Sludge removal process causing bad odour

13 February 2021

Contractors are in the process of removing sludge stockpiled at Potsdam Wastewater Treatment Works, and the disruption of the stockpile is causing a bad odour, as anticipated. The City regrets the discomfort to residents, and every effort is being made to suppress the smell while the work is underway.

Removal of the stockpile in the sludge pond commenced on the afternoon of 28 January 2021, and all sludge that could be directly loaded onto trucks was removed by 3 February 2021. During those six days, over 1000 tons of sludge cake was removed from the sludge pond stockpile, and this included all stockpiled primary sludge cake.
 
All the water contained in the sludge cake stockpile moved to the bottom of the pond over time, and therefore the remaining sludge in the pond was too wet to be removed by truck immediately. Further processing was required to ensure that the sludge is sufficiently dry to be transported by truck. This process is time-consuming and does release odour, which is contributing to the ongoing odour around the plant.
 
Odour suppression and masking have continued throughout the removal operation. This has been ongoing since 4 February, and removal of the remaining sludge, which is expected to be fully processed/dry, will begin today,13 February 2021. This should see a reduction in odours. It is envisaged that the pond will be completely cleaned out in approximately two weeks.  Furthermore, it is also noted though that the trucks disposing the sludge do have a very strong odour and are probably the cause of some significant odour along its route to the disposal site.  The plant has requested the drivers of the vehicles transporting sludge to hose the vehicles down before leaving the site, which should also further aid in reducing odours in the area.
 
The City apologises for the severe impact and inconvenience caused by the odours. Every effort is being made to clear the rest of the sludge that is too wet to transport as soon as possible.
 
 
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Published by:
City of Cape Town, Media Office