Effect of cetyltrimethylammonium chloride on various Escherichia coli strains and their inactivation kinetics by ozone and monochloramine

Cethyltrimethylammonium chloride (CTMA) is one of the most used quaternary ammonium compounds (QACs) in consumer products. CTMA and other QACs are only partially eliminated in municipal wastewater treatment and they can interact with bacteria in biological processes. Currently, there is only limited information on the antimicrobial efficiency of CTMA in matrices other than standard growth media and if and how CTMA influences conventional chemical disinfection. The results obtained in this study showed that the susceptibility of E. coli to CTMA was significantly enhanced in phosphate-buffered saline, lake water and wastewater compared to broth. In broth, a minimum inhibitory concentration (MIC) of CTMA of 20mgL−1 was observed for E. coli, whereas a 4-log inactivation occurred for CTMA concentrations of about 4 mgL−1 in buffered ultra-purified water, a lake water and wastewater effluent. The impacts of the pre-exposure and the presence of CTMA on inactivation by ozone and monochloramine were tested with three different E. coli strains: AG100 with the efflux pump acrAB intact, AG100A with it deleted and AG100tet with it overexpressed. Pre-exposure of E. coli AG100 to CTMA led to an increased susceptibility for ozone with second-order inactivation rate constants (∼ 106 M−1s−1) increasing by a factor of about 1.5. An opposite trend was observed for monochloramine with second-order inactivation rate constants (∼ 103 M−1s−1) decreasing by a factor of about 2. For E. coli AG100tet, the second-order inactivation rate constant decreased by a factor of almost 2 and increased by a factor of about 1.5 for ozone and monochloramine, respectively, relative to the strain AG100. The simultaneous presence of CTMA and ozone enhanced the second-order inactivation rate constants for CTMA concentrations of 2.5 mgL−1 by a factor of about 3. For monochloramine also an enhancement of the inactivation was observed, which was at least additive but might also be synergistic. Enhancement by factors from about 2 to 4.5 were observed for CTMA concentrations > 2.5 mgL−1.

Elimination of micropollutants in wastewater treatment plants: Ozonation or activated carbon? Conclusions of a one-year pilot project

David Andrew Barry, Nathalie Chèvre Rossi, Luiz Felippe De Alencastro, Anoys Magnet, Jonas Margot, Luca Rossi

Many organic micropollutants present in wastewater, such as pharmaceuticals and pesticides, are poorly removed in conventional wastewater treatment plants (WWTP). To reduce the release of these substances into the aquatic environment, advanced treatments are necessary. Two advanced treatments were tested in pilot systems over more than one year at the municipal WWTP of Lausanne, Switzerland. The first pilot involves the ozonation of the effluent to oxidize organic substances. It is followed by sand filtration (SF) to remove the readily biodegradable reaction products. The second pilot consists of a powdered activated carbon (PAC) addition into the effluent to sorb micropollutants. It is followed either by a membrane filtration (ultrafiltration) or a sand filtration to separate the PAC from the treated water. A selection of 58 potentially problematic substances (pharmaceuticals, pesticides, endocrine disruptors) were regularly measured at different stages of treatment by ultra performance liquid chromatography coupled to a tandem mass spectrometer, and a large battery of ecotoxicological tests (16 in vitro and 9 in vivo assays with different organisms) were performed to evaluate the toxicity of the effluents. The results showed that most compounds were removed over 80% with an average ozone dose of about 5.5 mgO3/l or a PAC dose between 10 and 20 mg/l. Only some single compounds, such as X-ray contrast media, were only partially eliminated in both cases. A clear reduction in toxicity was also observed after the two treatments in most of the cases. These two processes (ozonation and PAC addition) are therefore effective to reduce the release of micropollutants into surface waters. Ozonation-SF and PAC-SF proved to be feasible in terms of implementation and operation at large-scale in WWTP, for relatively similar investment and operation costs (about 0.1 to 0.15 € per m3 treated based on local costs). Each technique has its advantages and disadvantages. Therefore the method selection should be made case by case for each WWTP depending on the local constraints (e.g. space, security, energy costs, existing treatment processes, sludge disposal process, need for disinfection, etc.), the quality and the quantity of incoming water and the desired output water quality

2011

Treatment of micropollutants in municipal wastewater: Ozone or powdered activated carbon?

David Andrew Barry, Luiz Felippe De Alencastro, Anoys Magnet, Jonas Margot, Luca Rossi

Many organic micropollutants present in wastewater, such as pharmaceuticals and pesticides, are poorly removed in conventional wastewater treatment plants (WWTPs). To reduce the release of these substances into the aquatic environment, advanced wastewater treatments are necessary. In this context, two large-scale pilot advanced treatments were tested in parallel over more than one year at the municipal WWTP of Lausanne, Switzerland. The treatments were: i) oxidation by ozone followed by sand filtration (SF) and ii) powdered activated carbon (PAC) adsorption followed by either ultrafiltration (UF) or sand filtration. More than 70 potentially problematic substances (pharmaceuticals, pesticides, endocrine disruptors, drugs metabolites and other common chemicals) were regularly measured at different stages of treatment. Additionally, several ecotoxicological tests such as the yeast estrogen screen, a combined algae bioassay and a fish early life stage test were performed to evaluate effluent toxicity. Both treatments significantly improved the effluent quality. Micropollutants were removed on average over 80% compared with raw wastewater, with an average ozone dose of 5.7 mg O3 l-1 or a PAC dose between 10 and 20 mg l-1 (Figure 1). Depending on the chemical properties of the substances (presence of electron-rich moieties, charge and hydrophobicity), either ozone or PAC performed better. Both advanced treatments led to a clear reduction in toxicity of the effluents, with PAC-UF performing slightly better overall. As both treatments had, on average, relatively similar efficiency, further criteria relevant to their implementation were considered, including local constraints (e.g., safety, sludge disposal, disinfection), operational feasibility and cost. For sensitive receiving waters (drinking water resources or recreational waters), the PAC-UF treatment, despite its current higher cost, was considered to be the most suitable option, enabling good removal of most micropollutants and macropollutants without forming problematic by-products, the strongest decrease in toxicity and a total disinfection of the effluent.

2013

Benchmarking Organic Micropollutants in Wastewater, Recycled Water and Drinking Water with In Vitro Bioassays

Xiaowei Zhang

Thousands of organic micropollutants and their transformation products occur in water. Although often present at low concentrations, individual compounds contribute to mixture effects. Cell-based bioassays that target health-relevant biological endpoints may therefore complement chemical analysis for water quality assessment. The objective of this study was to evaluate cell-based bioassays for their suitability to benchmark water quality and to assess efficacy of water treatment processes. The selected bioassays cover relevant steps in the toxicity pathways including induction of xenobiotic metabolism, specific and reactive modes of toxic action, activation of adaptive stress response pathways and system responses. Twenty laboratories applied 103 unique in vitro bioassays to a common set of 10 water samples collected in Australia, including wastewater treatment plant effluent, two types of recycled water (reverse osmosis and ozonation/activated carbon filtration), stormwater, surface water, and drinking water. Sixty-five bioassays (63%) showed positive results in at least one sample, typically in wastewater treatment plant effluent, and only five (5%) were positive in the control (ultrapure water). Each water type had a characteristic bioanalytical profile with particular groups of toxicity pathways either consistently responsive or not responsive across test systems. The most responsive health-relevant endpoints were related to xenobiotic metabolism (pregnane X and aryl hydrocarbon receptors), hormone-mediated modes of action (mainly related to the estrogen, glucocorticoid, and antiandrogen activities), reactive modes of action (genotoxicity) and adaptive stress response pathway (oxidative stress response). This study has demonstrated that selected cell-based bioassays are suitable to benchmark water quality and it is recommended to use a purpose-tailored panel of bioassays for routine monitoring.

American Chemical Society2014