Novel and Simple Method for Quantification of 2,4,6-Trichlorophenol with Microbial Conversion to 2,4,6-Trichloroanisole.

Contamination with 2,4,6-trichloroanisole (TCA) often causes taste and odor (T&O) problems in drinking water due to its low odor threshold concentration. Microbial O-methylation of the precursor 2,4,6-trichlorophenol (TCP) would be the dominant mechanism for TCA formation. Simple and rapid measurement of TCP in the low concentration range is necessary to control the problems induced by TCA. In this study, the combination of microbial conversion and instrumental analysis was proposed as a method of TCP quantification. Fungi and bacteria were isolated from various water samples and examined for their ability to produce TCA from TCP. As a result, a strain exhibiting quantitative TCA production and a high growth rate was obtained and named Mycolicibacterium sp. CB14. The conversion rate of TCP to TCA by this strain was found to be high and stable (85.9 ± 5.3%), regardless of the applied TCP concentration, although within the range of 0.1-10 µg/L. The limits of detection and quantification for TCP by this proposed method were determined to be 5.2 ng/L and 17.3 ng/L, respectively. By improving the methods, Mycolicibacterium sp. CB14 could be used for the quantification of TCP at very low concentration levels, which is sufficient to manage the T&O problem caused by TCA.

Monitoring Carbapenem-Resistant Enterobacterales in the Environment to Assess the Spread in the Community.

The usefulness of wastewater-based epidemiology (WBE) was proven during the COVID-19 pandemic, and the role of environmental monitoring of emerging infectious diseases has been recognized. In this study, the prevalence of carbapenem-resistant Enterobacterales (CRE) in Japanese environmental samples was measured in the context of applying WBE to CRE. A total of 247 carbapenem-resistant isolates were obtained from wastewater, treated wastewater, and river water. Treated wastewater was shown to be an efficient target for monitoring CRE. The results of the isolate analysis showed that WBE may be applicable to Escherichia coli-carrying New Delhi metallo-ß-lactamase (NDM)-type carbapenemase, the Enterobacter cloacae complex and Klebsiella pneumoniae complex-carrying IMP-type carbapenemase. In addition, a certain number of CRE isolated in this study carried Guiana extended spectrum (GES)-type carbapenemase although their clinical importance was unclear. Only a few isolates of Klebsiella aerogenes were obtained from environmental samples in spite of their frequent detection in clinical isolates. Neither the KPC-type, the oxacillinase (OXA)-type nor the VIM-type of carbapenemase was detected in the CRE, which reflected a low regional prevalence. These results indicated the expectation and the limitation of applying WBE to CRE.

Prevalence of ESBL-producing Escherichia coli and carbapenem-resistant Enterobacteriaceae in treated wastewater: a comparison with nosocomial infection surveillance.

The increasing prevalence of extended-spectrum ß-lactamase (ESBL)-producing Escherichia coli and carbapenem-resistant Enterobacteriaceae (CRE) is a worldwide health threat. Monitoring of these resistant bacteria in the environment can provide regional prevalence reflecting both healthy and infected populations, although the quantitative monitoring of those resistant bacteria, especially CRE, is difficult due to their low proportion in the total Enterobacteriaceae population and the possible interference by autochthonous species with intrinsic resistance. In this study, these resistant bacteria in treated wastewater were quantified at 12 different treatment plants. The proportions of cefotaxime-resistant and ESBL-producing E. coli in the total E. coli population in the chlorinated effluents in Tokyo were 5.7 and 5.3%, respectively. The estimated proportion of CRE was 0.007% with the constituting species of Klebsiella spp. and Enterobacter spp., although the conditions during the first incubation may have affected the estimation even after the correction by the proportion of resistant population in the isolates. The observed resistant proportions in this study were lower than those in the surveillance on nosocomial infection not only for inpatients but also for outpatients, and higher than those in the veterinary monitoring.

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.

Removal of the insect repellent N,N-diethyl-m-toluamide (DEET) by laccase-mediated systems.

Numerous efforts have been made to remove emerging trace organic contaminants, such as pharmaceuticals and personal care products (PPCPs). This study examined the removal of N,N-diethyl-m-toluamide (DEET) by Trametes versicolor laccase and its laccase-mediator systems. Experimental results showed that DEET was poorly removed by laccase alone. The poor removal efficiency of DEET by laccase may be attributed to the presence of strong withdrawing electron group (-CO-N [CH2-CH3]2) in the chemical structure of DEET. Experimental results also indicated that DEET might be indirectly oxidized by laccase-mediator systems. More than 50% initial DEET amount was removed by laccase in the presence of a redox mediator, such as 2,2'-azino-bis[3-ethylbenzothiazoline-6-sulphonic acid] (ABTS) or 1-hydroxybenzotriazole (HBT). However, laccase activity was considerably decreased in the presence of a redox mediator (ABTS or HBT). Further studies on identification of degradation byproducts and degradation pathways are recommended.

Insight into metabolic and cometabolic activities of autotrophic and heterotrophic microorganisms in the biodegradation of emerging trace organic contaminants.

Many efforts have been made to understand the biodegradation of emerging trace organic contaminants (EOCs) in the natural and engineered systems. This review summarizes the current knowledge on the biodegradation of EOCs while having in-depth discussion on metabolism and cometabolism of EOCs. Biodegradation of EOCs is mainly attributed to cometabolic activities of both heterotrophic and autotrophic microorganisms. Metabolism of EOCs can only be observed by heterotrophic microbes. Autotrophic ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaeal (AOA) cometabolize a variety of EOCs via the non-specific enzymes, such as ammonia monooxygenase (AMO). Higher biodegradation of EOCs is often noted under nitrification at high ammonia loading rate. The presence of a growth substrate promotes cometabolic biodegradation of EOCs. Potential strategies for enhancing the biodegradation of EOCs were also proposed in this review.

The characteristics of enriched nitrifier culture in the degradation of selected pharmaceutically active compounds.

The biodegradation of 10 selected pharmaceuticals by enriched nitrifier cultures with ammonia oxidizing activity of 30mg NH(4)-N/gMLVSSh was investigated under various initial operating conditions such as in the presence of different growth substrates and inhibitors. The enriched nitrifier culture showed higher degradation of the target pharmaceuticals than the conventional activated sludge. The degradation efficiency of persistent pharmaceuticals such as clofibric acid (CA), diclofenac (DCF), carbamazepine (CBZ), and propyphenazone (PPZ) was increased with the increase in the ammonium concentration. A higher removal efficiency of CA, DCF, CBZ and PPZ was obtained when organic substrates were added. The contribution of autotrophs and heterotrophs in the biotransformation of the pharmaceuticals by the enriched nitrifier culture was successfully estimated by the addition of inhibitors. Experimental results showed that the high degradation of IBP and partial degradation of other selected pharmaceuticals were observed in the presence of allylthiourea (ATU), an ammonia monooxygenase inhibitor, reflecting the activity of heterotrophic bacteria, while the results with and without ATU addition showed that the contribution of the nitrification in the degradation of most pharmaceuticals was also dominant. The results suggest that nitrification can enhance the biotransformation of pharmaceutical substances.

Emission of volatile organic compounds from solid waste disposal sites and importance of heat management.

The emission of volatile organic compounds (VOCs) from a solid waste disposal site for municipal solid wastes was quantified. The VOCs contained in the landfill gas taken at the site were benzene, toluene, xylenes, ethyl benzenes, and trimethyl benzenes, while the concentrations of chlorinated compounds were very low. The concentration of benzene in the landfill gas samples ranged from below the detection limit to 20 mg m(-3), and the ratio of benzene to toluene ranged from 0.2 to 8. The higher concentrations of VOCs in landfill gas and in leachates were observed with the samples taken at high temperature areas of the target site. Polystyrene plastic waste was identified as one of the sources of VOCs in solid waste disposal sites at a high temperature condition. The appropriate heat management in landfill sites is an important countermeasure to avoid unusually high emission of VOCs because the heat generated by the biodegradation of organic solid wastes may promote the release of VOCs, especially in the case of sites which receive both biodegradable and plastic wastes.

Separate estimation of adsorption and degradation of pharmaceutical substances and estrogens in the activated sludge process.

The removal of three estrogens such as 17beta-estradiol, two endocrine disruptors like bisphenol A, and 10 pharmaceutical substances like ibuprofen (IBP) by activated sludge was experimentally examined. The contribution of adsorption and degradation to the overall removal was estimated separately and successfully. At the neutral pH condition, the target pharmaceutical substances showed little tendency of adsorption to the sludge and their water-sludge partition coefficients were lower than those of the target estrogens. On the other hand, the increasing tendency of adsorption was observed in the lower pH condition. A linear relationship between the log of the partitioning coefficient and logK(ow) was observed when pH was lowered to keep the pharmaceuticals neutral solutes. The acidic operational condition was preferable for the removal of acidic pharmaceutical substances because the limiting stage for the removal was not biodegradation but the transfer of substances from the water phase to the sludge phase.