GEORGE NEWS - The final phase of pre-construction required for the installation of the mechanical, electrical and instrumentation works at the Outeniqua Wastewater Treatment Works (OWTW) upgrade is currently underway with significant progress to date.
Several structures were completed in 2019, including the new concrete structure 10Ml/d biological reactor, a blower and electrical motor control centre housing facility, as well as other site and flow control structures to prepare for the switch-over and flow splitting between the existing and new facilities.
The contract includes an odour control facility at the inlet works to contain and treat odours originating from this part of the treatment works.
A number of construction activities are currently taking place on site. Most of these are civil engineering construction activities in preparation for the awaited mechanical and electrical equipment:
• A crane has been installed in the blower room for the handing of the equipment during installation and for maintenance purposes;
• Road construction is underway to create access to the new reactor;
• Various cable trenches have been excavated for the upgrading of the electrical system;
• The cone-shaped structure around the centre column in the settling tank has been constructed to prepare for the rotating bridge installation on the tank;
• Excavation is taking place around the inlet works for the indoor skips-handling facility, odour control facility and a rock catcher septage-receiving structure.
The cone-shaped concrete structure around the centre column in the settling tank has been constructed to prepare for the rotating bridge installation on the tank.
Designs approved
The majority of the mechanical and electrical designs have now been approved and orders have been placed for equipment. The delivery of the imported items to site is expected by the end of September. Local suppliers are busy with off-site manufacturing of steel structures to house some of the mechanical equipment. A wide range of equipment to be installed includes: three blower units to provide air for the fine bubble aeration system, 10 mixers, two Archimedean screw pumps, four vertical shaft surface aerators, three perforated mechanical screens, one hydro conveyor, two screenings washers, one septage unit, an odour control system and a chlorine gas scrubber, plus various minor items. Various pumps, actuated valves and sluice gates are also required.
Carousel reactor
The existing carousel reactor on site is also due for an upgrade, which will predominantly involve the replacement of the aged aerators in the reactor with larger aerators to provide additional capacity. This work is scheduled to begin once the assessment of the 30-year-old concrete and reinforcement steel has been finalised. The assessment will provide input on the strengthening of the existing structure to handle the additional loading of the heavier new aerators. Current indications are that the new plant will be operational by mid-2022 with all construction completed in early 2023.
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