Oil and Grit Separator
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
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:
- Third party laboratory testing of MTDs in accordance with the TRCA’s Procedure for Laboratory Testing of Oil Grit Separators and associated bulletins, and
- 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.