Multi-objective waste load allocation: application to Delhi stretch of the river Yamuna, India

Waste load allocation (WLA) models are developed as multi-objective models with conflicting objectives in terms of cost, equity and assimilative capacity. A total of four models consisting of one single and three multi-objective waste load allocation models are formulated. These are: 1) least cost model (LCM); 2) cost-equity model (CEM); 3) cost-assimilative capacity model (CAM); 4) cost-equity-assimilative capacity model (CEAM). The performance of these models is demonstrated on the 22 km long Delhi stretch of the river Yamuna, India. Optimal solutions of the models are obtained using the web-based interactive NIMBUS software. The cost functions in the optimisation models are developed as power functions of BOD removal using the regression module of the SPSS10 (1999) software. The response of waste loads on the water quality is quantified in terms of transfer coefficient calculated using the QUAL2E water quality simulation model. The results reveal that amongst all the models, LCM achieves the best practical solutions. In fact, LCM and CAM yields more or less similar results. The CEM does not yield very practical and optimal solution.