Water-Wise Cities and Sustainable Water Systems: Concepts, Technologies, and Applications最新文献

{"title":"Building resilience in water supply infrastructure in the face of future uncertainties: Insight from Cape Town","authors":"Upeshika Heenetigala, L. Kapetas, R. Fenner","doi":"10.2166/9781789060768_0201","DOIUrl":"https://doi.org/10.2166/9781789060768_0201","url":null,"abstract":"ions are perceived to also have a high resilience to flood events (Defra, 2015). 8.3.3.3 Option 3: wastewater reuse treatment plant Wastewater reuse provides a high degree of resilience to droughts and other extreme events due to the nature of the closed-loop system and should be considered as a baseline supply option as opposed to an additional source (Defra, 2015). However, similar to desalination, as the plant capacity is technically locked-in, it is unable to produce more water if demand increases beyond its capacity. 8.3.3.4 Option 4: surface water transfer scheme Surface water transfer schemes from river to reservoir are reliant upon rainfall and as the water resource is exposed, they have medium resilience to temperature extremes (Defra, 2015). However, reservoirs are able to store excess water when supply is plentiful, especially during high rainfall or flooding events, which can be utilised during low rainfall periods. This scheme has medium resilience to short term droughts but has low resilience for longer, multi-term droughts. 8.3.3.5 Summary of resilience characteristics analysis Table 8.2 summarises the results of the resilience assessment of the four options. The sum of the scores of the seven characteristics for each option show that wastewater reuse scores the highest, and hence can be deemed as the most resilient option. Figure 8.6 illustrates these results schematically. 8.3.4 Criteria 4 (C4): environmental impacts The environmental impacts of each of the options is assessed qualitatively in the following sections and scored subjectively based on low (1), moderate (2) and severe (3) negative impacts on the environment, relative to each other, and are summarised in Figure 8.7. 8.3.4.1 Option 1: desalination plant Plants between 100 000–200 000 m/day consume 3.5–4 kWh/m of energy (Zarzo & Prats, 2018), equating to 1.4–1.8 kg CO2 per cubic meter of produced water which makes the carbon footprint of large-scale desalination plants substantial (Elimelech & Phillip, 2011). This is particularly concerning since about 80% of South Africa’s primary energy needs are provided by coal, which is unlikely to change significantly in the next two decades (Energy RSA, 2018). Studies have shown that a major concern with SWRO desalination, as is being considered in Cape Town, is the effect that seawater intake will have on marine organisms – entrainment can kill a large number of fish and small planktonic organisms if open surface intakes are not implemented safely (Elimelech & Building resilience in water supply infrastructure in the face of future 217 Downloaded from http://iwaponline.com/ebooks/book/chapter-pdf/911929/9781789060768_0201.pdf by guest on 03 September 2021 Phillip, 2011). Furthermore, the increased salinity of SWRO brines, which is about twice that of seawater, and the chemicals used in the desalination process, also pose environmental risks to the marine ecosystem (Elimelech & Phillip, 2011). 8.3.4.2 Option 2: groundwater augmen","PeriodicalId":304829,"journal":{"name":"Water-Wise Cities and Sustainable Water Systems: Concepts, Technologies, and Applications","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125893955","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}