IMPACTS OF MUNICIPAL WASTEWATER TREATMENT PLANTS ON WATER QUALITY IN THE BERZE RIVER BASIN

Eutrophication caused by water pollution with nutrients (nitrogen (N) and phosphorus (P)) is one of the main environmental problems nowadays. Poor water quality might be caused by many natural and anthropogenic factors. The most common anthropogenic factors are water pollution caused by intensive agriculture (e.g. intensive fertilizer use, high density of livestock) and discharges from municipal waste water treatment plants (WWTP). In this study, nutrient load from WWTP to the river Berze basin in time period from the year 2005 to the year 2015 was described. In total, 23 WWTPs of the study area were analysed using descriptive statistics to calculate average values of nutrient amount and concentrations discharged to river Berze basin. From 2005 to 2015 average N and P load from WWTP to the river Berze basin have been reduced, but concentration of N and P in treated wastewater (WW) have increased. The largest WWTP of the study area - Krigeri (WWTP of city Dobele) is subject to the regulations of treated WW quality set by Republic of Latvia Cabinet Regulation No. 34. The WWTP Krigeri meets the regulations, but overall situation in the study area suggests that strict control of smaller WWTP should be made.