Laboratoire Central de la Prefecture de Police1, LEESU2
Keywords: alkylphenols, emission sources, greywaters, phthalates.
Alkylphenols and phthalates (or Phthalate Acid Esters) are classified as endocrine-disrupting compounds. Despite a small number of studies, some data suggest that phthalates could have a negative effect on reproduction in humans (BergÃ© et al., 2013; BergÃ© et al., 2012a). These two families of organic compounds are present in everyday life products. Indeed, phthalates are widely used in many industrial and household applications products such as adhesives, paints, inks and rubbers, surface treatment, etc. (BergÃ© et al., 2013). Alkylphenols are non-ionic surfactants extensively used as additives in detergents and in the production of alkylphenol ethoxylates. These substances have been used in a wide range of applications such as cosmetics, hair and body care-products, paints, solubilisers, etc. Globally, their production totaled 6 millions of tons for phthalates and about 500,000 tons for alkylphenols (BergÃ© et al., 2014).
Recently, BergÃ© et al. (2014) monitored alkylphenol and phthalate concentration in wastewater at the scale of Paris conurbation: a heavily urbanized but weakly industrialized catchment. Such type of catchment, with 8.5 million inhabitants and less than 2% of wastewater originate from industries, could therefore be used to model the fate of alkylphenols and phthalates for major cities located in industrialized countries. It has been shown that alkylphenols and phthalates are not rejected by the industry but they mainly originate from domestic wastewater. Indeed, it was observed that more than 95% of the load derived from domestic wastewater (BergÃ© et al., 2014). This finding was in good agreement with Eriksson et al. (2003). However the terms of contribution of the different type of greywater to the pollution by alkylphenols and phthalates was not addressed. Little is still known concerning the detailed production patterns and characteristics of grey wastewater Therefore, this work aims at filling in this gap. Six types of grey waters were analysed (water of showers, cleaning floor, washing machines, dishes, dishwasher and bathroom water). The concentration of 4 phthalates (DEP, DnBP, BBp and DEHP) and 2 alkylphenols (nonylphenol and octylphenol), among the most commonly studied congeners, were monitored in greywater. For each sample, analyses were carried out on both the dissolved and particulate fractions within 24-48 hours after sampling for the dissolved phase, to avoid microbial degradation, and after lyophilization for the particulate phase. Phthalates and alkylphenols were analyzed by gas chromatography coupled to a mass spectrometer (simple Quad, Agilent Technologies), equipped with a DB-5MS column (Agilent Technologies, 30 m).
Moreover, in order to find out whether or not a correlation exists between the concentration of the investigated contaminants and the quality of water, routine wastewater quality parameters were also monitored. That is to say: pH, total suspended solids (TSS), chemical and biochemical oxygen demands (COD and BOD5), total Kjeldahl nitrogen (TKN) and anionic detergents (MABS). All these analyses were performed using French and/or international standards (COD: NF T90-101; BOD5: NF ISO 1899-1; TSS: NF EN 872; TKN: NF EN 25663; anionic detergent: NF EN ISO 16265; pH: NF EN ISO 10523).
The loads of rejected alkylphenols and phthalates were estimated by multiplying, for each type of water, the median concentrations by the discharged flow. The results of this study are summarized in Table 1.
Table 1 : Loads of phthalates and alkylphenols (mg/inhab./d))
Table 1 compares the discharges of alkylphenols and phthalates from greywater and domestic wastewaters (these latter containing a mixture of both grey- and black- water). From this table, some differences were highlighted between these two types of water for alkylphenols. Indeed, the contribution of grey waters represents only 12% for the NP and 20% for the OP observed by BergÃ© et al. (2014) in the domestics wastewaters. On the other hand, for phthalates, it appears that grey waters are one of the main sources of their emissions: 40% for the DEP and almost 100% for DnBP.
Table 2 : loads of alkylphenols and phthalates in greywater (Âµg/inhab/d)
Table 2 helps identifying what types of grey waters reject mainly these compounds. Table 2 shows the individual load for all compounds in each types of water. As a consequence, we showed that two types of water were the main contributors: the showers and the washing machines.
Our study demonstrated the importance of grey waters on the release of phthalates in domestic wastewater. Among the investigated grey waters, it has been shown that showers and washing machines were the main sources for phthalates.
To identify more precisely the origin of alkylphenols, the degradation of alkylphenol ethoxylates in greywater should be investigated. Indeed, these compounds may be responsible for the presence of alkylphenols in wastewater systems (cladiÃšre, 2012).
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