WASTEWATER
The Zandvliet Wastewater Treatment Works (WWTW) is undergoing a substantial upgrade with the construction of a new primary treatment section, equipped to accommodate up to 90 Mℓ/day average dry weather flow (ADWF), and a new large-scale sludge dewatering treatment facility.
Six waste-activated sludge gravity belt thickener and belt press cascades
Constructing the largest dewatering facility in the Western Cape
W
ater and wastewater treatment specialist PCI AFRICA was awarded the design and build contract for associated mechanical, electrical, instrumentation, control and automation by the City of Cape Town, with the consulting engineers being Aurecon (now Zutari). This included new inlet works, primary sedimentation tanks, pump stations, as well as sludge dewatering and treatment facilities. “The Zandvliet WWTW deals with effluent from the eastern parts of Cape Town, including Delft, Blue Downs and Khayelitsha. The new upgrade will assist significantly with hydraulic load relief on the existing works, together with the ability to remove waste-activated sludge (WAS) from the existing bioreactors. Urgent rehabilitation and new additions were required to meet
Cobus Mellet, project manager at PCI AFRICA
the needs in this fast-growing catchment of Cape Town,” explains Cobus Mellet, project manager, PCI AFRICA.
PCI AFRICA • Candy Filter Company and The Paterson Engineering Company – from which the name Paterson Candy International SA is derived – were late Victorian pioneers in water treatment, dating back to the 1870s. • In South Africa, the first records of Candy Filters being sold was in 1897. • Paterson Candy, now trading as PCI AFRICA, has been registered and operating in South Africa since 1953. • As experts in the water treatment field, PCI AFRICA is particularly well known for dissolved air flotation and sand filtration designs across Africa.
New plant The new sections of the contract comprise: • Part A: dewatering plant located on the eastern side of Zandvliet WWTW • Part B: inlet and primary treatment plant located on the northern side of the Zandvliet WWTW. Currently, the dewatering plant is in the final preparation phase for commissioning, while the inlet works and primary treatment are in the installation phase. Flow enters the Zandvliet WWTW via three gravity sewers (Khayelitsha, Blue Downs and Delft). The Blue Downs sewer is not being utilised at present. Since the entrance level of the raw sewage is far below ground level, part of the new inlet M AY / J U NE 2021
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