilot testing of ozonation as the disinfectant should be carried out to assess the formation of DBPs, as well as its effectiveness, as the formation of DBPs will be site-specific (Metcalf & Eddy and AECOM, 2007). The off-gas from the ozonation process must be treated to destroy any remaining ozone, which is a toxic gas. Oxygen is formed by the ozone destruction process, which may be recycled if pure oxygen is being used to produce ozone (Metcalf & Eddy and AECOM, 2007).

Membrane separation systems can be used to remove human pathogens such as protozoan cysts, bacteria and viruses (U.S. EPA, 2004), but are not regarded to be disinfection processes.

4.5.7 Removal of Trace Contaminants of Emerging Concern

Trace contaminants of emerging concern (also known as "microconstituents") include endocrine disruptors, pharmaceuticals and chemicals used in personal care products. Table 4.13 presents examples of these contaminants typically found in effluent from municipal sewage treatment works. The need for removal of these trace organic contaminants from reclaimed water will depend on the end use of the water. Typically, direct or indirect potable use of reclaimed water, and surface augmentation require water of higher quality. Trace contaminants of emerging concern can be removed from effluent using chemical oxidation, advanced oxidation, adsorption or RO. These processes are not selective, and therefore a low level of organic matter is required in the effluent prior to the enhanced treatment in order to make these processes economically feasible.

Information on available technologies for the removal of trace contaminants of emerging concern and a review of the efficacy of these advanced treatment processes for potential application at municipal STPs can be found in MOE (2011). The study report also examined the jurisdictional use of treatment-based and non-treatment- based control measures for contaminants of emerging concern, such as source control, as well as the use of whole effluent toxicity as a monitoring surrogate.

In conventional oxidation processes, oxidizing chemical agents are added to water which directly reacts with the constituents in the water. The principal applications of conventional chemical oxidation in water reclamation systems include odour control, hydrogen sulphide control, colour removal, iron and manganese removal, disinfection, biofilm control in addition to oxidation of selected trace organic constituents. Typical oxidants used are chlorine, ozone, chlorine dioxide, permanganate and hydrogen peroxide.

Advanced oxidation processes can remove organic constituents which are not removed by conventional oxidation processes. The process involves generating a strong oxidant such as hydroxyl free radicals that can potentially mineralize certain dissolved organic constituents (Metcalf & Eddy, 2003). Chemicals such as hydrogen peroxide, Fenton’s reagent and ozone can be used, with or without UV irradiation and specific catalysts. The strong oxidant produced reacts with the organic constituents in the water. If ozone is used, the off-gas needs to be treated to destroy any excess ozone, which is a toxic gas. The pH of effluent to be treated with advanced oxidation should be less than 8, with an optimum pH typically in the range of 6.5 to 8. Therefore, pH correction of effluent may be required before using this treatment process.

Carbon adsorption is effective for removal of biodegradable and synthetic constituents, including endocrine disruptors (U.S. EPA, 2004). RO can also be used for the removal of trace contaminants of emerging concern, but this process is very energy intensive when compared with other options.

All polishing processes to remove contaminants of emerging concern have high capital and operational costs compared to conventional sewage treatment technologies. They typically require secondary treatment and filtration as pretreatment stages. In the case of RO, upstream MF or UF is necessary.

4.6 Important Factors and Considerations in the Selection of Water Reclamation/Reuse Applications and Technologies

Water reclamation and reuse applications are complex projects that require multi- objective planning methods and the involvement of various stakeholders. The selection of the end use(s) for the reclaimed water is dependent on a number of factors, including:

• the volume and flow rate of reclaimed water available
• the location of the end user(s) relative to the sewage treatment works, which can significantly affect distribution system capital and O&M costs, as well as could potentially impact the watershed if reuse is outside the watershed boundary
• public acceptance, which is a particular key requirement for Canada, where most areas have abundant water resources and the need to reuse water may be seriously questioned by the public (Exall, 2004) and significant public consultation will likely be required
• the cost to produce reclaimed water, which is dependent on the effluent quantity and quality required for reuse, as well as the type of enhanced treatment processes used.

The treatment requirements for reclaimed water are dependent on the following:

• the quality of the treated sewage from the sewage works
• the quality of reclaimed water needed, which is dependent on the end use; the lowest quality level acceptable will be based on the highest quality needed by any end user.

Consideration should be given to the energy requirements of the treatment processes employed and the associated greenhouse gas emissions, particularly for advanced treatment processes such as RO, which are energy-intensive. Other costs (e.g. chemical, labour) associated with producing and distributing reclaimed water requires a comprehensive review, and should be compared with the cost to produce and distribute potable water in each case. Further discussion of costs is presented in Section 4.8.

The complexity of the reclaimed water treatment system is an important factor in terms of the operation and maintenance requirements. Advanced treatment technologies may be better suited to mechanical sewage treatment works as the operator skill level is typically higher than for lagoon processes that are typically used in more rural areas.

In addition to these factors, consideration needs to be given to the risks associated with operating a reclaimed water scheme. Risks include the possibility that the end user may determine they can no longer use some or any of the reclaimed water at some time in the future.

The reliability of the treatment and monitoring system for reclaimed water is critical as the potential for adverse effects on public health and the environment are significant, particularly where there is potential for human contact or the reclaimed water is direct discharged into the environment (e.g. for stream augmentation). For this reason, process redundancy is required and a multi-barrier approach to water reclamation is needed. Multiple barriers are important considerations when selecting appropriate processes for reuse applications. In the case of indirect potable water reuse, the concept is based on establishing a series of barriers to preclude the passage of pathogens and potentially harmful organic and inorganic contaminants into the water system to the greatest extent practicable (WEF, 1997). Other factors to consider include compatibility with existing systems, process flexibility and reliability, storage and treatment systems location and design (i.e., use of adjacent properties, available area for buffer zone etc.) and waste residuals (Exall, 2004; Metcalf & Eddy and AECOM, 2007). Standby power should be considered to ensure the reliability of reclaimed water treatment and distribution.

4.7 Distribution and Storage of Reclaimed Water

The distribution network for water reclamation systems includes pipelines, pumping stations and storage facilities. Some facilities may use tanker trucks or rail to transport reclaimed water to users.

Currently, many sewage treatment works are located in lower-lying areas, by a lake or river, to allow gravity flow as much as possible. This would necessitate pumping of reclaimed water to users. For future sewage treatment works considering reuse/reclamation schemes as part of the design, consideration could be given to siting in more upstream locations to reduce pumping energy and costs for reclaimed water distribution.

In order to protect health and assure safe operation, reclaimed water pipes should be identified clearly when installed, as outlined in Section 7.7 of the Ontario Building Code Act, 1992 regulation (O.Reg. 350/06). The most common method is the use of purple-coloured pipe or by colour coding the pipe with purple tape or purple tags. The use of purple, which is a generally accepted industry standard for reuse water, is also extended to distribution system appurtenances, such as valves and sprinkler heads.

The MOE's Procedure F-6-1 (Procedures to Govern Separation of Sewers and Watermains) specifies that sewers and watermains should be constructed in separate trenches and have a minimum horizontal separation distance of 2.5 metres. The definition of "sewers" in this procedure does not include reclaimed water, but it is considered that the same separation requirements for reclaimed water pipelines and watermains should apply.

Most jurisdictions that have implemented water reuse schemes have adopted a set of practices to guide distribution system design and installation. A priority is to ensure that cross-connections are not made between the potable and non-potable water distribution systems. The U.S. Department of Energy (DOE) has best management practices intended for federal facilities that use, or are considering the use of non- potable reuse water. With respect to the supply of reclaimed water, the U.S. DOE has published the following guidelines:

• Colour Coding – pipes that are used to supply reclaimed water must be colour coded with purple tags or tape according to the standards set by the American Water Works Association (AWWA) to minimize the potential for cross- connections with potable water supplies.
• Signage – signs should be used liberally to indicate that reclaimed water is non-potable.
• Pressure – the pressure in reclaimed water pipes should be kept 69 kPa (10 psi) lower than potable water mains to prevent backflow and siphonage in case of accidental cross-connection.
• Subsurface Location – reclaimed water pipes should be at least 30 cm (12 inches) lower in elevation than potable water mains, and should be at least 1.5 m (5 feet) away horizontally.

Reclaimed water distribution systems typically experience more challenges with internal and external corrosion when compared to potable water systems. Internal corrosion potential is higher in reclaimed water systems because the water typically contains more minerals, has a higher conductivity and chloride level, and lower pH than potable water (U.S. EPA, 2004).

Reclaimed water distribution systems have similar O&M requirements to potable water systems. Isolation valves should be installed to allow repair to part of the system without affecting a large area. Line flushing should be conducted after construction to prevent sediment from accumulating, hardening and becoming a serious future maintenance problem. Periodic flushing will also be required after construction, and the distribution system design should allow for this. If the reclaimed water is chlorinated, monitoring of the chlorine residual is required to ensure adequate disinfection has been achieved. Flow monitoring and recording through the use of flow meters allows the system to be managed to allow for growth of the system. Pressure throughout the system should be monitored as a means of identifying system problems, such as leaks and blockages.

Reclaimed water that is continuously generated and cannot be used immediately should either be stored until there is a demand or disposed of. The size of storage required will depend on the volume and pattern of projected reuse demands. Storage may be required during periods of low demand for subsequent use during peak demand periods. Longer storage may be required if reuse is seasonal (e.g. irrigation).

The cost associated with the storage can be significant, especially if the water degrades in the storage due to algae growth and requires re-treatment to maintain the required water quality.

Traditional storage systems with finite capacities such as tanks, ponds and reservoirs will typically be large in comparison to the design flows in order to provide 100 percent equalization for off-peak demands.

Reclaimed water stored in a subsurface formation and recovered for use at a later time is referred to as "aquifer storage and recovery" (ASR). Reclaimed water can be stored during the wet season when demands are low and recovered during the dry season when demands are high. The storage capacity of an ASR system is virtually unlimited, making these systems desirable over traditional storage techniques.

The pattern of reclaimed water use will vary with each type of use and thereby impact the storage needs. Primary factors controlling the amount of reclaimed water needed for irrigation are evapotranspiration and rainfall. Temperature strongly affects evapotranspiration. Evaporation will be the lowest in colder months and highest in mid-summer. The amount of rainfall varies by location and by season. Once evapotranspiration and rainfall have been identified and quantified, reclaimed water irrigation demands throughout the seasons can be estimated. Other considerations include vegetation cover as this may impact the reclaimed water required for irrigation. Drought conditions will affect the system’s demands and should be examined when determining storage requirements (U.S. EPA, 2004).

Factors that drive demand for reclaimed water for industrial reuse will depend on the needs of the specific industrial facility. Demands for reclaimed water can be estimated based on past water use records. Diurnal fluctuations in demand and supply should be considered in order to provide adequate storage for the reclaimed water system, which is also the case for commercial and residential reuse. The supply and demand over a 24-hour period will determine the storage volume required. In order to determine the design requirements an investigation of the proposed use is needed. The best source of information for the storage design is historical records of actual use, if available.

If all the reclaimed water cannot be used or stored, disposal methods can include surface water discharge, injection wells, land application and wetland application (U.S. EPA, 2004).

4.8 Costs and Energy Requirements for Production and Distribution of Reclaimed Water

The greatest barrier to implementing water reuse can be cost, including that associated with energy use. Water reclamation and reuse represents a sustainable approach to water resources management and can be cost-effective over the long term. In the short term, however, capital costs associated with increased levels of wastewater treatment and installation of distribution systems specifically for reclaimed water can be prohibitive in comparison with other options (U.S. EPA, 1998). Furthermore, when the cost of producing and distributing potable water are relatively low, this low cost may represent a barrier to implementing a water reuse scheme.

4.8.1 Capital Costs

The actual cost of a water reuse or reclamation scheme depends on the treatment processes used, the quality standards that the reclaimed water must meet, and the distance between the reclaimed water source and the end user(s). It also includes the retrofit cost to the end user’s existing water system to accommodate the reclaimed water pumps, piping and appurtenances.

Treatment

In a 2005 study, the average capital cost of a water reuse project in the U.S. was reported to be on the order of $1,200 per cubic metre per day of capacity (Media Analytics, 2005). A 2003 investigation of water reuse potential for the City of Atlanta in Georgia, for example, determined the capital cost for treatment of wastewater for non-potable reuse ranged from $530 to just under $1,850 per cubic metre of capacity ($2 to $7 per gallon) (Yari, 2002).

The capital cost for a reclaimed water treatment system will vary significantly with the level of quality required, i.e., higher quality reclaimed water will typically have a higher capital cost. The requirement for redundancy and other safeguards to ensure public safety will have an impact on capital costs and in some cases may render the cost of a reclaimed water facility more expensive than a potable treatment system using conventional raw water sources.

Distribution

Pipe installation accounts for the majority of capital costs associated with a reuse water distribution system. A study of the Greater Chicago Area found that pipe installation costs accounted for approximately 90 percent of the water reuse distribution system (Anderson et al., 2008), with costs ranging from $250 to $650 per metre of pipe installed, depending on the degree of existing development.

Examination of the ratio of the demand (Q) for reclaimed water to the length (L) of the secondary distribution system can be useful for water reuse planning and optimization. Calculating the Q-to-L ratio for specific users or clusters of users can facilitate comparison of the economics of supplying different end users. In general, higher Q-to-L ratios indicate higher priority users.

4.8.2 Operating Costs

Similar to the case with capital costs, the O&M costs associated with a water reuse scheme will depend on the treatment processes used, the quality standards that the reclaimed water must meet, and the distance between the reclaimed water source and the end user(s).

The cost to operate a water reuse system may be lower than those for a potable water system. The main savings come from reductions in pumping energy and treatment chemical costs. However, the costs are significantly affected by the treatment processes required for the reclaimed water as well as the distance (horizontal and vertical) between the sewage treatment works and users of the reclaimed water.

In addition to energy required for treatment and pumping, there may be treatment chemical costs for water reuse. Furthermore, waste solids production or other waste streams from certain treatment processes (e.g. sludge from biological treatment or chemical precipitation, reject stream from membrane processes) will need to be disposed of and may require treatment prior to disposal.

Labour requirements will include operators to operate treatment systems and monitor the quality of reclaimed water, as well as maintenance of the treatment and pumping systems. Operator training and competence are essential to ensure that the reclaimed water will be acceptable for its intended use. The system operator’s actions have the potential to adversely affect reclaimed water quality and public perception of the water reclamation system; therefore, a knowledgeable and attentive operator is critical.

A 2005 study estimated the average operating cost for water reclamation to be $0.35 per cubic metre globally (Media Analytics, 2005). Operating costs for the Salina Valley Reclamation Project in California amount to US$0.23 per cubic metre (excluding secondary treatment costs but including debt service and O&M costs) (Crook, 2010). Treatment for reuse included chemical coagulation and flocculation of secondary effluent followed by dual-media gravity filtration. These figures are comparable to the cost for potable water supplies.

4.8.3 Energy Use

Energy requirements, including future energy costs, should be estimated if cost- effective water reclamation systems are to be designed. The design process should also evaluate whether stand-by power is required or whether the system can be disrupted safely in the event of a power failure.

An assessment of the impact of each treatment process on energy use should be undertaken during treatment selection. For example, different filtration processes will have different energy requirements - depth filtration and surface filtration will have lower energy requirements compared to MF or UF processes (Metcalf & Eddy and AECOM, 2007). NF, RO, electrodialysis and advanced oxidation have high energy requirements. Further information on energy use by treatment processes is provided in Section 5.3.

It is possible that the energy needed to treat and distribute reclaimed water can exceed the energy needed to supply potable water. Care should be taken to ensure this is avoided, unless there is no alternative supply of source water. To help minimize the energy associated with pumping, water reuse customers should be as close as possible to the water reclamation facility.

4.8.4 Financial Analysis and Pricing Strategy

Beyond the capital and O&M costs associated with water reclamation and reuse schemes, there are other costs, and potential savings, to consider when determining pricing, such as:

• marketing reclaimed water to intended users
• cost of retrofitting
• the value of the nutrient content (which can result in cost savings to farmers due to reduced reliance on commercial fertilizer).

For many water reuse schemes, the pricing rationale is driven by the need to provide incentives to potential customers. As a result, discounting of reclaimed water is considered an effective incentive to displace potable water use.

It should be noted that only a minority of water reuse projects aim their pricing strategies at full cost recovery, i.e., the recovery of actual costs based on a life-cycle analysis. Most projects rely on sources of funding beyond the users, including intra- agency and inter-agency transfers. Justification for such transfers can be made when the full benefits of the water reuse scheme are evaluated as partof the costs and benefits.

Pricing structures for reclaimed water mirror those used for potable water and can include flat rates, unit rates, base fees plus unit rates, inclining and declining block rates, and/or bulk purchasing rates.

4.9 Case History Examples

4.9.1 City of Vernon Water Reclamation & Spray Irrigation, British Columbia

The Vernon Water Reclamation Centre (VWRC) is responsible for the treatment and beneficial use of all treated residential, commercial and industrial wastewater generated in the Greater Vernon area, serving a population of approximately 36,000.

The VWRC reclaims approximately 13,000 m³ of wastewater daily with secondary and tertiary treatment and chlorination. Treatment processes include fine screening, grit removal, primary clarification, biological nutrient removal, secondary clarification, filtration and UV disinfection. Primary and secondary solids are blended, dewatered, composted and then sold to the community as a final product rich in nutrients.

Since 1978, all the reclaimed water has been pumped 7 km to a reservoir from which irrigation water is withdrawn and chlorinated to irrigate approximately 970 ha (2400 acres) of land from late April to early October. Areas irrigated include a golf course, seed orchard, a forestry centre and a nursery as well as large areas of agricultural land used for grazing and hay production (City of Vernon, 2009; Exall, 2004).

Updates and relevant information pertaining to the projects can be found at the City’s website (City of Vernon, 2009).

4.9.2 City of Edmonton Water Reclamation Scheme, Alberta

The City of Edmonton reviewed and evaluated membrane treatment technologies for the Gold Bar Wastewater Treatment Plant (WWTP) in 2003 as part of an upgrade that included adding a new reactor and clarifier to their BNR treatment process. Membranes were considered as a means of meeting future regulatory discharge requirements and to produce a potential supply of reclaimed water for industrial users, thus a pilot-scale membrane treatment study was carried out at the WWTP.

At around the same time that the City was reviewing membrane treatment at the Gold Bar WWTP, Petro-Canada undertook the Edmonton Diesel Desulphurisation (EDD) project, which requires the supply of hydrogen and steam. Air Products agreed to supply the hydrogen and steam needed, but required Petro-Canada to supply the water needed for the hydrogen plant. Petro-Canada considered two options to obtain the water needed: pump and treat water from the North Saskatchewan River, or use treated effluent from the City of Edmonton’s Gold Bar WWTP. After an assessment of these two options, Petro-Canada decided on using reclaimed water from the City. This option was also considered a suitable source of water supply for future operations at the Petro-Canada refinery.

The City agreed to design, build and operate the reclaimed water treatment plant and Petro-Canada agreed to construct the distribution pipeline and pay for the construction of the membrane treatment system.

The reclamation project has three phases: the supply of 5,000 m³/d of reclaimed water in phase one (2005) and 20,000 m³/d in phase two (2008), with an ultimate flow rate of 40,000 m³/d in the future.

The treatment system consists of hollow-fibre microfiltration membranes that were installed in an existing secondary clarifier. Effluent from the activated sludge aeration tank flows to the membrane system before being chlorinated. After chlorination, the reclaimed water is pumped to the Air Products facility.

The reclaimed water distribution system consists of a 5.5 km pipeline through two city parks and through a provincial park in order to carry the water from the STP to the hydrogen plant, and in the future to the Petro-Canada refinery.

The agreement between the City and Petro-Canada guarantees that the water quality will meet the parameters specified in Table 4.14.

The above information is a case study based on information from Watsonet al. (2006).

4.9.3 Ballantrae Golf & Country Club, Ballantrae, Ontario

A privately owned and operated treatment facility treats 1,045 m³/d of sewage from a 900-person residential development and a golf course. The treatment facility contains full biological and tertiary treatment. There is no receiving stream for the sewage treatment plant effluent. The STP was designed to pump effluent through gravity sand filters to remove particulate matter prior to discharge via an UV disinfection system. The minimum retention time through the UV system is approximately 11 seconds, with a design based on 65 percent UV transmission at 254 nm. The effluent is contained in one of two holding ponds, before it is pumped to an irrigation system in the summer or into the ground in the winter.

Typically, golf courses use significant amounts of water for irrigation. Using the reclaimed water from the STP has allowed this facility to meet its irrigation needs while operating in a location that is not serviced by a municipal water supply.

Table 4.15 presents a summary of the effluent criteria for this facility as specified in the CofA for this private sewage works. The compliance limits are based on monthly average concentrations, with the exception of E. coli, which is based on a monthly geometric mean.

The above information is a case study based on information from McIntyre (2008).

4.9.4 City of Santa Rosa Water Reuse System, California

The City of Santa Rosa, California located in Sonoma County has been using reclaimed water for over 40 years. The Laguna Wastewater Treatment Plant treats sewage from homes, businesses and industry located within the Santa Rosa Subregional Water Reuse System. Since 1968, the facility has increased its production of reclaimed water from 7,571 m³/d (2 U.S. mgd) to approximately 80,000 m³/d (21 U.S. mgd).

Reclaimed water that leaves the Laguna Wastewater Treatment Plant is treated to a tertiary level that meets or exceeds the California water recycling regulation (Title 22). Wastewater treatment includes screening, grit removal, primary clarification, activated sludge, secondary clarification and filtration prior to disinfection. UV disinfection of the tertiary treated effluent is used to deactivate pathogens prior to reuse. After treatment the water is sent to holding ponds; these ponds are rich with wildlife, including a wide variety of waterfowl. The reuse system utilizes 45 pumping stations that deliver reclaimed water to buried-pipe and above-ground irrigation systems.

The reclaimed water is used for agricultural irrigation, urban reuse, and by the Geysers Geothermal Plant for electricity generation. The reclaimed water is used to irrigate approximately 2,590 ha (6,400 acres) of agricultural lands used to grow hay, pasture, vegetables, turf and wine grapes. Urban reuse includes irrigation of parks, school yards and landscape areas, including Sonoma State University. Reclaimed water is also used to create artificial wetlands that provide a habitat for many species of birds, amphibians and mammals.

The Geysers Recharge Project is a geothermal plant which uses the reclaimed water to generate electricity for over 85,000 homes. The reclaimed water is injected into the depleted steam wells. One of the major benefits of the Geysers Recharge Project is the ability to use the reclaimed water year-round, as the Geysers' steam field uses the reclaimed water when other reuse options (such as agricultural irrigation) are not available. If all of the reclaimed water cannot be reused, the City has the option to discharge to adjacent receiving waters from the months of October to May.

The above information is based on a case study presented in the U.S. EPAGuidelines for Water Reuse (2004) and the City of Santa Rosa, California website (City of Santa Rosa, 2009).

4.9.5 Western Corridor Recycled Water Project, Queensland, Australia

In response to severe drought and an expanding population, the Australian state of Queensland is implementing programs to provide sufficient drinking water supplies in the future. The Western Corridor Recycled Water Project (WCRWP) is the largest water reclamation project in the Southern Hemisphere and the third largest in the world.

The WCRWP is an AUS$2.4 billion (CAN$2.5 billion) water supply network and funding for the project was provided by the Queensland Government and the Australian National Water Initiative as part of a Commonwealth Government Grant program.

Reclaimed water is produced by three advanced reclaimed water treatment plants: Bundamba Water Treatment Plant (WTP ), Gibson Island WTP and Luggage Point WTP. Treated effluent supplied by six sewage treatment plants is further treated at each of the three WTPs through another five-stage purification process to remove suspended solids, dissolved salts, organic chemicals, viruses, bacteria and parasites. The incoming secondary effluent is treated with microfiltration membranes, reverse osmosis membranes, advanced oxidation and chemicals for stabilization and disinfection.

The three WTPs produce approximately 232,000 m³/d (61.3 U.S. mgd) of reclaimed water, which is distributed through 200 km of underground pipeline to power stations, where it is used for cooling water, and to the Wivenhoe Dam to supplement drinking water supplies. The system includes nine storage tanks and 12 pumping stations. The WCRWP aims to enhance the security of the water supply to South East Queensland through the increasing use of water supplies that are less dependent on climate.

The above information is a case study based on information from Wallis-Lageet al. (2009) and the Queensland Government website (Queensland Government, 2009).

4.9.6 City of Yelm, Washington

The City of Yelm, Washington commissioned a water reclamation plant in August of 1999 in response to the public health risk associated with septic systems in the area. The City did not want to go ahead with the original plan to treat and discharge effluent to the environmentally sensitive Nisqually River, which supports five species of Pacific salmon and starts in Mount Rainier National Park and ends at a national wildlife refuge.

The plant reclaims approximately 871 m³/d (230,000 U.S. gal/d) of effluent and has a design capacity to reclaim up to 44 L/s (1.0 U.S. mgd). The plant consists of a septic tank effluent collection and pumping system, biological treatment with nitrogen removal using a Sequencing Batch Reactor (SBR), an automated chemical feed system with in-line static mixers to coagulate and flocculate remaining solids prior to filtration, upflow sand media filtration, and chlorine disinfection.

On-line computer monitoring of flow, turbidity and chlorine residual is carried out. Only reclaimed water that meets the required standard is sent for reuse. Quality requirements for the finished water include daily average turbidity of less than 2.0 NTU with no value above 5.0 NTU, total coliform less than 2.2 counts per 100 mL as a 7-day median value, and total nitrogen below 10 mg/L.

The reclaimed water is used for landscape irrigation, groundwater recharging, power generation, washing of treatment plant equipment, treatment plant processes, fire fighting, street cleaning and dust control. Constructed surface and subsurface submerged wetlands at the 3.2 ha (8 acre) City park polish the reclaimed water prior to recharging to the groundwater. During winter, there is not enough demand for reclaimed water for irrigation purposes and the excess water is sent to generate power in the Centralia Power Canal, which is a diversion of the Nisqually River. The reuse system is capable of using all of the reclaimed water generated and ultimately ensuring that effluent is not discharged to an environmentally sensitive area.

The above information is a case study presented in the U.S. EPA Guidelines for Water Reuse (2004).

4.9.7 NEWater, Singapore

A water reclamation study was initiated in Singapore in 1998 to determine if the reclaimed water could be used as a source of water to supplement Singapore’s raw water supply. As a result of that study, Singapore currently has four facilities producing reclaimed water (known as "NEWater"), and a fifth facility is planned. It is estimated that these five reclamation facilities will produce and supply 30 percent of the water demand for Singapore by the end of 2010.

Conventional secondary treated municipal effluent is further treated using microfiltration, followed by RO and UV irradiation. Most of the reclaimed water is used by industries, and a small percentage is used as indirect potable water. Indirect potable reuse involves pumping reclaimed water into reservoirs, from where the reclaimed water is mixed with raw water for potable use after treatment. Approximately 1 percent of potable water for Singapore comes from reclaimed water.

The above information was obtained from the website of PUB (PUB, 2008), which is Singapore’s national water agency.