Arthur Carter of Zimbali writes:
Zimbali is a premier, multi-million rand environmental friendly eco estate in which I have resided for nigh on 20 years.
The early morning and late evening stench being emitted from the Sembcorp sewerage and wastewater plant has become worse and intolerable over the past two years.
I have discussed this problem with the plant manager Mr Koos Duvenahage who acknowledges that there is a problem with the inlet of raw anaerobic waste and that it can get worse due to the plant’s limited capacity, new residential developments requiring waste water treatment and the bad location of the plant in relation to adjacent residences.
The plant utilities are of insufficient design capacity to satisfactorily treat the current and future area requirements.
He advised that the plant was in the throes of convening a meeting regarding the pumping regime.
He recommended to the writer that this matter be reported to Zema in order for a solution to be determined.
Depending on the technology employed for the sewerage treatment, as well as plant design and location, living near a sewerage plant may be most inconvenient and highly detrimental to property values.
Treatment plants without gas containment and treatment can have objectionable odours, particularly downwind when the temperature drops at night and in the early morning.
Hydrogen sulphide is dangerous even at low levels.
Prolonged exposure to sewer gas can cause irritability, headaches, fatigue, sinus infections, bronchitis, pneumonia, loss of appetite, poor memory and dizziness. It affects people and wildlife that are exposed to it over a long period of time.
How is Sembcorp controlling the odours that are emitted from its sewerage plant?
Over the years the stench has been exacerbated by the increased throughput as a result of development in Ballito and the other areas that are reliant on the plant to process the increased input of waste water.
Siza Water Managing Director Shyam Misra replies:
The Frasers Wastewater Treatment Works is a conventional activated sludge treatment works with the first module having been commissioned in the 1980s and an additional 6 Ml/day was commissioned in 2005.
The total capacity of the plant is 12 Ml/day (12 million litres of sewage per day) and the inflow is 6.9 Ml/d and mainly treats domestic household sewage.
Our sewer treatment capacity for the greater Dolphin Coast is in excess of 18 million litres of sewer per day and we currently receive eight million litres of sewage from all three of our sewage treatment works (Frasers, Shakaskraal and Sheffield).
The additional capacity we have is to create an enabling environment for development.
We further recently updated our bulk water and sanitation master plan that caters for current as well as future developments within our service area.
Our plants are also capable of expanding their capacity by an additional 18 million litres and these upgrades will be phased in prior to the existing capacity being reached.
There are no issues regarding the operations at any of our treatment plants, including Frasers.
We recently did have an issue at the Shakaskraal treatment works and this has since been remedied.
Our staff based at the sewer treatment works have worked at the plant for many years and undergo medical surveillance checks in line with the Occupational Health and Safety Act and to date there have been no issues of any health risks that staff could have developed by working at the plant or risks associated with sewage.
We even have persons that have worked in a sewer environment for approximately 40 years and there are no signs of any of these conditions.
Our oldest employee at the plant is in excess of 60 years of age.
The breakdown of carbon, ammonia and sulphate is under aerobic conditions without the nasty odour when the breakdown is anaerobic.
The water quality of the inflow as well as the final outflow is tested at the plant on an hourly basis seven days a week, in addition on a weekly basis an accredited independent laboratory also conducts tests on the incoming raw sewage as well as the final effluent from the treatment works.
The operation of the plant is optimum and in compliance with all legislation.
To place on record, Frasers Wastewater Treatment Works is one of the best ranked plants in South Africa and has won awards from the Water Institute of South Africa and the Department of Water and Sanitation as well as special commendations.
By its very nature, sewage does create odour and there is generally an increase during winter or with a temperature decrease.
This results in hydrogen sulphide, a heavy gas which accumulates at the bottom and usually releases during the early morning (from 4-8am) when the temperature changes.
Hydrogen sulphide has a low odour threshold with the smell being detected below 1 mg/l.
The concentration of hydrogen sulphide measured at the fence line of the treatment works is still very low, with concentrations being 0-5mg/l.
We take these complaints very seriously and have requested the address of the complainant from the managing agent so we can conduct a more thorough investigation regarding this matter.
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