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0 viewsA wastewater treatment plant has been operating in the Gansbaai area since 2009, providing the Overstrand municipality with much-needed water, and using an innovative new technology to do so. SSI, a South African engineering and environmental consultancy company, made a breakthrough at Gansbaai when it commissioned the first full-scale domestic demonstration sewage treatment plant in Africa. The plant implements a cost-effective and sustainable treatment technology called Nereda.
The global challenges in the water sector (both in water treatment and in water management) are daunting, with challenges like water safety, sanitation and adapting to climate change to name a few. Innovative, cost-effective and sustainable new technology is what the water sector needs, and the Nereda technology fits all the criteria. Nereda has proved more attractive than other alternatives in several applications, like green fields, retrofits and hybrid extensions, and it can be applied in new facilities as well as upgrades of municipal and industrial wastewater treatment facilities.
Heinz Strohwald, principal specialist from SSI explains that “what makes the Nereda technology interesting is that it uses a purifying micro-organism that is known as ‘aerobic granular biomass’. Where conventional processes use ‘activated sludge’ (a sewage and wastewater treatment process which uses air and a biological floc, or chemical precipitate), and the micro-organisms are present as small sludge flocs, the purifying strength of Nereda is concentrated in naturally growing compact granules”.
These granules settle much faster than the flocs, and the higher biomass concentrations mean that much smaller reactor tanks are needed, which results in a much smaller overall plant footprint. Polluting nutrients like nitrates and phosphates are removed biologically (known as simultaneous denitrification) in this process, which also means it is a chemical-free operation. Compared to conventional aerobic treatment, the Nereda system removes these nutrients easily and efficiently, and the treatment plants use less energy and construction material. This results in a reduced carbon footprint and lowers construction and operation costs, making Nereda a much more sustainable option.
In 2009, the Gansbaai project received the SAICE Technical Excellence Award and a CESA Engineering Excellence commendation. Next on the agenda is that the treated effluent from the treatment plant will be of such a high quality that it will be re-used as irrigation water in surrounding areas. Park and sports field irrigation, for example, will benefit from the new water source, and some of the water will be released into the Berg River. Very strict quality requirements have been set so that no sub-standard water is released into the river.
With Gansbaai proving to be a model plant, there are now plans for a second wastewater treatment plant to open in the Stellenbosch municipality, where the existing Wemmershoek Wastewater Treatment Works will be upgraded. The installation for this second plant is underway and due for commissioning mid-way through next year.
Image 1: Arial view of Africa’s first full-sized Nereda WWTW at Gansbaai in the Western Cape. A second installation at Wennershoek near Stellenbosch is underway and due for commissioning during the second half of 2012.
Image 2: Nereda biomass (left) and activated sludge (right) after five minutes of settling.
Image 3: Ronald Niermans of DHV demonstrates how the granular aerobic biomass works at the International Water Week held in Amsterdam in November.
Images courtesy of DHV
The DHV group is a Dutch consultancy that provides engineering services to several markets, and is the parent company of SSI, which has been instrumental in the design of over 100 water and wastewater treatment plants in the country. The Nereda technology was developed by DHV in conjunction with Delft University in the Netherlands, and has received awards in many fields around the world.