Rehabilitation of Aisleby 3 waste water station
THE rehabilitation and commissioning of the plant and equipment at Aisleby 3 waste water station will improve real time monitoring of influent and effluent, making it easier for plant operators to vary plant parameters according to the loading of the plant, an official has said.
Bulawayo City Council deputy director of engineering services Engineer Mente Ndlovu said the plant is a Bio-Nutrient Removal Plant (BNR) meaning it uses biological organisms or bacteria to remove nutrients such as phosphorous and nitrates, which are hazardous to the environment.
This plant receives sewage from Queens Park West, Mahatshula North and South, Glengary, Khumalo, Parklands, Selbourne Park, Woodlands and parts of Hillside.
“The rehabilitation of the outfall sewers will facilitate inflows of up to 7.5ML a day at Aisleby 3 and add another 10ML to Aisleby 1 and 2. The deep section at Sauerstown is expected to be commissioned end of November.
“The tender for rehabilitation of Aisleby 1 and 2 is at adjudication stage and we expect works to be commissioned around June 2017,” said Engineer Ndlovu.
Real time monitoring of processes data such as process inflows and outflows, motor run hours and levels of dissolved oxygen are possible through a Programmable Logic Controller (PLC) and a local Wi-Fi network that has been setup at the plant.
“We are working on expanding this network to our Tower Block offices so that we can also monitor the plant from the comfort of our offices.
“The bio-reactor aerators have been automated to respond to levels of dissolved oxygen, the main variable in the bio-reactor process.
“This automation will result in energy savings in that the aerators will only run when dissolved oxygen levels are critically low,” said Engineer Ndlovu.
He said through this network, it is also possible to analyse trends on the performance of the plant over time so as to fine tune its settings.
“It makes it easier to implement preventative maintenance strategies on the plant. In a BNR plant, bio-reactor processes consume up to 60 percent of the energy consumed in the whole plant,” said Engineer Ndlovu.
Because the BCC was heavily laden by a huge wage bill, most of it being overtime worked by security personnel safeguarding council infrastructure, palisade fencing with razor wire and remote alarm sensing was put up at the plant.
“Council was under pressure to achieve the 70/30 ratio of service delivery to salaries and this project was implemented as one of the quick win strategies.
‘‘ This project is a first of its kind in water and waste water pump stations and as the City of Bulawayo we continue in our endeavour to be the leader in local government excellence through innovation.
‘‘As the first phase of installing palisade fencing and remote alarm systems, 33 sites made up of clear water reservoirs, sewer, water and reclaimed water pump stations in the city were identified and equipped accordingly. Each of these sites has several lines of defence against would -be intruders,” said Engineer Ndlovu.
A dilapidated sewer pipe removed from the Marvel outfall sewer