Intensive historical and worldwide use of pesticide formulations
containing hexachlorocyclohexane (HCH) has led to widespread contamination.
We derived four anaerobic enrichment cultures from HCH-contaminated
soil capable of sustainably dechlorinating each of α-, β-,
γ-, and δ-HCH isomers stoichiometrically to benzene and
monochlorobenzene (MCB). For each isomer, the dechlorination rates,
inferred from production rates of the dechlorinated products, MCB
and benzene, increased progressively from <3 to ∼12 μM/day
over 2 years. The molar ratio of benzene to MCB produced was a function
of the substrate isomer and ranged from β (0.77 ± 0.15),
α (0.55 ± 0.09), γ (0.13 ± 0.02), to δ
(0.06 ± 0.02) in accordance with pathway predictions based on
prevalence of antiperiplanar geometry. Data from 16S rRNA gene amplicon
sequencing and quantitative PCR revealed significant increases in
the absolute abundances of Pelobacter and Dehalobacter, most notably in
the α-HCH and δ-HCH cultures. Cultivation with a different
HCH isomer resulted in distinct bacterial communities, but similar
archaeal communities. This study provides the first direct comparison
of shifts in anaerobic microbial communities induced by the dechlorination
of distinct HCH isomers. It also uncovers candidate microorganisms
responsible for the dechlorination of α-, β-, γ-,
and δ-HCH, a key step toward better understanding and monitoring
of natural attenuation processes and improving bioremediation technologies
for HCH-contaminated sites.
Biochemical methane potential assays (BMP assays) were performed to study the potential of anaerobic treatment of in-mill wastewaters. The assay results indicated that condensate and the BCTMP effluent, which are currently treated with the anaerobic internal circulation reactors, were the best streams for anaerobic treatment because of their relatively high degradability (>80%) and initial rates of biogas production. The softwood dewatering process stream was the worst with the lowest degradability (~30%). The hardwood stream was more degradable than the softwood stream from the same process. Biogas production was found to be additive and predictable in blended samples. In addition, degradability was found to be negatively correlated to the concentration of dehydroabietic acid and tannin-lignin compounds. The anaerobic treatment of the suitable streams has great potential value with significantly reduced sludge production and energy savings.
Wastewater surveillance has rapidly emerged as an early warning tool to track COVID-19.
However, the early warning measurement of new SARS-CoV-2 variants of concern (VOCs) in
wastewaters remains a major challenge. We herein report a rapid analytical strategy for
quantitative measurement of VOCs, which couples nested polymerase chain reaction and
liquid chromatography–mass spectrometry (nPCR-LC-MS). This method showed a
greater selectivity than the current allele-specific quantitative PCR (AS-qPCR) for
tracking new VOC and allowed the detection of multiple signature mutations in a single
measurement. By measuring the Omicron variant in wastewaters across nine Ontario
wastewater treatment plants serving over a three million population, the nPCR-LC-MS
method demonstrated a better quantification accuracy than next-generation sequencing
(NGS), particularly at the early stage of community spreading of Omicron. This work
addresses a major challenge for current SARS-CoV-2 wastewater surveillance by rapidly
and accurately measuring VOCs in wastewaters for early warning.
Intensive historical and worldwide use of the persistent pesticide technical-grade 26 hexachlorocyclohexane (HCH), composed of the active ingredient γ -HCH (called lindane) along 27 with several other HCH isomers, has led to widespread contamination. We derived four 28 anaerobic enrichment cultures from HCH-contaminated soil capable of sustainably 29 dechlorinating each of α -, β -, γ -, and δ -HCH isomers stoichiometrically and completely to 30 benzene and monochlorobenzene (MCB). For each isomer, the dechlorination rates increased 31 progressively from <3 µM/day to ~12 µM/day over two years. The molar ratio of benzene to 32 MCB produced was a function of the substrate isomer, and ranged from β (0.77±0.15), α 33 (0.55±0.09), γ (0.13±0.02) to δ (0.06±0.02) in accordance with pathway predictions based on 34 prevalence of antiperiplanar geometry. Cultivation with a different HCH isomer resulted in 35 distinct bacterial communities, but similar archaeal communities. Data from 16S rRNA gene 36 amplicon sequencing and quantitative PCR revealed significant increases in the absolute 37 abundance of Pelobacter and Dehalobacter, especially in the α -HCH and δ -HCH cultures. This 38 study provides the first direct comparison of shifts in anaerobic microbial communities induced 39 by the dechlorination of distinct HCH isomers. It also uncovers candidate microorganisms 40 responsible for the dechlorination of α -, β -, γ -, and δ
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