Evaluation of total nitrogen pollution reduction strategies in a river basin: a case study.

The enrichment of groundwater and rivers by nutrients (nitrogen and phosphorus compounds) and their consequences is one of the most severe problems across Europe as well in Slovenia. Transfer of nutrients from different sources into the environment causes eutrophication of surface waters, nitrate accumulation in groundwater, and others. In this paper, the methodology of the material flow analysis is presented and applied to develop a nitrogen balance in a river basin and to evaluate different scenarios for total nitrogen pollution reduction. Application of the methodology is illustrated by means of a case study on the Krka river, Slovenia. Different scenarios are to be considered: the present level of sewerage and treatment capacities, different stages of wastewater treatment and management of agricultural activities on land. The results show that beside effluents from wastewater treatment plants, agriculture contributes significantly to the total annual nitrogen load. Beside reduction of point sources by means of wastewater collection and implementation of nutrient removal technology, managing agricultural nitrogen in order to protect river water quality and drinking water supply should become a major challenge in the Krka river basin.