The biotransformation of diclofenac during wastewater treatment was investigated. Attached growth biomass from a carrier-filled compartment of a hybrid-MBBR at the wastewater treatment plant (WWTP) in Bad Ragaz, Switzerland was used to test the biotransformation. Laboratory-scale incubation experiments were performed with diclofenac and carriers and high-resolution LC-QTof-MS was implemented to monitor the biotransformation. Up to 20 diclofenac transformation products (TPs) were detected. Tentative structures were proposed for 16 of the TPs after characterization by MS(2) fragmentation and/or inferring the structure from the transformation pathway and the molecular formula given by the high resolution ionic mass. The remaining four TPs were unambiguously identified via analytical reference standards. The postulated reactions forming the TPs were: hydroxylation, decarboxylation, oxidation, amide formation, ring-opening and reductive dechlorination. Incubation experiments of individual TPs, those which were available as reference standards, provided a deeper look into the transformation pathways. It was found that the transformation consists of four main pathways but no pathway accounted for a clear majority of the transformation. A 10-day monitoring campaign of the full-scale plant confirmed an 88% removal of diclofenac (from approximately 1.6 μg/L in WWTP influent) and the formation of TPs as found in the laboratory was observed. One of the TPs, N-(2,6-dichlorophenyl)-2-indolinone detected at concentrations of around 0.25 μg/L in WWTP effluent, accounting for 16% of the influent diclofenac concentration. The biotransformation of carriers was compared to a second WWTP not utilising carriers. It was found that in contact with activated sludge, similar hydroxylation and decarboxylation reactions occurred but at much slower rates, whereas some reactions, e.g. reductive dechlorination, were not detected at all. Finally, incubation experiments were performed with attached growth biomass from a third WWTP with a similar process configuration to Bad Ragaz WWTP. A similarly effective removal of diclofenac was found with a similar presence of TPs.
The present study revealed the effects of fly ash (FA) and phosphoric rock (PR) on stabilization of sewage sludge (SS) after vermicomposting for 60 days. The earthworms in all vermibeds showed significant increases in tissue metal; however, the bioconcentration factors (BCFs) of all investigated metals (except Zn) differed among treatments. Additionally, significant differences were observed in the final system weight and SS+Passivant weight reduction among treatments, but not in the percentage reduction of total system weight and organic matter (OM). pH decreased from the initial levels, eventually reaching neutrality. Significantly greater earthworm heavy metals content, growth and reproduction rates and BCFs were observed, while a decreased percentage of total heavy metals concentration and a proportional decrease of extractable metals (except Cu and Zn) were observed in treatments mixed with FA and PR. Furthermore, significant linear correlations between BCFs and a reduction in percentage concentration of total metals (Cu, Pb, Cd and As) were shown, as well as BCF-Cu and relative proportional changes in extractable Cu. These results indicate that vermicomposting with proportions of FA and PR is better for stabilization and remediation of SS in a short period of time.
Anaerobic digestibility of the waste activated sludge (WAS) discharged from large-scale membrane bioreactors (MBRs) and conventional activated sludge processes (CASs) were compared using batch trials. Four wastewater treatment plants were sampled. Results showed that the sludge from MBRs had poor anaerobic digestibility as it had lower volatile solid (VS) reduction rate and lower maximum biogas production rate. The partial sludge stabilization during the long sludge retention time (SRT) typically applied in MBRs was the possible reason. On the other hand, the difference in wastewater composition had a great impact on the properties of activated sludge and the downstream sludge digestion. Inorganic matter accumulation in the WAS may hinder the access of microorganisms to substrate. The humic-like substances accumulating in the activated sludge was expected to contribute to the worse digestibility and these substances were observed to be released during anaerobic digestion through three-dimensional excitation-emission matrix (EEM) fluorescence spectra.
A laboratory-scale submerged anaerobic membrane bioreactor (SAnMBR) treating sewage was used to investigate the membrane fouling mechanism. Characterization of cake layer formed on membrane surface showed that cake layer was hydrated, rich of extracellular polymeric substances (EPS) and negative charged with the charge density of 0.21-0.46meq/kg MLSS. Detailed analysis revealed a new membrane fouling mechanism, osmotic pressure during cake layer filtration process due to the interception of ions. An osmotic pressure model was then developed to elaborate the existence of osmotic pressure and to estimate the contribution of osmotic pressure to membrane fouling. The calculated results showed that osmotic pressure accounted for the largest fraction of total operation pressure, indicating that osmotic pressure generated by the retained ions was one of the major mechanisms responsible for membrane fouling problem in MBRs. These findings provided a new insight into membrane fouling in MBRs.
The formation of thick stable brown foams within the activated sludge process has become a familiar operational problem. Despite much research having already been carried out into establishing the causes of activated sludge foaming there is still no general consensus on the mechanisms involved. Historically investigation into activated sludge foaming has involved either measuring, under aeration conditions, the propensity of mixed liquor samples to foam, or evaluating different physico-chemical properties of the sludge which have previously been linked to activated sludge foaming. Both approaches do not present a means to quantify the risk posed to the treatment plants once foams have started to develop on the surface of aeration basins and final clarifiers. The Foaming Scum Index (FSI) is designed to offer a means to quantify risk on the basis of different foam characteristics which can easily be measured. For example, foam stability, foam coverage, foam suspended solids content and biological composition. The FSI was developed by measuring foam samples taken from several different domestic and municipal wastewater treatment sites located in Greater Dublin area (South-East Ireland). Path analysis was used to predict co-dependencies among the different sets of variables following a number of separate hypotheses. The standardized beta coefficients (β) produced from the multivariate correlation analysis (providing a measure of the contribution of each variable in the structural equation model) was used to finalise the weighting of each parameter in the index accordingly. According to this principal, foam coverage exerted the greatest influence on the overall FSI (β = 0.33), whilst the filamentous bacterial composition in terms of the filament index of foam, provided the least (β = 0.03). From this work it is proposed that the index can be readily applied as a standard tool in the coordination of research into the phenomenon of activated sludge foaming.
The occurrence of sixteen pharmaceutically active compounds in influent and effluent wastewater and in primary, secondary and digested sludge in one-year period has been evaluated. Solid-water partition coefficients (K(d)) were calculated to evaluate the efficiency of removal of these compounds from wastewater by sorption onto sludge. The ecotoxicological risk to aquatic and terrestrial ecosystems, due to wastewater discharges to the receiving streams and to the application of digested sludge as fertilizer onto soils, was also evaluated. Twelve of the pharmaceuticals were detected in wastewater at mean concentrations from 0.1 to 32μg/L. All the compounds found in wastewater were also found in sewage sludge, except diclofenac, at mean concentrations from 8.1 to 2206μg/kg dm. Ibuprofen, salicylic acid, gemfibrozil and caffeine were the compounds at the highest concentrations. LogK(d) values were between 1.17 (naproxen) and 3.48 (carbamazepine). The highest ecotoxicological risk in effluent wastewater and digested sludge is due to ibuprofen (risk quotient (RQ): 3.2 and 4.4, respectively), 17α-ethinylestradiol (RQ: 12 and 22, respectively) and 17β-estradiol (RQ: 12 and 359, respectively). Ecotoxicological risk after wastewater discharge and sludge disposal is limited to the presence of 17β-estradiol in digested-sludge amended soil (RQ: 2.7).
The efficiency of two extraction techniques-ultrasound-assisted extraction and pressurized liquid extraction-are compared and evaluated in the determination of parabens in compost samples. The extraction parameters for each technique were accurately optimized. The selected compounds were detected and quantified using ultra-performance LC MS/MS, operating in negative ESI and in SRM mode. The analytes were separated in less than 5 min. Ethylparaben (ring-(13) C6 labeled) was used as an internal standard. Two selective, sensitive, and accurate analytical methods were developed and validated. The LODs of the methods ranged from 3 to 7 ng/g and the LOQs from 10 to 23 ng/g, while inter- and intraday variability was under 6% in all cases. The methods were validated separately by using matrix-matched calibration and recovery assays with spiked samples. Recovery rates ranged from 94.0 to 105.0%. Compost samples were taken from different composting plants. Although the statistical comparison demonstrated no statistically significant differences between the two extraction techniques, the method based on pressurized liquid extraction was more sensitive than the ultrasound extraction based method.
We investigated 33 pharmaceuticals and personal care products (PPCPs) with emphasis on anthelmintics and their metabolites in human sanitary waste treatment plants (HTPs), sewage treatment plants (STPs), hospital wastewater treatment plants (HWTPs), livestock wastewater treatment plants (LWTPs), river water and seawater. PPCPs showed the characteristic specific occurrence patterns according to wastewater sources. The LWTPs and HTPs showed higher levels (maximum 3000 times in influents) of anthelmintics than other wastewater treatment plants, indicating that livestock wastewater and human sanitary waste are one of principal sources of anthelmintics. Among anthelmintics, fenbendazole and its metabolites are relatively high in the LWTPs, while human anthelmintics such as albendazole and flubendazole are most dominant in the HTPs, STPs and HWTPs. The occurrence pattern of fenbendazole’s metabolites in water was different from pharmacokinetics studies, showing the possibility of transformation mechanism other than the metabolism in animal bodies by some processes unknown to us. The river water and seawater are generally affected by the point sources, but the distribution patterns in some receiving water are slightly different from the effluent, indicating the influence of non-point sources.
The aim of this study was to define a new indicator for the quality of wastewaters that are released into the environment. A quality index is proposed for wastewater samples in terms of the inertness of wastewater samples toward enzyme activity. This involves taking advantage of the sensitivity of enzymes to pollutants that may be present in the waste samples. The effect of wastewater samples on the rate of a number of different enzyme-catalyzed reactions was measured, and the results for all the selected enzymes were analyzed in an integrated fashion (multi-enzymatic sensor). This approach enabled us to define an overall quality index, the “Impact on Enzyme Function” (IEF-index), which is composed of three indicators: i) the Synoptic parameter, related to the average effect of the waste sample on each component of the enzymatic sensor; ii) the Peak parameter, related to the maximum effect observed among all the effects exerted by the sample on the sensor components; and, iii) the Interference parameter, related to the number of sensor components that are affected less than a fixed threshold value. A number of water based samples including public potable tap water, fluids from urban sewage systems, wastewater disposal from leather, paper and dye industries were analyzed and the IEF-index was then determined. Although the IEF-index cannot discriminate between different types of wastewater samples, it could be a useful parameter in monitoring the improvement of the quality of a specific sample. However, by analyzing an adequate number of waste samples of the same type, even from different local contexts, the profile of the impact of each component of the multi-enzymatic sensor could be typical for specific types of waste. The IEF-index is proposed as a supplementary qualification score for wastewaters, in addition to the certification of the waste’s conformity to legal requirements.
Thousands of chemicals have been identified as contaminants of emerging concern (CECs), but prioritizing them concerning ecological and human health risks is challenging. We explored the use of sewage treatment plants as chemical observatories to conveniently identify persistent and bioaccumulative CECs, including toxic organohalides. Nationally representative samples of sewage sludge (biosolids) were analyzed for 231 CECs, of which 123 were detected. Ten of the top 11 most abundant CECs in biosolids were found to be high-production volume chemicals, eight of which representing priority chemicals, including three flame retardants, three surfactants and two antimicrobials. A comparison of chemicals detected in nationally representative biological specimens from humans and municipal biosolids revealed 70% overlap. This observed co-occurrence of contaminants in both matrices suggests that the analysis of sewage sludge can inform human health risk assessments by providing current information on toxic exposures in human populations and associated body burdens of harmful environmental pollutants.