High-rate stormwater clarification with polymeric flocculant addition

Abstract

Treatment of urban stormwater by clarification, with flocculant addition, was studied in Toronto, Canada using a pilot-scale clarifier with removable lamellar plates. Almost 90 stormwater runoff events were characterised at the study site and found fairly polluted. The previous research phase indicated good treatability of this stormwater by lamellar clarification with flocculant addition (total suspended solids, TSS, removal of 84%, at a surface load of 15 m/h), but there were concerns about cleaning plates after storm events. With the aid of numerical modelling, hydraulic improvements to the clarifier inlet zone were retrofitted in 2004 and permitted the removal of the lamellar pack without a loss in treatment efficiency. In the modified clarifier, a cationic polymeric flocculant dosage of 4 mg/L with conventional clarification provided a TSS removal of 77%, at surface loads up to 43 m/h. The use of the polymer did not increase the acute toxicity of the treated effluent. The clarifier sludge was severely polluted by several heavy metals and would require special disposal. The treatment process tested could be well applied in projects requiring intensive stormwater treatment at compact sites.

Polymer-assisted hydraulic dredging for quality control of stormwater pond sediment and reject water – Influence of polymer choice and its preparation

“…Described utilization of polymers in stormwater management is sparse in scientific literature. Examples include promising results with polymer-amended infiltration media [33], engineered composite materials with polymers as a sorbent material for treating heavy metal polluted stormwater [34,35], sediment-logs with polymer for treating construction run-off [36] and lamella clarification of stormwater with polymers [37].…”

Urban Wet‐Weather Flows

“…A Hydro-Brake Flow Control and stormwater storage facility is being used by the Seven Trent Water Company to alleviate flooding in Leicestershire village. The other benefit is that it operates under a fluctuating head and has no moving parts and needs no power (Anonymous 2005f).Mackie(2005) reviewed the installation of Storm Monsters™ -overflow screens -that are designed to remove particulate pollutants from CSOs Wood et al (2005). examined the use of high-rate stormwater clarification with polymeric flocculant addition.…”