WHILE South Africa struggles under the burden of loadshedding, another problem, a shortage of water, is increasingly manifesting itself, creating headaches not only for consumers but also for the commercial sector, particularly large commercial developments.
“Many South Africans are becoming familiar with the phenomenon of watershedding, where municipal water supplies are cut off for extended periods,” says technical director at WEC Projects, Dr Gunter Rencken. WEC Projects is a local EPC contractor specialising in engineered solutions for water and wastewater treatment. “There are several causes behind this, including deteriorating infrastructure; equipment theft; damage to pumping and treatment systems due to loadshedding; extended loadshedding which sees reservoirs empty without being refilled due to pump outages; reductions in water quality etc. These challenges are creating a perfect storm for commercial developments, traditionally heavy users of water, as it directly affects the viability of their businesses. It is not hard to imagine the problems created in a large development such as a shopping centre, office building or hospital when there is no water for toilets, human consumption or fire suppression systems.”
According to Dr Rencken, the solution to this challenge is similar to that used to alleviate loadshedding – an uninterruptible or backup water supply that can operate until normal service is restored. “At its very basic level, installing backup water tanks onsite provides a simple solution to the problem. Another solution is to separate the plumbing system into potable drinking water and non-drinking water. After appropriate treatment, the waste (grey) water is then recycled for use in non-drinking water applications (toilets, irrigation and the like). Another option is rainwater harvesting where rainwater is used for non-drinking water usage as well as potable water with the proper filtration, treatment and disinfection system in place. Borehole water is also an option in areas where there are sufficient, high quality groundwater resources. As an option for non-potable use, they are generally cost-effective (depending on factors such as depth and sustainable yield of the borehole). In addition, with the integration of a treatment system, borehole water can be brought up to potable standards.”
These are solutions that can be integrated into building plans at the design stage of a commercial development but, in many cases, this is simply not economically or physically possible for existing installations. Such water backup systems require considerable space for the storage tanks and there is also the issue of the additional plumbing required to integrate it into the building’s existing water reticulation system. While it is possible to integrate such solutions into existing buildings, factors such as the size and design of the building, floor space, number of users, and overall water consumption need to be considered to determine its economic and physical viability.
On-site sewage treatment, i.e. treatment systems which feature small footprints and low operating costs, can also be considered for new and existing developments. At the outset, it requires differentiating potable and non-potable water use. WEC Projects offers a wide range of biological treatment options such as trickle filters, activated sludge and membrane\biological combination systems as well as treatment and disinfection systems, e.g. sand filtration, activated carbon filtration and ultraviolet disinfection. A segregated system sees water from wastewater sources recycled for use in toilets and other non-drinking applications. Such systems can be used continually (not just when water supplies are interrupted) and can realise considerable savings in overall water consumption, particularly in larger developments. However, such savings have to be compared to the design and installation costs, particularly on an existing commercial development, before deciding to implement such a solution.
Wastewater can also be recycled and treated for reuse as potable water, but this requires a more sophisticated multi-barrier treatment system, including deodorisation and disinfection for the water to comply with applicable standards for consumption. This concept is gaining traction in Africa due to the low quality or scarcity of water in many regions. Such systems employ coagulation, flocculation, sand and/or activated carbon filtration and ultrafiltration membrane technology for the removal of particulate matter, organic compounds, microorganisms and viruses. In addition, membrane-based reverse osmosis
technology is used to remove contaminants such as dissolved salts, nitrates, ammonia and phosphates. UV radiation and ozonation are commonly installed for the elimination of viruses. This is usually followed by chlorination or chlorine dioxide dosing as a final disinfection stage.
Advanced oxidation processes (AOPs) are an emerging technology that can be used for the degradation of pollutants in wastewater. In a broad sense, AOPs are designed to remove organic and sometimes inorganic materials in water and wastewater by oxidation with hydroxyl radicals. They are also very effective in destroying harmful bacteria and viruses. While AOPs can achieve the result of producing safe potable water, they are still regarded in many quarters as an extreme solution that is expensive. However, they may be the only solution available for generating safe potable water from “risky” wastewater such as from hospitals. It should also be stressed that if potable water is generated from wastewater, it is very important that the final produced water is continuously monitored to ensure potable water quality standards are maintained.
Adds Dr Rencken, “Like loadshedding, watershedding is a reality for South Africa. While the larger metropolitan areas are usually spared the extremes of water outages, many small to medium municipalities are buckling under the twin challenge of power and water outages which places a heavy burden on the commercial sector’s economic activities. WEC Projects offers commercial users looking to mitigate the water shortage problem comprehensive advice and guidance in determining the viability of a solution, whether it be a simple storage or recycling system or a complete treatment plant for recycling and producing potable water. In addition, the company can develop a complete solution from design and engineering to construction, installation and operation according to particular requirements.”