Fane S A, Ashbolt N J, White S B
Institute for Sustainable Futures, University of Technology, Sydney, NSW, Australia.
Water Sci Technol. 2002;46(6-7):281-8.
The non-potable reuse of treated sewage in urban areas provides significant conservation of potable supplies beyond that available through water use efficiency. Effluent reuse is also an inevitable requirement in novel decentralised wastewater systems. At present, urban water reuse, where pursued, usually involves large-scale schemes based on new or existing centralised sewage treatment plants. This is despite the diseconomy of scale inherent in pipe networks that balances economies of scale in sewage treatment and negates any cost advantage for wastewater systems with more than around 1,000 connections. In light of this, the theoretical relationship between effluent reuse system scale and pathogen risks was examined at various effluent qualities. Waterborne disease was seen to be a significant factor when reusing effluent in urban areas and smaller systems were found to pose a lower risk of waterborne infection, all other things being equal. Pathogen risks were then included within an economic analysis of system scale. It was concluded that with the inclusion of pathogen risks as a costed externality, taking a decentralised approach to urban water reuse would be economically advantageous in most cases. This conclusion holds despite an exact evaluation of increased waterborne disease due to effluent reuse remaining problematic.
城市地区经处理污水的非饮用水回用，除了通过提高用水效率来节约饮用水外，还能大量节省饮用水供应。在新型分散式废水处理系统中，废水回用也是一项必然要求。目前，在推行城市中水回用的地方，通常采用基于新建或现有集中式污水处理厂的大规模方案。尽管管网存在规模不经济问题，这种不经济与污水处理的规模经济相抵消，使得连接数超过约1000个的废水处理系统无法获得任何成本优势，但仍采用这种方式。有鉴于此，研究了不同出水水质下废水回用系统规模与病原体风险之间的理论关系。在城市地区回用废水时，水源性疾病被视为一个重要因素，并且在其他条件相同的情况下，较小的系统水源性感染风险更低。随后，在系统规模的经济分析中纳入了病原体风险。得出的结论是，将病原体风险作为一项计入成本的外部因素考虑在内，在大多数情况下，采用分散式方法进行城市中水回用在经济上是有利的。尽管由于废水回用导致水源性疾病增加的精确评估仍然存在问题，但这一结论依然成立。
