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Biofilm formation can help to mitigate the stress placed on organisms during biological treatment of high-salinity wastewaters, such as "produced water" resulting from oil and gas extraction. This study investigated the implementation of two different biofilm-based biological reactors, activated carbon as an adsorptive biofilm surface (Bio-GAC) and aerobic granular sludge (AGS), and a conventional activated sludge (CAS) reactor for the treatment of synthetic produced water (PW) under hypersaline conditions (85,000 mg/L NaCl). A mixture of benzyl alcohol, o-cresol, and phenol were used as a carbon source with concentrations of 100, 100, and 250 mg/L, respectively. The performance of Bio-GAC was higher than AGS, with overall removal efficiencies for aromatic compounds of 100% and 93%. The presence of catechol in all three reactors during the reaction cycle confirmed that biodegradation was occurring. The performance of CAS was significantly lower in terms of removal efficiency for aromatic compounds (73%) and resilience to high salinity. Scanning electron microscopy showed that biofilm-based biosystems establish stronger biofilm texture. Microbial community analysis showed that carbon source and biosystem type played a crucial role in selecting for microbiome structure. These findings show that biofilm reactors can be used to successfully biodegrade toxic organic contaminants in a high-salinity environment, and that the hybrid Bio-GAC process is particularly promising for treating PW. [ABSTRACT FROM AUTHOR]

Tetrabromobisphenol A [2,4'-isopropylidenebis(2,6-dibromophenol)] has been identified in wastewater samples collected from the Guelph municipal wastewater treatment plant (GWWTP). In order to assess the kinetics and metabolic mechanisms of the dissolved TBBPA, bench scale experiments were completed with batch bioreactors. The biodegradation test was conducted by taking aerobic sludge from the conventional activated sludge reactor (CAS) and membrane bioreactor (MBR), and bioaugmenting both reactors with soil based strains of Bacillus brevis and Bacillus pumilus. This novel biodegradation process showed that the CAS bioreactor had a biodegradation rate of 0.127 d-1, while the sludge from the MBR had a biodegradation rate of 0.171 d-1. This is the first reported aerobic biodegradation of TBBPA by heterotrophic and nitrifying bacteria in an activated sludge bioreactor system. A tentative biotransformation metabolic scheme for TBBPA biodegradation and metabolite formation has been proposed as well. [ABSTRACT FROM AUTHOR]

Pharmaceutical and personal care products (PPCPs) can evade degradation in sewage treatment plants (STPs) and can be chronically discharged into the environment, causing concern for aquatic organisms, wildlife, and humans that may be exposed to these bioactive chemicals. The ability of a common STP process, conventional activated sludge (CAS), to remove PPCPs (caffeine, di(2-ethylhexyl)phthalate, estrone, 17α-ethinylestradiol, ibuprofen, naproxen, 4-nonylphenol, tonalide, triclocarban and triclosan) from a synthetic wastewater was evaluated in the present study. The removal of individual PPCPs by the laboratory-scale CAS treatment plant ranged from 40 to 99.6%. While the efficiency of removal for some compounds was high, remaining quantities have the potential to affect aquatic organisms even at low concentrations. Juvenile rainbow trout (Oncorhynchus mykiss) were exposed to influent recreated model wastewater with methanol (IM, solvent control) or with PPCP cocktail (IC), or CAS-treated effluent wastewater with methanol (EM, treated control) or with PPCP cocktail (EC). Alterations in hepatic gene expression (evaluated using a quantitative nuclease protection plex assay) and plasma vitellogenin (VTG) protein concentrations occurred in exposed fish. Although there was partial PPCP removal by CAS treatment, the 20% lower VTG transcript levels and 83% lower plasma VTG protein concentration found in EC-exposed fish compared to IC-exposed fish were not statistically significant. Thus, estrogenic activity found in the influent was retained in the effluent even though typical percent removal levels were achieved raising the issue that greater reduction in contaminant load is required to address hormone active agents. [ABSTRACT FROM AUTHOR]

Elimination of alkylphenol ethoxylates (APEO) and their degradation products (alkylphenols and alkylphenoxy carboxylates), as well as linear alkylbenzene sulfonates (LAS) and coconut diethanol amides (CDEA), was studied in a pilot plant membrane bioreactor (MBR) working in parallel to a full-scale wastewater treatment plant (WWTP) using conventional activated sludge (CAS). In the CAS system 87% of parent long ethoxy chain NPEOs were eliminated, but their decomposition yielded persistent acidic and neutral metabolites which were poorly removed. The elimination of short ethoxy chain NPEOs (NP1EO and NP2EO) averaged 50%, whereas nonylphenoxy carboxylates (NPECs) showed an increase in concentrations with respect to the ones measured in influent samples. Nonylphenol (NP) was the only nonylphenolic compound efficiently removed (96%) in the CAS treatment. On the other hand, MBR showed good performance in removing nonylphenolic compounds with an overall elimination of 94% for the total pool of NPEO derived compounds (in comparison of 54%-overall elimination in the CAS). The elimination of individual compounds in the MBR was as follows: 97% for parent, long ethoxy chain NPEOs, 90% for short ethoxy chain NPEOs, 73% for NPECs, and 96% for NP. Consequently, the residual concentrations were in the low μg/l level or below it. LAS and CDEA showed similar elimination in the both wastewater treatment systems that were investigated, and no significant differences were observed between the two treatment processes. Nevertheless, for all studied compounds the MBR effluent concentrations were consistently lower and independent of the influent concentrations. Additionally, MBR effluent quality in terms of chemical oxygen demand (COD), concentration and total suspended solids (TSS) was always superior to the ones of the CAS and also independent of the influent quality, which demonstrates high potential of MBRs in the treatment of municipal wastewaters. [Copyright &y& Elsevier]

For the removal of toxic and recalcitrant organic substances intermittently appearing in wastewater, bioaugmentation with bacteria having specific degradation ability could be a powerful tool to improve the treatment process. 2,4-Dichlorophenol (2,4-DCP) was chosen as the target recalcitrant substance and a 2,4-DCP degrading special mixed culture was used as bioaugmentation microorganisms. The feasibility and strategies to combine bioaugmentation into a conventional activated sludge (CAS) system in terms of enhancing its efficiency and reliability was investigated. Results showed that for domestic wastewater with multiple chlorophenols, bioaugmentation with a 2,4-DCP degrading culture in a CAS system not only enhanced the removal of 2,4-DCP effectively, but also improved the removal of other chlorophenols such as 4-monochlorophenol (4-MCP) and 2,4,5-trichlorophenol (2,4,5-TCP). A separate bioaugmented bioreactor was combined into the original CAS system at different locations and the effects of the bioaugmentation location on the performance of the combined biotreatment process were studied. Results indicated that the CAS-Bioaug system, in which the bioaugmented bioreactor was set at a location after the original CAS reactor, performed better than the Bioaug-CAS system, in which the bioaugmented bioreactor was placed before the original CAS reactor. Bioaugmentation could be used as an effective and efficient method to improve a CAS process facing sudden toxic pollutant shock loading. [Copyright &y& Elsevier]

Efficient and reliable removal of recalcitrant compounds, which are present in wastewater intermittently, is critically important to prevent toxicity discharge and system upset, especially for those biotreatment systems with poor anti-shock loading capacity such as conventional activated sludge (CAS) systems. In this study, 2,4-dichlorophenol (2,4-DCP) was chosen as a model recalcitrant substance. 2,4-DCP degrading mixed culture was bioaugmented to a CAS system in terms of enhancing 2,4-DCP removal and maintaining system stability under shock loading conditions. The effects of bioaugmentation on the performance of CAS systems after single inoculation were investigated under long-term continuous operation, during which four times shock loading occurred. Results showed that the two bioaugmented CAS systems, which were inoculated with 5% and 15% 2,4-DCP degrading mixed culture, respectively, demonstrated and maintained stronger ability to degrade 2,4-DCP than the non-supplemented control one during the first three shock loading periods within the first month after the first inoculation. For the fourth 2,4-DCP shock loading which occurred 100 days after inoculation, the advantages demonstrated by the bioaugmented systems were greatly reduced compared to those of the previous three runs. In addition, ribosomal intergenic spacer analysis method was used to track the supplemented special culture and assay the effect of bioaugmentation on the changes of microbial community structure. [Copyright &y& Elsevier]

This work aims at achieving a better understanding of the mechanisms and the operative conditions regulating the removal of a set of relevant micropollutants in conventional activated sludge (CAS) systems to maximize their removal and, if possible, biodegradation. Eight compounds from the EU Watch list (clothianidin, thiacloprid, methiocarb, E1, E2, EE2, diclofenac and erythromycin) were spiked at 2 μg/L in CAS systems and their behaviour was studied in 6-h batch tests. The role of sorption was also investigated. Information on the removal of the pesticides clothianidin, thiacloprid and methiocarb is here presented for the first time to the best of the authors' knowledge. With the aim of enhancing the removal of the selected compounds in wastewater treatment, four parameters were explored: biomass concentration, temperature, pH and redox conditions. For each parameter, a low and a high value were chosen, based on the ranges usually applied in wastewater treatment plants (WWTPs). Results show that biomass concentration is the most relevant parameter among the ones investigated, followed by the redox conditions. The operational conditions that maximized removal rates were: 5 g/L of biomass, aerobic conditions, 25 °C and pH 7.5. High variability in removal rates was observed for compounds such as E1, erythromycin and methiocarb. The pesticides clothianidin and thiacloprid did not prove to be easily degradable. The highest removal rates were recorded for the hormones, particularly E2, with a transformation rate of at least 96% under all conditions. Sorption proved to be a relevant removal route for EE2, for which the highest sorption rates were recorded, and diclofenac, where the adsorption mechanisms was hypothesised for its prevalence at lower pH values. Unlabelled Image • (Bio)degradation of 8 Watch list compounds studied in conventional activated sludge • Fate of clothianidin, thiacloprid and methiocarb presented for the first time • Maximum overall removal: aerobic conditions, 5 g/L biomass, 25 °C and pH 7.5 • Sorption is relevant for certain compounds, particularly EE2 and diclofenac. • Removal rates generally unsatisfactory except for E2. Great variability observed [ABSTRACT FROM AUTHOR]