Water quality monitoring of Madlabekken constructed wetlands
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As urbanized areas grow in scale, the negative impact on urban surface runoff increases. This fact creates the urge to take proper measures to control and prevent the downside effects of urbanization on natural water resources. This study analyzed the water quality of Madlabekken stream and Madlabekken constructed wetland. The main focus of this work is to evaluate whether the inlet to the wetland is urban area runoff, or if it contains periodic household wastewater contributions. In addition, estimating the wetland’s efficiency is the secondary objective. Weekly samplings were collected from January to May 2018 continuously, and some grab samplings were done before this period between October to December 2017. Evaluation of water quality parameters including TSS, CODt, CODs, TP, PO4-3, TN and NH4+ at both inlet and outlet of the wetland was achieved by performing weekly analyses of water samples. The overall results showed that the quality of water is in range of urban storm runoff and in some cases much lower. The analyzed samples did not show a trace of wastewater and sewage. The highest concentrations were observed in February due to temperatures below zero which caused low levels of water in channels. Also, due to low concentrations, this constructed wetland did not show high efficiency in removing pollutants. Nevertheless, generally removal efficiency found to increase in the higher concentration of TSS and nutrients, and it was close to similar CWs removal efficiency in higher concentrations. TSS was reduced by 46%, and the reduction percentage for CODt and CODs was 22% and 6% respectively. For TP and PO4-3, in average the reduction is approx. 25% and 5% respectively. For TN and NH4+, considering the removal efficiency variation in different months, on average no reduction was found from influent to effluent. Ultimately, comparing to similarly CWs, this wetland has a lower removal efficiency.
Master's thesis in Environmental Technology