HCC fails to assess toxic effluent

HARARE’s water quality has been a topical issue for years, with the local  authority arguing that it is safe for consumption while others say the huge amounts of effluent being discharged into the water make purification a challenge.

An audit report presented to the Harare City Council recently revealed that companies were discharging more toxic waste and the local authority stood to lose a lot of revenue if the situation was not contained.

HCC only managed to sample 3,9 percent of companies as compared to the potential of companies eligible for sampling. The audit revealed that in March 2014, only 279 out of 5 057 companies were sampled of which 82 have already closed shop.
According to the report, sampling of companies enables the chief chemist to determine the toxicity of effluent discharged into the city sewer system.

“Companies that discharge more toxic waste (above the strength factor of 80) are charged more over and above the standard rate levied to all companies disposing effluent.

“The city stands to lose a lot of revenue if companies disposing effluent  are not assessed as the blanket rate is applied albeit the fact that many  companies are discharging effluent with strength factors of as much as 600 percent,” read part of the report.
Simon Muserere, HCC waste water manager said the current Chemical Oxygen Demand (COD) as of May 26, 2015 is 1 026 milligrams per litre which is very strong sewage.

Muserere said the COD tells the engineers whether our sewage is in the low medium or high strength and this can determine how much sewer can be treated at the plant.

The engineer said in the last quarter the shooting up of the COD could be attributed to various factors like low availability of water and an increase in discharges into the sewer system.
He said a recent assessment of the COD levels showed that they were mostly caused by domestic and not industrial effluent.
“If the pollution increases they are blocking other developments coming in as a result you now fail to treat the volume of sewage coming and the pollution downstream.

“All our sewer treatment plants are biological processes. They run on simple bacterial activity, which converts the entire sewer to nitrogen and carbon dioxide gas and at the end of the plant you will no-longer have the dirt. If toxins are discharged at the industries, they may  kill the bacteria so at the end the bio activity are affected,” Muserere  said.

Muserere added that because bacteria operate at a specific temperature, if  altered ammonia which is harmful to aquatic life could be traced in the water. He said such harmful discharges in the water have also cost council thousands through fines.
In the first quarter of 2015, council was fined nearly $2 000 for effluent traced in the water by the Environmental Management Agency (Ema).

Muserere said heavy metals such as lead, mercury, toxic levels of iron and phosphates have also been traced in the waste water.
“Phosphates in the water are commonly caused by soaps and detergents we use daily to bath and do our chores. If a phosphate ban is implemented, we can reduce the quantity that is discharged in our water.

“If that ban is not there countries like South Africa which have these bans can just dump their high phosphate products in Zimbabwe. So when we bath, do our laundry and go about other cleaning activities, those phosphates end up at the treatment plant,” he said.

According to the World Health Organisation, lead in the body is distributed to the brain, liver, kidney and bones. The organisation said no levels of lead exposure are considered safe however poisoning by the metal is preventable.

It is stored in the teeth and bones, where it accumulates over time. Human exposure is usually assessed through the measurement of lead in blood.

Mercury poisoning disrupts any tissue it comes in contact with and can cause shock, cardiovascular collapse, acute renal failure and severe gastrointestinal damage.

Council will therefore launch four programmes together with the University of Zimbabwe (UZ), aimed at improving water quality in the city.

The first; named Solar Bee research will be used to aerate Lake Chivero while also removing toxins at the same time. The machinery used in the research can target 11 hectares of water, which according to Muserere can clean the Lake completely in five years if effectively implemented.

Vermuculite; will remove phosphates from the water, Cryptosporidium will rid the water of pathogens and the Green Bridges project will use plants to naturally purify the water.
Tamuka Nhiwatiwa, UZ biological sciences lecturer, said the most common discharges in Harare’s water sewage effluent from domestic sources and some from industrial effluent and illegal dumping of wastes such as used oil and other contaminants.
Nhiwatiwa said the growing population of Harare has surpassed the current capacity of the city to deal with the large volumes of untreated sewage.

“Secondary issues such as electricity problems have forced residents to use firewood and when finished they scrub their pots with sand which ends up causing blockages and affecting council treatment facilities such as Firle,” he said.

“Our main problem in Harare is our water sources are also where we dispose of our waste water.  This is not an ideal design as Salisbury was designed for a small white population not it’s current size.

The biological sciences lecturer said together with council they are working on Integrated Lake Basin management (ILBM) approach, which encourages people participation as waste does not come from council alone.

He said the project will primarily focus on improving the quality of water at source lakes Chivero and Manyame. The UZ lecturer said all the rivers in Harare have been dead for more than 15 years as there is no meaningful aquatic life due to waste being discharged into them.

“15 years ago we used to catch all types of fish but today there is nothing. People used to survive on angling at the junction of Mukuvisi and Manyame rivers but today there is nothing, the destruction is almost total.

“Notwithstanding all the water weeds that have cropped up and the blue green algae that has messed up the ecology of lake Chivero,” Nhiwatiwa said.

Nhiwatiwa said apart from dealing with the problem at the source there was also a need to preserve wetlands, which are slowly diminishing due to construction and peri-urban activities.
According to Ema, there are 1 117 wetlands in Zimbabwe covering 1,28 hectares of land, while Harare sits on  30 of them.
Environmental expert and UZ professor Christopher Mugadza said Lake Chivero  will still remain polluted after the rehabilitation of the sewerage works unless wetlands are harnessed to purify run-off in a process called the diffuse source pollution.

Mugadza said engineering in the form of waste water management will take away a lot of money to reduce phosphorus content to make the water suitable for consumption.
He also said there is need to purify the lake itself and not completely rely on rehabilitating the sewerage works, if a significant change will be realised.

“The most common method of treating water for consumption is applying chlorine but if the water has a lot of organic material from pollution, chlorine will combine with that material to produce chlorocarbon that is far much more dangerous,” he said, adding; “You produce water that may be free of bacteria but is full of chemicals that cause cancer. —Hellen Kadirire

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