The Ekurhuleni metro has finally decided on a system for cleaning the Boksburg Lake water, and said the identified programme will ultimately help address the sad state of the lake water.
According to metro spokesperson Themba Gadebe, the identified solution to address the immediate need to restore the water quality of the Boksburg Lake is to facilitate the natural processes.
It is, however, unclear as to how long it will take for the system being implemented to deliver the desired results.
This process will entail the following various interventions:
1. Installation of aerators to increase dissolved oxygen in the lake – results expected to show from three months or more.
2. Construction of a low crest weir that will contain the sewage laden inflow from the main storm water pipes into a holding area separate from the main body of the lake without creating impoundment – results expected upon the finalisation of the weir construction.
3. Installation of floating wetlands to take up nutrients from the lake with the aim of controlling odours and preventing the growth and infestation of invasive alien plants – results will be ongoing.
4. Installation of litter traps (to trap solid waste) in all storm water outlets – results will be realised upon completion of installations.
Gadebe pointed out that the critical problem with the Boksburg Lake is the constant inflow of suspended solids and nutrients from the sewerage leaking into the municipal stormwater system that drains into the lake.
“A staggered approach will be taken due to the dynamic interaction of lake chemistry, plants, microbes and how they respond to the intervention.
“Once the dissolved oxygen (DO) levels are raised and the aerobic conditions are restored and maintained, the natural process will be able to cope with the high suspended solids (SS) levels negating any further interventions. The transfer of oxygen from the atmosphere to the top layer of the lake ensures a surface layer of varying depth that keeps nature in equilibrium,” said Gadebe.
He said urbanisation drastically increases pollutants into the lakes, thus exceeding the capacity the water body can handle on its own and turning the oxidative layer into anaerobic conditions.
“Aerators have proven that they increase the ability of lakes to survive pollution, increased nutrient levels and eutrophication.
“By providing sub surface aeration with directional mixing, the water moves in a circular pattern around the entire lake, breaks up stratification and increases in DO levels.
“The aerators assist nature in returning a healthy state of aerobic equilibrium. The next step would be to filter out the SS. The removal of the SS will require the construction of a low crest weir.
“The purpose of the low crest weir is to contain the sewage laden inflows from the main stormwater pipes into a holding area separate from the main body of the lake without creating impoundment that would cause water during a storm event to back up and exacerbate the flooding that is experienced under the railway bridge on Trichardts Road,” explained Gadebe.
The contractor to carry out the job has not been appointed as yet, as the metro is going through the supply chain management process to procure a contractor.
Gadebe said the construction commencement is reliant on the finalisation of the supply chain management process, but it is anticipated that the contractor will be on site by November.
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