Winning the pooh
Effluent leaving the Knysna wastewater treatment works (WWTW) is now compliant according to the town’s Estuary Authorities Pollution Committee.
SA National Parks (Sanparks) has led the committee since 2019 in partnership with Knysna and Garden Route District municipalities, the Breede-Gouritz Catchment Management Agency (BGCMA) and the Knysna Basin Project.
E. coli water samples taken at the WWTW plant and its outlet showed a steady decline since a reported incident in February this year.
Knysna park manager Megan Taplin said, “We are pleased with this progress at the WWTW where E. coli levels are compliant according to the Department of Water Affairs and Sanitation standards. According to the South African water-quality guideline for recreational use, recreational areas must have an E. coli bacteria level lower than the 500cfu/100ml mark.”
Cfu stands for the colony-forming unit, an estimate of viable bacteria or fungal cells in a single sample. Results are thus reported as CFU/milliliter for liquids.
Multiple interventions
Multiple interventions by partners led to this positive outcome. The municipality replaced screens at the WWTW to monitor inflow into the plant. This is important to retain solids that could have caused blockages in the system and further improved its functioning. All clarifiers were also recently restored to operation.
Further upgrades, which include civil work, are planned for September.
Knysna Municipality in partnership with the district municipality traced sources of “new pollutants” such as oil/grease, solvents and dyes into the WWTW. Oil and grease samples are now being taken at different times of the day at the WWTW in order to try to pinpoint the businesses that might be contributing to pollution loads. The municipality introduced an oil-eating enzyme as well as loads of beneficial bacteria to relieve the system. While oil and grease disposed into the system was the cause of the February contamination of the WWTW and this still has an influence at times, there are also other pollutants that play a role.
Pilot survey
The committee partners are conducting a pilot survey of the Industrial Area to gain a better understanding of potentially harmful substances that are being discharged into stormwater which may affect the health of the estuary.
Of the 30 different sites sampled by the municipalities since 2009, the number of times the Bongani Stream was noncompliant amounted to 83%, while the Ashmead Channel was noncompliant 55% of the sample time. Valuable information is being provided by the Knysna Basin Project which is conducting an ongoing survey into the Bongani and Bigai catchments feeding into the estuary. Water samples conducted are tested for E. coli, ammonia, phosphates and nitrates, high levels of which can negatively influence estuary health. This information will assist in determining problems with pollution arising higher up in the catchment.
Partners are working at various solutions, including a rehabilitation project in the Bongani catchment, with the municipality. A digital survey is set to commence shortly to boost an educational drive to get residents to work with the municipality on reducing pollution of the estuary.
Read a previous article here: Positive report from Knysna action pollution committee
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Source: Knysna Plett Herald News