Chapter 5 - A planning framework for wastewater reuser
TABLE 5.6
Water reuse: examples of project alternatives Functional category
Example of alternatives or variations
Freshwater supply (single purpose)
No project (existing infrastructure) Surface water storage (dams) Groundwater augmentation and storage (recharge, aquifer storage and recovery) Interbasin transfers Desalination (seawater or brackish water
Water demand management
Urban and agricultural water conservation
Wastewater management (single purpose)
No project (existing infrastructure) More WWTPs Alternative treatment technologies Stream discharge of treated wastewater Land application of treated wastewater with or without beneficial reuse
Water reuse (single or multiple purpose)
No project (existing infrastructure) Alternative uses of reclaimed water Alternative locations for use of reclaimed water Decentralised treatment locations to increase accessibility to more use locations (satellite treatment plants) Alternative treatment technologies Alternative levels of treatment (existing and new, primary, secondary, tertiary, advanced) Alternative routes for distribution pipelines or canals Inter-regional or intersectoral shifts in freshwater entitlements (water rights trading) One or multiple levels of treatment One or multiple wastewater treatment plants
One approach is to accept certain BOX 5.2 criteria as paramount, and to treat the Criteria for Project Choice planning exercise as maximising (or optimising) the primary criterion(a) Economic justification subject to meeting the constraints Financial feasibility imposed by other criteria. For Public health impact example, the primary objective might Public acceptability be minimising the economic cost of Environmental impact obtaining extra freshwater for cities, Technical feasibility subject to satisfactory safeguards for Market and demand public health, environment, etc., and Legal and institutional feasibility its feasibility on technical, legal and Etc. market demands. Another approach is through multicriteria analysis (MCA) which involves scaling, scoring and weighting of each criterion (Snell, 1997). This is a formal mathematical optimising method, which can be applied flexibly to accommodate the subjective or explicitly imposed weights of decision makers, regulators or politicians. This flexibility comes from maximizing first a single criterion subject to acceptable levels to the others and then varying the criterion and the weights. MCA may well prove to be a more acceptable and durable method of making planning decisions since it contains information about all the key considerations entailed in each situation, including non-monetary impacts.
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