Ūdeņu kvalitātes uzlabošanas efektivitāte un risinājumi mākslīgajos mitrājos Latvijā: promocijas darbs zinātniskā doktora (Ph. D) grāda iegūšanai vides inženierijas un enerģētikas zinātņu nozarē

The dissertation is based on the topicality to examine the environmentally oriented and nature-based biological method for water quality improvement. Constructed wetlands are well known in different countries and include widely used method for water treatment, but in Latvia wetlands haven`t been proved as surely effective. Constructed wetlands are the wastewater treatment method based on physical, biological and biochemical processes and doesn’t require electricity. The first chapter of the dissertation provides an overview of the possibilities of using constructed wetlands in treating different types of wastewater. Various constructive solutions of wetlands are provided according to the conditions and needs in Latvia. The research is based on the data from two objects in study site Mezaciruli, were two separate constructed wetlands were designed, built and operated, and one monitoring object with constructed wetland in the study site Zante. All the information of the study sites, monitoring data and methods are described in the second chapter of the dissertation. In the chapter of results and discussion the efficiency of nutrient removal in study sites is analysed and the impact of climate, maintenance and conditions of Latvia on the removal efficiency is investigated. The average reduction of concentrations of ammonia nitrogen, nitrate nitrogen and total nitrogen was observed by 17%, 67% and 54%, respectively, in the subsurface flow constructed wetland. During the study period in the surface flow constructed wetland in Mezaciruli the average concentrations of nitrate nitrogen, ammonia nitrogen and total nitrogen were reduced by 10%, 24% and 9%, respectively. The median and average concentrations of nitrogen compounds showed an increase in the surface flow constructed wetland in Zante. The average concentrations of orthophosphate phosphorous and total phosphorus were reduced by 67% and 72% in the subsurface flow constructed wetland, and decreases by 5% to 27% in the surface flow wetlands in Mezaciruli, and with no changes in Zante. The concentrations of suspended solids were reduced on average by 62% at the subsurface flow wetland and by 11% at the surface flow constructed wetland in Mezaciruli, and by 8% in Zante. The median value for biochemical oxygen demand and chemical oxygen demand concentrations decreased by 91% and 83%, respectively. Based on the efficiency of constructed wetlands observed during this study at the monitoring sites, the methodology for calculations of the dimensions of constructed wetlands has been approbated and a calculation algorithm model for dimensions has been developed. The aim of the study Based on the empirical observations at the study sites, to approbate the technical solutions and develop dimensioning methodology of constructed wetlands in Latvia in order to reduce water pollution caused by economic activities. Research objectives: 1. To evaluate the possibilities of application of different design constructed wetlands in Latvia according to origin, composition and volume of various wastewaters. 2. To determine and analyse the reduction of pollutants including nitrogen and phosphorus compounds, suspended solids, biochemical and chemical oxygen demand after wastewater treatment in constructed wetland. 3. To evaluate the efficiency of pollutant reduction in two different types of constructed wetlands considering the most significant geographical and physical influencing factors 4. To develop and apply a calculation methodology and tool for the constructed wetlands to improve the quality of different types, volume and content of wastewater. Research hypotheses: Properly designed and dimensioned constructed wetlands improve water quality by reducing the concentrations of one or several pollutants in the water.