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

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).

Screening of antimicrobials, fragrances, UV stabilizers, plasticizers and preservatives in sewage treatment plants (STPs) and their risk assessment in India

Community/industrial wastewater is the prime source of anthropogenic chemicals, its treatment is often a daunting task and unaffordable for many countries. Emerging Contaminants (ECs) have been drained into wastewater after continuous use/misuse and Conventional treatments in STPs do not remove them completely. ECs including antimicrobial agents, synthetic musks, Benzotriazole UV stabilizers (BUVSs), plasticizers, and preservatives are frequently reported in environment, and cause health effects to non-target organisms. Monitoring of ECs is important to understand their status in aquatic environment. Hence, it was aimed to monitor ECs (n = 21) from 11 STPs in Tamil Nadu, India. The detection frequency of most of these analytes was >90%. Antimicrobials ranged from 247 to 22,714 ng/L and 11-14,369 ng/L in influents and effluents, respectively. The synthetic musks were in the order of Tonalide > Galaxolide > Musk Ketone. BUVSs ranged from 4 to 1632 ng/L (influents) and < LOD to 29,853 ng/L (effluents). Concentration of phthalates in influents and effluents were < LOD - 11,311 ng/L and < LOD - 17,618 ng/L, respectively. Parabens were found in the order of Prophyl > Methyl > Ethyl > Butyl in influents and Methyl > Prophyl > Butyl > Ethyl in effluents. Mass loads of ECs through STPs were found as antimicrobials > plasticizers > fragrances > BUVSs > Preservatives. This study reveals increasing usage of ECs and inadequate treatment processes at STPs in India. Also helps to adopt suitable treatment processes to remove ECs from wastewater and to reuse the wastewater.

Elucidating the intensifying effect of introducing influent to an anaerobic side-stream reactor on sludge reduction of the coupled membrane bioreactors

Three anoxic/oxic membrane bioreactors (AO-MBRs) coupled with the anaerobic side-stream reactor (ASSR) with different influent flow distribution ratios (IFDRs) were assessed to elucidate how IFDR in the ASSR affected pollutants removal, sludge reduction, membrane fouling, and potential co-occurrence network of microorganisms. When the IFDR in the ASSR was increased from 0% (ASSR₀-MBR), to 25% (ASSR₂₅-MBR) and 75% (ASSR₇₅-MBR), chemical oxygen demand removal was enhanced and nutrient removal was comparable. Compared to ASSR₀-MBR, ASSR₂₅- and ASSR₇₅-MBR further improved the sludge reduction by 7.6% and 10.9%, respectively. ASSR₂₅-MBR followed cake-complete model due to the weak membrane surface scouring and high concentration of extracellular polymeric substances, while ASSR₀- and ASSR₇₅-MBR fitted cake-standard model. The increased IFDR in the ASSR boosted the relative abundance of hydrolytic and slow-growing bacteria. The co-occurrence networks of sludge reduction, nutrient removal and membrane fouling propensity indicated that the symbiotic relationships were dominant.

Comparison of anaerobic, cycling aerobic/anoxic, and sequential anaerobic/aerobic/anoxic digestion to remove triclosan and triclosan metabolites from municipal biosolids

The antimicrobial triclosan (TCS) is a pervasive and persistent environmental micropollutant which can contaminate land, biota, and water through the land application of biosolids. Many existing sludge management techniques have limited effectiveness against TCS and TCS metabolites including triclosan-sulfate (TCS-SO₄). The objective of this study was to evaluate the impacts of different digestion types (anaerobic, aerobic/anoxic, and sequential anaerobic + aerobic/anoxic), temperatures, and digester sludge retention times (SRTs) on the destruction of organic matter, and on TCS/TCS metabolites. Conventional mesophilic anaerobic digesters (AD), room temperature cycling aerobic/anoxic digesters (AERO/ANOX), and sequential AD + AERO/ANOX digesters were all effective in removing organic matter. The optimum single-stage AD, and AERO/ANOX scenarios were both 20-day SRTs which had 52.3 ± 1.4 and 47.1 ± 3.7% chemical oxygen demand (COD) removals, respectively. Sequential AD + AERO/ANOX digesters improved organic matter destruction, removing up to 68.2 ± 2.1% of COD at an 8-day AD + 12-day AERO/ANOX second-stage (mesophilic) SRTs. While AD showed modest levels of TCS removals (all <40%), TCS was substantially more degradable aerobically with AERO/ANOX removing up to 80.3 ± 2.5% of TCS and nearly all TCS-SO₄ entering the digester at a 20-day SRT. Sequential AD + AERO/ANOX removed virtually all TCS-SO₄ entering the system and improved TCS removals from first stage ADs. However, they were less effective than a single-stage AERO/ANOX digester operating at the same overall SRT. These results demonstrate that AERO/ANOX and sequential AD + AERO/ANOX processes could be used to reduce the amount of TCS, TCS-SO₄ and TCS-related compounds in digested sludge, minimizing the environmental burden of the land application of biosolids.

Sludge reduction based on microbial metabolism for sustainable wastewater treatment

Sludge reduction via microbial metabolism does not require extra energy and resource inputs and thus merits attention as an alternative approach for sustainable wastewater treatment. This review presents a summary and analysis of the existing literatures on sludge reduction based on microbial metabolism, as well as interprets these sludge reduction mechanisms using bacterial thermodynamics and stoichiometry. Future efforts should be directed toward using advanced analytical techniques to further reveal sludge reduction mechanisms. The feasibility of coupling sludge reduction and nutrient removal by microorganism metabolism needs to be further evaluated to minimize the effect of sludge reduction on nutrient removal. A comprehensive life cycle assessment of sludge reduction strategies is recommended to effectively confirm their sustainability. Full-scale research is needed to verify the results obtained from bench- and pilot-scale experiments. This review presents the future opportunities and challenges for sludge reduction based on microbial metabolism in the excess sludge disposal.

Rapid degradation of clozapine by heterogeneous photocatalysis. Comparison with direct photolysis, kinetics, identification of transformation products and scavenger study

In this study TiO₂-mediated photocatalytic degradation of the persistent drug clozapine under the simulated solar radiation was studied for the first time. The experiments were conducted both in the ultrapure and river water, which enabled the assessment of the organic matrix impact. The direct and indirect photolysis experiments were conducted for a comparison. Influence of the catalyst loading on the efficiency of the process was also assessed, and the highest catalyst loading (300 mg L^-1) was found to be the most effective. The TiO₂ photocatalysis was extremely effective for clozapine degradation - the decomposition was almost 300 times faster in comparison to the direct photolysis (t_1/2 = 1.7 min, neither clozapine, nor the intermediates were detected after 20 min of irradiation), and presence of the organic matrix did not negatively affect the process. Nevertheless the photocatalytic process turned out to be highly sensitive to act of the ROS scavengers. Thirteen transformation products (TPs) were found and their structures were elucidated by the means of high resolution mass spectrometry. Properties - toxicity, biodegradability, BCF and BAF - of TPs and the parent molecule were estimated with the use of computational methods. Identified TPs were found as generally less toxic and more biodegradable than clozapine.

Synthesis and applications of biogenic nanomaterials in drinking and wastewater treatment

The continuous increase in water pollution by various organic & inorganic contaminants has become a major issue of concern worldwide. Furthermore, the anthropogenic activities for the manufacturing of various products have boosted this problem manifold. To overcome this serious issue, nanotechnology has initiated to explore various proficient strategies to treat waste water in a more precise and accurate way with the support of various nanomaterials. In recent times, nanosized materials have proved their applicability to provide clean and affordable water treatment technologies. The exclusive features such as high surface area and mechanical properties, greater chemical reactivity, lower cost and energy, efficient regeneration for reuse allow the nanomaterials perfect for water remediation. But the conventional routes of synthesis of nanomaterials encompass the involvement of hazardous and volatile chemicals; therefore the use of nanomaterials further creates the secondary pollution. This issue has intrigued the scientists to develop biogenic pathways and procedures which are environmentally safer and inexpensive. It has led to the new trends that involve developing bio-inspired nano-scale adsorbents and catalysts for the removal and degradation of a wide range of water pollutants. Carbohydrates, proteins, polymers, flavonoids, alkaloids and several antioxidants obtained from plants, bacteria, fungi, and algae have proven their effectiveness as capping and stabilizing agents during manufacture of nanomaterials. Application of biogenic nanomaterials for waste water treatment is relatively newer but rapidly escalating area of research. In the present review, promises and challenges for the synthesis of various biogenic nanomaterials and their potential applications in waste water treatment and/or water purification have been discussed.

Sustainable power generation from sewage and energy recovery from wastewater with variable resistance using microbial fuel cell

Wastewater from sewage sources contribute significantly to water pollution from domestic waste; one way to recover energy from these sources while at the same time, treating the water is possible using Microbial Fuel Cell. In this work, a two chambered microbial fuel cell was designed and fabricated with carbon cloth electrodes and Nafion-117 membrane, having Platinum as the catalyst. Wastewater from an organic load of 820 ± 30 mg/l reduced to around 170 mg/l, with the change in pH from 7.65 ± 0.6 to 7. 31 ± 0.5; over the time of operation the biochemical oxygen demand from an initial 290 ± 30 mg/l reduced to 175 ± 10 mg/l. Open circuit voltage was achieved mostly between 750-850 mV, with inoculated sludge produced a peak open circuit voltage of 1.45 V between fed-batch cycles. For characterization of power generated, polarization curves are evaluated with varying resistance to examine system stability with varying resistance. The current density and power density are reported to peak at 0.54 mA/m² and 810 ± 10 mW/m² respectively. The development of stable biofilms on the anode contributes to the power generation and was evaluated using microscopic analysis, this shows bacteria present in wastewater are electroactive microbial species which can donate electron to an electrode using conductive appendages or nanowires, while consuming the organic matter present in the wastewater. Such systems employ microbial metabolism for water treatment and generate electricity.

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.