Globally, drinking water sources are polluted with poly- and perfluoroalkyl substances (PFAS). The toxicity and persistent properties of these industrial chemicals raised concerns about environmental and public health. As a result, drinking water companies are removing PFAS from drinking water using separation technologies. Anion exchange and nanofiltration membranes have been proven to be effective drinking water treatment methods for the removal of PFAS. However, these drinking water technologies produce large volumes of PFAS-containing waste streams, which poses new challenges for the drinking water industry. To prevent toxic PFAS from re-entering the environment, these waste streams must be treated. This can be done by PFAS destruction, however, due to the large volumes of the waste streams, this is very expensive and energy-intensive. Therefore, concentrating the drinking water waste streams before destruction is desired. This research examined existing PFAS-concentration technologies and compared their PFAS removal efficiency, volume reduction, and cost-effectiveness in concentrating the PFAS waste streams produced during drinking water treatment. These waste streams include the concentrate of nanofiltration and the brine from anion exchange. The analysed concentration technologies are foam fractionation, adsorption of PFAS onto DEXSORB+ and all-silica BEA zeolites, and nanofiltration. Foam fractionation removes PFAS from the waste stream by injecting air bubbles. Two laboratory setups were made for the injection mechanism of the air bubbles. First, by passing pressurized air through an air stone, and second, by adding pressurized water (i.e. white water) to the waste stream. The adsorbents were tested in the laboratory by conducting equilibrium batch experiments with different adsorbent dosages. The laboratory experiments were performed on both drinking water waste streams. The performance of concentrating the anion exchange brine solution with nanofiltration membranes was evaluated with the use of IMS Design models.

Surface water tracing experiments help to identify the flow paths of in-stream mass transport. This provides useful information for developing mitigation measures for contamination, and thereby for solving environmental problems. Salts, fluorescent dyes and isotopes are commonly used tracer substances. However, it is well known these tracers have several drawbacks, including, for example, a finite number of unique tracers with similar transport properties, which limits the possibility to repeat an experiment due to system memory. Additionally, it is difficult to perform multi-tracer experiments, due to a lack of specificity. Lastly, the detection limit becomes an important constraint when using a tracer in larger water bodies or over longer travel distances, due to the vast dilution. The recently developed silica encapsulated synthetic DNA nanoparticle with a superparamagnetic core (SiDNAMag), can theoretically overcome the aforementioned limitations of existing tracers. SiDNAMag particles can be recovered from a sample by magnetic separation. This limits the influence of water quality on the qPCR analysis and provides an easy method for up-concentration of samples. However, with the presence of natural colloids, particulate matter, and river bed sediments, SiDNAMag particles are likely to undergo complex interaction processes in addition to dispersion and advection. Moreover, little is known about the possible SiDNAMag tracer sinks during transport. The focus of this work is to identify the transport behaviour of the SiDNAMag tracer in terms of breakthrough curves (BTC) and hydrodynamic dispersion as well as to study the interactions with the natural environment, specifically water quality and sediments. This was investigated by comparing SiDNAMag particles to NaCl, a widely used solute tracer, and silica microparticles. To do so, open channel injection experiments using SiDNAMag particles were performed in the laboratory in different river water types and with the presence of sediments at the channel bottom. The resulting BTCs were interpreted with a 1D advection and dispersion model with transient storage (OTIS), to determine the hydrodynamic dispersion coefficient. Mass recovery was calculated by integrating the BTC. The results show that SiDNAMag particles have a reproducible but different transport behaviour than NaCl solutes. The SiDNAMag particles arrive, peak and return to background concentrations earlier than NaCl solutes. Furthermore, the interpretation of the data with a 1D advection and dispersionmodel showed that the dispersion coefficient for SiDNAMag was lower (0.34E-3m2/s – 0.88E-3m2/s) than that of NaCl (0.81E-3m2/s – 2.31E-3m2/s). Literature on solutes and colloids in the aquatic environment supports the possible difference in the transport behaviour of solutes and colloids. No relation between the transport behaviour and presence of bottom-sediments was found. The mass recoveries for SiDNAMag experiments were between 36% and 131%, which could be partly explained by the bottom-sediments which detained between 0.16% and 16.94% of the SiDNAMag mass during the experiments. No relationship was found between the three natural water types and the observed mass losses. Additionally, the silica microparticle injection experiment showed the same BTC characteristics for silica microparticles as SiDNAMag though without mass loss, indicating mass loss occurred in the lab analysis. Due to the uncertainties in the lab analysis, no accuratemass recovery for the SiDNAMag tracer could be calculated. Furthermore, the observed scatter in the measurement data could be explained by the uncertainties in lab analysis as well as possible differences in transport behaviour of solutes and colloids. In conclusion, the results of the laboratory experiments with the SiDNAMag particle show that it is a promising hydrological tracer in surface water tracing experiments to trace colloids. Thereby it can be a valuable tool to gain information on the movement ofmicroparticles, like microplastics and pathogens, in the natural environment. The next step towards achieving this goal is performing a field experiment, for which upscaling of the SiDNAMag tracer production is required.

This research explores the potential effect of Subsurface Iron removal (SIR) on the removal of organic micropollutants (OMPs). The presence of OMPs and their transformation products in the water environments globally, have raised concerns due to the potential environmental and human health risks they are posing. Recent technologies often fail to remove OMPs completely or require high energy levels and costs. Previous findings by Vitens water company have indicated that SIR application resulted in the attenuation of certain OMPs. Therefore, the effect of SIR as an alternative, cost-effective removal method of OMPs was investigated. A continuous flow column experiment was conducted in order to simulate the processes which take place under oxic conditions at SIR for the removal of 5 targeted OMPs (bentazone, metformin, caffeine, carbamazepine and atrazine). Two columns were filled with iron oxides (FeOx) coated sand and manganese oxides (MnOx) coated sand respectively, in order to simulate the two precipitation zones created in the subsurface. The aim of the study was to investigate the removal efficiencies of the selected OMPs in both columns in order to understand if the SIR environment is favourable for the removal of OMPs. Results indicated that for most compounds there was removal observed after 65 pore volumes of continuous flow. Metformin was hardly removed (<10% removal rate) in both materials. A higher removal efficiency was observed at the FeOx column for bentazone (65%), caffeine (54%) and carbamazepine (29%), while atrazine was the only compound which had a greater affinity for MnOx, with a removal rate of 87%. These findings suggest that SIR has a potential on the removal of certain OMPs. It is suggested that during SIR the OMPs existing in the subsurface, pass through the two precipitation zones and undergo removal processes within both zones. However, based on their respective affinities to each of these zones, their removal extents vary accordingly. Ultimately, the water extracted from the undergoing SIR exhibits a reduced concentration of OMPs, which is a result of the combined removal mechanisms operating within both precipitation zones.

A novel activated carbon-iron composite material has been developed as an adsorbent for water treatment. Due to its activated carbon (AC) content, the material could be used to remove pollutants such as organic micropollutants (OMP). Fast AC bed exhaustion makes adsorption a cost-intensive solution. Regeneration of AC is done off-site and requires transport and high energy consumption for heat treatment. Due to the iron and graphite content of the novel adsorbent, catalytic regeneration could allow for in-situ regeneration. This property would present a major advantage over common AC. Regeneration could potentially be realized by applying an electric current across an exhausted bed of this adsorbent. Such a setup is called a “particle electrode”, where electrically conductive particles are placed between an anode and cathode. Upon application of an electric current across an exhausted bed of adsorbent, two mechanisms are hypothesized to result in the restoration of adsorption capacity: (1) desorption and (2) degradation of the pollutant. This study evaluated the adsorption capacity and rate constants for 17 OMP on two different versions of this partly graphitized carbon (with and without iron content) as an alternative to conventional AC for drinking water treatment. By batch adsorption experiments, the adsorption properties of this novel carbon were investigated. Oxidation of zero-valent iron on the iron containing version of carbon resulted in yellowish water. This version was therefore considered not appropriate for general drinking water treatment, and the remaining experiments were conducted only with the version without iron. The material adsorbed a great variety of OMP, including different charges and hydrophobicity. Its graphite content probably promoted the adsorption of neutral compounds. A negatively charged layer formed by NOM accumulation on adsorbent surfaces assisted positively charged compounds adsorption. Investigation of regeneration efficiency was conducted with alternative cycles of adsorption and regeneration with high OMP concentration solutions. This material could be electrochemically regenerated. Reverse adsorption could be achieved on neutral, positively and negatively charged compounds in multiple cycles of regeneration. Electrodesorption is probably the major mechanism responsible for regeneration. Permanent and partial loss of adsorption capacity was recorded, probably due to poor NOM desorption and change in surface chemistry. Regeneration efficiency was not positively correlated with elevating applied current. Increasing cell voltage is not always beneficial to the electrochemical process. Prolonged treatment time improved the regeneration efficiency, but the marginal benefit was considered to be uneconomical. Poor NOM regeneration was responsible and more concerning for the loss of adsorption capacity. Long-chain PFAS regeneration was achieved over cycles of regeneration. Short-chain PFAS regeneration was unfavorable due to blockage of micropores.

Over the last decade, a wide range of organic micropollutants (OMP) has been regularly detected in surface water, groundwater and wastewater treatment plant (WWTP) effluent. These OMPs consist mainly of synthetic organic compounds (SOC) such as pharmaceuticals and pesticides. Although their concentrations in water bodies are usually low, they can cause potential risks to disturbance and affect human as well as environmental health, which has attracted the attention of governments and institutions to search for reliable and simple methods with low cost to remove them. Powdered activated carbon (PAC) adsorption is considered to be an efficient, convenient and cheap method to remove OMPs with low concentrations. However, the adsorption capacity of PAC is not fully used due to a short contact time in the traditional adsorption treatment of dosing PAC into water directly. Therefore, some processes such as the Actiflo Carb or PAC membrane reactors, recirculate PAC in order to increase the contact time. Predicting the performance of older, recirculated PAC is difficult. The objective of this project was to simulate performance of aged PAC using a simple lab-scale experiment. Three different water matrices (tap water, WWTP effluent and diluted WWTP effluent) were used to make the OMPs solutions with 18 selected OMPs of 10 ug/L. PAC was added into the OMPs solutions to make two concentrations of PAC suspension (0.5 g/L and 0.25 g/L). Samples were collected at fixed time intervals. The breakthrough behavior of selected OMPs for aged PAC was then investigated and determined by analyzing the OMPs concentration, UV254 and DOC of samples. The setup was successfully used to record breakthrough curves of 5 different OMPs (Gabapentin, Sulfadimethoxine, Sulfamethoxazole, Metformin and Clofibric acid) and UV254 in 3 different water matrices. Gabapentin was the least adsorbable in tap water and the breakthrough occurred after 10 hours, while in WWTP effluent, Sulfadimethoxine was the least adsorbable OMP with the complete breakthrough time of 14 hours. Propranolol was the most adsorbable compound in both tap water and WWTP effluent. The breakthrough of UV254 was observed later in tap water and WWTP effluent, about 24 hours and 22 hours, respectively. However, parameter DOC can not be used to predicate the breakthrough of OMPs accurately. Model fitting based on the experimental adsorption data was also included.