## 10 Focus on Sewage Treatment
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Citation** & **Method** & **No. Criteria** & **Notes** \\ \hline
[81; 82; 83] & SAW & 4 & Noted SAW method is sensitive to number of alternatives considered. \\ \hline
[85] & Factor comparison & & \\ \hline
[87] & AHP and Delphi & 6 (major groups) & Interesting use of the Delphi technique to elicit information from stakeholder workshops. \\ \hline
[88] & SAW & 7 & Includes standards codes in consideration of criteria \\ \hline
[89] & ANP & 10 & Stakeholder questionnaires used Likert scale for responses. \\ \hline
[90] & AHP and MAUT & Up to 32 & Uses questionnaire surveys of office space designers and users. \\ \hline
[91] & Not specified & n.a. & Interactions of urban ecological elements with building cladding- energy and noise. \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Examples of MCDA applications in building cladding decisions. Sewage treatment produces a treated wastewater effluent requiring disposal. In some cases, this is via dilution in rivers. However, there is increasing pressure to find more sustainable disposal options that do not directly affect the quality of freshwaters. Such options include irrigation, re-use in some industries, spreading in green space such as forests or as land spreading in arid regions [105]. In some areas, the liquid outputs from sewage treatment can be used as irrigation water, but many factors control the suitability of areas for this, including the characteristics of the waste water, the soil and climate, crop type and aquifer vulnerability and these can be incorporated into a GIS-based decision support system to indicate suitable areas [106]. That study used 11 criteria spanning the environmental, technical, and financial domains. Deciding the contribution of treated wastewater to the mix of water from a variety of sources to meet water requirements in an arid area was investigated using AHP and 16 criteria [107] (for criteria see Table 1 in [107]). Choosing locations for decentralized sewage treatment plants in a large city in Iraq was addressed by [108] who used AHP and five criteria (area, distance to nearest green area, slope, population density, and depth to the sewer connection). The depth to the sewer connection was important because of potential pumping costs. In contrast, the SAW method has been used with six criteria (energy required, sludge produced, grit production, biogas production, employment, and running costs) in deciding upgrade strategies of a centralized cluster of sewage treatment plants in Italy [109]. In Greece, [110] described a tools to assist with site selection for sewage treatment plants that can take account of 30 criteria, divided into five main categories (General including costs, land planning, geomorphological, hydrogeological and specialized criteria) and uses the PROMETHEE or ELECTRE methods. In cities with combined sewer systems, inflows to sewage treatment works can be reduced using sustainable urban drainage systems (SUDS) to reduce rainwater inflows to the sewers. In Spain, [111] used SAW with a graphical display to select appropriate techniques using 4 criteria (total cost, GHG reduction from reduced treatment, aquifer recharge due to infiltration of rainwater and educational benefits). Some key papers are summarized in Table 9.