Emerging substances: Towards an absolute barrier (ESTAB)

Water ManagementCivil Engineering and Geoscience

Organic micropollutant removal during river bank filtration

This study investigated the factors influencing the main removal mechanisms (adsorption and biodegradation) for organic micropollutant (OMP) removal during river bank filtration (RBF) and the possibility of developing a predictive model of this process for OMP removal during RBF. Chapter 2 analysed the sorption and biodegradation behaviour of 14 OMPs in soil columns filled with technical sand (representative of the first meter of oxic conditions in RBF systems. Breakthrough curves were modelled, based on the advection-dispersion equation, to differentiate between OMP sorption and biodegradation. Retardation factors (indicators for OMP sorption) for most compounds were close to 1, indicating little sorption of these compounds and thus the mobile behaviour of these compounds during passage in soils. The influence of active and inactive biomass (bio-sorption), sand grains and the water matrix on OMP sorption was found to be negligible under the conditions investigated in this chapter. Although trends were observed between charge or hydrophobicity of charged OMPs and their biodegradation rates, a statistically significant linear relationship for the complete OMP mixture could not be obtained using these physico-chemical properties. However, a statistically significant relationship was obtained between OMP biodegradation rates and the functional groups present in the molecular structure of the OMPs. The presence of ethers and carbonyl groups increased biodegradability, while the presence of amines, ring structures, aliphatic ethers and sulphur decreased biodegradability. Chapter 3 examined relationships between functional groups present in the molecular structure of a mixture of 29 OMPs (of which 11 were the same as in Chapter 2) and their biodegradation rates obtained from lab-scale soil columns and constructed a multi-linear regression model for biodegradation rate prediction based on this. This model was then validated with field data. In contrast to Chapter 2, where technical sand was used to fill the columns, lab-scale columns here were filled with soil from an operational RBF site. A statistically significant relationship was found between OMP biodegradation rate and the functional groups present in the molecular structures of the OMPs. OMP biodegradation rate increased in the presence of carboxylic acids, hydroxyl groups, and carbonyl groups, but decreased in the presence of ethers, halogens, aliphatic ethers, methyl groups and ring structures in the molecular structure of the OMPs. Differences between the predictive models obtained in Chapter 2 and 3 could be explained by the different soil types and water qualities used (Schie Canal water and technical sand in Chapter 2, Lek River water and soil from an operational RBF site in Chapter 3). The predictive model obtained from the lab-scale soil column experiment in Chapter 3 gave a good indication of biodegradability for approximately 70% of the OMPs monitored in the field (80% excluding the glymes). The model was found to be less reliable for the more persistent OMPs (OMPs with predicted biodegradation rates lower or around the standard error = 0.77 d-1) and OMPs containing amide or amine groups. These OMPs should be carefully monitored in the field, to determine their removal during RBF. Water quality was reported to be an important factor in OMP removal during soil passage, however it is unclear if this is the only important factor and therefore Chapter 4 explored the effect of soil type on OMP removal. Sorption and biodegradation behaviour of 20 OMPs was investigated in lab-scale columns filled with two different soil types and fed with the same water quality - the columns were simulating RBF under oxic conditions. Differences in retardation factors and OMP biodegradation rates were statistically not significant between the two soil types, although these soil types were characterized by a different cationic exchange capacity, organic matter and sand/silt/clay content. This result was supported by the microbial community composition (richness, evenness) of the two soils that became more similar during the course of the experiments as a result of feeding both columns with the same water quality. This indicates that microbial community composition and thereby OMP removal in soils is primarily determined by the aqueous phase (organic matter quantity and quality, nutrients) rather than the soil phase. These results imply that different RBF sites located along the same river may show similar OMP removal (in case of similar water quality and residence time). Chapter 5 investigated the effect of the water quality in more detail, and more precisely the effect of different organic carbon fractions (hydrophilic, hydrophobic, transphilic and the complete river water organic carbon) obtained from river water on the OMP biodegradation rate. Additionally, the effect of short-term OMP and DOC shock-loads (e.g. quadrupling the OMP concentrations and doubling the DOC concentration) on OMP biodegradation rates was investigated to assess the resilience of RBF systems to, for example, climate change. The results imply that – in contrast to what is observed for soil systems operating on wastewater effluent - OMP biodegradation rates during RBF are not affected by the type of organic carbon fraction (obtained from river water) fed to the soil column, in case of stable operation. No effect of a short-term DOC shock-load on OMP biodegradation rates was observed, for none of the different organic carbon fractions dosed. This means that the RBF site investigated in this chapter is resilient towards transient higher DOC concentrations in the river water (e.g. following a decrease in river discharge due to seasonal effects). However, a temporary OMP shock-load increased OMP biodegradation rates for the river water organic matter and hydrophilic organic carbon fractions. These increased biodegradation rates could not be explained by any of the parameters investigated in this chapter (ATP, DOC removal, SUVA, richness/evenness of the soil microbial population or OMP category (hydrophobicity/charge). The effect of redox condition on OMP biodegradation rate as well adaptive behaviour of a mixture of 15 OMPs (largely similar to the OMP mixtures used in Chapter 3, 4, and 5) in laboratory-scale soil columns fed with river water was analysed in Chapter 6. Dimethoate, diuron, and metoprolol showed redox dependent removal behaviour with degradation rates larger for the oxic zone compared to the suboxic/anoxic zone. OMPs that showed persistent behaviour in the oxic zone (atrazine, carbamazepine, hydrochlorothiazide and simazine) were also not removed under more reduced conditions. Adaptive behaviour was observed for five OMPs: dimethoate, chloridazon, lincomycin, sulfamethoxazole and phenazone. Newly developed, or existing, RBF sites exposed to these OMPs for the first time may require up to 9 months following start-up to reach full removal capacity. For some chemicals, such as dimethoate, even longer start-up times could be required since full removal capacity was not reached in our tests even after 15 months. The adaptation time observed for some OMPs could not be explained by their physico-chemcial properties (hydrophobicity, charge, molecular weight) or functional groups. Finally, adaptive behaviour of the biomass towards OMPs was found to be an important factor that should be incorporated in predictive models for OMP removal during RBF. Chapter 7 presents the conclusions, implications for the practical application and recommendations for future research.Water ManagementCivil Engineering and Geoscience

Performance assessment of different pre-treatment techniques for the advanced oxiation process

Dunea Duin en Water provides drinking water for 1.2 million people in de western part of the province Zuid-Holland. As a source, for their drinking water production, surface water from the river Meuse is used. Organic micro pollutants (OMPs), although in extremely low concentrations, have occasionally been detected in the river Meuse. Obviously, the presence of OMPs in drinking water is very undesirable. The effect of OMPs on human health, when ingested for a prolonged period of time or as a mixture of compounds, is still unknown. Moreover, the increased media attention for OMPs could lead to a loss of consumers trust in drinking water companies as safe and reliable drinking water producers. As a result, customers might tend to use bottled water instead of tap water which is undesirable from a environmental point of view.Sanitary EngineeringWatermanagementCivil Engineering and Geoscience

Drinking water treatment technologies in Europe: State of the art - vulnerabilities - research needs

Eureau is the European Federation of National Associations of Water and Wastewater Services. At the request of Eureau Commission 1, dealing with drinking water, a survey was made focusing on raw drinking water sources and drinking water treatment technologies applied in Europe. Raw water sources concerned groundwater, surface water, surface water with artificial recharge and river bank filtration. Treatment schemes concerned no treatment, conventional treatment, advanced treatment and conventional plus advanced treatment. The response covered 73% of the population to which drinking water is supplied by the utilities joint in Eureau. Groundwater and surface water are the major raw water sources (>90%). In total, 59% of the drinking water supply concerns nottreated drinking water or drinking water treated with only conventional technologies, while 12% of the drinking water is not disinfected. Vulnerabilities of the European drinking water supply are the contamination of raw water sources with emerging substances, the absence of disinfection and the potential formation of disinfection by-products. Based on this, research needs are the development of quantitative structure activity relationships (QSARs) to better understand and predict the removal rates of treatment technologies for emerging contaminants, the introduction of Water Safety Plans to prevent hygienic contamination of drinking water, and the optimization of disinfection processes and strategies.Water ManagementCivil Engineering and Geoscience

Regenwater als bron voor drinkwater in Nederland: een haalbare kaart?

Het idee om van regenwater drinkwater te maken wordt door steeds meer mensen omarmd. Is regenwater schoon, hoeveel neerslag valt er eigenlijk, en wat zijn de gevolgen, voor zowel drinkwaterbedrijven als huishoudens van het gebruik van regenwater om er drinkwater van te maken? Uit literatuuronderzoek blijkt dat er via daken minder neerslag kan worden opgevangen dan veel mensen denken, dat er toch wel verontreinigingen in kunnen voorkomen en dat het heel lastig wordt om de veiligheid te garanderen als hier drinkwater uit gemaakt wordt.Sanitary Engineerin

Transformation of organic micropollutants during river bank filtration: Laboratory versus field data

This paper investigates the degradation behavior of 14 organic micropoliutants (OMPs), selected for their different physico-chemical properties (e.g., molecular weight, hydrophobicity and charge). In soil columns simulating the conditions prevailing in the first meter of river bank filtration (RBF) media. The results from the column system are compared to RBF field data obtained from the Vitens drinking water company in The Netherlands. The study explores the role of sorption media (sand filled columns and polyethylene tubes) as carrier material for the biomass. Polyethylene tubes with the same specific surface area as sand in the columns, were operated under similar conditions to compare OMP removal in the two systems. Both the column and field data indicate that negatively charged OMPs with Log D ranging from 0.65 to 1.95, positively charged OMPs with Log D ranging from -0.59 t o 0.21 and neutral OMPs with Log D (-1.9 t o 1.12) were more susceptible to biodegradation. The compounds that persisted (carbamazepine, atrazine, phenytoin, lincomycin) were positively charged with lower Log D (-1.33) or neutral with higher Log D (1.56 t o 2.64). Hydrochlorothiazide showed poor biodegradabiiity despite being neutral and having a lower log D (-0.71); it is an exception to the above behavior for reasons that have not yet been identified. A comparison of OMP removal in a biologically active polyethylene tube with a biologically active column showed that the biomass established in either systems removed the same OMPs and to similar extent for a majority of the OMPs. This finding supports the use of polyethylene tubes as a simple, cheap and quick method for investigating the trends in OMP removal in RBF.Water ManagementCivil Engineering and Geoscience

Rainwater Harvesting for Drinking Water Production: A Sustainable and Cost-Effective Solution in The Netherlands?

An increasing number of people want to reduce their environmental footprint by using harvested rainwater as a source for drinking water. Moreover, implementing rainwater harvesting (RWH) enables protection against damage caused by increasing precipitation frequency and intensity, which is predicted for Western Europe. In this study, literature data on rainwater quality were reviewed, and based on Dutch climatological data the usable quantity of rainwater in the Netherlands was calculated. For two specific cases, (1) a densely populated city district and (2) a single house in a rural area, the total costs of ownership (TCO) for decentralized drinking water supply from harvested rainwater was calculated, and a life cycle assessment (LCA) was made. For the single house it was found that costs were very high (€60-€110/m 3 ), and the environmental impact would not decrease. For the city district, costs would be comparable to the present costs of centralized drinking water production and supply, but the environmental benefit is negligible (≤1‰). Furthermore, it was found that the amount of rainwater that can be harvested in the city district only covers about 50% of the demand. It was concluded that the application of rainwater harvesting for drinking water production in the Netherlands is not economically feasible. Sanitary Engineerin