Role of nitrification in the biodegradation of selected artificial sweetening agents in biological wastewater treatment process

Artificial sweeteners in wastewater treatment plants: A systematic review of global occurrence, distribution, removal, and degradation pathways

The widespread use of artificial sweeteners in foods, drinks, and pharmaceuticals has led to rising concentrations in wastewater, with specific sweeteners raising concerns due to demonstrated toxicological risks to ecosystems and humans. To date, a comprehensive summary of the occurrence, distribution, and removal status of artificial sweeteners in wastewater treatment plants (WWTP) is lacking, making it difficult to evaluate the associated risks and environmental impacts. We conducted a systematic review of scientific literature and grey literature with rigorous screening covering 24 countries and 6 continents. Globally, sucralose, acesulfame, saccharin, and cyclamate are prevalent artificial sweeteners in WWTP, with concentrations of 0.6-303.0 µg/L in influent and 0.1-81.2 µg/L in effluent. Sucralose showed obvious increasing concentrations over time in wastewater in the United States and Canada, with an increase of 5.6-5.7 µg/L·y in influent and 4.7-5.5 µg/L·y in effluent. Summer wastewater usually contains 11.1-33.3 % higher concentrations of artificial sweeteners than other seasons. Saccharin and cyclamate are the most easily removable sweeteners (>90.0 % removal) in WWTP, followed by acesulfame (25.0-70.1 %) and sucralose (-10.0-10.0 %). Wastewater treatment processes with longer HRT and more diverse microbial communities showed better performance in sucralose removal, while processes with aerobic conditions showed better performance in acesulfame and saccharin removal than anaerobic processes. Increasing trends for persistent sucralose and acesulfame removal have been observed globally, suggesting potential microbial evolution/adaptation. This review contributes to a comprehensive understanding of the spatiotemporal distribution and ever-evolving biodegradation of artificial sweeteners in WWTP, providing future perspectives and potential policy requirements.

Microbial regulation of interspecific interaction and metabolism in anammox process to achieve coadaptation to artificial sweeteners

Artificial sweeteners (ASs) were frequently detectable in wastewater, which pose high risks to human health and ecological security. The feasibility of anaerobic ammonium oxidation (anammox) process for treatment of ASs-containing wastewater was evaluated in this study. The 86-d continuous flow experiment results showed that 0-30 μg L-1 cyclamate and acesulfame did not significantly affect the nitrogen removal efficiency (NRE) of anammox processes, which were 94.5 ± 3.0 % and 96.6 ± 2.5 %, respectively. Simultaneously, specific anammox activity (SAA) was inhibited by 15 μg L-1 ASs. Fortunately, anammox consortia adapted to the ASs stress by secreting extracellular polymeric substance (EPS). The relative abundances of Candidatus Kuenenia slightly decreased by 0.2 % and 2.3 % under stress of two ASs, and the microbial diversity increased. In addition, the anammox consortia regulated metabolites expression by cell energy allocation. The dominant metabolic pathways were amino acid metabolism, lipid metabolism and nucleotide metabolism. Particularly, the abundances of 5-hydroxylysinonorleucine and L-hypoglycin A significantly increased with ASs concentrations, which were crucial for bacterial proliferation. The co-metabolism between different bacteria might contribute to the biodegradation of ASs. This work demonstrates the feasibility of anammox process to treat the ASs-containing wastewater and reveals the regulation and adaptation mechanism of anammox microbiota, which further drives the implementation and development of anammox process.

Key role of NH4+-N in the removal of oxacillin during managed aquifer recharge: Reconsidering the recharge limitation

Frequent occurrence of trace antibiotics in reclaimed water is concerning, which inevitably causes aquifer contamination in the case of managed aquifer recharge (MAR). Global governments have formulated strict reclaimed water standards to ensure the safety of water reuse. Recent studies have found that improved antibiotics removal is intimately associated with high ammonia-oxidizing activity. However, the role of NH4+-N in the removal of residual antibiotics of reclaimed water during MAR remains unknown. NH4+-N removal and the effects of ammonia oxidation on antibiotics biodegradation in the aquifer are the most significant facts for solving the above collision. In this work, the effects of NH4+-N (0, 1 and 5 mg/L) in a model refractory antibiotic (oxacillin (OXA), 100 μg/L) attenuation were deciphered by employing three individual simulated MAR columns, which so called N0, N1 and N5. The results showed that 5 mg/L NH4+-N in influent upregulated the abundance of amo genes by 28.9 %-68.0 % in N5. And the enriched functional genes encoding key degradation enzymes enhanced the OXA removal by 18.7 % and alleviated the oxidative stress caused by antibiotics. Subsequently, antibiotic resistance genes (ARGs), mobile gene elements (MGEs) and human bacterial pathogens (HBPs) abundance were all significantly decreased. Moreover, the intimate association between ammonia-oxidizing microorganisms (AOM) and candidate OXA degraders based on microbial network analysis further supported the significance of AOM on OXA biodegradation. This study provides comprehensive evidence that appropriate amounts of NH4+-N are beneficial in antibiotics and antibiotic resistance risk reduction, providing compelling insights for refine NH4+-N recharge limitation.

EFSA Panel on Food Additives and Flavourings (FAF), Castle L, Andreassen M, Aquilina G, Bastos ML, Boon P, Fallico B, FitzGerald R, Frutos Fernandez MJ, Grasl‐Kraupp B, Gundert‐Remy U, Gürtler R, Houdeau E, Kurek M, Louro H, Morales P, Passamonti S, Batke M, Bruzell E, Chipman J, Cheyns K, Crebelli R, Fortes C, Fürst P, Halldorsson T, LeBlanc J, Mirat M, Lindtner O, Mortensen A, Ntzani E, Shah R, Wallace H, Wright M, Barmaz S, Civitella C, Georgelova P, Lodi F, Mazzoli E, Rasinger J, Maria Rincon A, Tard A, Zakidou P, Younes M. Re-evaluation of saccharin and its sodium, potassium and calcium salts (E 954) as food additives

This opinion deals with the re-evaluation of saccharin and its sodium, potassium and calcium salts (E 954) as food additives. Saccharin is the chemically manufactured compound 1,2-benzisothiazol-3(2H)-one-1,1-dioxide. Along with its sodium (Na), potassium (K) and calcium (Ca) salts, they are authorised as sweeteners (E 954). E 954 can be produced by two manufacturing methods i.e. Remsen-Fahlberg and Maumee. No analytical data on potential impurities were provided for products manufactured with the Maumee process; therefore, the Panel could only evaluate saccharins (E 954) manufactured with the Remsen-Fahlberg process. The Panel concluded that the newly available studies do not raise a concern for genotoxicity of E 954 and the saccharins impurities associated with the Remsen-Fahlberg manufacturing process. For the potential impurities associated with the Maumee process, a concern for genotoxicity was identified. The data set evaluated consisted of animals and human studies. The Panel considered appropriate to set a numerical acceptable daily intake (ADI) and considered the decrease in body weight in animal studies as the relevant endpoint for the derivation of a reference point. An ADI of 9 mg/kg body weight (bw) per day, expressed as free imide, was derived for saccharins (E 954). This ADI replaces the ADI of 5 mg /kg bw per day (expressed as sodium saccharin, corresponding to 3.8 mg /kg bw per day saccharin as free imide) established by the Scientific Committee on Food. The Panel considered the refined brand-loyal exposure assessment scenario the most appropriate exposure scenario for the risk assessment. The Panel noted that the P95 exposure estimates for chronic exposure to saccharins (E 954) were below the ADI. The Panel recommended the European Commission to consider the revision of the EU specifications of saccharin and its sodium, potassium and calcium salts (E 954).

Occurrence and source identification of antibiotics and antibiotic resistance genes in groundwater surrounding urban hospitals

Urban groundwater, serving as a critical reservoir for potable water, faces susceptibility to contamination from discrete sources such as hospital wastewater. This study investigates the distribution and plausible origins of antibiotics and antibiotic resistance genes (ARGs) in urban groundwater, drawing comparisons between areas proximal to hospitals and non-hospital areas. Ofloxacin and oxytetracycline emerged as the prevalent antibiotics across all samples, with a discernibly richer array of antibiotic types observed in groundwater sourced from hospital-adjacent regions. Employing a suite of multi-indicator tracers encompassing indicator drugs, Enterococci, ammonia, and Cl/Br mass ratio, discernible pollution from hospital or domestic sewage leakage was identified in specific wells, correlating with an escalating trajectory in antibiotic contamination. Redundancy analysis underscored temperature and dissolved organic carbon as principal environmental factors influencing antibiotics distribution in groundwater. Network analysis elucidated the facilitating role of mobile genetic elements, such as int1 and tnpA-02 in propagating ARGs. Furthermore, ARGs abundance exhibited positive correlations with temperature, pH and metallic constituents (e.g., Cu, Pb, Mn and Fe) (p < 0.05). Notably, no conspicuous correlation manifested between antibiotics and ARGs. These findings accentuate the imperative of recognizing the peril posed by antibiotic contamination in groundwater proximal to hospitals and advocate for the formulation of robust prevention and control strategies to mitigate the dissemination of antibiotics and ARGs.

Insight into the evolution of microbial communities and resistance genes induced by sucralose in partial nitrification system with triclosan pre-exposure

Sucralose (SUC), an artificial sweetener widely used in food, beverages and pharmaceuticals, is frequently detected in various environmental matrices. Triclosan (TCS) is commonly used as a disinfectant and often co-exists with SUC in sewage environments. This study investigated the effects of SUC (0.1-10 mg/L) on the transmission of intracellular and extracellular antibiotic resistance genes (ARGs) in the partial nitrification systems with and without TCS pre-exposure. The reactors operated for 150 days, and SUC did not affect ammonia oxidation performance, while TCS led to the maintenance of partial nitrification. The types and abundances of extracellular ARGs in sludge and free ARGs in water increased significantly after TCS pre-exposure when faced SUC stress, which might be caused by a decrease in α-Helix/(β-Sheet + Random coil). SUC was more easily to enrich ARGs in partial nitrification systems with TCS pre-exposure, exacerbating the risk of ARGs transmission. The microbial community showed stronger relationships to cope with the direct stress of SUC, and the functional bacteria (Thauera and Nitrosomonas) in TCS pre-exposure system might be potential hosts of ARGs. This study might provide insights for better understanding the fates of SUC in partial nitrification systems and the ecological risks in wastewater containing TCS and SUC. ENVIRONMENTAL IMPLICATION: Sucralose (SUC) is often detected in the environment and considered as an emerging contaminant due to its soaring consumption and environmental persistence. Triclosan (TCS) is an antibacterial agent that often co-exists with SUC in personal care products and sewage environments. During 150 d, two partial nitrification reactors with and without TCS pre-exposure were established to study the effects of SUC on nitrification performance, antibiotic resistance genes (ARGs) and microbial communities. This study showed the refractory nature of SUC, and SUC led to the transmission of extracellular ARGs in partial nitrification system with TCS pre-exposure, exacerbating the risk of ARGs dissemination.

Isolation and characterization of the aspartame-degrading strain Pseudarthrobacter sp. AS-1

Aspartame is one of the main varieties of artificial sweeteners. Although it has been approved as a food additive, the environmental hazards and ecological risks posed by aspartame are attracting more and more attention. In the present study, strain Pseudarthrobacter sp. AS-1 was isolated and characterized as an efficient aspartame degrader. Strain AS-1 was capable of degrading 200 mg L-1 aspartame within 10 h under conditions optimized at 30 °C and pH 8.0. At the same time, it was found that enzymes degrading aspartame in strain AS-1 were induced and secreted extracellularly. Degradation of aspartame in Pseudarthrobacter sp. AS-1 was identified as following: it was first demethylated to aspartyl-phenylalanine, then degraded to phenylalanine and aspartate, and finally the two amino acids were further degraded. In addition, strain AS-1 was able to remove more than 85% of aspartame in soil and river water. It is the first time that pure bacterial cultures were reported to have the capability of aspartame degradation. These findings add to our knowledge of the microbial metabolic mechanisms of aspartame.

Environmental persistence assessment of heterocyclic polyaromatic hydrocarbons - Ultimate and primary biodegradability using adapted and non-adapted microbial communities

Heterocyclic polyaromatic hydrocarbons (heterocyclic PAHs) are of increasing concern and their environmental and human health impacts should be assessed due to their widespread presence and potential persistence in the environment. This study investigated the ultimate and primary biodegradability of ten heterocyclic PAHs, nine of which were found to be non-readily biodegradable. To generate a microbial community capable of degrading such compounds, a bacterial inoculum isolated from the effluent of a wastewater treatment plant (WWTP) was adapted to a mixture of heterocyclic PAHs for one year. Throughout the adaptation process, bacterial samples were collected at different stages to conduct primary biodegradation, ultimate biodegradation, and inoculum toxicity tests. Interestingly, after one year of adaptation, the community developed the ability to mineralize carbazole, but in the same time showed an increasing sensitivity to the toxic effects of benzo[c]carbazole. In two consecutive primary biodegradation experiments, degradation of four heterocycles was observed, while no biodegradation was detected for five compounds in any of the tests. Furthermore, the findings of this work were compared with predictions from in silico models regarding biodegradation timeframe and sorption, and it was found that the models were partially successful in describing these processes. The results of study provide valuable insights into the persistence of a representative group of heterocyclic PAHs in aquatic environments, which contributes to the hazard assessment of this particular class of substances.

Levels, consumption, and variations of eight artificial sweeteners in the wastewater treatment plants of Dalian city, China

Artificial sweeteners (ASs) are emerging contaminants in the environment, primarily derived from wastewater treatment plant (WWTP) effluents. In this study, the influents and effluents of three WWTPs in the Dalian urban area, China, were analyzed for the distribution of 8 typical ASs to investigate their seasonal fluctuations in the WWTPs. The results showed that acesulfame (ACE), sucralose (SUC), cyclamate (CYC), and saccharin (SAC) were both detected in the influent and effluent water samples of WWTPs, with concentrations ranging from not detected (ND) to 14.02 μg·L-1. In addition, SUC was the most abundant ASs type, accounting for 40 %-49 % and 78 %-96 % of the total ASs in the influent and effluent water, respectively. The WWTPs revealed high removal efficiencies of CYC, SAC, and ACE, while the SUC removal efficiency was poor (26 % ± 36 %). The ACE and SUC concentrations were higher in spring and summer, and all ASs showed lower levels in winter, which may be caused by the high consumption of ice-cream in warmer months. The per capita ASs loads in the WWTPs were determined in this study based on the wastewater analysis results. The calculated per capita daily mas loads for individual ASs ranged from 0.45 g·d-1·1000p-1 (ACE) to 2.04 g·d-1·1000p-1 (SUC). In addition, the relationship between per capita ASs consumption and socioeconomic status showed no significant correlation.

Acesulfame allows the tracing of multiple sources of wastewater and riverbank filtration

Aquifers providing drinking water are increasingly threatened by emerging contaminants due to wastewater inputs from multiple sources. These inputs have to be identified, differentiated, and characterized to allow an accurate risk assessment and thus ensure the safety of drinking water through appropriate management. We hypothesize, that in climates with seasonal temperature variations, the sweetener acesulfame potassium (ACE) provides new pathways to study wastewater inputs to aquifers. Specifically, this study investigates the temperature-driven seasonal oscillation of ACE to assess multiple sources of wastewater inputs at a riverbank filtration site. ACE concentrations in the river water varied from 0.2 to 1 μg L^-1 in the cold season (T < 10 °C) to 0-0.1 μg L^-1 in the warm season (T > 10 °C), due to temperature-dependent biodegradation during wastewater treatment. This oscillating signal could be traced throughout the aquifer over distances up to 3250 m from two different infiltration sources. A transient numerical model of groundwater flow and ACE transport was calibrated over hydraulic heads and ACE concentrations, allowing the accurate calculation of mixing ratios, travel times, and flow-path directions for each of the two infiltration sources. The calculated travel time from the distant infiltration source was of 67 days, while that from the near source was of 20 days. The difference in travel times leads to different potential degradation of contaminants flowing into the aquifer from the river, thus demonstrating the importance of individually assessing the locations of riverbank infiltration. The calibrated ACE transport model allowed calculating transient mixing ratios, which confirmed the impact of river stage and groundwater levels on the mixing ratio of the original groundwater and the bank filtrate. Therefore, continuous monitoring of ACE concentrations can help to optimize the management of the water works with the aim to avoid collection of water with very short travel times, which has important regulative aspects. Our findings demonstrate the suitability of ACE as a transient tracer for identifying multiple sources of wastewater, including riverbank filtration sites affected by wastewater treatment plant effluents. ACE seasonal oscillation tracking thus provides a new tool to be used in climates with pronounced seasonal temperature variations to assess the origins of contamination in aquifers, with time and cost advantages over multi-tracer approaches.

Seasonal biodegradation of the artificial sweetener acesulfame enhances its use as a transient wastewater tracer

The persistence of the artificial sweetener acesulfame potassium (ACE) during wastewater treatment and subsequently in the aquatic environment has made it a widely used tracer of wastewater inputs to both surface water and groundwater. However, the recently observed biodegradation of ACE during wastewater treatment has questioned the validity of this application. In this study, we assessed the use of ACE not only as a marker of wastewater, but also as a transient wastewater tracer that allows both the calculation of mixing ratios and travel times through the aquifer as well as the calibration of transient groundwater flow and mass transport models. Our analysis was based on data obtained in a nearly 8-year river water and groundwater sampling campaign along a confirmed wastewater-receiving riverbank filtration site located close to a drinking water supply system. We provide evidence that temperature controls ACE concentration and thus its seasonal oscillation. River water data showed that ACE loads decreased from 1.5-4 mg·s^-1 in the cold season (December to June; T<10 °C) to 0-0.5 mg·s^-1 in the warm season (July to November; T>10 °C). This seasonal variability of >600% was detectable in the aquifer and preserved >3 km, with ACE concentrations oscillating between <LOQ in the warm season up to 1 μg·L^-1 in the cold season. The large seasonal variation in ACE concentrations during wastewater treatment, compared to the other sweeteners (sucralose, cyclamate, and saccharin) and chloride enables its use as a transient tracer of wastewater inflows and riverbank filtration. In addition, the arrival time of the ACE concentration peak can be used to estimate groundwater flow velocity and mixing ratios, thereby demonstrating its potential in the calibration of groundwater numerical models.

Different acesulfame potassium fate and antibiotic resistance propagation pattern in nitrifying and denitrifying sludge systems

Acesulfame potassium (ACE-K) is a widely utilized sugar substitute with increasing demand, which is frequently detected in various environmental matrix due to recalcitrance. However, a general consensus on the contribution of nitrifying and denitrifying process to ACE-K removal is lacking. Therefore, ACE-K removal, its effects on antibiotic resistant genes (ARGs) propagation and microbial community in nitrifying sequencing batch reactor (N-SBR) and denitrifying sequencing batch reactor (D-SBR) inoculated with the identical activated sludge were investigated. In this study, ACE-K can be eliminated in N-SBR with satisfying removal efficiency (96.76 ± 8.33 %) after 13 d acclimation, while it remained persistent (average ACE-K removal efficiency of 2.24 ± 1.86 %) in D-SBR during 84 d exposure. Moreover, ACE-K hardly affected the performances of these two types of reactors and had little impact on nitrifying and denitrifying functional genes. However, initial contact with ACE-K would increase ARGs abundance, network analysis showed functional bacteria in each reactor were possible ARGs hosts. Potential ACE-K degrading genera Chelatococcus, Bosea and Aquamicrobium were found in both reactors. LefSe analysis showed that Phyllobacteriaceae containing Aquamicrobium genus was a differentially enriched family in N-SBR. This research might provide a perspective for better understanding factor affecting ACE-K fate in wastewater treatment process and its ecological risks.

Seasonal occurrence, removal and mass loads of artificial sweeteners in the largest water reclamation plant in China

Artificial sweeteners (ASs) are of growing concern as an emerging contaminant. In the study, the seasonal occurrence, removal and mass load of six ASs in sewage, suspended particulate matter (SPM) and sludge were investigated throughout the treatment process of the largest water reclamation plant in China. The highest ASs concentrations in the influent (13.0 μg/L), effluent (2.22 μg/L), SPM (4.48 μg/g) and sludge (0.15 μg/g) were observed in the dry season, which were 1.24- to 5.0-fold higher than in the normal season and 1.06- to 37.5-fold higher than the flood season. Following treatment, ASs concentrations decreased by 24.3 %, 51.7 % and 5.1 % (on average) in primary, secondary and reclaimed processes, respectively. Among the investigated ASs, acesulfame (93.1 %) and cyclamate (98.4 %) were removed most efficiently, with removal occurring mainly in secondary processes, while sucralose exhibited the lowest removal efficiency (38.7 %). Seasonal characteristics affect the consumption of ASs, which subsequently changes the input and discharge ASs loads of STPs. The maximum mass load of ASs occurred in the dry season, ranging from 0.002 (neotame) to 1.33 mg/d/person (cyclamate), while the maximum emission load occurred in the flood season, ranging from 0.003 (neotame) to 0.83 mg/d/person (sucralose). The mass and emission load of ASs in Beijing is significantly lower than in European or the United States, due to Beijing having low per capita consumption of ASs (5.50 mg/d/person). The highest ASs risk in the receiving water occurred in the flood season due to the input of other pollution sources by rainfall runoff. Meanwhile, attention should be paid to the risk of receiving water close to the STP outlet in the dry seasons for the highest ASs concentration in the STP effluent in the season. The present study provides important guidance on controlling the input and reducing the emission of ASs in different seasons.

Role of ammonia-oxidizing microorganisms in the removal of organic micropollutants during simulated riverbank filtration

Biodegradation plays an important role in the removal of organic micropollutants (OMPs) during riverbank filtration (RBF) for drinking water production. The ability of ammonia-oxidizing microorganisms (AOM) to remove OMPs has attracted increasing attention. However, the distribution of AOM in RBF and its role in the degradation of OMPs remains unknown. In this study, the behavior of 128 selected OMPs and the distribution of AOM and their roles in the degradation of OMPs in RBF were explored by column and batch experiments simulating the first meter of the riverbank. The results showed that the selected OMPs were effectively removed (82/128 OMPs, >70% removal) primarily by biodegradation and partly by adsorption. Inefficiently removed OMPs tended to have low molecular weights, low log P, and contain secondary amides, secondary sulfonamides, secondary ketimines, and benzyls. In terms of the microbial communities, the relative abundance of AOM increased from 0.1%-0.2% (inlet_-sand) to 5.3%-5.9% (outlet_-sand), which was dominated by ammonia-oxidizing archaea whose relative abundance increased from 23%-72% (inlet_-sand) to 97% (outlet_-sand). Comammox accounted for 23%-64% in the inlet_-sand and 1% in the outlet_-sand. The abundances of AOM amoA genes kept stable in the inlet_-sand of control columns, while decreased by 78% in the treatment columns, suggesting the inhibition effect of allylthiourea (ATU) on AOM. It is observed that AOM played an important role in the degradation of OMPs, where its inhibition led to the corresponding inhibition of 32 OMPs (5/32 were completely suppressed). In particular, OMPs with low molecular weights and containing primary amides, secondary amides, benzyls, and secondary sulfonamides were more likely to be removed by AOM. This study reveals the vital role of AOM in the removal of OMPs, deepens our understanding of the degradation of OMPs in RBF, and offers valuable insights into the physiochemical properties of OMPs and their AOM co-metabolic potential.

EFSA Panel on Food Additives and Flavourings (FAF), Younes M, Aquilina G, Castle L, Degen G, Engel K, Fowler PJ, Frutos Fernandez MJ, Fürst P, Gundert‐Remy U, Gürtler R, Husøy T, Manco M, Mennes W, Moldeus P, Passamonti S, Shah R, Waalkens‐Berendsen I, Wright M, Batke M, Boon P, Bruzell E, Chipman J, Crebelli R, FitzGerald R, Fortes C, Halldorsson T, LeBlanc J, Lindtner O, Mortensen A, Ntzani E, Wallace H, Cascio C, Civitella C, Horvath Z, Lodi F, Mech A, Tard A, Vianello G. Re-evaluation of neohesperidine dihydrochalcone (E 959) as a food additive

The present opinion deals with the re-evaluation of neohesperidine dihydrochalcone (E 959) when used as a food additive. It is obtained by catalytic hydrogenation of a flavanone - neohesperidine - which is naturally occurring and thus isolated by alcohol extraction in bitter oranges (Citrus aurantium). Based on in vivo data in rat, neohesperidine dihydrochalcone is likely to be absorbed, also in humans, and to become systemically available. It does not raise a concern regarding genotoxicity. The toxicity data set consisted of studies on subchronic and prenatal developmental toxicity. No human studies were available. The data set was considered sufficient to derive a new acceptable daily intake (ADI). Based on the weight of evidence (WoE) analysis, the Panel considered unlikely that neohesperidine dihydrochalcone would lead to adverse effects on health in animals in the dose ranges tested. The Panel also considered that a carcinogenicity study was not warranted and that the lack of human data did not affect the overall confidence in the body of evidence. The Panel derived an ADI of 20 mg/kg bodyweight (bw) per day based on a no observed adverse effect level (NOAEL) of 4,000 mg/kg bw per day from a 13-week study in rat, applying the standard default factors of 100 for inter- and intraspecies differences and of 2 for extrapolation from subchronic to chronic exposure. For the refined brand-loyal exposure assessment scenario, considered to be the most appropriate for the risk assessment, the exposure estimates at the mean ranged from < 0.01 to 0.09 mg/kg bw per day and at the 95th percentile (P95) from 0.01 to 0.24 mg/kg bw per day. Considering the derived ADI of 20 mg/kg bw per day, the exposure estimates were below the reference value in all age groups. Therefore, the Panel concluded that dietary exposure to the food additive neohesperidine dihydrochalcone (E 959) at the reported uses and use levels would not raise a safety concern.

Tracking the fate of artificial sweeteners within the coastal waters of Shenzhen city, China: From wastewater treatment plants to sea

Artificial sweeteners (ASs), as a new emerging pollutant, the fate from wastewater treatment plants (WWTPs) to sea is growing concerned. In this study, the distribution and polluted loading of six typical ASs were analyzed based on the measurement in influent, primary effluent, secondary effluent, tertiary effluent, suspended particulate matter (SPM), and sludge from four WWTPs and receiving waters near the coast of Shenzhen city, China. Elevated levels of ASs were detected in WWTPs located near a highly populated area (about 14,000 people km^-2). Sucralose was predominant in all water samples (0.1-22.2 μg L^-1), and had a 1.6-704.0 times higher concentration than the means of other ASs detected. Aspartame were mainly distributed in SPM and sludge, and the fractions in offshore water exceeded 45%. Acesulfame, sucralose, cyclamate and saccharin could be effectively removed by secondary biochemical treatment. The average daily loading (4.2 g d^-1 1000people^-1) and discharge loading (0.4 g d^-1 1000people^-1) of sucralose in WWTPs was higher than those of the other ASs. Dissolved organic carbon and UV₂₅₄ can affect the fate of ASs, and SPM mainly affects the distributions of aspartame and neotame. As a potential sewage indicator, neotame deserves further attention.

The wasted chewing gum bacteriome

Here we show the bacteriome of wasted chewing gums from five different countries and the microbial successions on wasted gums during three months of outdoors exposure. In addition, a collection of bacterial strains from wasted gums was set, and the biodegradation capability of different gum ingredients by the isolates was tested. Our results reveal that the oral microbiota present in gums after being chewed, characterised by the presence of species such as Streptococcus spp. or Corynebacterium spp., evolves in a few weeks to an environmental bacteriome characterised by the presence of Acinetobacter spp., Sphingomonas spp. and Pseudomonas spp. Wasted chewing gums collected worldwide contain a typical sub-aerial biofilm bacteriome, characterised by species such as Sphingomonas spp., Kocuria spp., Deinococcus spp. and Blastococcus spp. Our findings have implications for a wide range of disciplines, including forensics, contagious disease control, or bioremediation of wasted chewing gum residues.

National wastewater reconnaissance of artificial sweetener consumption and emission in Australia

Artificial sweeteners are used as sugar substitutes in our daily lives yet consumption and release patterns are currently unknown in Australia. The spatial distribution of artificial sweetener consumption and WWTP effluent emission in Australia was estimated by wastewater analysis. Wastewater influent and effluent samples were collected from 69 WWTPs across Australia during the week of the 2016 Australian census. Mean population-weighted per capita loads for individual artificial sweeteners (cyclamate, aspartame, acesulfame, sucralose, saccharin) ranged from 0.12 ± 0.14 mg d^-1p^-1 for aspartame to 6.9 ± 2.8 mg d^-1p^-1 for acesulfame with 1004 kg of these artificial sweeteners being consumed daily in Australia. Significant removal of aspartame (100%), cyclamate (92 ± 18%) and saccharin (88 ± 21%) was observed during wastewater treatment. The average per capita release to the environment for individual artificial sweeteners (cyclamate, acesulfame, sucralose, saccharin) ranged from 230 ± 780 mg d^-1 1000p^-1 (cyclamate) to 3800 ± 1400 mg d^-1 1000p^-1 (sucralose). The daily release of artificial sweeteners from Australian WWTPs was estimated to be 142 kg suggesting that 14% of the artificial sweeteners consumed in Australia are released into the environment. To the best of our knowledge, this is the first wastewater study to estimate the occurrence and population-normalized artificial sweetener consumption and emission in Australia.

A Review of the Environmental Fate and Effects of Acesulfame-Potassium

The use of low and no calorie sweeteners (LNCSs) has increased substantially the past several decades. Their high solubility in water, low absorption to soils, and reliable analytical methods facilitate their detection in wastewater and surface waters. Low and no calorie sweeteners are widely used in food and beverage products around the world, have been approved as food additives, and are considered safe for human consumption by the United States Food and Drug Administration (USFDA) and other regulatory authorities. Concerns have been raised, however, regarding their growing presence and potential aquatic toxicity. Recent studies have provided new empirical environmental monitoring, environmental fate, and ecotoxicity on acesulfame potassium (ACE-K). Acesulfame potassium is an important high-production LNCS, widely detected in the environment and generally reported to be environmentally persistent. Acesulfame-potassium was selected for this environmental fate and effects review to determine its comparative risk to aquatic organisms. The biodegradation of ACE-K is predicted to be low, based on available quantitative structure-activity relationship (QSAR) models, and this has been confirmed by several investigations, mostly published prior to 2014. More recently, there appears to be an interesting paradigm shift with several reports of the enhanced ability of wastewater treatment plants to biodegrade ACE-K. Some studies report that ACE-K can be photodegraded into potentially toxic breakdown products, whereas other data indicate that this may not be the case. A robust set of acute and chronic ecotoxicity studies in fish, invertebrates, and freshwater plants provided critical data on ACE-K's aquatic toxicity. Acesulfame-potassium concentrations in wastewater and surface water are generally in the lower parts per billion (ppb) range, whereas concentrations in sludge and groundwater are much lower (parts per trillion [ppt]). This preliminary environmental risk assessment establishes that ACE-K has high margins of safety (MOSs) and presents a negligible risk to the aquatic environment based on a collation of extensive ACE-K environmental monitoring, conservative predicted environmental concentration (PEC) and predicted no-effect concentration (PNEC) estimates, and prudent probabilistic exposure modeling. Integr Environ Assess Manag 2020;16:421-437. © 2020 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Sated by a Zero-Calorie Sweetener: Wastewater Bacteria Can Feed on Acesulfame

The widely used artificial sweetener acesulfame K has long been considered recalcitrant in biological wastewater treatment. Due to its persistence and mobility in the aquatic environment, acesulfame has been used as marker substance for wastewater input in surface water and groundwater. However, recent studies indicated that the potential to remove this xenobiotic compound is emerging in wastewater treatment plants worldwide, leading to decreasing mass loads in receiving waters despite unchanged human consumption patterns. Here we show evidence that acesulfame can be mineralized in a catabolic process and used as sole carbon source by bacterial pure strains isolated from activated sludge and identified as Bosea sp. and Chelatococcus sp. The strains mineralize 1 g/L acesulfame K within 8-9 days. We discuss the potential degradation pathway and how this novel catabolic trait confirms the "principle of microbial infallibility." Once the enzymes involved in acesulfame degradation and their genes are identified, it will be possible to survey diverse environments and trace back the evolutionary origin as well as the mechanisms of global distribution and establishment of such a new catabolic trait.

Evaluation of the artificial sweetener sucralose as a sanitary wastewater tracer in Narragansett Bay, Rhode Island, USA

Narragansett Bay is an urban estuary that historically has been impacted by long-term discharge of sanitary wastewater (WW) effluents. High-density water sampling was conducted in Narragansett Bay, RI, USA, in an effort to understand the distribution and behavior of sucralose, an artificial sweetener that has shown utility as a sanitary wastewater tracer. Water samples were collected at sixty-seven sites and analyzed for sucralose, whose performance was compared to other tracers present in wastewater effluents. Concentrations of sucralose were much higher than the other tracers measured, carbamazepine and caffeine, ranging from 18 to 3180 ng/L and corresponded well with salinity (r² = 0.88), demonstrating conservative behavior throughout the Bay. Mapped interpolation data using an empirical bayesian kriging model clearly show the spatial trends of WW and how estuarine processes influence dilution and dispersion throughout the Bay. These findings provide further evidence of the efficacy of sucralose as a wastewater tracer in large urban estuaries where continuous high-volume discharge of WW occur.

Removal and transformation pathways of benzothiazole and benzotriazole in membrane bioreactors treating synthetic municipal wastewater

Lab-scale membrane bioreactors (MBRs), with aerated activated sludge and internal microfiltration module, were used for the treatment of municipal wastewater containing high, yet environmentally relevant, concentrations of benzothiazole (BT) and benzotriazole (BTA). These high production volume compounds are commonly used in the industry and households, and therefore occur ubiquitously in municipal wastewater and the aquatic environment. The aim of this study was to assess the removal of BT and BTA from synthetic municipal wastewater in MBRs and to estimate the contribution of elimination processes and to identify potential biotransformation products. The overall removal of BT and BTA was high, and after the adaptation period, it reached 99.8% and 97.2%, respectively, but recurring periods of unstable BTA removal occurred. The removal due to biotransformation was 88% for BT and 84% for BTA and the disposal with waste sludge accounted for only <1% of the removed load. The remaining fraction of the removed load of BT and BTA was attributed to be retained by phenomena associated with membrane fouling. The adaptation process was reflected in multifold increase in biodegradation kinetic coefficient (k_biol) for BT (reported for the first time) and BTA. Biodegradation was attributed to catabolic mechanism rather than to cometabolism. Hydroxylation was observed to be the main transformation reaction for BT, whereas for BTA hydroxylation, methylation and cleavage of benzene ring were noted. This study has shown the feasibility of treating municipal wastewater with high concentrations of BT and BTA in MBRs and identified potential challenges for the removal of BTA.

Roles of ammonia-oxidizing bacteria in improving metabolism and cometabolism of trace organic chemicals in biological wastewater treatment processes: A review

While there has been a significant recent improvement in the removal of pollutants in natural and engineered systems, trace organic chemicals (TrOCs) are posing a major threat to aquatic environments and human health. There is a critical need for developing potential strategies that aim at enhancing metabolism and/or cometabolism of these compounds. Recently, knowledge regarding biodegradation of TrOCs by ammonia-oxidizing bacteria (AOB) has been widely developed. This review aims to delineate an up-to-date version of the ecophysiology of AOB and outline current knowledge related to biodegradation efficiencies of the frequently reported TrOCs by AOB. The paper also provides an insight into biodegradation pathways by AOB and transformation products of these compounds and makes recommendations for future research of AOB. In brief, nitrifying WWTFs (wastewater treatment facilities) were superior in degrading most TrOCs than non-nitrifying WWTFs due to cometabolic biodegradation by the AOB. To fully understand and/or enhance the cometabolic biodegradation of TrOCs by AOB, recent molecular research has focused on numerous crucial factors including availability of the compounds to AOB, presence of growth substrate (NH₄-N), redox potentials, microorganism diversity (AOB and heterotrophs), physicochemical properties and operational parameters of the WWTFs, molecular structure of target TrOCs and membrane-based technologies, may all significantly impact the cometabolic biodegradation of TrOCs. Still, further exploration is required to elucidate the mechanisms involved in biodegradation of TrOCs by AOB and the toxicity levels of formed products.

Ecotoxicity and environmental fates of newly recognized contaminants-artificial sweeteners: A review

Artificial sweeteners (ASs) are used in countless application in daily life. ASs are newly recognized as pollutants due to their high detection frequency in various environmental media, which has aroused great concern. This review presents the current knowledge of AS ecotoxicity and possible elimination routes in the environment. The obtained results indicate that the negative impacts of ASs are more severe than previously expected. More attention should be paid to the chronic and metabolite toxicities of ASs. Moreover, numerous processes (physical, chemical and biological) have been reported to be able to degrade ASs. However, the elimination efficiency varies greatly depending on the specific AS and the particular experimental conditions. Cyclamate and saccharin are easily removed, while sucralose and acesulfame are generally persistent. Additionally, there is a large gap in the ASs removal efficiency between bench tests and full-scale studies. The potential for microbial degradation of persistent ASs was reported in some regions, but clarification of the underlying mechanisms is necessary to increase the likelihood of using this approach in wide applications with a satisfactory performance.

Insights into the variability of microbial community composition and micropollutant degradation in diverse biological wastewater treatment systems

The biological potential of conventional wastewater treatment plants to remove micropollutants mainly depends on process conditions and the predominant microbial community. To explore this dependence and to connect the occurrence of genera with operating conditions, five pilot-scale reactors with different process conditions were combined into two reactor cascades and fed with the effluent of the primary clarifier of a municipal WWTP. All reactors and the WWTP were analyzed for the removal of 33 micropollutants by LC-MS/MS and the presence of the microbial community using 16S rRNA gene sequencing. The overall removal of the micropollutants was slightly improved (ca. 20%) by the reactor cascades in comparison to the WWTP while certain compounds such as diatrizoate, venlafaxine or diclofenac showed an enhanced removal (ca. 70% in one or both cascades). To explore the diverse bacteria in more detail, the general community was divided into a core and a specialized community. Despite their profoundly different operating parameters (especially redox conditions), the different treatments share a core community consisted of 143 genera (9% of the overall community). Furthermore, the alpha- and beta-biodiversity as well as the occurrence of several genera belonging to the specialized microbial community could be linked to the prevalent process conditions of the individual treatments. Members of the specialized community also correlated with the removal of certain groups of micropollutants. Hence, the comparison of the specialized community with micropollutant removal and operating conditions via correlation analysis is a valuable tool for an extended evaluation of prevalent process conditions. Based on an extended data set this approach could also be used to identify organisms as indicators for operating conditions which are beneficial for an improved removal of specific micropollutants.

Assessment of the origin and transport of four selected emerging micropollutants sucralose, Acesulfame-K, gemfibrozil, and iohexol in a karst spring during a multi-event spring response

The assessment of vulnerability in karst systems reveals to be extremely challenging since it varies significantly with time and highly depends on the identification of diffuse and concentrated infiltration from surface karst features. The origin, consumed loads, and transport mode of selected micropollutants (MPs) including two artificial sweeteners (ASWs) Sucralose (SUC) and Acesulfame-K (ACE-K), in addition to other less investigated pharmaceuticals such as the lipid regulator Gemfibrozil (GEM), and the contrast media Iohexol (IOX) were investigated in a karst system under dynamic conditions. A detailed analysis of selected spring responses' chemograph and hydrograph following a multi precipitation event shows that three of the tracked MPs, especially ACE-K, and to the exception of IOX, can be used as specific indicators for point source domestic wastewater in karst systems. They have revealed to be persistent, source specific, conservative, and highly correlated with in-situ parameters easily measurable at the spring (chloride and turbidity). Even if the selected MPs are found in the system during low flow periods, they are mostly transported to the spring through fast flow pathways from flushed wastewater with surface water or flood rainwater. The highest mass inflow of ACE-K, IOX and GEM originated from a sinking stream, while SUC infiltrated exclusively through fast infiltration points (dolines). Their breakthrough curves coincide with the arrival of new waters and turbidity peaks. Unlike IOX, the mass fluxes of ASWs, and GEM to a lesser extent, can be linearly correlated with chloride mass fluxes and turbidity flux. Moreover, the variance of the normalized breakthrough curves of the MPs with respect to a mean transit time, increases in that order IOX<GEM<Turbidity<SUC<ACE-K indicating a higher restitution time for ACE-K with respect to other spring signals.

Occurrence and fate of emerging contaminants in municipal wastewater treatment plants from different geographical regions-a review

Emerging contaminants, such as antibiotics, pharmaceuticals, personal care products, hormones, and artificial sweeteners, are recognized as new classes of water contaminants due to their proven or potential adverse effects on aquatic ecosystems and human health. This review provides comprehensive data on the occurrence of 60 emerging contaminants (ECs) in influent, treated effluent, sludge, and biosolids in wastewater treatment plants (WWTPs). In particular, data on the occurrence of ECs in the influents and effluents of WWTPs are systematically summarized and categorized according to geographical regions (Asia, Europe, and North America). The occurrence patterns of ECs in raw influent and treated effluents of WWTPs between geographical regions were compared and evaluated. Concentrations of most ECs in raw influent in Asian region tend to be higher than those in European and North American countries. Many antibiotics were detected in the influents and effluents of WWTPs at concentrations close to or exceeding the predicted no-effect concentrations (PNECs) for resistance selection. The efficacy of EC removal by sorption and biodegradation during wastewater treatment processes are discussed in light of kinetics and parameters, such as sorption coefficients (K_d) and biodegradation constants (k_biol), and physicochemical properties (i.e. log K_ow and pK_a). Commonly used sampling and monitoring strategies are critically reviewed. Analytical research needs are identified, and novel investigative approaches for future monitoring studies are proposed.

Emerging Biodegradation of the Previously Persistent Artificial Sweetener Acesulfame in Biological Wastewater Treatment

The persistence of acesulfame (ACE) in wastewater treatment (and subsequently the aquatic environment) has led to its use as a marker substance for wastewater input into surface water and groundwater. However, ACE degradation of >85% during summer and autumn was observed in nine German wastewater treatment plants (WWTPs). Annual removal performance was more stable in larger plants, enhanced by low biological oxygen demand and impeded by water temperatures below 10 °C. Literature data suggest that the potential to degrade ACE emerged in WWTPs around the year 2010. This development is ongoing, as illustrated by ACE content in the German rivers Elbe and Mulde: Between 2013 and 2016 the ACE mass load decreased by 70-80%. In enrichment cultures with ACE as sole carbon source the carbonaceous fraction of ACE was removed completely, indicating catabolic biotransformation and the inorganic compound sulfamic acid formed in quantitative amounts. Sequencing of bacterial 16S rRNA genes suggests that several species are involved in ACE degradation, with proteobacterial species affiliated to Phyllobacteriaceae, Methylophilaceae, Bradyrhizobiaceae, and Pseudomonas becoming specifically enriched. ACE appears to be the first micropollutant for which the evolution of a catabolic pathway in WWTPs has been witnessed. It can yet only be speculated whether the emergence of ACE removal in WWTPs in different regions of the world is due to independent evolution or to global spreading of genes or adapted microorganisms.

Removal of artificial sweeteners and their effects on microbial communities in sequencing batch reactors

Concern is growing over contamination of the environment with artificial sweeteners (ASWs) because of their widespread existence in wastewater treatment plants (WWTPs). To evaluate ASWs removal and the effect on activated sludge, acesulfame (ACE), sucralose (SUC), cyclamate (CYC) and saccharin (SAC) were introduced individually or in mixture to sequencing batch reactors (SBRs) in environmentally relevant concentrations (100 ppb) for 100 days. Comparisons between ACE removal in a full-scale WWTP and in lab-scale SBRs were conducted. Results showed that CYC and SAC were completely removed, whereas SUC was persistent. However, ACE removal in lab-scale SBRs was significantly greater than in the full-scale WWTP. In SBRs, chemical oxygen demand (COD), ammonia nitrogen (NH₄⁺-N) and total nitrogen (TN) removal appeared unchanged after adding ASWs (p > 0.05). Adenosine triphosphate (ATP) concentrations and triphenyl tetrazolium chloride-dehydrogenase activity (TTC-DHA) declined significantly (p < 0.05). The mixed ASWs had more evident effects than the individual ASWs. Microbial community analyses revealed that Proteobacteria decreased obviously, while Bacteroidetes, Chloroflexi and Actinobacteria were enriched with the addition of ASWs. Redundancy Analysis (RDA) indicated ACE had a greater impact on activated sludge than the other ASWs.

Fate of artificial sweeteners through wastewater treatment plants and water treatment processes

Five full-scale wastewater treatment plants (WWTPs) in China using typical biodegradation processes (SBR, oxidation ditch, A²/O) were selected to assess the removal of four popular artificial sweeteners (ASs). All four ASs (acesulfame (ACE), sucralose (SUC), cyclamate (CYC) and saccharin (SAC)) were detected, ranging from 0.43 to 27.34μg/L in the influent. Higher concentrations of ASs were measured in winter. ACE could be partly removed by 7.11–50.76% through biodegradation and especially through the denitrifying process. The A²/O process was the most efficient at biodegrading ASs. Adsorption (by granular activated carbon (GAC) and magnetic resin) and ultraviolet radiation-based advanced oxidation processes (UV/AOPs) were evaluated to remove ASs in laboratory-scale tests. The amounts of resin adsorbed were 3.33–18.51 times more than those of GAC except for SUC. The adsorption ability of resin decreased in the order of SAC > ACE > CYC > SUC in accordance with the pKa. Degradation of ASs followed pseudo-first-order kinetics in UV/H₂O₂ and UV/PDS. When applied to the secondary effluent, ASs could be degraded from 30.87 to 99.93% using UV/PDS in 30 minutes and UV/PDS was more efficient and economic.

Artificial Sweeteners Reveal Septic System Effluent in Rural Groundwater

It has been widely documented that municipal wastewater treatment plant effluents are a major source of artificial sweeteners to surface waters. However, in rural areas, the extent to which septic systems contribute these same compounds to groundwater aquifers is largely unknown. We examined the occurrence of four commonly used artificial sweeteners in an unconfined sand aquifer that serves as a water supply for rural residents, as a receptor of domestic wastewater from septic systems, and as a source of baseflow to the Nottawasaga River, ON, Canada. Groundwater from the Lake Algonquin Sand Aquifer in the southern Nottawasaga River Watershed was collected from private domestic wells and as groundwater seeps discharging along the banks of the Nottawasaga River. Approximately 30% of samples had detectable levels of one or more artificial sweeteners, indicating the presence of water derived from septic system effluent. Using acesulfame concentrations to estimate the fraction of septic effluent in groundwater samples, ∼3.4 to 13.6% of the domestic wells had 1% or more of their well water being derived from septic system effluent. Similarly, 2.0 to 4.7% of the groundwater seeps had a septic effluent contribution of 1% or more. No relationship was found between the concentration of acesulfame and the concentration of nitrate, ammonium, or soluble reactive phosphorus in the groundwater, indicating that septic effluent is not the dominant source of nutrients in the aquifer. It is expected that the occurrence of artificial sweeteners in shallow groundwater is widespread throughout rural areas in Canada.

Fate of trace organic contaminants in oxic-settling-anoxic (OSA) process applied for biosolids reduction during wastewater treatment

This study investigated the fate of trace organic contaminants (TrOCs) in an oxic-settling-anoxic (OSA) process consisting of a sequencing batch reactor (SBR) with external aerobic/anoxic and anoxic reactors. OSA did not negatively affect TrOC removal of the SBR. Generally, low TrOC removal was observed under anoxic and low substrate conditions, implicating the role of co-metabolism in TrOC biodegradation. Several TrOCs that were recalcitrant in the SBR (e.g., benzotriazole) were biodegraded in the external aerobic/anoxic reactor. Some hydrophobic TrOCs (e.g., triclosan) were desorbed in the anoxic reactor possibly due to loss of sorption sites through volatile solids destruction. In OSA, the sludge was discharged from the aerobic/anoxic reactor which contained lower concentration of TrOCs (e.g., triclosan and triclocarban) than that of the control aerobic digester, suggesting that OSA can also help to reduce TrOC concentration in residual biosolids.

Biodegradation of the artificial sweetener acesulfame in biological wastewater treatment and sandfilters

A considerable removal of the artificial sweetener acesulfame (ACE) was observed during activated sludge processes at 13 wastewater treatment plants (WWTPs) as well as in a full-scale sand filter of a water works. A long-term sampling campaign over a period of almost two years revealed that ACE removal in WWTPs can be highly variable over time. Nitrifying/denitrifying sequencing batch reactors (SBR) as well as aerobic batch experiments with activated sludge and filter sand from a water works confirmed that both activated sludge as well as filter sand can efficiently remove ACE and that the removal can be attributed to biologically mediated degradation processes. The lab results strongly indicated that varying ACE removal in WWTPs is not associated with nitrification processes. Neither an enhancement of the nitrification rate nor the availability of ammonium or the inhibition of ammonium monooxygenase by N-allylthiourea (ATU) affected the degradation. Moreover, ACE was found to be also degradable by activated sludge under denitrifying conditions, while being persistent in the absence of both dissolved oxygen and nitrate. Using ion chromatography coupled with high resolution mass spectrometry, sulfamic acid (SA) was identified as the predominant transformation product (TP). Quantitative analysis of ACE and SA revealed a closed mass balance during the entire test period and confirmed that ACE was quantitatively transformed to SA. Measurements of dissolved organic carbon (DOC) revealed an almost complete removal of the carbon originating from ACE, thereby further confirming that SA is the only relevant final TP in the assumed degradation pathway of ACE. A first analysis of SA in three municipal WWTP revealed similar concentrations in influents and effluents with maximum concentrations of up to 2.3 mg/L. The high concentrations of SA in wastewater are in accordance with the extensive use of SA in acid cleaners, while the degradation of ACE in WWTPs adds only a very small portion of the total load of SA discharged into surface waters. No removal of SA was observed by the biological treatment applied at these WWTPs. Moreover, SA was also stable in the aerobic batch experiments conducted with the filter sand from a water works. Hence, SA might be a more appropriate wastewater tracer than ACE due to its chemical and microbiological persistence, the negligible sorbing affinity (high negative charge density) and its elevated concentrations in WWTP effluents.

Metabolic and Co-Metabolic Transformation of Diclofenac by Enterobacter hormaechei D15 Isolated from Activated Sludge

The presence of non-steroidal anti-inflammatory drugs, such as diclofenac (DCF), in the environment, is an emerging problem due to their harmful effects on non-target organisms, even at low concentrations. We studied the biodegradation of DCF by the strain D15 of Enterobacter hormaechei. The strain was isolated from an activated sludge, and identified as E. hormaechei based on its physiological characteristics and its 16 S RNA sequence. Using HPTLC and GC-MS methods, we demonstrated that this strain metabolized DCF at an elimination rate of 52.8%. In the presence of an external carbon source (glucose), the elimination rate increased to approximately 82%. GC-MS analysis detected and identified one metabolite as 1-(2,6-dichlorophenyl)-1,3-dihydro-2H-indol-2-one; it was produced as a consequence of dehydration and lactam formation reactions.

Enhanced biodegradation of phenolic compounds in landfill leachate by enriched nitrifying membrane bioreactor sludge

The role of autotrophic nitrification on the biodegradation of toxic organic micro-pollutants presented in landfill leachate was assessed. A two-stage MBR system consisting of an inclined tube incorporated anoxic reactor followed by aerobic submerged membrane reactor was operated under long sludge age condition in which nitrifying bacteria could be enriched. During the reactor operation, organic removal efficiencies were more than 90% whereas phenolic compounds including bisphenol A (BPA) and 4-methyl-2,6-di-tert-butylphenol (BHT) were removed by 65 and 70% mainly through biodegradation in the aerobic reactor even at high feed concentrations of 1000μg/L for both compounds. Batch experiments revealed that enriched nitrifying sludge with nitrifying activities could biodegraded 88 and 75% of BPA and BHT, largely improved from non-nitrifying sludge and enriched nitrifying sludge with the presence of inhibitor. The first-order kinetic rates of BHT and BPA removal were 0.0108 and 0.096h^-1, also enhanced by 44% from the non-nitrifying sludge.

Biodegradation of Methyl tert-Butyl Ether by Co-Metabolism with a Pseudomonas sp. Strain

Co-metabolic bioremediation is supposed to be an impressive and promising approach in the elimination technology of methyl tert-butyl ether (MTBE), which was found to be a common pollutant worldwide in the ground or underground water in recent years. In this paper, bacterial strain DZ13 (which can co-metabolically degrade MTBE) was isolated and named as Pseudomonas sp. DZ13 based on the result of 16S rRNA gene sequencing analysis. Strain DZ13 could grow on n-alkanes (C₅-C₈), accompanied with the co-metabolic degradation of MTBE. Diverse n-alkanes with different carbon number showed a significant influence on the degradation rate of MTBE and accumulation of tert-butyl alcohol (TBA). When Pseudomonas sp. DZ13 co-metabolically degraded MTBE with n-pentane as the growth substrate, a higher MTBE-degrading rate (V_max = 38.1 nmol/min/mg_protein, K_s = 6.8 mmol/L) and lower TBA-accumulation was observed. In the continuous degradation experiment, the removal efficiency of MTBE by Pseudomonas sp. Strain DZ13 did not show an obvious decrease after five times of continuous addition.

rRNA Gene Expression of Abundant and Rare Activated-Sludge Microorganisms and Growth Rate Induced Micropollutant Removal

The role of abundant and rare taxa in modulating the performance of wastewater-treatment systems is a critical component of making better predictions for enhanced functions such as micropollutant biotransformation. In this study, we compared 16S rRNA genes (rDNA) and rRNA gene expression of taxa in an activated-sludge-treatment plant (sequencing batch membrane bioreactor) at two solids retention times (SRTs): 20 and 5 days. These two SRTs were used to influence the rates of micropollutant biotransformation and nutrient removal. Our results show that rare taxa (<1%) have disproportionally high ratios of rRNA to rDNA, an indication of higher protein synthesis, compared to abundant taxa (≥1%) and suggests that rare taxa likely play an unrecognized role in bioreactor performance. There were also significant differences in community-wide rRNA expression signatures at 20-day SRT: anaerobic-oxic-anoxic periods were the primary driver of rRNA similarity. These results indicate differential expression of rRNA at high SRTs, which may further explain why high SRTs promote higher rates of micropollutant biotransformation. An analysis of micropollutant-associated degradation genes via metagenomics and direct measurements of a suite of micropollutants and nutrients further corroborates the loss of enhanced functions at 5-day SRT operation. This work advances our knowledge of the underlying ecosystem properties and dynamics of abundant and rare organisms associated with enhanced functions in engineered systems.

Role of ammonia-oxidizing bacteria in micropollutant removal from wastewater with aerobic granular sludge

Nitrifying wastewater treatment plants (WWTPs) are more efficient than non-nitrifying WWTPs to remove several micropollutants such as pharmaceuticals and pesticides. This may be related to the activity of nitrifying organisms, such as ammonia-oxidizing bacteria (AOBs), which could possibly co-metabolically oxidize micropollutants with their ammonia monooxygenase (AMO). The role of AOBs in micropollutant removal was investigated with aerobic granular sludge (AGS), a promising technology for municipal WWTPs. Two identical laboratory-scale AGS sequencing batch reactors (AGS-SBRs) were operated with or without nitrification (inhibition of AMOs) to assess their potential for micropollutant removal. Of the 36 micropollutants studied at 1 μg l(-1) in synthetic wastewater, nine were over 80% removed, but 17 were eliminated by less than 20%. Five substances (bisphenol A, naproxen, irgarol, terbutryn and iohexol) were removed better in the reactor with nitrification, probably due to co-oxidation catalysed by AMOs. However, for the removal of all other micropollutants, AOBs did not seem to play a significant role. Many compounds were better removed in aerobic condition, suggesting that aerobic heterotrophic organisms were involved in the degradation. As the AGS-SBRs did not favour the growth of such organisms, their potential for micropollutant removal appeared to be lower than that of conventional nitrifying WWTPs.

Fecal pollution source tracking toolbox for identification, evaluation and characterization of fecal contamination in receiving urban surface waters and groundwater

The quality of surface waters/groundwater of a geographical region can be affected by anthropogenic activities, land use patterns and fecal pollution sources from humans and animals. Therefore, the development of an efficient fecal pollution source tracking toolbox for identifying the origin of the fecal pollution sources in surface waters/groundwater is especially helpful for improving management efforts and remediation actions of water resources in a more cost-effective and efficient manner. This review summarizes the updated knowledge on the use of fecal pollution source tracking markers for detecting, evaluating and characterizing fecal pollution sources in receiving surface waters and groundwater. The suitability of using chemical markers (i.e. fecal sterols, fluorescent whitening agents, pharmaceuticals and personal care products, and artificial sweeteners) and/or microbial markers (e.g. F+RNA coliphages, enteric viruses, and host-specific anaerobic bacterial 16S rDNA genetic markers) for tracking fecal pollution sources in receiving water bodies is discussed. In addition, this review also provides a comprehensive approach, which is based on the detection ratios (DR), detection frequencies (DF), and fate of potential microbial and chemical markers. DR and DF are considered as the key criteria for selecting appropriate markers for identifying and evaluating the impacts of fecal contamination in surface waters/groundwater.

Sorption and biodegradation of artificial sweeteners in activated sludge processes

There is limited information on the occurrence and removal of artificial sweeteners (ASs) in biological wastewater treatment plants, and in particular, the contribution of sorption and biodegradation to their removal. This study investigated the fate of ASs in both the aqueous and solid phases in a water reclamation plant (WRP). All the four targeted ASs, i.e. acesulfame (ACE), sucralose (SUC), cyclamate (CYC) and saccharine (SAC), were detected in both the aqueous and solid phases of raw influent and primary effluent samples. The concentrations of CYC and SAC in secondary effluent or MBR permeate were below their method detection limits. ACE and SUC were persistent throughout the WRP, whereas CYC and SAC were completely removed in biological treatment (>99%). Experimental results showed that sorption played a minor role in the elimination of the ASs due to the relatively low sorption coefficients (Kd), where Kd<500L/kg. In particular, the poor removal of ACE and SUC in the WRP may be attributed to their physiochemical properties (i.e. logKow<0 or logD<3.2) and chemical structures containing strong withdrawing electron functional groups in heterocyclic rings (i.e. chloride and sulfonate).

A critical review on characterization strategies of organic matter for wastewater and water treatment processes

The presence of organic matter (OM) in raw wastewater, treated wastewater effluents, and natural water samples has been known to cause many problems in wastewater treatment and water reclamation processes, such as treatability, membrane fouling, and the formation of potentially toxic by-products during wastewater treatment. This paper summarizes the current knowledge on the methods for characterization and quantification of OM in water samples in relation to wastewater and water treatment processes including: (i) characterization based on the biodegradability; (ii) characterization based on particle size distribution; (iii) fractionation based on the hydrophilic/hydrophobic properties; (iv) characterization based on the molecular weight (MW) size distribution; and (v) characterization based on fluorescence excitation emission matrix. In addition, the advantages, disadvantages and applications of these methods are discussed in detail. The establishment of correlations among biodegradability, hydrophobic/hydrophilic fractions, MW size distribution of OM, membrane fouling and formation of toxic by-products potential is highly recommended for further studies.

Selection of organic process and source indicator substances for the anthropogenically influenced water cycle

An increasing number of organic micropollutants (OMP) is detected in anthropogenically influenced water cycles. Source control and effective natural and technical barriers are essential to maintain a high quality of drinking water resources under these circumstances. Based on the literature and our own research this study proposes a limited number of OMP that can serve as indicator substances for the major sources of OMP, such as wastewater treatment plants, agriculture and surface runoff. Furthermore functional indicators are proposed that allow assessment of the proper function of natural and technical barriers in the aquatic environment, namely conventional municipal wastewater treatment, advanced treatment (ozonation, activated carbon), bank filtration and soil aquifer treatment as well as self-purification in surface water. These indicator substances include the artificial sweetener acesulfame, the anti-inflammatory drug ibuprofen, the anticonvulsant carbamazepine, the corrosion inhibitor benzotriazole and the herbicide mecoprop among others. The chemical indicator substances are intended to support comparisons between watersheds and technical and natural processes independent of specific water cycles and to reduce efforts and costs of chemical analyses without losing essential information.

Removal of micropollutants, facultative pathogenic and antibiotic resistant bacteria in a full-scale retention soil filter receiving combined sewer overflow

Combined sewer systems collect surface runoff as well as wastewater of industrial and domestic origin. During periods of heavy rainfall the capacity of the sewer system is exceeded and the overflow is discharged into receiving waters without any treatment. Consequently, combined sewer overflow (CSO) is considered as a major source of water pollution. This study investigates the effectiveness of a retention soil filter (RSF) for the removal of micropollutants as well as facultative pathogenic and antibiotic resistant bacteria from CSO. The removal of organic group parameters like total organic carbon was excellent and the removal efficiency for micropollutants of the RSF and the wastewater treatment plant (WWTP), which treats wastewater of the same origin during dry and normal weather conditions, was comparable. Compounds of high environmental concern like estrogens or certain pharmaceuticals, e.g. diclofenac, were completely eliminated or removed to a high degree during RSF passage. RSF treatment also reduced the number of E. coli, enterococci and staphylococci by 2.7, 2.2 and 2.4 log-units (median values), respectively. Obviously, some Staphylococcus species can better adapt to the conditions of the RSF than others as a shift of the abundance of the different species was observed when comparing the diversity of staphylococci obtained from the RSF influent and effluent. RSF treatment also decreased the absolute number of antibiotic resistant bacteria. The percentage of antibiotic resistant E. coli and staphylococci isolates also decreased during passage of the RSF, whereas the percentage of resistant enterococci did not change. For E. coli ampicillin and for enterococci and staphylococci erythromycin determined the antibiotic resistance level. The results demonstrate that RSFs can be considered as an adequate treatment option for CSO. The performance for the removal of micropollutants is comparable with a medium sized WWTP with conventional activated sludge treatment. The number of facultative pathogenic and antibiotic resistant bacteria was considerably decreased during RSF passage. However, as RSF effluents still contained antibiotic resistance genes and traces of micropollutants; receiving waters may still be at risk from negative environmental impacts.