Filtration Manufactured Treatment Devices

Plan view of an upflow filtration MTD with filter cartridges. This example for the U.K provides four separate stages of treatment for influent water including: 1) oil retention, 2) chemical separation, 3) filtration and 4) sedimentation (Source: 3P Technik UK Ltd, 2023).

Overview

Filtration Manufactured Treatment Devices (MTDs) are structures with one or more chambers containing filtration media, membranes and/or filtration cartridges that remove solids and debris/trash from runoff. Some units may have oil separation functions and pretreatment chambers for coarse sediment and debris. The filter components are designed to remove the coarse and fine sediment fraction of suspended solids and associated pollutants in stormwater runoff and may also target removal of dissolved pollutants such as phosphorus or metals through biological and/or chemical processes.

Example of a high flow curb inlet filtration MTD with proprietary soil media installed and monitored at the Kortright Centre in Vaughan, Ontario. (Source: STEP, 2020).

Application

Filtration MTDs are suitable for pre-treatment or may be installed as stand alone if third party performance testing shows that they achieve enhanced level water quality protection (i.e. lower 95th percentile removal efficiencies of 80% or greater).

Since Filtration MTDs contain filters that restrict flow rates, they are normally designed for much lower hydraulic loading rates than Oil-Grit Separator MTDs and have longer detention times. Flow restriction occurs due to the small pore size openings of filters and the clogging of pores and/or the formation of films either on the surface of the filter or within the filter matrix filter. For this reason, inspection and maintenance intervals for Filtration MTDs are normally shorter than for OGS MTDs. The method of maintenance typically involves sediment removal with a hydro vacuum truck as well as filter cleaning or replacement.

Further guidance on how the data and information generated from verified laboratory testing of OGS technologies should be interpreted and factored into regulatory agency approvals and procurement decisions for stormwater management is provided in this publicly available specification The Canadian Procedure for Field Testing of Stormwater Filtration Manufactured Treatment Devices, developed by TRCA and the Standards Council of Canada that addresses both OGS and Filtration MTDs.

Further guidance on how the data and information generated from verified field testing of Filtration MTDs should be interpreted and factored into regulatory agency approvals and procurement decisions for stormwater management is provided in this Publicly Available Specification that addresses both OGS and Filtration MTDs.

The technique of removing pollutants from runoff as it infiltrates through the soil.

Deposition of material of varying size, both mineral and organic away from its site of origin by the action of water, wind, gravity or ice.

Settling-out or deposition of particulate matter suspended in runoff.

The technique of removing pollutants from runoff as it infiltrates through the soil.

The portion of water precipitated onto a catchment area, which then flows as surface discharge from the catchment area past a specified point.

Water from rain, snow melt, or irrigation that flows over the land surface.

Initial capturing and removal of unwanted contaminants, such as debris, sediment, leaves and pollutants, from stormwater before reaching a best management practice; Examples include, settling forebays, vegetated filter strips and gravel diaphragms.

Soil, sand and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals and cloud the water so that needed sunlight might not reach aquatic plans. Careless farming, mining and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls.

Sustainable Technologies Evaluation Program

The total mass of a pollutant entering a waterbody over a defined time period.

The net amount of something (e.g. chemical, such as phosphorus), calculated as the product of concentration and volume in a given time. Some BMPs significantly reduce loading of pollutants to the environment by reducing volume more so than concentration.

The temporary storage of stormwater to control discharge rates, and allow for sedimentation.

Systems designed to remove trash, debris and some amount of sediment, oil and grease from stormwater runoff based on the principles of sedimentation for the grit and phase separation for the oil.

Toronto and Region Conservation Authority

A shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation.