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San Aqua HCA

A cost-effective solution for South Africa’s wastewater treatment

Erratic rainfall, urbanisation, ageing infrastructure and a combination of shortage of funds and technical skills in municipalities are contributing to a gradual deterioration in South Africa’s drinking water quality.

While it is still safe to drink tap water in the country’s larger cities, it is becoming riskier in smaller cities.

Drinking water is sourced from rivers and streams, into which poorly managed waste water treatment plants, particularly in rural areas, are emitting millions of litres a day of partially-treated or untreated water. With rainfall patterns changing as a result of global warming, there is less fresh water available to dilute contaminants.

According to the department of water and sanitation’s latest Green Drop report, most of the country’s waste water treatment plants were in the high risk category by this year, and one-quarter required urgent intervention.

Professor Anthony Turton of the Centre for Environmental Management at the University of the Free State said SA produced five-billion litres of sewage a day, of which only 20% was treated to a standard safe to discharge into water sources. He said water constraints presented both risks and opportunities.

One of the companies that sees an opportunity is Cape Town-based San Aqua HCA, which has designed and patented a solution called HydroChemical Activation (HCA). It has run informal tests with 1.8-, 0.5-and 0.25-megalitre/day municipal water treatment plants, which San Aqua HCA co- founder Pamela Alborough said surpassed expectations.

HCA is an improvement on an existing process called electrochemical activation, in which an electrical charge is applied to water to sterilise it. HCA, which uses platinum group metals and other catalysts, eliminates the need for separate anode and cathode cells and puts a higher effective current through the water. The reactor cells create a high frequency magnetic field which disrupts the molecules, generating peroxide and ozone. Peroxide and ozone sanitise the water. The process also coagulates inorganic material, which can more easily be filtered out and sent to a landfill site for disposal. The HCA system can also incorporate sensors feeding information on the quality of the water and system performance to a central computer.

Alborough said HCA was designed to be an add-on to an existing municipal waste water treatment plant of between 0.1 and 50 megalitres/day. It did not replace the existing infrastructure needed for a municipal plant, but could double capacity because it enabled contaminants to be removed faster and more effectively.

Alborough also said that HCA required no special skills to operate. It needs a power source, but uses only the equivalent of eight light bulbs of electricity at a flow rate of one megalitre a day. To treat one megalitre, the equipment consisted of an electronic power supply (in a small box) and two mini reactor units, about 16 centimetres in diameter. The reactors can be doubled in size and quantity as volumes increase, making the system scaleable.

The capital cost of a full municipal waste water plant is about R8-million (about $530,000) per megalitre of capacity. The HCA plant could cut this to about R4-5million/Ml. It also reduced operating costs because fewer chemicals were needed.

But municipalities are conservative decision-makers so San Aqua is marketing the solution to businesses and high-density residential estates, anticipating that once municipal managers see it working in the private sector they will be prepared to adopt it.

Sputnik Ratau, spokesman for the department of water affairs and sanitation, said new technologies were of interest but there was no “one size fits all” solution. Each municipality and its selected service provider would decide what was best. At least five municipal treatment works around the country were using new or alternative treatment technologies.

San Aqua is a semi-finalist in this year’s Global Cleantech Innovation Programme, which assists entrepreneurs to commercialise new technology addressing energy and environmental challenges.

By Charlotte Mathews

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