Potsdam Wastewater Treatment Works (WWTW) is one of the major treatment works of the City of Cape Town. Due to significant yearly increases in flow, the Cape Town City Council decided in 2004 to expand its capacity from 35 Ml/d to 47 Ml/d. At the same time, the older section of the works, which consisted of biofilters, would be closed down due to effluent not complying with the standard set by the Department of Water Affairs. Aurecon was appointed to carry out the feasibility investigation, preliminary and detail design and implementation of the new extension, sized to treat 30 Ml/d.
Due to delays in obtaining approval for the expansion, the existing Works was severely overloaded when construction began; meaning capacity was required as soon as possible. Innovative thinking saw the aerobic digesters and a primary settling tank constructed first and used as the biological reactor and secondary settling tank, thus providing 8 Ml/d of additional capacity within one year.
The remainder of the works was constructed over a number of years to suit our client’s annual budget allocations. Features of the treatment works include:
A new inlet works
A new raw sewage pump station
Three 33m diameter primary sludge tanks (PST)
A biological reactor
Six 35m diameter secondary settling tanks
Maturation ponds and UV disinfection system
Because the WWTW is situated close to residential areas, all of the more odorous parts of the works, such as the inlet works, PST and sludge handling sections, were provided with covers and the air below them extracted and treated before being released into the atmosphere. This resulted in an important 99.5% reduction in odours.
The Potsdam WWTW has ensured the ongoing and essential treatment of about 50 Ml/d wastewater for the City of Cape Town. The on-time completion of this project removed a possible bottleneck to development along the western seaboard.