Occurrence of emerging contaminants, priority substances (2008/105/CE) and heavy metals in treated wastewater and groundwater at Depurbaix facility (Barcelona, Spain)
Introduction
The reuse of water originating from sewage treatment plants for environmental applications, and risk assessment studies have traditionally focused on clogging processes (Coppola et al., 2004), salinity aspects (Candela et al., 2007), public health (Cooper, 1991) or presence of pathogenic organisms in soil and water (Stott et al., 2003). It has generally been assumed that possible polluting agents are eliminated through sewage treatment. However, not all polluting agents are removed through standard treatments (Ternes, 1998, Ternes et al., 2002). A number of compounds are known to persist through tertiary treatment process in an unaltered form. Between these persistent compounds is the emergent polluting agent group, constituted by chemicals of a highly diverse origin, characterised by its high production and consumption entailing its continuous presence in the environment (Daughton & Ternes, 1999, Sedlak et al., 2000, Daughton, 2004). Since the last decade, a great interest has been taken in studying these compounds as reflected in the great number of publications (www.epa.gov/ppcp/lit.html), whose effects on the environment and human health still remain unknown. Among them, drugs (antibiotics, painkillers, etc.), diagnosis products, steroids and hormones, antiseptics, personal care products (sun creams, fragances, etc.), petrol additives, heavy metals and metalloids, surfactants endocrine disruptors, etc. are covered by this term. Many pharmaceuticals are non-prescription drugs and may be potentially hazardous for humans or ecosystems. Based on the chemical properties of 2986 pharmaceuticals, Sanderson et al. (2004) predicted that 33% were very toxic to aquatic organisms.
Although in the literature a great number of studies dealing with the application of reclaimed water exist, the quality criteria used (Levine and Asano, 2004) do not contemplate the presence of these polluting agents. However, its presence in water is undesirable even if compounds have low or acute toxicity. At present, they are not routinely monitored by water treatment companies due to the lack of regulatory requirements, as standards do not exist for most of the compounds. Furthermore, there is an extreme cost involved for monitoring thousands of potential contaminants that are expected to be removed after treatment. Attention has been especially directed towards the fate of compounds in sewage treatment facilities and surface waters in many parts of the world. So far, few studies have looked at the occurrence of these compounds in groundwater (Heberer et al., 1997, Drewes et al., 2003; http://ca.water.usgs.gov/gama/).
In the Barcelona metropolitan area (Spain), water is a limited resource and of great importance due to the presence of an extended industrial activity and water supply demand. To cope with water scarcity, growing demand and to comply with the environmental policies, increasing attention has been given to the use of non-conventional water resources, mainly desalinated and reclaimed (urban treated wastewater) water reuse. In the Llobregat area (Fig. 1) the production of reclaimed water from the Depurbaix wastewater treatment plant (Cazurra, 2006) is intended, thus contributing to the sustainable and integrated management of water resources. The volume of water to be reused at the Depurbaix facility is destined to satisfy different demands such as the contribution to ecological flow, agricultural irrigation, maintenance of wetlands and the construction of a hydraulic barrier against sea water intrusion in the Llobregat delta deep aquifer. Reclaimed water to satisfy environmental uses and agricultural irrigation is discharged 18 km north of the wastewater plant by two pumping stations after tertiary treatment, however only results of the hydraulic barrier (first phase) are presented in this paper.
As the risk of pollution by chemicals are of critical importance for the future safety of the aquifer, it is important to validate the system performance addressing groundwater quality (www.cdph.ca.gov/healthinfo/environhealth/water/pages/waterrecycling.aspx). Also this may allow an evaluation of any anticipated water quality changes.
The aim of this study was to investigate the occurrence of 170 emerging contaminants of different group classes, priority substances defined in the 2008/105/EC Directive and heavy metals from a municipal wastewater tertiary treatment plant (WWTP) and from water with an additional treatment of ultrafiltration, reverse osmosis and UV disinfection (WWATP) for the seawater hydraulic barrier injection. The level of the occurrence of different compounds in the Llobregat deep aquifer has also been studied in order to assess the injected water impact into the aquifer. This work is also the first project providing groundwater data from such a large group of compounds.
Section snippets
Study site
The Llobregat river delta, located southwest of the city of Barcelona (Spain) as shown in Fig. 1A, is a Quaternary age coastal formation covering 97 km2 of unconsolidated sediments varying from clay to gravel and is deposited over blue clay of the Pliocene age, except at the northern boundaries, which overlies materials of an older age. The southern boundary is the Mediterranean sea.
From the hydrogeological point of view two aquifers are distinguished, the upper unconfined, extending along all
Results and discussion
Results of contaminants according to their group of action and composition detected in the WWTP, WWATP and groundwater sampling sites for all sampling campaigns (found in at least in one sample) are presented in Fig. 3 and Table 3, Table 4, Table 5, Table 6. Obtained results are discussed for all sampled sites and each group separately.
Table 3 illustrates all priority substances concentrations (2008/105/EC) at sampling sites. Table 4 shows only those compounds appearing in the WWATP (injected
Conclusion
Findings of the study indicate that not all active compounds monitored and consumed will end up in the environment. When compounds are divided into categories based on their type of use, pharmaceuticals were the class most commonly detected in all sampled waters. Individual pharmaceutical concentrations showed a large variability within therapeutic classes, indicating that behaviour was not necessarily related to therapeutic action. Compounds daily consumed such as Caffeine and Nicotine, were
Acknowledgements
The authors would like to thank Project CONSOLIDER-TRAGUA financed by the Plan Nacional de I + D + i (Spain) for the financial support. We are also very grateful to J.F Garcia-Reyes, B. Gilbert-López, and J. Robles-Molina (University of Jaen). Special thanks are due to CUADELL and ACA for their support in the sampling campaigns.
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