Lab-scale experimental strategy for determining micropollutant partition coefficient and biodegradation constants in activated sludge

Microbial diversity and metabolic inference of diclofenac removal in optimised batch heterotrophic-denitrifying conditions by means of factorial design

Using the Response Surface Methodology (RSM) and Rotational Central Composite Design (RCCD), this study evaluated the removal of DCF under denitrifying conditions, with ethanol as cosubstrate, in batch reactors, being 1 L Erlenmeyer flasks (330 mL of reactional volume) containing Dofing medium and kept under agitation at 130 rpm and incubated at mesophilic temperature (30 °C). It considered the individual and multiple effects of the variables: nitrate (130 - 230 mg NO3- L-1), DCF (60-100 µg DCF L-1) and ethanol (130 - 230 mg EtOH L-1). The highest drug removal efficiency (17.5%) and total nitrate removal were obtained at 176.6 ± 4.3 mg NO3 -L-1, 76.8 ± 3.7 µg DCF L-1, and 180.0 ± 2.5 mg EtOH L-1. Under such conditions, the addition of ethanol and nitrate was significant for the additional removal of diclofenac (p > 0.05). The prevalence of Rhodanobacter, Haliangium and Terrimonas in the inoculum biomass (activated sludge systems) was identified through the 16S rRNA gene sequencing. The potential of these genera to remove nitrate and degrade diclofenac was inferred, and the main enzymes potentially involved in this process were α-methylacyl-CoA racemase, long-chain fatty acid-CoA ligase, catalases and pseudoperoxidases.

Contaminants of emerging concerns (CECs) in a municipal wastewater treatment plant in Indonesia

This study provides the first set of quantitative data on the occurrence and fate of a wide range of contaminants of emerging concerns (CECs) in Indonesia's largest wastewater treatment plant (WWTP). The WWTP employs waste stabilization ponds (WSPs) as the secondary treatment before discharging the effluent to the Citarum River. Fourteen out of twenty-two monitored CECs were detected in the wastewater influent, and seven were present in the effluent, with a total concentration of 29.8 ± 0.4 µg/L and 0.5 ± 0.0 µg/L, respectively. The occurrence of the CECs in this study was found to be well correlated with their possible use and known detection in surface waters in Indonesia. Caffeine (CAF) at 12.2 ± 0.1 µg/L, acetaminophen (ACT) at 9.1 ± 0.1 µg/L, N,N-diethyl-m-toluamide (DEET) at 5.0 ± 0.1 µg/L, ibuprofen (IBU) at 2.3 ± 0.0 µg/L, and triclosan (TCS) at 470 ± 64 ng/L were discovered as the five most prevalent CECs, followed by bisphenol A (BPA), trimethoprim (TMP), Tris(2-chloroethyl) phosphate (TCEP), sulfamethazine (SMZ), carbamazepine (CBZ), fluoxetine (FLX), benzotriazole (BTA), sulfamethoxazole (SMX), and metformin (METF). Biodegradable CECs (SMX, SMZ, ACT, IBU, TCS, BPA, CAF, DEET, and TMP) were efficiently removed (83-100%) by the WSP. In contrast, recalcitrant CECs achieved poor removal efficiencies (e.g., FLX at 24%), and for others, treatment processes even resulted in elevated concentrations in the effluent (CBZ by 85%, TCEP by 149%, and BTA by 92%). The CECs' influent concentrations were determined to pose a moderate aquatic cumulative risk, while no such risk was associated with their effluent concentrations. The study demonstrates the importance of conventional WWTPs in reducing the concentrations of CECs to minimize their aquatic contamination risk. The findings are relevant for countries, such as Indonesia, with limited resources for advanced centralized wastewater treatments, and which are exploring the efficacy of centralized WSP against the existing decentralized treatments.

Influence of metabolism and microbiology on organic micropollutants biotransformation in anoxic heterotrophic reactors

There is scarce information about the biotransformation of organic micropollutants (OMPs) under anoxic conditions. In this study, a heterotrophic denitrifying bioreactor was set up to study the fate of several OMPs from metabolic and microbiological points of view. Primary metabolic activity was increased by adding progressively higher nitrogen loading rates during the operation (from 0.075 to 0.4 g N-NO₃^- L^-1 d^-1), which resulted in an important shift in the microbial population from a specialized biomass to a more diverse community. Such a change provoked a significant increase in the removal efficiency of erythromycin (ERY), roxithromycin (ROX) and bisphenol-A (BPA), and some bacterial taxa, such as Rhodoplanes, were identified as possible indicators related to the biodegradation of these compounds. The increasing primary metabolic activity in the reactor did not enhance the OMP-specific removal rates, suggesting that the bacterial composition is more influential than cometabolism.

Combining sequential extraction and 3D fluorescence to investigate the behavior of antibiotic and polycyclic aromatic hydrocarbons during solar drying of sewage sludge

Solar drying and liming are commonly used for sludge treatment, but little is known about their efficiency on antibiotics and Polycyclic Aromatic Hydrocarbons (PAHs) removal. This study aimed to investigate the removal of antibiotics and PAHs during solar drying of Limed Sludge (LS) and Non-Limed Sludge (NLS). Thus, organic matter fractionation and 3D fluorescence were used to assess the accessibility and the complexity of organic matter. 2 experiments have been conducted using LS and NLS for 45 days of drying in a pilot scale tunnel. Physicochemical results indicated significant decrease of water content (90%) for both sludge samples within 15 days of drying. For both treatments, the removal of total organic carbon and total nitrogen was low and similar for both treatments. Through this study, it has been confirmed that liming and drying contributed to a strong modification of the organic matter quality with an increase of its accessibility. On the other hand, drying alone increased the less accessible compartments, while the presence of lime affected the interconnexion between the organic matter pools. 3D fluorescence confirmed the obtained results and indicated that LS leads to obtaining more simple molecules in the most accessible compartments, while NLS leads to obtaining more complex molecules in the less accessible compartments. In addition, solar radiations and leaching may contribute to the significant removal (p < 0.01) of roxithromycin, benzo(a)anthracene, chrysene, benzo[k]fluoranthene, benzo[a]pyrene, and benzo(g, h, i) perylene in the presence of lime. Furthermore, the evolution of organic matter pools in terms of accessibility and complexity may drive the bioavailability of these pollutants, leading to their significant removal.

A review of the adsorption-biological hybrid processes for the abatement of emerging pollutants: Removal efficiencies, physicochemical analysis, and economic evaluation

The limited efficiency of conventional wastewater treatment plants (WWTPs) in emerging pollutants (EPs) removal encourages the development of alternative technologies for the adequate treatment of wastewater, due to its adverse effects on human health and ecosystems. The biological, physical or chemical hybrid technologies to treat EPs results interesting since they can enhance the performance of WWTPs. Among them, hybrid adsorption/biological technology could offer different possibilities that are explored in this work (PAC-MBR, PACT/GAC-CAS, BAC configurations). In this way, different variations in the adsorption process have been considered: the form of the adsorbent, the feed to the system, and the type of biological process, either conventional activated sludge (CAS), membrane bioreactor (MBR) or biofilm systems. For each combination, the removal efficiency of micropollutants, classified according to their use into pharmaceuticals, personal care products (PCPs) and other micropollutants (mainly benzotriazoles) was analysed. From reported data, it was observed a beneficial synergistic effect of dipole moment and octanol-water partition coefficient on the removal efficiency of micropollutants by adsorption/biological hybrid technology. Finally, a preliminary economic evaluation of the powdered activated carbon in a conventional activated sludge reactor (PACT), powdered activated carbon-membrane bioreactor (PAC-MBR) and biological activated carbon (BAC) hybrid systems was carried out by analysing the capital expenditure (CAPEX) of plants for capacities up to 75,000 m³d^-1. Likewise, estimations of adsorbent concentration for a hypothetical plant with a capacity of 10,000 m³d^-1 is presented. Among these hybrid configurations, PAC-MBR achieved the highest micropollutant elimination percentages; however, it presents the highest CAPEX and activated carbon requirements.

Cometabolic removal of organic micropollutants by enriched nitrite-dependent anaerobic methane oxidizing cultures

The innovative and recently discovered n-damo process, based on anaerobic methane oxidation with nitrite, was developed in a membrane-based bioreactor and evaluated in terms of organic micropollutants (OMPs) removal. The main singularity of this study consisted in the evaluation of organic micropollutants (OMPs) removal in the biological reactor. A strategy consisting on progressively increasing the nitrogen loading rate in order to increase the specific denitrification activity was followed to check if the selected OMPs were co-metabolically biotransformed. Significant nitrite removal rate (24.1 mg N L^-1 d^-1) was achieved after only 30 days of operation. A maximum specific removal of 186.3 mg N gVSS^-1 d^-1 was obtained at the end of the operation, which is one of the highest previously reported. A successfully n-damo bacteria enrichment was achieved, being Candidatus Methylomirabilis the predominant bacteria during the whole operation attaining a maximum relative abundance of about 40 %. The natural hormones (E1 and E2) were completely removed in the bioreactor. The specific removal rates of erythromycin (ERY), fluoxetine (FLX), roxithromycin (ROX) and sulfamethoxazole (SMX) were successfully correlated with the specific nitrite removal rates, suggesting a co-metabolic biotransformation.

Performance comparison of different types of constructed wetlands for the removal of pharmaceuticals and their transformation products: a review

This paper presents a comprehensive and critical comparison of four types of constructed wetlands (CWs): free water surface CW (FWSCW), vertical flow CW (VFCW), horizontal flow CW (HFCW), and hybrid CW (HCW) for the removal of 29 pharmaceuticals (PhCs) and 19 transformation products (TPs) using a global data compiled for 247 CWs reported in 63 peer-reviewed journal papers. Biodegradation (aerobic being more efficient than anaerobic) is the major removal mechanism for 16 out of 29 PhCs besides the influence of other processes (e.g., adsorption/sorption, plant uptake, and photodegradation). The HCW performed better followed by VFCW, HFCW, and FWSCW. The comparatively better removal in HCW might be due to the coexistence of aerobic and anaerobic conditions and longer hydraulic retention time considering more than one compartment enhances the removal of PhCs (e.g., diclofenac, acetaminophen, sulfamethoxazole, sulfapyridine, trimethoprim, and atenolol), which are removed under both conditions and adsorption/sorption processes. The augmentation in dissolved oxygen by the application of artificial aeration improved the removal of PhCs, which are degraded under aerobic conditions. Furthermore, the better performance of aerated CWs could be due to the establishment of various microenvironments with different physicochemical conditions (aerobic and anaerobic), which facilitated the contribution of both aerobic and anaerobic metabolic pathways in the removal of PhCs. The removal of some of the PhCs takes place by the formation of their TPs and the nature of these TPs (persistent or non-biodegradable/biodegradable) plays a major role in their removal process.

Modeling of micropollutant removal in full-scale membrane bioreactors: calibration and operations to limit the emissions

Micropollutants are a major concern for aquatic organisms and human health. Membrane bioreactors (MBRs) are an efficient wastewater treatment and water reuse solution, but their micropollutant removal performances are still not fully determined. Modeling micropollutant behavior in MBRs could help better understand and optimize the removal process. Here we provide detailed explanation on a model of micropollutant removal in MBRs that predicts biodegradation and sorption rates. Parameters were calibrated following an iterative two-step procedure developed in this work and using data from two full-scale plants. The calibrated set of parameters was then used (i) to determine the influence of MBR operating conditions such as the duration of aerobic time and the sludge concentration in bioreactor, on micropollutant removal, and (ii) to better understand micropollutant behavior and removal performances in MBRs in response to sudden changes in operating conditions (rain event, F:M ratio). These predictive simulations showed that increasing sludge concentration in bioreactor can decrease effluent concentrations of most of the micropollutants studied by up to 15%, and increasing the duration of aerobic time decreases effluent concentrations of few organic micropollutants tested by up to 15%. Rain events and F:M ratio can increase effluent concentrations of six out of nine micropollutants tested by more than 15%.

Understanding the sorption and biotransformation of organic micropollutants in innovative biological wastewater treatment technologies

New technologies for wastewater treatment have been developed in the last years based on the combination of biological reactors operating under different redox conditions. Their efficiency in the removal of organic micropollutants (OMPs) has not been clearly assessed yet. This review paper is focussed on understanding the sorption and biotransformation of a selected group of 17 OMPs, including pharmaceuticals, hormones and personal care products, during biological wastewater treatment processes. Apart from considering the role of "classical" operational parameters, new factors such as biomass conformation and particle size, upward velocity applied or the addition of adsorbents have been considered. It has been found that the OMP removal by sorption not only depends on their physico-chemical characteristics and other parameters, such as the biomass conformation and particle size, or some operational conditions also relevant. Membrane biological reactors (MBR), have shown to enhance sorption and biotransformation of some OMPs. The same applies to technologies bases on direct addition of activated carbon in bioreactors. The OMP biotransformation degree and pathway is mainly driven by the redox potential and the primary substrate activity. The combination of different redox potentials in hybrid reactor systems can significantly enhance the overall OMP removal efficiency. Sorption and biotransformation can be synergistically promoted in biological reactors by the addition of activated carbon. The deeper knowledge of the main parameters influencing OMP removal provided by this review will allow optimizing the biological processes in the future.

Effects of chronic pollution and water flow intermittency on stream biofilms biodegradation capacity

A mesocosm case study was conducted to gain understanding and practical knowledge on biofilm emerging contaminants biodegradation capacity under stressor and multiple stressor conditions. Two real life scenarios: I) biodegradation in a pristine intermittent stream experiencing acute pollution and II) biodegradation in a chronically polluted intermittent stream, were examined via a multifactorial experiment using an artificial stream facility. Stream biofilms were exposed to different water flow conditions i.e. permanent and intermittent water flow. Venlafaxine, a readily biodegradable pharmaceutical was used as a measure of biodegradation capacity while pollution was simulated by a mixture of four emerging contaminants (erythromycin, sulfisoxazole, diclofenac and imidacloprid in addition to venlafaxine) in environmentally relevant concentrations. Biodegradation kinetics monitored via LC-MS/MS was established, statistically evaluated, and used to link biodegradation with stress events. The results suggest that the effects of intermittent flow do not hinder and may even stimulate pristine biofilm biodegradation capacity. Chronic pollution completely reduced biodegradation in permanent water flow experimental treatments while no change in intermittent streams was observed. A combined effect of water flow conditions and emerging contaminants exposure on biodegradation was found. The decrease in biodegradation due to exposure to emerging contaminants is significantly greater in streams with permanent water flow suggesting that the short and medium term biodegradation capacity in intermittent systems may be preserved or even greater than in perennial streams.

Biotransformation of acyclovir by an enriched nitrifying culture

This work evaluates the biodegradation of the antiviral drug acyclovir by an enriched nitrifying culture during ammonia oxidation and without the addition of ammonium. The study on kinetics was accompanied with the structural elucidation of biotransformation products through batch biodegradation experiments at two different initial levels of acyclovir (15 mg L^-1 and 15 μg L^-1). The pseudo first order kinetic studies of acyclovir in the presence of ammonium indicated the higher degradation rates under higher ammonia oxidation rates than those constant degradation rates in the absence of ammonium. The positive correlation was found between acyclovir degradation rate and ammonia oxidation rate, confirming the cometabolism of acyclovir by the enriched nitrifying culture in the presence of ammonium. Formation of the product carboxy-acyclovir (P239) indicated the main biotransformation pathway was aerobic oxidation of the terminal hydroxyl group, which was independent on the metabolic type (i.e. cometabolism or metabolism). This enzyme-linked reaction might be catalyzed by monooxygenase from ammonia oxidizing bacteria or heterotrophs. The formation of carboxy-acyclovir was demonstrated to be irrelevant to the acyclovir concentrations applied, indicating the revealed biotransformation pathway might be the dominant removal pathway of acyclovir in wastewater treatment.

The potential of the innovative SeMPAC process for enhancing the removal of recalcitrant organic micropollutants

SeMPAC is an innovative process based on a membrane sequential batch reactor to which powdered activated carbon (PAC) is directly added. It was developed with the aim of obtaining a high quality effluent in terms of conventional pollutants and organic micropollutants (OMPs). High COD removal and nitrification efficiencies (>95%) were obtained already during the operation without PAC, although denitrification was enhanced by PAC addition. OMPs were followed in the solid and liquid matrixes so that biotransformation, sorption onto the sludge and adsorption onto the PAC could be assessed. Recalcitrant compounds, such as carbamazepine and diazepam, were readily removed only after PAC addition (>99%). Progressive saturation of PAC was observed, with increasing concentrations of OMPs in the solid phase. Removal efficiencies for recalcitrant compounds were used as indicators for new additions of PAC. An improvement in the moderately biodegradable OMPs removal was observed after PAC addition (e.g. fluoxetine, trimethoprim) which was attributed to the biofilm that grew onto the sorbent, as well as to adsorption onto PAC.