Optimized plan of centralized and decentralized wastewater reuse systems for housing development in the urban area of Xi'an, China

Abstract

In an arid and water deficient urban area, such as Xi'an in the northwest region of China, gardening and forestation often use large amounts of tap water. Therefore, there is a need for treated wastewater reuse for such purpose to mitigate urban water shortage, especially in the newly developed housing area, where a high green coverage is often required for both commercial value and living condition improvement. Supply of the treated wastewater through a centralized system which has been planned and partially constructed is one measure to meet such need, but it may require an extension of the distribution system for a full coverage of the whole city area. A supplementary measure is to construct decentralized wastewater treatment and reuse (DESAR) systems in areas that are distant from the planned centralized system. In order to optimize the plan of wastewater reuse for housing development in the urban area, the authors analyzed the existing plan of centralized wastewater reuse and the envisaged plan of housing development in Xi'an urban area. A method was proposed for selection of a feasible way of reclaimed water reuse from two options, namely centralized and decentralized ones, by introducing a critical distance L0 which depends on the relationship between the cost for DESAR system installation and that for water delivery pipeline construction. If the distance from the project site to the nearest access point of the centralized system L is shorter than L0 then using reclaim water from the centralized system becomes more feasible, and otherwise DESAR system installation becomes more feasible. A distribution map was thus obtained to show an optimized plan of centralized and decentralized wastewater reuse systems for housing development in Xi'an city. An example was also given to show the advantage of a DESAR system installed.

Wastewater

“…There are numerous cases of water reuse for the creation of artificial lakes and restoration of natural wetlands which have demonstrated significant environmental and recreational benefits (Wang et al 2008;Wang et al 2010). To conserve their limited water supply, governments in countries such as Kuwait, are investing in water reclamation system such as Sulaibya-the world's largest membrane-based water reclamation facility.…”

“…To conserve their limited water supply, governments in countries such as Kuwait, are investing in water reclamation system such as Sulaibya-the world's largest membrane-based water reclamation facility. With large landscapes serving as leisure areas for residents in Beijing and Xi'an, China, similar driving factors of urban expansion, decreased water availability and frequent droughts have increased reclaimed water use for irrigation, urban planning and river and lake restoration (Wang et al 2008). The reclaimed water is mixed with brackish water and then supplied for non-potable uses, such as irrigation of landscapes along highways, public gardens in Kuwait city and agricultural lands and groundwater recharge.…”

“…The plant also provides potable quality water at approximately $ 0.65 per m 3 ($ 0.40 per m 3 for conventional wastewater treatment and pipeline costs and $ 0.38 per m 3 for tertiary treated wastewater). From a cost-effectiveness point of view, greywater reclamation and reuse at a cost of $ 0.17 per m 3 remains a competitive alternative, when compared to using tap water at a cost of $ 0.47 per m 3 (Wang et al 2008;Wang et al 2010). With large landscapes serving as leisure areas for residents in Beijing and Xi'an, China, similar driving factors of urban expansion, decreased water availability and frequent droughts have increased reclaimed water use for irrigation, urban planning and river and lake restoration (Wang et al 2008).…”

Reuse-oriented decentralized wastewater and sewage sludge treatment for rural settlements in Brazil: a cost-benefit analysis

“…Decentralization and the potential it provides for the reuse of wastewater in agriculture are considered among the most important factors in terms of the advantages and benefits when treating wastewater in places close to the generation site (Venhuizen 1991;Wilderer & Schreff 2000;Tchobanoglous et al 2004). The possibility of using DWM systems is addressed by (Wang et al 2008) from the point of view named by some authors as decentralized wastewater treatment and reuse (DESAR). Several authors considered the reuse capabilities of decentralized wastewater treatment solutions as an advantage for its application in small communities and rural areas (Massoud et al 2009; van Afferden et al 2010;Lienhoop et al 2014; van Afferden et al 2015).…”

The Economics of Sustainable Urban Water Management: the Case of Beijing

“…Some carry out the comparison between centralized and decentralized water treatment sys-tems from the point of view of technology (Norton 2009;Wilderer and Schreff 2000), and others make the comparison from the perspective of cost (Fane et al 2002;Gratziou et al 2005;Jia et al 2005;Wang et al 2008). Rarely centralized and decentralized wastewater reuse systems are compared from the perspectives of economics.…”