The Hartebeestfontein WCW was built in 1977 and receives effluent from industries in Spartan and Isando as well as households in the Kempton Park area.

The Hartebeestfontein WCW original design differed from the traditional activated sludge works in that it utilised a two-stage, two-culture activated sludge process. Each stage is a complete processing unit comprising of aeration, clarification and sludge return. The primary stage is aimed principally at COD (Chemical Oxygen Demand) removal and the secondary stage for nitrification. The initial configuration comprised of three 10 Mℓ/d treatment modules totalling 30 Mℓ/d.

In 1986 a side-stream Phostrip (biological phosphate removal) plant was retrofitted. This was followed by the addition of a third inlet works module in 1992 and a single 15 Mℓ/d treatment works resulting in a total treatment capacity of 45 Mℓ/d. The works was recently refurbished at a cost of R65 million, including the building of a new balancing dam and the increase of reactor volume and aeration capacity.

In 1995 a tertiary treatment system was designed and implemented to handle chemical dosing to ensure an even more effective phosphate removal process. In 2014 the plant capacity was increased to 50 Mℓ/d by modifying module 4 and currently treats 63 Mℓ/d by the addition of two Final Settling Tanks. Each module consists of one primary settling tank, one activated sludge reactor and two final settling tanks. The aerobic reactor is divided into two zones with the first zone being fine bubble diffused aeration and the second zone surface aeration.

Effluent from the Hartebeestfontein works flows via the Swartspruit to the Rietspruit in quaternary catchment A21A. Bio-solids treated from the 9 x 2 m³ anaerobic digesters are applied to land and ploughed in.