WATER & WASTEWATER TREATMENT
Aerial view of the Nooitgedagt WTW
The Nooitgedagt/ Coega Low Level Supply Scheme (NCLLS) increases the supply of treated water (sourced from the Gariep Dam) from an average of 70 Mℓ/day to 160 Mℓ/day for Nelson Mandela Bay Municipality (NMBM). Phase 3 – the last phase of the scheme – is nearly complete. By Kevin McRae
Kevin McRae, COO, AfriCoast Consulting Engineers
NOOITGEDACHT WATER SCHEME NEARING COMPLETION
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nitially, the NCLLS was to be implemented as a single project under multiple contracts. However, due to funding constraints, the scheme had to be implemented in phases.
Phase 1: On completion (1993), Nooitgedagt Water Treatment Works (WTW) had a capacity of 70 Mℓ/day and a hydraulic peak capacity of 84 Mℓ/day. A fourth pump was added to the pump station, boosting pumping output to 92 Mℓ/day with three pumps operating and one pump on standby. In 2008, two additional pulsator clarifiers were built, increasing the capacity of Nooitgedagt WTW to 100 Mℓ/day. Additional sludge lagoons and a 10 Mℓ balancing reservoir at Olifantskop Farm was constructed. There was also the implementation of bulk electrical supply to the WTW,
and the rising (1 200 mm) and gravity (1 400 mm) mains from the WTW to Motherwell and the Coega Industrial Development Zone. Phase 2: This included the low-lift pump station building, as well as the construction of the western bank with six additional filters, and pumping equipment, electric and control systems for the low-lift scheme. Phase 3: This comprised a complete standalone 70 Mℓ/day treatment module at the Nooitgedagt WTW, a 45 Mℓ balancing reservoir at Olifantskop Farm, installation of cathodic protection systems on both the original Nooitgedagt to Motherwell highlevel pipeline and the low-level pipeline built under Phase 1. The building of various bulk pipelines and rehabilitation of structures, as well as the replacement
of certain valves and fittings on the Motherwell to Chelsea pipeline was also included. Nooitgedacht WTW – design Sited on the right bank of the Sundays River, the Nooitgedagt WTW is supplied with raw water from the Scheepersvlakte Balancing Dam on the left bank via a 9.1 km long 1 470 mm diameter gravity pipeline. It is now the largest WTW serving NMBM. The water treatment process at Nooitgedagt is conventional, comprising chemical dosing, flocculation, settling, filtration and disinfection, followed by distribution. Ultraviolet treatment is added between the settling tanks and filters to guard against Cryptosporidium and Giardia. Designed as a zero-effluent works where dirty backwash water and settled M A R/ A P R 2022
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