Development of least-cost water-quality control policies for the Nitra River Basin in Slovakia

The Nitra is one of the most polluted rivers in Slovakia due to numerous municipal and industrial discharges, as well as the low level of wastewater treatment. The ongoing economic transition and lack of financial resources for water quality management calls for the development of short-run least-cost policies on the basis of ambient standards or a combination of ambient and effluent ones. A water quality control policy model was developed which incorporates dissolved oxygen simulation models, alternative municipal treatment plans and dynamic programming. Least-cost policies to achieve various water quality goals were developed and compared to effluent standard based strategies (including that deriving from the application of the ‘best available technology’). The role of industrial emissions was demonstrated in a sensitivity fashion, while the influence of parameter uncertainty on the developed policies was analyzed in a multiobjective framework. The analyses show that significant cost savings are possible in comparison to uniform, effluent standard policies. They also suggest that a long-term strategy should be realized on the basis of a sequence of properly phased least-cost policies corresponding to ambient standards to be tightened gradually.