Preliminary screening of small-scale domestic wastewater treatment systems for removal of pharmaceutical and personal care products
Introduction
The widespread occurrence of pharmaceuticals and personal care products (PPCPs) in the aquatic environment is a recognized problem of unknown consequences (Daugthon and Ternes, 1999). One of the sources of PPCPs in aquatic environments is the effluent from wastewater treatment plants (WWTPs), since it is known that PPCPs are not completely removed during treatment. Hence, variable amounts of PPCPs are released to surface, ground and coastal waters depending on the elimination rates in the WWTPs (Kolpin et al., 2002). The elimination rates of PPCPs in different types of WWTPs vary, but generally systems with efficient removal of conventional wastewater constituents (BOD5 and NH4+) also have good removal of many PPCPs.
In Denmark about 10% of the population lives in rural areas not connected to a public sewerage system, and therefore their sewage is generally poorly treated or even untreated. Conventional centralised WWTPs with high removal efficiencies are not economically feasible for sanitation for these sparsely populated areas. Consequently, more cost-effective decentralised and/or individual household treatment solutions are typically preferred. In Denmark, several types of treatment technologies have been established following the adoption of wastewater treatment regulations for rural areas (Ministry of Environment and Energy, 1997). The systems that have been applied include compact biofilters, biological sand filters as well as different types of constructed wetlands (CWs). Horizontal subsurface flow CWs (HFCWs) and biological sand filters have been applied in Denmark for more than 25 years, whereas compact biofilters and vertical flow CWs (VFCWs) have been used for less than 10 years.
Although the removal of some PPCPs in lagoons (Shappell et al., 2007), free water surface constructed wetlands (FWSCWs) (Matamoros et al., 2008), HFCWs (Matamoros and Bayona, 2006, Matamoros et al., 2007), VFCWs (Matamoros et al., 2007) and biofilters (Conn et al., 2006) have already been studied, most of these studies have been performed in pilot plants with controlled flow parameters and/or focused on very few PPCPs. In fact, many of the papers published on small-scale onsite wastewater treatment systems include none or only a limited number of PPCPs and non-ionic surfactants (Hinkle et al., 2005, Carrara et al., 2008, Huntsman et al., 2006). In addition, many of these studies deal with only primary treatment in septic tanks and/or soil vadose zones. Hence, there is little information yet about the occurrence and removal of PPCPs in small-scale and field-site engineered treatment units for household systems (secondary wastewater treatments).
The goals of this work were to assess the occurrence and removal efficiency of PPCPs in a variety of onsite confined domestic wastewater treatments serving sparsely populated areas. Thirteen small-scale secondary wastewater treatment plants serving from 2 to 280 inhabitants, including biological sand filters, compact biofilters, VFCWs and HFCWs, were used as a basis of the study. This is one of the first reports on the occurrence and removal of a considerable number of PPCPs in secondary small-scale decentralised domestic wastewater treatment systems.
Section snippets
Chemicals
Trace analysis GC grade (Suprasolv) hexane, methanol, ethyl acetate, acetone, and dichloromethane were obtained from Merck (Darmstadt, Germany). Analytical grade acetic acid and hydrogen chloride were obtained from Panreac (Barcelona, Spain). Higher grade (i.e. >95%) hydrocinnamic acid, oxybenzone, furosemide, carbamazepine, ibuprofen, caffeine, methyl dihydrojasmonate, naproxen, ketoprofen, salicylic acid, diclofenac, 2,2′-dinitrophenyl (surrogate), and dihydrocarbamazepine (surrogate) were
Conventional wastewater parameters
Table 2 shows TSS, BOD5, and NH4+ concentrations, measured in each system, where an efficient removal for all the parameters studied was observed. The high BOD5 and NH4+ removal is consistent with the prevailing oxic and nitrifying conditions in the treatment systems suggesting that aerobic pathways to remove organic matter are predominant, which has been previously reported for VFCWs and unsaturated systems (Brix and Arias, 2005). Higher NH4+ removal was observed in VFCWs than in HFCWs because
Conclusion
A range of pharmaceuticals and personal care products have been identified in wastewater influent, effluent and receiving water body samples. Removal efficiencies of BOD5, TSS and NH4+ as well as PPCPs were similar in all the household wastewater treatment systems studied. Nevertheless, VFCWs appeared to be the most reliable and robust in terms of PPCPs and NH4+ removal efficiency.
In summary, compact biofilters, biological sand filters and constructed wetlands are feasible technologies to
Acknowledgments
This research has been supported by the Spanish Ministry of Science and Education through the CONTWET (CTM2005-06457-CO5-04/TECNO) project and the Aarhus University.
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