Feature

Shamwari Private Nature Reserve leads the way in adopting new, clean sewerage treatment technology

By Dr Garth Cambray

The 30 person IAPS at Shamwari situated in a peaceful pristine valley.

Sewerage often smells like its main solid components, and for many people the best place for sewerage is out of sight, out of mind. Conventional sludge treatment methods such as activated sludge systems provide the viewer with little out of sight, out of mind convenience - powerful paddles agitate sewerage and inject air into it, releasing vast quantities of smelly organic compounds into the air, and ensuring that if you cannot see it, you definitely can smell it.

Prof Peter Rose and his team at the Environmental Biotechnology Research Unit (EBRU) at Rhodes University have for ten years tested and refined a quiet alternative to standard sewerage treatment technologies - the Integrated Algal Ponding System (IAPS), which is a simple sewerage treatment system that works with nature to keep all the unpleasant aspects of sewerage out of sight and mind.

In beautiful pristine places, such as Shamwari Private Game reserve in the Eastern Cape, the issue of effective treatment of sewerage is of great importance. Bayethi Lodge, when fully occupied represents the equivalent of 30 people, requiring a sewerage system able to deal with this. Situated in a valley with clay soils, French drains will not work here as the sewerage, once digested in the French drain, does not dissipate into the soil, and instead overflows, creating bad smells and negative environmental impacts. To solve this problem, Shamwari has recently constructed, with assistance from Mr Dave Render of EBRU, an IAPS system.

How the IAPS system works

In the IAPS system, sewerage enters a digestor pit in a large open topped tank as shown in the image below. The rate of sewerage inflow into this pit is lower than the settling velocity of 'solid matter' and also conveniently lower than the settling velocity of all parasite eggs. Hence, solids remain in the pit and are digested by bacteria into smaller and smaller compounds until eventually all that remains is liquid effluent. Methane and carbon dioxide gas rises to the surface of the pond, into the so called facultative region, where algae grows on the surface. The algae produce oxygen, and various bacteria thrive on the oxygen produced by the algae and use this oxygen to further break down any smelly organic compounds. Hence this section of the process is largely odor free.

The IAPS system at the Environmental Biotechnology Research Unit stationed at the Grahamstown Municipal Sewerage works. Diagram courtesy of Prof. Peter Rose, EBRU.

The effluent then flows continuously from this tank into a 300mm deep algal raceway, termed the High Rate Algal Pond (HRAP) where paddle wheels circulate the liquid, ensuring it is oxygenated. Algae thrive in this environment and produce large amounts of oxygen, and at maximum solar intensity raise the pH of the water temporarily to above that at which pathogenic intestinal bacteria such as those that cause typhoid and cholera can survive.

The HRAP at EBRU in mid summer - note the dark green of the algae growing in very high concentrations in this water.

The semi-treated effluent then flows from this raceway into a final polishing raceway, where additional algae scrub the remaining nutrients and dangerous bacteria from the water. A small trickle from this pond is then allowed to pass into a settling tank, where the algae is separated from the water, which flows into the nearby stream as clean, clear water. The algae is periodically removed from the settling pond and can be used to make compost.

Speaking to Prof. Peter Rose and Mr David Render about the IAPS it becomes evident that in many ways, this system is the ideal way to help deal with sewerage problems in sparsely populated areas where high quality treated water can be reused for irrigation, or discharged into water courses in such a way that there is little environmental impact.

Conventional sewerage treatment systems, such as activated sludge systems, are labour intensive and require very skilled operators who are expensive and in short supply. The IAPS requires roughly the same amount of attention as one would dedicate to maintaining a lawn.

Potential applications of this South African technology include treating sewerage from rural communities where water can be used for farming afterwards, lodges in secluded areas such as Shamwari Private Nature Reserve, private housing estates and golf courses where water can be reused for irrigation, as well as university, school and company campuses where similar uses for the water can be found.

Dave Render of EBRU advised on the construction of this IAPS at Shamwari. Here, the paddle wheels are visible which circulate the algae in the raceway. In this case a red algae has established itself in the raceway during the cold winter months. As conditions become warmer, green algae are likely to become dominant.

More information:

  For more information on the IAPS please visit the EBRU website and contact the staff at EBRU for further assistance.

Phone: + 27 (0) 46 622 2656

Email: ebru@ru.ac.za 

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