Decision support for the planning of integrated wastewater reuse projects in South Africa

摘要

Wastewater reuse is an attractive option for supplementing available water supplies. Benefits ofnreuse include pollution abatement due to the reduction of effluent discharge to surface waternbodies, the decrease in the use of freshwaters from sensitive ecosystems, replenishment of soilnnutrients in agriculture, enhancement of groundwater recharge and delay in the future expansionnof water supply infrastructure. This paper presents ongoing research in developing and testing ofna decision support system (DSS) for assessing the feasibility of implementing wastewater reusenprojects in South Africa. The DSS employs multi-criteria qualitative assessment across technical,nenvironmental, social, institution and water resources. The database of the DSS contains 33nwastewater treatment unit processes with known information on performance, costs andnqualitative criteria obtained from literature. The knowledge base on the other hand, consists of anset of rules for combining the treatment units to form treatment trains and contains informationnon maximum allowable values for different water quality parameters for five end users.nThe weighted average method was used to aggregate scores obtained from the assessment ofnthe different criteria to generate an indicative value that could form the basis for decisionnmaking. Testing of the DSS was applied to the Parow wastewater treatment plant in Cape Town.nResults of the analysis shows that only the water resources evaluation score (1.0) is considerednexcellent for reuse implementation while the institutional evaluation score is weak (0.35)nin guaranteeing success. Social evaluation and treatment train technical/environmental havenqualitative evaluation scores of 0.76. The desirable score for all the criteria is 1.0 in order tonfacilitate the successful implementation of any reuse project. The quality of treated effluent fromnthe proposed treatment trains meets the quality requirement in most of the pollutant determinednexcept total phosphorus (2.88). The value is acceptable if the use of the effluent is limited tonirrigation. If decision makers give adequate attention to the criteria highlighted in this model,nsuccess of a reuse project in South Africa can be better enhanced.