The access to clean water is one of the prerequisites for a modern, industrialized society. The amount of water withdrawn for human activities has risen exponentially during the last 100 years. This rise in water use is accompanied by the production of vast quantities of contaminated water. These wastewaters may be contaminated by substances ranging from heavy metals and organic compounds to nutrients like nitrogen and phosphorous. The aggregate effect of combinations of water contaminants can be difficult to predict as different contaminant substances may interact, leading to additive, synergistic or antagonistic toxic effects in a receiving aquatic ecosystem. With increasing water quality legislation, the pressure to characterize and potentially treat contaminated waters increases. Suitable effect-based assessment methods may greatly reduce the costs of both the wastewater characterization process and the water treatment evaluation. The overall aim of this thesis was to show how a combination of ecotoxicity bioassays may be employed in water treatment method development for initial characterization, assessment of treatment requirements and finally treatment evaluation. The wastewaters characterized originated from different activities such as waste management, metal surfacing and explosives destruction. To fully assess the hazard of the waters sampled, a holistic approach using a combination of chemical tests and bioassays was taken. A combination of acute and chronic assays was used to determine mode-of-action effects and apical endpoints in the aquatic environment. The basic battery consisted of the acute Vibrio fischeri test, the chronic algae test using Pseudokirchneriella subcapitata and either the planktonic crustacean Daphnia magna (for aqueous samples) or the meiobenthic crustacean Heterocypris incongruens (for whole-sediment/soil samples).  In addition to the basic test battery, the mode-of-action Salmonella typhimurium test was used to assess genotoxic effects. Results from the water hazard characterization show that ecotoxicological tests contribute to the evaluation of treatment methods for complex wastewaters by assessing the aggregate biological effect of water treatment. The tests may be used as a screening method to indicate where further treatment may be required, even when chemical measurements show a satisfactory reduction of known contaminants. The toxic effect exerted by the assessed waters did not always correlate with measured levels of contaminants or the chemical measures of bioavailability, e.g. leached fraction. The water treatment evaluation showed that the industrial by-product pine bark is an effective adsorbent for capturing metal contaminants from landfill leachates and stormwater. The pine bark column filter had higher zinc removal efficiency than the polonite filter and the combination filter column with pine bark/polonite. In conclusion, a pine bark filter is a suitable alternative to activated carbon for small-scale, decentralized treatment of wastewaters. Furthermore, the ecotoxicity tests were able to detect effects of unknown contaminants and provided unique characterization data, which complemented the information provided by the chemical analyses. / CLEAN / BIOREX

Traditional water monitoring encounter limitations due to the large number of contaminants present in our waters possible giving raise to mixture effects. This thesis aimed to investigate how the emerging omics approaches (transcriptomics, proteomics and metabolomics) can be used as an effect-based monitoring approach to assess and predict adverse effects in the freshwater environment. Moreover, this thesis analysed challenges and barrier with omics. A systematic literature search was conducted using Scopus and Web of Science to find case-studies using omics in field studies and reviews regarding challenges and barriers. The results in this thesis suggest that the use of fish species (either collected in the wild or in situ set-ups), transcriptomics and investigations of WWTP recipient was the most common way to apply omics. In order to interpret omics-data multiple studies conducted chemical monitoring in conjunction, investigated additional traditional biomarkers and/or used omics to identify altered biological or functional pathways that possible could lead to adverse effects at higher levels. According to the challenges and barriers identified in this thesis, the future of omics in environmental monitoring rely on the possibility to characterise and quantify natural variability, define appropriate critical effect sizes (i.e. thresholds of critical effects) and define baseline data. Moreover, it is necessary to develop frameworks and standardisations for omics-approaches (e.g. study-designs) to promote the interpretation of the results. Future research is also needed to develop and increase the understanding of how the proteomics and metabolomics can be applied. By improving the use of omics a more holistic water monitoring can be achieved including screenings for biological responses and the ability to detect early warnings which will enhance the prioritisation and site management of polluted water bodies, including those with limited prior knowledge regarding potential contaminants.

Organic pollutants such as carbon and nitrogen are effectively removed through nature-based solutions, particularly treatment wetlands, research is increasingly focusing on the behavior of and effects to the environment caused by micropollutants. The release of these anthropogenic chemicals into the environment creates a complex mixture of chemicals that can cause quantifiable adverse biological effects. While resent studies indicate the ability of treatment wetlands to remove micropollutants, major questions regarding the removal efficacy of biological effects, the most efficient design aspects (aerated vs. non-aerated; planted vs. non-planted; single-stage vs. two-stage), the resiliency of a treatment wetland, and the potential for optimization are still unsolved. This dissertation investigated these topics by combining cutting-edge methods from engineering, analytical chemistry, and environmental toxicology. The existing knowledge gaps were addressed and the understanding of treatment technologies as well as the potential of treatment technologies to reduce micropollutants and biological effects was improved. In this research, seven treatment wetlands and a municipal wastewater treatment plant were examined over the course of an entire year, to identify the most effective design of the treatment plants in terms of biological effect removal. Intensified wetlands showed higher annual removal efficacy (41 - >99%) than the non-aerated (conventional) horizontal flow wetland (24 – 78%) for investigated micropollutants and biological effects. Removal efficacy for carbamazepine, which is considered to be resistant to aerobic biodegradation, was observed to be higher in the non-aerated horizontal flow treatment wetland than in the intensified wetlands (24 %, 0 – 3 %, respectively). Benzotriazole, diclofenac, activation of aryl hydrocarbon receptor, activation of peroxisome proliferator-activated receptor gamma, and oxidative stress response were removed to a greater extend through the intensified treatment wetlands than by the municipal wastewater treatment plant. Also, for the first time, the effluent qualities of the treatment wetlands were compared with recently proposed effect-based trigger (EBT) values for surface water. The effluent bioanalytical equivalent concentrations (BEQs) for all intensified treatment wetlands and the municipal wastewater treatment plant were close to or even below the surface water EBTs, except for estrogenicity. This indicates the great benefit of using nature-based solutions for water treatment because the treated effluent would not impose a negative ecological effect on a receiving water. Aeration and therefore an elevated oxidation reduction potential was identified as a key environmental condition for increased removal of micropollutants and biological effects. In particular, the two-stage system (aerated vertical flow constructed wetland followed by an unsaturated vertical flow sand filter) achieved the highest removal efficacies for conventional parameters (66 to >99%), micropollutants (94 – 99%, except carbamazepine: 3%) and biological effects (91 – 99%). But also, the less cost-intensive one-stage treatment wetlands (aerated horizontal flow and aerated vertical flow) achieved high quality effluents for the observed parameters. With different aeration strategies, aerobic and anaerobic zones were created in an aerated horizontal flow treatment wetland. The sharp increase of the oxidation reduction potential resulted in a higher mass removal for the moderately biodegradable micropollutants benzotriazole (> 91 %; test system with 50% aeration), and diclofenac (81 %; test system with 50% aeration). But the removal efficacy of biological effects decreased with the enlargement of the non-aerated zone in the treatment wetland. Nevertheless, the combination of aerated and non-aerated zones can reduce moderate micropollutants. The advantage of high removal efficacy for micropollutants and biological effects through aeration comes with the susceptibility to technical disturbances such as a power failure or an air pump failure. A simulated aeration interruption of six days resulted in a poorer water quality (comparable to that of a conventional non-aerated horizontal flow treatment wetland). After switching the aeration back on, the investigated system recovered within a few days for most of the conventional wastewater parameters (8 – 22 d) and micropollutants (3 – 22 d). Results showed that removal of biological effects are negatively affected for a longer period of time (>22 d) than what was indicated by classical parameters or micropollutants alone. These results mark the importance of the use of bioassays for future water quality assessment. With respect to the removal of biological effects, three treatment wetland designs can be recommended: the two-stage system (aerated vertical flow treatment wetland followed by an unsaturated vertical flow sand filter); and the less cost-intensive one stage systems: aerated horizontal flow treatment wetland and aerated vertical flow treatment wetland. The aerated horizontal flow treatment wetland is also resistant to an aeration interruption of a couple of days and recovers, even if it takes longer (indicated by the in vitro bioassays) than indicated through conventional wastewater parameters and micropollutants. The complementary approach of this dissertation contributes to the further understanding of treatment wetlands. Furthermore, the research work provides new insights into removal efficacy of biological effects under various treatment wetland design aspects. This dissertation is intended to help generate and better understand a new generation of treatment technologies.

The performance of an aerated horizontal subsurface flow treatment wetland was investigated before, during and after a simulated aeration failure. Conventional wastewater parameters (e.g., carbonaceous biological oxygen demand, total nitrogen, and Escherichia coli) as well as selected micropollutants (caffeine, ibuprofen, naproxen, benzotriazole, diclofenac, acesulfame, and carbamazepine) were investigated. Furthermore, the removal of biological effects was investigated using in vitro bioassays. The six bioassays selected covered environmentally relevant endpoints (indicative of activation of aryl hydrocarbon receptor, AhR; binding to the peroxisome proliferator-activated receptor gamma, PPARγ; activation of estrogen receptor alpha, ERα; activation of glucocorticoid receptor, GR; oxidative stress response, AREc32; combined algae test, CAT). During the aeration interruption phase, the water quality deteriorated to a degree comparable to that of a conventional (non-aerated) horizontal subsurface flow wetland. After the end of the aeration interruption, the analytical and biological parameters investigated recovered at different time periods until their initial treatment performance. Treatment efficacy for conventional parameters was recovered within a few days, but no complete recovery of treatment efficacy could be observed for bioassays AhR, AREc32 and CAT in the 21 days following re-start of the aeration system. Furthermore, the removal efficacy along the flow path for most of the chemicals and bioassays recovered as it was observed in the baseline phase. Only for the activation of AhR and AREc32 there was a shift of the internal treatment profile from 12.5% to 25% (AhR) and 50% (AREc32) of the fractional length.