REFURBISHMENT OF AND EXTENSIONS TO THE BOSPOORT WATER PURIFICATION WORKS

The Bospoort Water Purification Works was originally equipped with filtration equipment by the Candy Filtration Company in the 1950’s, and over the years became redundant, due to the raw water source becoming contaminated, and was subsequently mothballed for approximately two years before the refurbishment occurred. Raw Water is pumped from the Bospoort Dam, and enters the Inlet structure and is split into two equal streams, each of 6 Ml/day for further chemical treatment, thus enabling the plant to achieve a total capacity of 12 Ml/day.

The major components of the project were new Dissolved Air Flotation (DAF) units, refurbishing the existing Rapid Gravity Sand (RGS) Filters, as well as the newly constructed Granular Activated Carbon (GAC) Filters.

Dissolved Air Flotation (DAF) Units – Two off DAF units were constructed each measuring 8,5m long x 6,5m wide x 5,25 meters deep. Two mild steel (rubber lined) Saturator vessels (with magnetic level control switches) were provided with two off (duty / standby) Atlas Copco rotary screw air compressors to provide air to these units. The automatic control of these Saturator units is PLC controlled, and due to the design of the scum flushing operation, two electrically operated descum outlet valves are opened during this operation, for each DAF unit.

The de-scum operational frequency, and length of the de-scumming period is determined via the PLC SCADA system, which is a fully automatic operation on an adjustable timed basis for both interval and duration.

Granular Activated Carbon (GAC) Filters – Six new GAC Filters were constructed, each bed measuring 5,22m long x 3,5m wide x 4,6m deep. Each Filter basin contains a 0,5m wide central collection channel, as well as a 0,7m wide central washout channel, (at high level) running along the total length of each Filter bed. Each GAC Filter basin was equipped with the PCI type ”DA” underdrain system consisting of thin walled laterals and three part polypropylene nozzles encased in 200 mm thick concrete, complete with a triple layer of media for filtration purposes.

Rapid Gravity Sand (RGS) Filters – Four existing RGS Filters were refurbished on the contract, each bed measuring 6,096m long x 5,33m wide x 3,430m deep. Each Filter basin contained an existing 0,405m wide central collection channel, as well as a 0,61m wide offset wash out channel, both running along the total length of the Filters. As part of the refurbishment, new stainless steel inlet shafts (dropper boxes) complete with sluice gates were installed, to control the flows of the incoming water to the Filters.

Similar to the GAC Filters, each RGS Filter basin was equipped with the PCI type ”DA” underdrain system consisting of thin walled laterals and three part polypropylene nozzles encased in 200 mm thick concrete, complete with a triple layer of media for filtration purposes.