Epsilon Archive for Student Projects

Abstract

In the past decade, water reuse and nutrient recycling of wastewater has gained more attention as sustainable water cycle management solutions, driven by the increasingly noticeable resource restrictions of the 21st century. One of these possible solutions is source separated treatment of latrine or blackwater for nutrient recovery. However, one major issue of wastewater recycling are micropollutants released into the environment, which can affect ecosystems and human health. This study investigated the fate and removal efficiency of two emerging groups of micropollutants, pharmaceutically active compounds (PhACs) and perfluoroalkyl substances (PFASs), in two source separating wastewater treatments. The first treatment investigated was laboratory-based anaerobic degradation of latrine under mesophilic (37 °C) and thermophilic (52 °C) conditions. The second was a full-scale blackwater treatment, including wet composting and sanitation with urea. Occurrences and concentrations in different steps of the treatments of 29 PhACs and 26 PFASs in the liquid and solid phase of latrine and blackwater were determined.
The results showed high environmental concentrations of PhACs in latrine and blackwater with values up to hundred µg L-1 and µg g-1 dry weight (d.w.) in the liquid and solid phase, respectively. The concentrations measured in latrine and blackwater were higher than those found in conventional wastewater effluents, due to lower dilution. The average removal rates of PhACs were 45 % under mesophilic and 31 % under thermophilic conditions of latrine and a slightly higher removal rate was determined in blackwater, 49 %. Some compounds showed close to complete removal, such as most antibiotics (up to 100 %, n=4). The majority of PFASs were not detected and the ones detected showed low environmental concentrations in the range of low ng L-1 and ng g-1 d.w. in the liquid and solid phase, respectively. In the removal analysis, increased concentrations have been found for PFASs in mesophilic treatment (in average 24 %), possibly due to degradation of PFAS precursors, and a low average removal rate in the thermophilic experiment (in average 4 %). No evaluation could be made about the fate of PFASs in blackwater, due to no significant concentrations measured. It is concluded that latrine and blackwater are no major sources of PFASs and therefore do not represent a major threat to the environment.
The removal efficiency of the two source separated treatments revealed moderate to low removal rates for PhACs and PFASs. But since the occurrence of PFASs in latrine and blackwater is low, their removal might not have to be considered in the source separated wastewater such as latrine and blackwater. Regarding the PhACs additional advance treatments might be necessary or efforts to find a better suitable treatment technique need to be made, as the treated end-product of blackwater is reused as fertilizer in agricultural fields.