(formerly referenced by 08-01)

1.0 Rationale

Effluent requirements within the Province of Ontario are determined under the provisions of Procedure B-1-1: "Water Management-- Guidelines and Procedures of the Ministry of Environment and Energy (The "Blue Book")". In accordance with the procedures outlined in that publication, effluent requirements are established on a case-by-case basis considering the characteristics of the receiving water body, as well as Federal and Provincial effluent regulations and procedures, where applicable.

For discharges from municipal and private sewage treatment works, Provincial jurisdiction applies, except for Federal facilities. Federal facilities are covered by the effluent guidelines, "Guidelines for Effluent Quality and Wastewater Treatment at Federal Establishments". Normally, the Federal government consults with the Province to ensure that the effluent from Federal plants will be consistent with Provincial policies.

Guideline F-5 takes the approach that all sewage treatment works shall provide secondary treatment or equivalent as the "normal" level of treatment, unless individual receiving water assessment studies indicate the need for higher levels of treatment. In setting the "normal" level of treatment as secondary, various factors were considered, including: minimization of adverse health-related and environmental effects, aesthetic nuisance and toxic effects of effluent discharges from heavily populated areas to rivers and streams or to littoral zones of lakes where intensive water use and re-use occur; minimization of potential interference of effluent discharges with other water uses; possibility of more stringent future phosphorus removal requirements and the capability of secondary sewage treatment processes to be upgraded to meet such requirements; relatively low additional cost and significant additional benefits of secondary treatment over primary treatment with respect to removal of conventional contaminants and, potentially, the removal of hazardous trace organics.

2.0 Definitions

2.1 Ministry

For purposes of Guideline F-5 and its procedures, the term Ministry is defined as the Ministry of Environment and Energy, unless otherwise stated.

2.2 Municipal and Private Sewage Treatment Works

The term "municipal and private sewage treatment works", for purposes of Guideline F-5 and its associated procedures, includes works owned by municipalities, private groups or companies, institutions or government agencies, treating either strictly domestic, or combinations of domestic, commercial and industrial waste, which are owned by municipalities, private groups or companies, institutions or government agencies, which discharge their effluent to surface waters, but does not include sewage works exempted from the requirement of Section 53 of the OWR Act (R.S.O. 1990).

2.3 Secondary Treatment, or Equivalent

Secondary treatment, or equivalent, may be that provided by biological processes including the activated sludge variations or lagoon systems, physical-chemical, or combinations of these processes producing an effluent quality as stated in Table 1.

Sewage treatment works which provide only primary settling of solids and the addition of chemicals primarily for the purpose of improving the removal of total phosphorus and/or solids are not considered as secondary treatment, or equivalent for purposes of Guideline F-5.

2.4Five Day Biochemical Oxygen Demand "BOD5"

For purposes of Guideline F-5, BOD5 is defined as carbonaceous BOD5. It is a measure of the oxygen utilized over a 5 day period for the bio-chemical degradation of organic materials and the oxygen utilized to oxidize such inorganic materials as sulfides and ferrous ion.

3.0 Guidelines

In selecting the level of treatment required for municipal and private sewage treatment works discharging to surface waters, the following shall be adhered to:

3.1 Receiving Water Assessment

Receiving water assessments must be performed in all cases. Technical guidance for water assessment studies may be obtained from Regional staff or staff of the Science and Technology Branch. The carrying out of receiving water assessment studies and the interpretation of results will be the responsibility of the proponent of any new sewage treatment works or of any works undergoing expansion. Any relevant data in the possession of the Ministry will, upon request, be made available for such assessments. In certain cases, the necessary receiving water assessment may have already been carried out by the Ministry and, if so, all pertinent information will be made available to the proponent. If not the Ministry may at its discretion agree to do such assessments, or assist in their completion.

3.2 Higher Than Normal Treatment

If the effluent requirement determined by the receiving water assessment is more stringent than the "normal" level of treatment as required in the Provincial guideline, then the treatment requirement derived from the assessment will be imposed.

Since BOD5 does not include the oxygen demand due to the bio-chemical oxidation of total ammonia, for those sewage treatment works discharging into receivers where nitrogenous oxygen demand is important, a total ammonia nitrogen "(NH3+NH4+)-N" and/or total kjeldahl nitrogen limits should be derived and incorporated into the works' Certificates of Approval.

3.3 Sewage Bypass From Nominally Separate Sewer Systems

Bypassing of raw sewage and primary effluent from nominally separate sewerage systems will not be allowed except in emergency conditions.

In accordance with Section 15 of the Environmental Protection Act (R.S.O. 1990), and with Section 30(2) OWR Act (R.S.O. 1990), bypass incidence shall be recorded and the appropriate agencies (i.e., MOEE Region and/or Spills Action Centre, and Medical Officer of Health) notified. In addition, the measured or estimated volume, duration and reasons for bypassing shall be documented and reported to the MOEE Regional office.

For new works, emergency bypass facilities which permit by-passing from sewers, sewage pumping stations and sewage treatment works of sewage not satisfying the prescribed treatment requirements, must receive approval as required by Section 24 to 53 of the OWR Act. It is understood, however, that the approval required is an integral part of normal review procedures for sewers, pumping stations or treatment works in question and that a separate approval is not required. These emergency bypasses will be permitted only to provide protection from basement flooding, to prevent damage to equipment at treatment works or pumping facilities or to prevent treatment process wash-out.

To reduce the frequency and volume of sewage discharged from emergency by-passes to an acceptable minimum, measures shall be taken to provide adequate sewer and pumping station capacity, stand-by equipment, stand-by power, reserve storage capacity in sewers, and/or at treatment facilities and adequate capacity in sewage treatment works. For recommended design criteria, reference should be made to "Guidelines for the Design of Sewage Treatment Works" and to "Guidelines for the Provision of Equipment to Handle Emergency Conditions in New Sewage Works".

Where existing sewer systems are found to experience excessive infiltration/inflow problems, which result in unacceptable frequencies or quantities of raw sewage and/or primary effluent by-passing, and where the above measures alone are either impractical or uneconomical to reduce the by-passing to acceptable levels, staged programs should be developed for the ultimate containment of these flows by a combination of the above measures and the reduction of infiltration/inflow to the sewer systems. These programs should outline the approaches to solving the problems along with the anticipated timing of when the changes to the sewer systems could be made.

3.4 Bypassing from Combined Sewer Systems

It is the goal of the Ministry to abate all discharges of untreated sanitary wastewater. With combined sewer systems, it is realized that a certain degree of overflowing will occur for some period both during and shortly after severe storm events and spring melts . All municipalities serviced by combined sewerage should however prepare a staged program leading towards the ultimate goal of total containment for treatment of all sewage flows. This program should outline the sewerage works required along with their anticipated timing of implementation. Details of requirements are discussed in the Ministry Guideline (draft, copy enclosed) dealing with by-passing and combined sewage overflows. New or expanded sewage treatment works servicing sewer systems containing combined sewer areas should be designed taking into account the problem of combined sewage overflows.

3.5 Excess Primary Treatment Capacity

Where reduction and/or containment followed by secondary treatment of extraneous wet weather flows is impractical or uneconomical , secondary/tertiary sewage treatment works may be designed with excess primary treatment capacity to accommodate the extraneous wet weather peak flows.

For the present, effluent criteria need not be specified for excess primary effluent discharged in wet weather. Consequently, no compliance assessment program is currently necessary, although the frequencies of occurrence, volume and duration should be measured or estimated, recorded and reported to the Ministry Regional office as secondary by-pass. The Region in consultation with Program Development Branch, in specific instances may require both effluent criteria and a compliance assessment program for excess primary effluent discharges. The details of requirements including the means of assessing non-compliance will be specified by the Ministry for such cases.

3.6 Non-compliance of Existing Sewerage Systems

Existing municipal and private sewerage works not complying with Guideline F-5 shall be upgraded to meet the requirement of this guideline as soon as possible. It will be the responsibility of the Ministry’s Regions to develop upgrading schedules taking into account local, national and international obligations.

3.7 Effluent Design Objectives and Effluent Guidelines

Table 1 is provided to assist in selection of sewage treatment processes to meet specific effluent quality criteria. Two sets of effluent criteria are given in Table 1 -Effluent Design Objectives and Effluent Guidelines. The Effluent Design Objectives are those levels of performance which can be achieved by treatment processes treating normal strength municipal sewage under optimum conditions. The Effluent Guidelines criteria were developed based upon the effluent quality data of sewage treatment works in operation in Ontario in 1982 and earlier. Sewage treatment works designed in accordance with the Ministry "Guidelines for the Design of Sewage Treatment Works" should be able to produce annual average effluent quality approximately equal to the Effluent Design Objectives, but not to exceed the Effluent Guidelines criteria.

There will be some circumstances, when sewage treatment works will be required to achieve somewhat better quality than the Effluent Guidelines criteria in order to satisfy effluent requirements determined from receiving water assessment studies. For example, a situation could occur where the receiving water assessment study for a proposed plant indicates that the effluent BOD5 should be 17 mg/L and the suspended solids should be 25 mg/L. Plant performance better than the Effluent Guidelines criteria (25 mg/L BOD5) for conventional activated sludge plants will, therefore, be necessary, but the effluent requirement is still within the possible range for conventional activated sludge plants, since under optimum conditions such a plant should be capable of meeting the Effluent Design Objectives criteria (15 mg/L BOD5). In this circumstance, a conventional activated sludge plant could be approved with effluent BOD5 and suspended solids requirements of 17 and 25 mg/L. Reference should be made to Procedure F-5-3: "Derivation of Sewage Treatment Works Effluent Requirements for the Incorporation of Effluent Requirements into Certificates of Approval for New or Expanded Sewage Treatment Works" for the parameters requiring documentation and the procedures required to determine compliance with the effluent requirements.

While many primary sewage treatment plants are being upgraded to provide secondary treatment or equivalent, some primary plants will remain in service for a few more years. In the interim, effluent guidelines for primary treatment without total phosphorus removal shall remain as 30% and 50% removal of BOD5 and suspended solids, respectively; the guidelines for primary treatment with total phosphorus removal shall remain as 50% and 70% removal of BOD5 and suspended solids, respectively.

3.8 Industrial Wastes

In selecting a sewage treatment process, consideration must be given to industrial waste inputs to ensure that the sewage treatment process will be compatible with the waste requiring treatment. Pre-treatment of industrial wastes may be necessary. In all cases, sewer use by-laws should be in effect and under enforcement to control the wastes being discharged to the sewer system by industries.

3.9 Sewage From Pressure or Vacuum Sewer Systems

Special consideration may be required in selecting and designing a sewage treatment process for municipalities serviced either wholly or extensively by pressure or vacuum sewers. The sewage quality tends to be more concentrated in such systems since it is unlikely to be affected by inflow/infiltration.

Table 1 Effluent Criteria

Secondary treatment or equivalent
Treatment Level and Processes Effluent Design Objectives 1 (mg/L) - BOD5 Effluent Design Objectives 1 (mg/L) - SS Effluent Design Objectives 1 (mg/L) - TP Effluent Design Objectives 1 (mg/L) - (NH3+NH4+)-N Effluent Guidelines 2 (mg/L) - BOD5 Effluent Guidelines 2 (mg/L) - SS
Conventional Activated Sludge without TP removal 15 15 n/a n/a 25 25
Conventional Activated Sludge with TP removal 15 15 1.0 n/a 25 25
Contact Stabilization without TP removal 20 20 n/a n/a 25 25
Contact Stabilization with TP removal 20 20 1.0 n/a 25 25
Extended Aeration without TP removal 15 15 n/a n/a 25 25
Extended Aeration with TP removal 15 15 1.0 n/a 25 25
Continuous Discharge Lagoon without TP removal 25 30 n/a n/a 30 40
Continuous Discharge Lagoon with TP removal 25 30 1.0 n/a 30 40
Seasonal Retention Lagoon without TP removal 25 30 n/a n/a 30 40
Seasonal Lagoon with TP removal by batch chemical dosage 15 20 0.5 to 1.0 n/a 25 25
Seasonal Retention Lagoon with TP removal by continuous chemical dosage 25 30 1.0 n/a 30 40
Physical-chemical Treatment 20 20 1.0 n/a 25 25
Advanced treatment
Treatment Level and Processes Effluent Design Objectives 1 (mg/L) - BOD5 Effluent Design Objectives 1 (mg/L) - SS Effluent Design Objectives 1 (mg/L) - TP Effluent Design Objectives 1 (mg/L) - (NH3+NH4+)-N Effluent Guidelines 2 (mg/L) - BOD5 Effluent Guidelines 2 (mg/L) - SS
Conventional Activated Sludge with TP removal and filtration 10 5 0.3 n/a ---3 ---3
Conventional Activated Sludge with nitrification 15 15 n/a <1.04 ---3 ---3
Extended Aeration with TP removal and filtration 5 5 0.3 n/a ---3 ---3

1 Expected effluent quality under optimum conditions when treating raw sewage with BOD5=170 mg/L, soluble BOD5=50%, SS=200 mg/L, TP=7 mg/L, (NH3+NH4+)-N= 20 mg/L.

2 Criteria which the average annual effluent quality should not exceed (based upon performance data collected in 1983 of sewage treatment works in operation in Ontario).

3 Effluent quality and permissible periods of discharge will be stipulated as a result of receiving water assessment studies. Where effluent BOD5 and suspended solids concentrations are not found to be critical, then Effluent Guideline BOD5 and suspended solids concentrations of 25 and 25 mg/L should be used.

4 Expected warm weather effluent concentration.