Rudinė river environmental state‘s assesment and improvement

Abstract

This article analyses the Ignalina city wastewater treatment plant‘s (WWTP) impact on water quality of the river Rudinė and presents assessment of environmental quality of this surface water body. Assessment is based on data about the quality of wastewater during the 1998-2008, provided by JSC „Ignalina water“. Anthropogenic impact on water quality of the river Rudinė is evaluated taking into account both point and diffuse pollution sources. Concentrations of total nitrogen (N), total phosphorus (P) and biochemical oxygen demand (BOD7) in three different sections of the river Rudinė are modeled by employing surface water quality mathematical model MIKE BASIN and compared with maximum allowable concentrations (MAC) defined in national legislation. According to the results of mathematical modeling, Ignalina WWTP significantly affects total P concentration in the river section from WWTP to the tributary Narsupė: estimated increase is up to 0.6 mg/l and MAC is exceeded 6 times. Total N concentration increases only slightly, while BOD7 even decreases. The largest amount of diffuse pollution comes from inhabitants who generate wastewater not treated in a centralized system (approximately 78% of BOD7, 65% of total N, 92% of total P). BOD7 constitutes the largest part among the common pollution indicators of the river Rudinė (78 %). The tributary Narsupė also has a significant impact on water quality in the river: concentrations of BOD7, total N and total P in this river segment are respectively 6.37 mg/l, 2.51 mg/l and 0.47 mg/l, and exceed respective maximum allowed concentrations of 6 mg/l for BOD7, 2.5 mg/l for total N and 0.1 mg/l for total P. Analysis of tax for environmental pollution shows that reconstruction of the WWTP in 2003 has resulted in reduction of this tax approximately by 90% and clearly proves the necessity and viability of the reconstruction.