Water, Sewage & Effluent May-June 2017 - Page 23

DWS
of reusing water is becoming increasingly competitive with the traditional supply alternatives and this will be a key driver for increasing reuse of water in future .
The typical increasing cost of different water sources is reflected conceptually in Figure 2 . Water reuse must be considered as one of several options to augment water supply to a city , industry or mine , once the conventional fresh water resources are fully developed or the cost of water reuse becomes comparable to the development of conventional water sources .
The economic value / cost of water must also be seen in the broader context of affordability , reliability , and responsible use of a limited resource .
Figure 2 : Comparative cost of different water sources .
Therefore , considerable potential exists to substantially expand the use of treated wastewater for irrigation purposes in South Africa . This will bring many benefits . Irrigation is often labour intensive and expanding the area under irrigation may create jobs . Wastewater return flows are typically available close to urban areas and thus close to urban markets for agricultural produce , provided suitable land is available for irrigation .
Treated wastewater can substitute for freshwater , thus making more freshwater available for other uses .
Any such reuse of water by agriculture will have to be balanced by other competing requirements and historical allocations of water in the specific water management area .
Municipal sector : non-potable water
The main source of water for reuse in municipal ( urban ) areas is wastewater from municipal treatment works . This typically comprises a mix of domestic sewage and other wastewater . Other sources of water for reuse include grey water ( usually available at the household / water user level only ) and industrial effluents .
The main potential uses of treated wastewater from municipal wastewater treatment works is for the irrigation of public open spaces ( like parks ), sports fields ( municipal , schools , and clubs ), golf courses , and cooling ( related to industry and power generation ). The return flows from wastewater treatment works can also be important for urban water systems ( rivers , lakes , dams , and wetlands ).
Treated wastewater and / or grey water can also be used for firefighting , toilet flushing , cooling systems , street cleaning , dust control , and a variety of applications that do not require potable water .
Of the total volume of municipal wastewater treated , it is estimated that only a small fraction is reused ; most of it is for the irrigation of public open spaces , sports fields , golf courses , and cooling systems . In the past , the urban / municipal reuse of treated wastewater was not actively promoted due to the cost of such systems and the potential public health risks . Some reuse of water , for example in the irrigation of recreational areas and golf courses , may be in competition with other essential water uses .
Municipal sector : potable water
Used water can be treated to a standard that is fit for domestic use ( drinking purposes ). Treated water can be supplied directly to households ( direct reuse ) or be discharged back to the ( fresh ) water resource where it is blended with other water and subsequently abstracted , treated , and distributed for use ( indirect reuse ).
The majority of these schemes are based on an indirect reuse approach . Indirect water reuse for potable purposes is well established in South Africa . It is common for a treated wastewater effluent to be discharged to a river system and for water to be abstracted downstream of this discharge point and to be treated and used for drinking water . The direct reuse of used water for potable purposes has not been implemented in South Africa , but has been successfully implemented in Windhoek , Namibia , since the 1970s . u
There are many potable water reuse schemes in operation in the world . networking contributor industry debate environment infrastructure municipalities
Water Sewage & Effluent May / June 2017 21
The main source of water for reuse in municipal (urban) areas is wastewater from municipal treatment works. This typically comprises a mix of domestic sewage and other wastewater. Other sources of water for reuse Municipal sector: non-potable water Therefore, considerable potential exists to substantially expand the use of treated wastewater for irrigation purposes in South Africa. This will bring many benefits. Irrigation is often labour intensive and expanding the area under irrigation may create jobs. Wastewater return flows are typically available close to urban areas and thus close to urban markets for agricultural produce, provided suitable land is available for irrigation. Treated wastewater can substitute for freshwater, thus making more freshwater available for other uses. Any such reuse of water by agriculture will have to be balanced by other competing requirements and historical allocations of water in the specific water management area. Municipal sector: potable water Used water can be treated to a standard that is fit for domestic use (drinking purposes). Treated water can be supplied directly to households (direct reuse) or be discharged back to the (fresh) water resource where it is blended with other water and subsequently abstracted, treated, and distributed for use (indirect reuse). The majority of these schemes are based on an indirect reuse approach. Indirect water reuse for potable purposes is well established in South Africa. It is common for a treated wastewater effluent to be discharged to a river system and for water to be abstracted downstream of this discharge point and to be treated and used for drinking water. The direct reuse of used water for potable purposes has not been implemented in South Africa, but has been successfully implemented in Windhoek, Namibia, since the 1970s. u Figure 2: Comparative cost of different water sources. include grey water (usually available at the household/ water user level only) and industrial effluents. The main potential uses of treated wastewater from municipal wastewater treatment works is for the irrigation of public open spaces (like parks), sports fields (municipal, schools, and clubs), golf courses, and cooling (related to industry and power generation). The return flows from wastewater treatment works can also be important for urban water systems (rivers, lakes, dams, and wetlands). Treated wastewater and/or grey water can also be used for firefighting, toilet flushing, cooling systems, street cleaning, dust control, and a variety of applications that do not require potable water. Of the total volume of municipal wastewater treated, it is estimated that only a small fraction is reused; most of it is for the irrigation of public open spaces, sports fields, golf courses, and cooling systems. In the past, the urban/municipal reuse of treated wastewater was not actively promoted due to the cost of such systems and the potential public health risks. Some reuse of water, for example in the irrigation of recreational areas and golf courses, may be in competition with other essential water uses. of reusing water is becoming increasingly competitive with the traditional supply alternatives and this will be a key driver for increasing reuse of water in future. The typical increasing cost of different water sources is reflected conceptually in Figure 2. Water reuse must be considered as one of several options to augment water supply to a city, industry or mine, once the conventional fresh water resources are fu ǒFWfVVB"FR67BbvFW"&WW6R&V6W06&&RFFRFWfVVBb6fVFvFW 6W&6W2FRV6֖2fVR67BbvFW"W7B6&P6VVFR'&FW"6FWBbff&F&ƗG&VƖ&ƗGB&W76&RW6RbƖ֗FVB&W6W&6RFW&R&R琧F&RvFW"&WW6P66VW2W&FখFRv&BvFW"6WvvRbVffVVBVR#p#