Surplus sewage snag

2020-01-16 15:04
Midmar Dam.

Midmar Dam. (ian carbutt)

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The sewage flow into the Mpophomeni sewerage system is 20% more than its capacity, which contributed to the pollution of Midmar Dam during heavy rains last year.

Umgeni Water systems manager Mulalo Murigwathoho, briefing the uMgungundlovu­ District Municipality’s infrastructure portfolio committee in Howick on Wednesday, said that according to in-flow volume figures from March to November 2019, on average the Mpophomeni sewerage system has been getting close to six megalitres of sewage a day. “This excludes periods when it rains, when the number is much higher.

“The pump station capacity is just around five megalitres a day, which means there is a surplus of sewage that collects in the system.”

The Mpophomeni plant was decommissioned more than 20 years ago because its design limited its ability to treat sewage properly and it was contributing to the pollution of Midmar Dam. A pump station was then built to transport sewage from Mpophomeni to the Howick Wastewater Works.

In November, the Mpophomeni sewerage system collapsed, resulting in raw sewage flowing directly into the dam.

Murigwathoho said although the pump station can pump more, the pipeline that transfers sewage from Mpophomeni to Howick only takes 3,5 megalitres of sewage a day.

“On a daily basis, there is excess sewage that collects in that system,” Murigwathoho said.

She said the increase in the population at Mpophomeni over the years had also resulted in an overloaded system.

Murigwathoho said the excess sewage made its way into the dam because the storm dam and three ponds at the Mpophomeni plant were full. “The ponds were full at the time and the spill happened. However, an artificial wetland was built and that has assisted the system. The wetland offers some treatment before the sewage reaches the dam.”

She said the ponds, which are supposed to absorb sewage at the Mpophomeni plant, no longer had capacity.

“The capacity of the ponds at Mpophomeni has been reduced as a result of them being used so often. They are not supposed to be used on a daily basis.”

She dismissed “exaggerated” claims on social media about the degree of spillage into Midmar Dam, saying it was “fake news”.

“The quality from the Midmar plant did not change during that period because the treatment system is designed to deal with raw water of a different quality. There was no need for panic. The E. coli level was very low from what you would expect from the dam.”

She said in December the draining of ponds began, and a makeshift disinfection system will be installed to alleviate any future raw sewage spillages.

Bheki Mbambo, HoD for technical services in uMgungundlovu District Municipality, said a lack of community understanding regarding pollution also had to be remedied.

“The sewer network in the Mpophomeni area requires an upgrade, yes, but also there needs to be a lot of community engagement and teaching.”

Mbambo said protective screens found in piping had revealed a backflow of a lot of strange items.

“Some of the things we found were whole cow skins. We even found chickens thrown in there.”

He said this meant the community were dumping trash in maintenance holes. “What this means is that the community are opening manholes and dumping everything in there, which gets pushed back up by the rains.

“Naturally, it gets stopped by screens and pushes back into the manholes and spillages take place.”

On Wednesday, Umgeni Water said a R388-million upgrade of the wastewater treatment plant in Mpophomeni is under way, which should almost end sewage spillages into Midmar Dam.

Read more on:    pietermaritzburg
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