City’s sewage plant a stinking timebomb
The wastewater treatment plant was established in the 1950s and built to handle 28 mega litre of effluent, but currently has to deal with a massive 60 megalitre per day.
POLOKWANE – Residents in the city, especially in the Ladanna area, have had to live with the often unbearable stench emanating from the nearby wastewater treatment plant for several years now.
This stench is the result of severe neglect and lack of maintenance at the plant which enhances the problem caused by a severely overloaded sewage system.
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One of the reasons why residents of Ladanna and the north-western parts of the city have to put up with the smell emanating from the wastewater plant, is the ever-growing number of residents, Review was recently told by the municipality during an appointment with the mayor and senior managers responsible for water and sanitation.
The wastewater treatment plant was established in the 1950s and built to handle 28 mega litre of effluent, but currently has to deal with a massive 60 megalitre per day.
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What has not been revealed and a further investigation by Review found, was a tale of severe neglect and lack of maintenance.
Review further investigated the workings of a wastewater treatment plant and what steps effluent is going through in the treatment process and in this process found out about the deterioration due to the severe neglect and lack of maintenance.
An engineer was consulted as well as people who have worked at the plant and have resigned years ago, to garner information as to how the plant functions.
Insufficient staff
The staff component to oversee treatment has been drastically reduced: A couple of years ago three technicians and a maintenance team were maintaining the wastewater treatment plant, currently according to information, there is one technician and his team who is responsible for maintaining the Polokwane, Seshego, Mashinini and Mankweng treatment plants, as well as around four other pump stations.
Staff who resigned were not replaced, and management positions filled, are more than maintenance posts.
Dysfunctional main inflow area
The first step in the process is where effluent is pumped into the main inflow area.
Here, four huge rakes have to remove the solids from the water. These rakes have been removed around three to four years ago and are reportedly not yet in production again.
Two were reportedly installed, but are not working.
Solids are then thrown onto a belt from where it is dispersed to a tank. When full, the solids are removed and thrown into a hole, which, when full, is covered.
The whole plant as such could be said to be dysfunctional and not working currently, and around 60 megalitre of effluent is pumped into the system daily.
Non-operational primary settling tanks
From the pump station at the main inflow, effluent is pumped to four de-grit sumps where the sand settles at the bottom of the sump or chamber and is removed by a worm, while water falls back and flows through a canal to the primary settling tanks, three round concrete sedimentation tanks where more sand and solids sink to the bottom and sludge float at the top.
Another rake turns on the top and throws the sludge in a sump from where it goes to the oxidation ditch or Pasveer.
Grit removal is necessary, among other reasons, to reduce formation of heavy deposits in aeration tanks, aerobic digesters, pipelines, channels, and conduits and to protect moving mechanical equipment from abrasion and accompanying abnormal wear.
The removal of grit is essential for equipment with closely machined metal surfaces such as for instance centrifuges and high pressure diaphragm pumps.
Currently not one of the primary settling tanks work and a big crane needs to be fixed.
Non-functioning aerators
All solids go to the oxidation ditch, where aerators should blow air into the water to enhance the growth of bacteria which should consume the solids.
According to our information, almost 90% of blow aerators are currently not functioning.
This was, according to our information, the case for at least the last two years, as there is a sole agent who should repair it and electrical programming should be done when the aerators are repaired. This must be done by the installers.
Rusted and faulty biofilters
After the process in the oxidation ditches, the water is moved to secondary settling tanks, which have the same role as the primary settling tanks, with rakes.
Remaining solids are now pumped to the raw sludge pump, then pumped to bio-filters, from where it is pumped to the main pump station.
Sludge extracted from the secondary settling tanks is pumped to the main inflow and clean water is to be pumped to the main pump station. At the secondary settling pumps there are two effluent pumps.
Of the five bio filters, with pipe ‘arms’ spread outward, that should feed the clean water to fall on stones, not one is operational.
These pipes are rusted and should be replaced so water can be distributed and can flow through the stones.
Water then goes to the final pump station, from where water is distributed to three earth dams.
Should there be any solids still in the water, it would be recycled to the biofilters.
Dry beds
At the main pump station, the sludge is circulated continuously and sludge is pumped to dry beds where water trickles through and sludge is dried out.
The dry beds, more than 20, should be cleaned manually, but it does not happen often. Dry sludge can be purchased by farmers.
Systemic interaction
Any pump station or process in the complex system of septic tanks, biofilters and aerobic treatment systems becoming dysfunctional, should be repaired immediately, as it affects further processes, according to expert opinions.
At the end of the treatment process, water is pumped into dry dams before it is fed with gravity into the Blood and sand Rivers, where it is supposed to be filtered in an aquifer through sand, in a final cleansing process.
A lot of sand has been removed by companies mining sand, and this causes the filtration of water not to be very good, with a resultant risk of boreholes to the north west of the river to be contaminated.
Some of the water is sold for use on the mines.
• Odours emitted by sewage treatment are typically an indication of an anaerobic or ‘septic’ condition.
Early stages of processing will tend to produce foul-smelling gases, with hydrogen sulfide being most common in generating complaints.
Large process plants in urban areas will often treat the odors with carbon reactors, a contact media with bio-slime, small doses of chlorine, or circulating fluids to biologically capture and metabolise the noxious gases.
Other methods of odor control exist, including addition of iron salts, hydrogen peroxide and calcium nitrate among others to manage hydrogen sulfide levels.
The municipality is busy with outfall pipelines to transport the waste to the planned new regional wastewater plant, but the completion of the pipelines and phase one of this plant is still to take years.
The municipality was requested to comment on the situation at the Polokwane wastewater plant. No comment has been received.
