ENVIRONMENT AND ENERGY 43 Enhancing wastewater collection treatment (Part 2) Examining a number of options and responses for enhancing wastewater collection and treatment, with a special emphasis on the advantages of low-cost decentralised systems. Extracted from United Nations World Water Development Report 2017 DEWATS and low-cost sewerage are naturally complementary. DEWATS can also serve as a medium- term solution pending the large-scale design of centralised systems, and there is significant flexibility on their use. Indeed, large-scale centralised wastewater treatment systems may no longer be the most viable option for urban water management in many countries, due to high maintenance costs and resource needs. Moreover, they often require large areas of land and are too inflexible to meet the needs of rapidly expanding www.plumbingafrica.co.za urban areas. This holds true for water supply and wastewater infrastructure, rainwater collection and drainage. DEWATS serve individual or small groups of properties. They allow for the recovery of nutrients and energy, save freshwater and help secure access to water in times of scarcity. They may require less upfront investment than larger, centrally piped infrastructures, and are more effective in coping with the need to scale up (or down) services to needs. However, they do require individuals with a minimal amount of training to take care of their operation and maintenance. Through decentralised technologies, sustainable neighbourhoods in cities could partly replace traditional public systems. A challenge of DEWATS may be that local communities need to accept that they live close to the treatment facilities, so efforts must be made to make the plants aesthetically acceptable. For this reason, systems based on reed beds are often favoured. DECENTRALISED STORMWATER MANAGEMENT Decentralised stormwater drainage has a good potential for ‘source control’ technologies that handle stormwater near the point of generation. For instance, green roofs Part of a centralised wastewater treatment plant in Germany. August 2018 Volume 24 I Number 6 DECENTRALISED TREATMENT (DEWATS) In addition to centralised wastewater treatment plants, decentralised systems have also shown an increasing trend. Many of the approaches to decentralised wastewater treatment systems (DEWATS), pioneered by organisations such as the Bremen Overseas Research and Development Association (BORDA) and the Consortium for DEWATS Dissemination Society, have found their rightful place as a part of sanitation systems for rapidly expanding urban areas and also for certain isolated communities where conventional sewerage is precluded on economic grounds.