Xenobiotics in the Urban Water Cycle

Typical concentrations and quantitative mass flows of anthropogenic compounds (such as personal care compounds, bactericides, flame retardants, plasticizers, detergents, complexing agents, as well as mycotoxins) in waste water are compared to typical per person loads in the influents and effluents of waste water treatment plants. They are evaluated to assess their significance for the contamination of the aquatic environment. Usually the number of persons serviced by a waste water treatment plant (WWTP) is well known, as the design parameters of the WWTP heavily rely on the per person usage of water and the per person emissions of nutrients as well as organic carbon. It is the intention to use these basic data together with concentrations from some waste water treatment plants to make assessments on emissions from WWTPs, for which only basic design parameters are available. These data can be used for predictions of waste water contamination concerning pollutant loads and concentrations for waste water treatment plants that have not undergone extensive monitoring. The relevance of the respective pollutants for surface waters as well as sludge is demonstrated.

The focus of this chapter is on those compounds that are emitted continuously during dry weather. - No storm water issues will covered in this book chapter.

The sources and uses of xenobiotics in urban environments are very diverse, making structured approaches to source and use classification a fundamental requirement for effective pollution management. This chapter provides a general introduction to the topic of substance source and use identification, highlighting the key differences between different types of sources (e.g. processes vs. commodities; natural vs. anthropogenic etc.) and different types of uses (e.g. active vs. passive; dispersive vs. non-dispersive, etc.). Examples of relevant classification systems and their applications are also given, and the diversity of potential xenobiotic sources and uses is clearly demonstrated through the description of a series of ‘archetypes’ (i.e. model examples). The chapter concludes with an overview of useful source tracking approaches (e.g. database mining, marketing surveys, forensic approaches etc.).

In recent years, the presence of human-use compounds in the aquatic environment has been recognized as an important issue in environmental chemistry. Among them, illicit drugs have been described as a new unexpected group of water contaminants with potent psychoactive properties and unknown effects to the aquatic environment.

The presence of these drugs in water resources is of rising concern and several studies are being conducted all over the world estimating discharged levels of drugs of abuse. In this chapter, a summary of the last works studying and reporting the occurrence of illicit drugs in water resources is performed. Up to now, drugs of abuse have been already detected in wastewaters and surface waters in the USA, Italy, Germany, the UK and Spain. These drugs reach wastewater treatment plants either unaltered or in their main metabolite form. Depending on the removal efficiencies, they can persist through wastewater treatment and be detected in receiving waters, which in some cases are used for drinking water production. The presence of these compounds in raw waters and their elimination through the drinking water treatment must be considered as an issue with regard to the quality of water supplies.

The platinum group elements (PGE) belong to the rarest metals on our planet. During the last three decades three of the six PGE (platinum (Pt), palladium (Pd) and rhodium (Rh)) are found in increasing concentrations in different terrestrial and aquatic matrices. Anthropogenic sources of PGE are industrial discharges, road runoff as well as waste waters from hospitals and dental surgeries. As anthropogenic PGE are mostly emitted in elemental form, they were initially thought to be not relevant for biota. Laboratory studies, however, revealed that aquatic plants and animals are able to take up and accumulate PGE. Effect studies showed that animals exposed to PGE respond with increased levels of stress markers.

The most important factors influencing the bioavailability of PGE tend to be time, metal concentration in the medium, the chemical speciation of the metal and the presence of complexing agents. This chapter summarizes the present knowledge on the introduction of PGE into urban aquatic ecosystems and the behavior within these habitats. It draws attention to the increase of PGE contamination in different matrices, summarizes current PGE concentrations in the field, discusses the different bioavailability of Pt, Rh and Pd and evaluates the effects of PGE on aquatic organisms.

The sense of smell is our most emotional sense. Although not always being aware of it, it plays an important role in our everyday live. Scents are widely used in Personal Care Products (PCPs) such as shampoo, washing lotions or make up. They give a pleasant smell, mask unpleasant scents and may even bind consumers to a specific brand. As a result, scents are being applied more and more and in turn are being introduced in increasing volumes into the environment. Their fate and effect in the environment are to date mostly unclear. Because many organisms rely on scents as means of communication, the emerging amount of scents emitted by our civilization can cause disturbances, known as “infochemical effect”.

In this chapter, we give a short overview on the current usage and regulation of scents for Europe and the United States of America and possible risks of the introduction into the environment. For the University Medical Center Freiburg, we calculated the amount of used scents for the year 2006 from manufacturers’ information and give examples for used scents which also act as infochemicals.

The eutrophication of water resources, mainly attributed to antrophogenic activities such as sewage and agricultural runoffs, has led to a worldwide increase in the formation of cyanobacterial harmful algal blooms (Cyano-HABs). Cyano-HABs have the ability to produce and release toxic compounds, commonly known as cyanotoxins, which comprise a potent threat for human and animal health as well as negative economical impacts. This chapter presents an overview on the sources and occurrence of species of cyanobacteria and their association with the production of cyanotoxins throughout the world. The main bloom-forming cyanobacteria that have been detected include Microcystis, Cylindrospermopsis, Anabaena, Aphanizomenon, and Planktothrix. The main cyanotoxins related to these cyanobacteria are microcystins, cylindrospermopsin, anatoxin-a and saxitoxins.

The present chapter focuses on the identification of sources and fluxes of xenobiotic compounds in marine sediments to set strategies for minimizing impacts on the human life and environment. It is generally accepted that sediments constitute a sink for the more hydrophobic compounds, posing an unacceptable risk to aquatic biota, in which these compounds can bioaccumulate, and to human health through the ingestion of contaminated fish and shellfish.

Information is provided on the organic xenobiotics most frequently occurring in marine sediments, namely, polycyclic aromatic hydrocarbons (PAHs), surfactants, halogenated compounds, organotin compounds and pharmaceuticals. The development and optimization of analytical methods for the determination of those priority substances in marine sediments are discussed. Substantial improvements have been achieved in analysis performance towards optimal resolution of analytes, for example detection limits, and clean-up of environmental samples to detect low-level xenobiotics in complex mixtures such as the marine sediments.

Thus, this chapter aims at identifying the main challenges related to organic xenobiotics in marine sediments, underlying also existing gaps in legislation.

Sewage sludge contains a plethora of organic pollutants. In the present chapter, the experiences with respect to the applicability of sewage sludge as a matrix for the monitoring of persistent lipophilic contaminants released from the anthroposphere are reported and discussed. Polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organochlorine pesticides, phthalates, UV filters, biocides, synthetic fragrances, polybrominated flame retardants (BFRs) and surfactants were analyzed in stabilized sewage sludge from more than 20 sites (wastewater treatment plants, catchment area) of a monitoring network in Switzerland. The specific loads (mg or g per connected inhabitant and year) in sewage sludge were used for characterizing the emissions of the compounds. A background contamination from private households was observed for all analyzed substances. Synthetic fragrances predominantly occurred in domestic wastewater. An important additional source for PAHs, PCBs, biocides and BFRs was runoff from impervious surfaces contaminated with substances originating from atmospheric deposition or leaching from treated materials. Industrial wastewater and mainly urban catchments were responsible for further loads. The specific loads observed complied with consumption patterns of the compounds obtained from the literature.

Chlorinated organic compounds are the frequently detected xenobiotics in industrial effluents. They may enter surface water, groundwater and soil systems. Examples are presented on the level of these compounds in aquatic systems. The chapter then addresses the biological removal of these compounds by aerobicmetabolism in which the substrate is used as an energy and carbon source. However, the major part of chlorinated organic compounds is resistant to metabolic removal. Yet, some can effectively be removed through aerobic co-metabolism in bioremediation of polluted groundwater and soil and in wastewater treatment systems. In aerobic co-metabolic removal of these compounds different types of substrates can be used as primary growth-substrates such as phenol, toluene, propane, methane, ammonia and others which are extensively reviewed in this chapter. The basic features of natural and enhanced bioremediation are also outlined in the chapter. The aerobic co-metabolism is exploited mainly for bioremediation of chlorinated aliphatic compounds such as trichloroethylene (TCE) in groundwater and in some cases for chlorinated benzenes and phenols. Examples of field-, pilot- and laboratory studies are documented which deal with aerobic co-metabolic removal of chlorinated compounds.

In recognition of the growing concern regarding the photochemical transformation of pharmaceuticals in the aquatic environment, the focus of this chapter is on current knowledge on the photochemical transformation of selected pharmaceutical compounds in aquatic systems in order to reveal the key areas and perspectives of this research field. Some of the most important groups of pharmaceuticals known to occur in the environment, such as non-steroidal anti-inflammatory drugs, analgesics, antidepressants and estrogens, are discussed in this chapter. Processes considered include environmental photolysis and photochemical advanced oxidation processes (PAOPs) in homogeneous (UV/H₂O₂, Photo-Fenton and Photoelectron-Fenton) and heterogeneous (TiO₂/UV) media. The phototransformation of pharmaceuticals proceeds usually through the formation of long-lived intermediate species. Thus, we have attempted to provide an overview of the nature of principal organic intermediates, the degradation pathways followed and the evolution of the mineralization in the photochemical process considered. Major degradation pathways usually include hydroxylation, isomerization, dehalogenation, dealkylation, cyclization, decarboxylation, dimerization and ring opening (for aromatic compounds), leading to corresponding derivatives as well as carboxylic acids.

The environment is contaminated by a number of micropollutants and their degradation products, many of which still remain undetected. Nowadays, several European regulations require the inclusion of transformation products in environmental risk assessment and monitoring. In the last decade, intense efforts have been taken to recognize the identity, quantity, and toxicity of unknown transformation products. Liquid chromatography combined with mass spectrometry has become a key technique for environmental analysis, now allowing the development of screening, identification, confirmatory and quantitative methods for the trace analysis of polar compounds in complex environmental matrices. The combination of modern technologies comprising high resolution, high mass accuracy and mass fragmentation enables the identification of compounds without having the authentic standards or even the detection of unknown analytes. However, a reliable confirmation of proposed structures using NMR spectroscopy or available standards is still desirable. This chapter presents new analytical strategies to identify and quantify transformation products generated by human metabolism, microbial degradation, or other environmental breakdown processes. Various hyphenated mass spectrometric techniques used for structure elucidation, such as liquid chromatography coupled to time-of-flight mass spectrometry, quadrupole-time-of-flight and linear ion trap-Orbitrap hybrid mass spectrometry are presented on three case studies of pharmaceutical and pesticide transformation products in environmental matrices, such as wastewater and groundwater.

This chapter on urban water in large population centres like Halle/Saale and Leipzig (Germany) focuses on the source, distribution and transport behaviour of xenobiotics as indicator substances for anthropogenic impacts on urban water systems. The xenobiotics reported here are micropollutants including pharmaceuticals, personal care products (collectively known as PPCPs) and industrial chemicals, which show low concentrations in urban waters. Such chemicals can be endocrine disrupters or are otherwise eco-toxic. The concepts presented herein required a new methodology for assessing the impact of human activities on the urban water system and processes in urban watersheds. To this end, we used different approaches in relation to the hydrogeological and hydrodynamic settings of the cities of Halle and Leipzig. For the Halle urban area, a conceptual flow and transport model was developed based on interaction between the river Saale and groundwater, and mass fluxes were computed, based on water balance calculations. For Leipzig, as a first approach, we established a monitoring program that involved various urban land use types and investigated their influence on the urban water system. Multivariate statistics and integral pumping tests were applied to account for the spatially highly heterogeneous conditions and time-varying concentrations. At both sites, we demonstrated the use of indicators consisting of physico-chemical parameters, ions, isotopes and compound-specific patterns of xenobiotics. The chosen indicators of pH, temperature, electrical conductivity, redox conditions, nitrate, sulphate, chloride, boron, the isotopes of hydrogen, nitrogen, oxygen, sulphur and boron, as well as bisphenol A, carbamazepine, technical 4-nonylphenol (t-nonylphenol), galaxolide, tonalide, and gadolinium, helped to balance urban substance fluxes and assess urban effects on surface water quality. From our current quantification, it is clear that predicting contaminant behaviour in urban areas demands a detailed process understanding which cannot be derived from laboratory experiments or phenomenological analyses at the catchment scale. Through an installation of measuring equipment at the interfaces between the unsaturated and saturated zone as well as between ground- and surface water, in situ contaminant transport and fate can be quantified from the cm- up to the m-range.

Urban water cycles are threatened in many ways by human activities, including the discharge of chemicals by industrial and household effluents. Since more than a decade it has been recognised that the active ingredients of human pharmaceuticals contribute to the chemical contamination of urban surface waters and may pose a serious risk to the environment. Pharmaceuticals reach the aquatic environment due to their everyday use, excretion by humans and incomplete degradation in sewage treatment works. Their environmental concentrations are generally low. Due to their biologic activity, however, pharmaceuticals are considered as candidate compounds for low-level and chronic effects. Indeed, some pharmaceuticals, such as compounds interfering with reproductive hormones, provoke long-term effects on aquatic vertebrates in the ng/L range. Therefore, appropriate regulations for the environmental risk assessment as part of the approval of new medicines have been established. It was criticised, however, that these guidelines would not have been able to detect or predict the effects of some compounds with already known environmental impact. Thus, approaches for amending existing guidelines have been suggested. In this review, we give a brief overview on current and novel approaches for the prospective environmental risk assessment of human pharmaceuticals in the aquatic environment. In particular, we compare different strategies to identify potential ecotoxic effects and the possible applications within a regulatory framework. We indicate a number of tools that could improve the detection of compounds with potential low-level effects or hitherto unknown but relevant alternative mode of actions with implications for long-term effects.

Parabens are alkyl esters of p-hydroxybenzoic acid that could be encountered in various environmental waters; and there is little available information about the adverse effects of these compounds on aquatic organisms. Moreover, information concerning their levels and potential environmental long-term effects are currently missing.

This paper aims at increasing the knowledge on the potential hazard of parabens. Four microorganism model systems (Vibrio fischeri, Photobacterium leiognathi, Daphnia magna and Tetrahymena thermophila) have been used for this purpose. In addition, estrogenicity has been studied for parabens and binary mixtures of estrogenic compounds and parabens by using a recombinant yeast estrogen screen assay (YES). Following the EU EMEA Environmental Risk Assessment guideline for classification of dangerous substances and considering the results obtained with Daphnia magna, methyl, ethyl and n-propyl parabens should be classified as harmful substances for aquatic organisms, whereas n-butyl and benzyl parabens as toxic substances. Concerning the biological activity, parabens are 8,000-900,000-fold less estrogenic than estradiol, the most estrogenic one being the aromatic compound benzylparaben. Higher estrogenic effect has been observed when estrogenic compounds have been added to parabens.

The effluents from wastewater treatment plants are known to contribute significantly to the total emission of estrogenic compounds, both from natural and anthropogenic sources, into the aquatic environment. As a logical consequence, occurrence of these compounds affects the quality of our surface waters in general, while they may be able to interfere with aquatic wildlife through endocrine disruption.

In a comprehensive monitoring programme, the removal of natural estrogenic hormones, bisphenol A, nonylphenol and nonylphenol ethoxylates was investigated for a number of Dutch wastewater treatment plants. For quantification of these contaminants at very low levels (low ng/L for the hormones and bisphenol A, low μg/L for nonylphenol and its ethoxylates), both GC-MS and LC-MS techniques were applied. In addition, overall estrogenic activity in samples taken from various steps in the treatment cycle was determined by application of the ER-CALUX assay.

Apart from a standard approach for wastewater treatment, several additional treatment techniques, that is sand filtration, active coal filtration, membrane bioreactors (in series and stand-alone) were investigated as well.

None of the treatment techniques was able to remove all of the estrogenic activity. In the sewage treatment plant effluents, only estrone, bisphenol A, nonylphenol and nonylphenol ethoxylates were regularly detected, while 17β-estradiol was measured incidentally. In general, implementation of most additional treatment techniques further reduced the estrogenic activity to levels below 1 ng EEQ/L.

This work addresses the problem of micropollutants removal in sewage treatment plants trying to identify the main factors influencing their fate and behaviour. Firstly the most significant groups of substances that are continuously emitted into the environment are presented and the physico-chemical properties and biodegradability of representative compounds are discussed. This information is crucial to understand the main removal mechanisms occurring in sewage treatment plants, such as sorption, biodegradation and chemical transformation, as well as the distribution pathways of micropollutants once released into the environment. Selected case studies are discussed to identify some key operational factors which influence the removal of these compounds, including the use of additives, temperature, biomass concentration and characteristics (microbial diversity, structure, etc.), as well as hydraulic and sludge retention time. A discussion focused on comparison of data corresponding to several configurations of activated sludge systems and membrane biological reactors is presented. So far, it is not clear how the type of technology affects micropollutants removal. A number of conclusions trying to explain the influence of different factors and some guidelines useful to enhance the removal of micropollutants in sewage treatment plants are presented.

Organic micropollutants refer to a wide group of carbon containing chemical compounds, mainly of xenobiotic nature, created by industrial processes either intentionally or as by-products, such as pharmaceuticals, personal care products, hormones, pesticides, brominated flame retardants, plasticizers, perfluorinated compounds, etc. Some of these substances are being considered for inclusion in the list of Persistent Organic Pollutants (POPs), i.e. compounds that are resistant to environmental degradation through biological, chemical or photochemical processes, thus capable of long-range transport, bioaccumulation in human and animal tissue, biomagnification in food chains, and exerting potential significant impacts on human health and the environment (Katsoyiannis and Samara 2007; Clarke et al. 2008; Stockholm Convention on Persistent Organic Pollutants 2009). Moreover, a significant number of these substances, those defined as Endocrine Disrupting Compounds (EDCs), may exert estrogenic activity on various higher organisms (Kester et al. 2000).

During the last decade, the focus of environmental research has been extended from the more “classic” POPs such as organochlorine pesticides or Polychlorinated Biphenyls (PCBs) to the so called “emerging contaminants” such as Pharmaceuticals and Personal Care Products (PPCPs). Recent advances in analytical techniques, mainly related to the increasing use of Liquid Chromatography (LC) coupled with Mass Spectrometry (MS), have enabled the possibility of determining a wide variety of micropollutants which, although denoted as “emerging” because information about occurrence is fairly recent, have been discharged into the environment along decades, mainly in water bodies (Ternes 2007). That is the case of PPCPs or the most recently reported Perfluorinated Alkylated substances (PFAs), a large group of chemicals widely used to create inert surfaces for different industrial and consumer products since the 1950s, but recently detected in waste dumps or sewage (Clara et al. 2008). Although these compounds are present at low concentrations, many of them raise considerable toxicological concerns, either as sole compounds or also when present as components of complex mixtures.

The objective of this chapter is to present the main removal mechanisms that take place throughout Sewage Treatment Plants (STPs), since municipal wastewaters represent a significant emission source of micropollutants (Neumann et al. 2002; Joss et al. 2005). Most of the existing units operate with variations of the well known Activated Sludge (AS) process. However, one innovative technology that is nowadays gaining popularity is the Membrane Biological Reactor (MBR). Postreatment methods, such as activated carbon or through ozone or advanced oxidation technologies, although very interesting as a polishing step leading to almost complete removal of these substances, can be considered as an “externality” of the common primary-secondary treatment, and are not discussed in this chapter.

Small molecular weight xenobiotics are compounds of extreme concern in potable water applications due to their adverse human health and environmental effects. However, conventional water treatment processes cannot fully and systematically remove them due to their low concentrations in natural waters and wastewaters. Biological limitation to degrade such compounds is another cause for inefficient removal.

Physical barriers like membranes possessing pore sizes smaller than the compounds to be removed emerged as a good solution. Nanofiltration and reverse osmosis proved to be quite effective for xenobiotics removal in potable water production in the Paris purification plant of Méry-sur-Oise. However, even these very narrow pore membrane processes may result in incomplete removal: xenobiotics retention is high but factors such as adsorption, size exclusion and charge repulsion affect unpredictably their retention. The water solutions complexity to be treated renders xenobiotics removal predictions even more difficult due to interactions between xenobiotics and compounds in water.

Removal of xenobiotics by microfiltration and ultrafiltration is very low because adsorption on the membrane is the main retention mechanism. Combining those with other processes (e.g. activated carbon) can considerably improve xenobiotics removal.

The least studied processes in xenobiotics removal are electrodialysis, membrane distillation and pervaporation. Electrodialysis removal of organic xenobiotics shows a breakthrough through the membrane possibly due to adsorption followed by diffusion. Membrane distillation presents high removal rates of xenobiotics due to the compounds low vapour pressure. For volatile organic xenobiotics or solutions of trace amounts both membrane distillation and pervaporation can be used, xenobiotics interaction with the membrane being the key factor.

In this book chapter a thorough synopsis of current knowledge on xenobiotics removal is presented and balanced with recent fundamental studies of underlying mechanisms, informing both the practitioner regarding membrane capabilities for xenobiotics removal and the researcher with the current state-of-art.

Membrane bioreactor is no longer just a promising technology. Full scale applications in urban wastewater treatment plants are rapidly growing in number and in terms of treatment capacity. This modification of the conventional activated sludge process may enhance the removal of xenobiotics for two main reasons: (1) the effluent (permeate) is virtually free from suspended solids and associated pollutants; (2) there is a major flexibility for the operation of the biological process, which is distinguished from the sedimentation properties of the activated sludge. This chapter deals with the removal of xenobiotics from real urban wastewater showing and discussing a 10-year activity carried out in Italy on pilot, demonstration and full scale membrane bioreactors. Target xenobiotics were metals (As, Cd, Cr, Hg, Ni, Pb), industrial organic chemicals and products, such as PAHs, BTEXs, PCBs, PCDDs/PCDFs, etc. As far as metals are concerned, besides Cd and Hg, which were almost completely removed both in conventional and membrane systems, generally the enhanced biosorption and/or retention capability allowed the membrane bioreactor to be more effective than the conventional activated sludge systems in removal of Cr, Cu and Ni. High sludge age seemed to enhance the bioconversion of hydrophobic and partially recalcitrant substances such as dioxins, hexachlorobenzene and poly-chlorinated bi-phenyls. As for the power requirements of the membrane bioreactors, which still represent a bottleneck for the widespread urban application of the technology, full scale data demonstrated were close to sustainable values, especially when membrane filtration is coupled to energy-saving biological processes such as the intermittent and automatically controlled aeration. Moreover, although a significant decrease is being observed for investment costs, land cost still represents a real major driver for membrane bioreactors urban implementation.

Sequencing Batch Reactors (SBRs), characterised by a large variety of potential operating conditions and high operational flexibility, are an effective technological solution to the treatment of xenobiotic compounds, while also being able to generate a versatile micro-organism culture able to develop metabolic pathways required in the degradation of such recalcitrant substances. The main limitation in the operation of SBRs is the high concentrations of xenobiotic substrates that the biomass can experience, leading to a significant reduction in kinetic performance that is often not acceptable in practical applications (i.e. industrial wastewater treatment). The effects of substrate inhibition can be mitigated by a two phase partitioning system that is able to optimize “substrate delivery” to the cells in order to keep the substrate concentration at a level high enough to have reaction rates suitable for application but not inhibitory and/or toxic for the biomass. Immiscible organic solvents or solid polymers can be utilized as partitioning phases. Combining the two phase system with SBRs is a promising area to be investigated as a possible strategy when xenobiotic removal has to be achieved in critical conditions characterized by very high influent substrate concentrations.

In this chapter the principles of operation and an overview of the existing and potential applications for conventional and two phase sequencing batch systems are presented. In addition, the results obtained for the application of both technological approaches to the case study of 4-nitrophenol removal are reported.

Alkylphenol ethoxylates (APEOs) are produced in huge amounts and used in industrial cleansing processes. After use they are usually discharged into municipal sewer systems and afterward treated in wastewater treatment plants. Their environmental acceptability is strongly disputed because of potentially estrogenic metabolic products (two short ethoxy chain APEO oligomers [APE₁O and APE₂O] and fully de-ethoxylated alkylphenols [APs]) generated during wastewater treatment.

In this chapter the occurrence of APEOs and their metabolites in wastewaters and sludges is reviewed and their removal during wastewater treatment applying conventional activated sludge treatment and membrane bioreactors (MBR) is discussed. Biodegradation of APEO and formation of persistent metabolites is also discussed as a key phenomenon, as well as their removal by sorption onto sewage sludge.

Advanced oxidation processes (AOPs) constitute a family of redox technologies that have been involved in various environmental applications, including, amongst others, the treatment of municipal and industrial wastewater contaminated by various organic and inorganic compounds.

This chapter focuses on the science and engineering of water and wastewater treatment in relation to AOPs applications. The chapter gives a short but necessary description of the key AOPs employed in water treatment and then discusses process fundamentals, advantages and drawbacks. This is done providing recent paradigms from the literature on process integration aiming to improve degradation rates or separate pollutants, catalysts and chemicals prior to or after advanced oxidation.

The chapter includes also information on solar-driven applications (homogeneous and heterogeneous photocatalysis) as an excellent example of sustainable treatment technologies. This part discusses technological advances (development of non-concentrating collectors and scaling-up of photocatalytic reactors) and summarizes most of the recent research related to the degradation of water contaminants. The approach is exemplified through a combined solar photocatalysis and bio-treatment unit capable of destroying very persistent toxic compounds.

Finally, in this chapter, the use of AOPs in drinking water treatment is discussed with respect to both disinfection by-products control and micro-pollutants removal and compared to the efficiency of conventional treatment technologies.

In the present work, the rather limited data available regarding the sources, concentrations and treatability of naphthalene sulphonates in biological and chemical treatment systems is discussed and reviewed. Due to the refractory nature of most commercial naphthalene sulphonates, this review focused on the application of advanced oxidation processes for their efficient degradation by providing a deeper insight into the reaction mechanisms involved and products formed in advanced chemical and photochemical oxidation of important naphthalene sulphonates.

An overview on phytoremediation is presented, which includes basic definitions, advantages and potential drawbacks as well as information about recent developments in this field of research and applications, especially in the area of decontamination and cleaning of organic xenobiotics containing industrial and agricultural wastewaters.

The treatment of stormwater constitutes an integral part of precipitation water management in Germany. This finds its expression in a variety of treatment concepts which in turn form the basis for technological solutions to meet current demands concerning water quality. In this respect the requirements of the Water Framework Directive (2000/60/EU, WFD) continue to play a central role and provide a basis for discussion leading to further innovative solutions. In order to fulfil these requirements, major investments are necessary. In view of the high costs involved in the construction and maintenance of treatment plants, a key factor may be seen in the development of techniques for measuring their clearing efficiency.

Analysis of highway stormwater run-off has revealed the existence of priority substances as defined in Annex X of the WFD. The concentrations of heavy metals, metalloids, PAHs and benzothiazoles were determined in run-off water as well as in seepage water originating from a plant covered soil filter in the vicinity of a nature protection area from Hamburg. In addition, stormwater treatment plants located in a water protection area were investigated. The analysis of soil samples obtained from three of these filters showed a slight accumulation of Cu, Pb, Zn, Pt, and PAHs in each case in the upper soil horizon.

A test filter with modified adsorbent composition and mycorrhizal vegetation was installed in the plant stocked filter. The results show a high degree of retardation efficiency for metals and non-polar substances, but less for the polar ­compounds such as benzothiazoles and benzotriazoles.

Historically, the focus concerning emissions of xenobiotics has been on industrial effluents and point sources, but nowadays there is a recognition of the existence of diffuse emissions of hazardous substances from many different sources, including materials and consumer goods. In this chapter different mitigation strategies against such emissions are discussed. Mitigation is here defined as upstream source control. Removal of xenobiotics by sewage treatment methods is not covered. The main focus is on the options that national, regional and local authorities have to reduce emissions of hazardous substances at their sources but other actors, such as businesses and non-governmental organisations, are also discussed. The tools for mitigation include green procurement, use of current legislation, voluntary agreements, cooperation, financial initiatives, information campaigns, ecolabelling, etc. Examples of each tool are given and follow-up and costs are discussed.

The idea to compile this book arose from the COST Action 636 ‘Xenobiotics in Urban Water Cycle’ and this reflects on the knowledge and discussions assembled in the last three years in this Action. In parallel to working on this book and COST Action, several issues were discussed. Although some of these issues have been widely established on a research level, others still remain open and speculative. This book aims at providing the reader with a review of current issues on xenobiotics in urban waters.