As an arid country with a low average rainfall, South Africa faces the danger of its ground- and surface water resources becoming diminished if they are not managed more carefully. The reuse of wastewater as an alternative resource will be an absolute necessity when our natural sources run dry or become contaminated.

With the projected population growth over the next 10 years – coupled with the shifting weather patterns brought on by global warming – the use and reuse of wastewater in South Africa to augment natural resources is a great opportunity for increased sustainability.

South Africa has many large wastewater treatment works that are well established and near city metropoles. These offer a perfect opportunity to provide raw water sources to communities for further treatment; however, for this to be achieved, we need to design robust, versatile plants that incorporate proven technology in the treatment of wastewater to drinking water.

Activated sludge processes followed by a dissolved air flotation (DAF) system, as pre-treatment to membrane processes, as well the membrane processes themselves, have become cost-effective, energy-efficient methods in treating raw sewage to potable standards. This results in the efficient removal of not only suspended solids, but also chemical oxygen demand and phosphorus in wastewater.

In fact, DAF systems have now become a prerequisite as an intrinsic part of the process of treating wastewater. This trend is going to pick up over the next few years as the pressure to reuse wastewater grows exponentially.

The design and implementation of mobile, modular, cost-effective water treatment unit operations – and the combination of these units to form a complete process to transform typical wastewaters with high organic and suspended solids content into drinking water – is of paramount importance. A well-placed, well-designed train of modular unit operations offers unprecedented advantages for both up- and downstream processes, through both the removal of pollutants in wastewater and the protection of human life.

AquaPlan’s robust, skid-mounted systems are well suited for incorporation into current processes as pre-treatment to both ultrafiltration (UF) and reverse osmosis (RO) systems, as well as post-treatment to biological processes such as membrane bioreactor (MBR), moving bed biofilm reactor (MBBR) and sequential batch reactor (SBR) systems.

Coupled with well-designed biological systems, the removal and carry-over of suspended and organic matter to post-treatment processes poses a direct threat to the longevity and sustainability of membrane processes. The up- and downstream processes are very effective in removing unwanted suspended and dissolved solids.

A first for AquaPlan

AquaPlan was recently responsible for the design, manufacturing, supply, site construction and commissioning of one such plant for an office and recreational facility in the Western Cape.

The 0.8 MLD plant treats raw sewage to potable standards, recycling it back into the drinking water system, which feeds the office complex of approximately 10 000 people.

The plant comprises the complete process, including raw sewage collection and pumping, underground piping, activated sludge sewage treatment, DAF, sand filtration, activated carbon filtration, UF, RO and remineralisation, complete with chemical dosing for coagulation and flocculation needs.

The design, manufacturing, construction and site installation of the sub-R27 million, including all civils and electrical work, was done by AquaPlan, over a 10-month period.

The process has been specifically built around the customer’s needs and comprises a complete plant, with all process units included for a full and functional plant producing clean drinking water, ready for use by the customer.

AquaPlan has worked on numerous similar projects over the past 25 years and has plants running across South Africa, with similar, if not exact, unit operations running in isolation; however, none of those plants have all unit operations stacked side by side, to form a complete process, as in this application.

For the first time, AquaPlan has almost 15 unit operations running in a combination of series and parallel applications, to serve the client with a complete process that treats the full human and industrial waste stream to potable quality.

Shifting mindsets

The biggest challenge when it comes to rolling out this type of technology is changing people’s attitudes towards the use of wastewater that has been treated to potable standards.

As pristine natural resources become increasingly diminished and the environmental degradation of natural habitats becomes more evident as a direct result of industrial activity, the shift to utilising wastewater for drinking water will grow exponentially. The technology required to produce drinking water from a wide range of non-potable sources such as acid mine drainage, seawater and raw sewage at city outfall points has, in fact, existed for a long time.

Each person, as a responsible citizen, has a vested interest in not only minimising waste, but utilising our waste streams in environmentally responsible ways – reducing our carbon footprint and conserving energy. Drinking our own treated waste may not sound plausible at this point, but it is indeed our future.