Plumbing Africa August 2018 - Page 47

45 Reed beds are often included in both centralised and decentralised treatment systems. 1970s, anaerobic digestion became the preferred method to treat wastewater and sludge, on account of the reduced amount of energy available. The 1980s and 1990s saw an increased interest in nutrient removal, mainly in the developed world, as nutrient discharge had led to the eutrophication of water bodies in many regions of the world. During the same period, significant advances were made in the use of more natural treatment systems, such as waste stabilisation ponds and reed bed systems. These types of systems offer efficient reduction in pathogens with low capital and operational costs. Indeed, even in developed economies, they find a use in small-community treatment systems. The most recent trends have seen treatment systems that address the reduction of GHG emissions. In parallel, much research was undertaken, particularly in the developing regions of the world, on systems that focused on reducing the bacteriological hazards. SEWER MINING AND COMPONENT SEPARATION Active direct use of wastewater and the nutrients it contains has often been driven by necessity, but its use for recreation or other purposes has been documented in many developed regions. New technologies are emerging that allow for the upgrading of wastewater treatment plants to ‘factories’ in which the incoming materials are deconstructed to units such as ammonia, carbon dioxide and clean minerals. www.plumbingafrica.co.za ENVIRONMENT AND ENERGY This is followed by a highly intensive and efficient microbial re-synthesis process where the used nitrogen is harvested as microbial protein (at efficiencies close to 100%), which can be used for animal feed and food purposes. Another new approach has been proposed in which the used water is subjected to a procedure that allows the uptake of its organics and inorganics materials into fish biomass. The fish are harvested and processed to become a source of feed or food. The remaining water can be used for irrigation or discharged. Indeed, the organics and inorganics present in the incoming used water are removed to a large extent in the form of the harvested fish. The key features of both of these concepts for treating wastewater is that they do not follow the route of destroying the nutritive value which is present in the used water. On the contrary, they add a form of renewable energy to allow aerobic microbes to upgrade the nutrients to microbial cells growing in flocs, and they harvest the latter by fish grazing on them. In the latter case, biomass is then processed to become of further use as feed or food. Concerning the isolation and separation of useful wastewater components, it is likely that urine collection and use will become an increasingly important component of ecological wastewater management, as it contains 88% of the nitrogen and 66% of the phosphorus found in human waste. PA August 2018 Volume 24 I Number 6