Water Treatment Residual Filter Sock Media Trial

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Ecowaste Industries Ltd. and Metro Vancouver

Silt fencing is currently the industry standard used for sediment control in runoff, but this system does not effectively address dissolved compounds. One method which is gaining traction to treat surface runoff in the construction and the agricultural industry is the use of compost filter socks.  These socks typically contain a mixture of compost and wood chips and can contain selective sorbent and flocculant materials to aid in the removal of nutrients, trace elements, and dissolved sediments.

Water treatment residuals (WTR), such as those produced at Metro Vancouver's Seymour-Capilano Filtration Plant, offer a local, sustainable alternative to proprietary compost blends traditionally used as filter sock media. Although little previous research has been conducted on the use of WTR as a filter sock medium, it is reasonable to expect that WTR would provide similar benefits in filter socks as amended compost. WTR are high in organic matter to help adsorb ammonia/ammonium and trace elements, contain an alum-based flocculant to improve nutrient removal (specifically phosphorus), and their physical properties are such that use of a WTR filled sock will promote some retention of surface runoff behind the sock, improving the filtration of sediment and dissolved solids.

SYLVIS conducted a laboratory-based bench-scale test to provide a starting point to develop a filter sock WTR media blend appropriate for field-scale testing and use. Subsequent to the completion of the bench-scale trial, SYLVIS designed and constructed an isolated, controlled, small-scale trial with the goal of evaluating the efficacy of the mix(es) selected in the bench-scale trial.

Results of the trial indicate that WTR filter socks have the potential to reduce total suspended solids, ammonia, total dissolved phosphorus and total phosphorus in leachate and storm water runoff. SYLVIS continues to work with Metro Vancouver to evaluate different beneficial use options for WTR produced at the Seymour-Capilano Filtration Plant.