The JP Marais WCW is situated in Benoni and falls within the DD4 drainage district. Built in 1991, the plant is designed to treat 15 Mℓ/d of industrial effluent and raw sewage from the Benoni, Boksburg, Daveyton and Modderbee areas. The Modderbee Correctional Services project was discontinued and the facility moved to the new area. Conventional activated sludge is employed as the main sewage purification process.

A central inlet works, incorporating the process of screening and grit removal serves the works. The BNR activated sludge process includes primary sedimentation, a three stage Badenpho reactor basin and final clarification. The final effluent is chlorinated and discharged into a tributary of the Blesbokspruit.