RESUMO
Microplastics (MPs) research still at the budding stage in Estonia. A theoretical model build on substance flow analysis principles was developed. The goal of this study is to broaden understanding of MPs-types in wastewater and their contribution from known sources, quantify their presence based on model prediction and in-situ measurements. The authors estimate MPs from laundry wash (LW) and personal care products (PCPs)) in wastewater in Estonia. We found out that total estimated MPs load per capita from PCPs and LW in Estonia were between 4.25 - 12 tons/year, 3.52 - 11.24 tons / year respectively, and estimated load ended up in wastewater were between 700 - 30,000 kg/yr. and 2 - 1500 kg/yr. in WWTPs influent and effluent stream respectively. Finally. We conducted a comparison between estimated MPs load and on-site sample analysis and observed a medium-high level of MPs being discharged into the environment annually. During quantification and chemical characterization using µFTIR analysis, we found that microfibers with a length of 0.2-0.6 mm accounted for over 75% of the total MPs load in the effluent samples collected from four coastal WWTPs in Estonia. The estimation avails us broader overview about the theoretical MPs load in wastewater and gain valuable insight into developing process methods that prevent MPs accumulation in sewage sludge for safe application in agriculture.
RESUMO
Chemical pollution poses a threat to the aquatic environment and to human health. Wastewater treatment plants are the last defensive line between the aquatic environment and emissions of pollutants. This study focuses on identification of most relevant hazardous substances in Estonian municipal wastewater and their fate in the treatment process. During this study, seasonal wastewater and sewage sludge samples were collected from nine municipal wastewater treatment plants and analyzed for 282 hazardous substances, including EU (n = 45) and Estonian (n = 31) priority substances. Results of this study show that several substances that are subject to international restrictions (e.g. Stockholm Convention) are still present in untreated sewage. Wastewater treatment systems that had a greater level of complexity (TEC >5) were more successful in removing hazardous substances. Statistical analyses showed that removal efficiency of organic hazardous substances had significant (p-value <0.05) linear correlation with removal efficiencies of chemical oxygen demand (COD) and total suspended solids (TSS), but a monotonic relationship with operators' competency. This study showed that operators' competency had a strong influence on the stability of the wastewater treatment efficiency and removal of organic hazardous substances.
