Oil and Grit Separator

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Oil and Grit Separators (OGS) are Manufactured Treatment Devices (MTDs) used for water quality treatment of stormwater runoff through the removal of large particle suspended solids and associated pollutants, and debris. Some devices can also trap light liquids such as oil and other floatables. These MTDs are typically installed underground within the stormwater sewer system in an on-line or off-line configuration. They are distinguished from Filtration-based MTDs by their removal of solids through settling rather than filtration.


Oil and Grit Separators are suitable as pre-treatment to other downstream treatment systems such as ponds or LID features. Cost effective application of OGS for LID typically requires that the practice have a single inlet with a drainage area larger than 0.2 ha.

OGS normally require maintenance every year to function as designed. The cost and level of effort required to undertake the maintenance program over the full life cycle of the practice should be carefully considered when implementing this water quality treatment solution.

Testing and Verification[edit]

Several agencies across Canada require ISO 14034 Environmental Technology Verification (ETV) as a condition of technology acceptance. For OGS, the ISO 14034 verification process in Canada consists of two parts:

  1. Third party laboratory testing of MTDs in accordance with the TRCA’s Procedure for Laboratory Testing of Oil Grit Separators and associated bulletins, and
  2. Third party verification of the test in accordance with the 14034 ETV standard.

The ISO 14034 verification process is currently administered by Globe Performance Solutions and Verify Global. Completed ISO 14034 verification statements for OGS are posted to the former Canadian ETV website, here.

Note that ISO 14034 verification is a necessary, but not sufficient condition for approval agencies using the ISO/ETV process for technology acceptance. The technology must also be classified as an Oil Grit Separator (i.e. not include a filter) for the Procedure for Laboratory Testing of OGS to have been properly applied. This ETV Bulletin helps to provide clarification on this requirement: See table below for a list of current ISO 14034 verified OGS MTDs.

List of OGS MTDs
Verification Year (Initial) Technology Name Company Name Fact Sheet
2022 RWM-DM-1200 & DM-1200-OS Stormwater Systems Rainwater Management LTD. Fact Sheet
2019 Hydro International Downstream Defender® OGS Hydro International Fact Sheet
2019 SciCLONE™ Hydrodynamic Separator Bio Clean Environmental Inc. (A Forterra Company) Fact Sheet
2018 Hydro International First Defense® OGS Hydro International Fact Sheet
2018 Hydroworks® HydroStorm (HS) OGS HydroWorks, LLC Fact Sheet
2017 Stormceptor® EF and EFO Oil-Grit Separators Imbrium Systems, Inc., Fact Sheet
2017 CDS Hydrodynamic Separator® CONTECH Engineered Solutions LLC Fact Sheet
2016 SDD3 Oil Grit Separator® Next Stormwater Solutions (8091200 Canada Inc.) Fact Sheet

Performance Test Results[edit]

The Procedure for Laboratory Testing of Oil Grit Separators provides performance testing for the following performance measures based on a standard sediment particle size distribution:

  1. Sediment removal performance: Mass balance testing at seven surface loading rates to determine the capacity of MTDs to retain solids
  2. Sediment scour and re-suspension test: Sediment is pre-loaded into the unit and effluent concentrations are measure at five surface loading rates to determine how well the units retain captured sediment.
  3. Light liquid capture and retention test: An optional test in which beads with a density similar to motor oil are pre-loaded into the unit and the number of beads in the effluent are measured to assess the capacity of the unit to trap and retain light liquids.

There are currently eight OGS vendors with ISO 14034 verifications (as shown in the table above). The list of manufacturers and test results of all OGS products and other verified technologies can be found here. Sediment removal performance results were relatively consistent across different MTD designs, with slightly more variation at higher surface loading rates (see Graph below).

*Note: Oil Grit Separators do not achieve the 80% removal efficiency required for stand alone application in Ontario, even at very low flow rates.