Investigation of hydrolysis acidification process during anaerobic treatment of coal gasification wastewater (CGW): Evolution of dissolved organic matter and biotoxicity

Deciphering the core bacterial community structure and function and their response to environmental factors in activated sludge from pharmaceutical wastewater treatment plants

Pharmaceutical wastewater is recognized for its heightened concentrations of organic pollutants, and biological treatment stands out as an effective technology to remove these organic pollution. Therefore, a comprehensive exploration of core bacterial community compositions, functions, and their responses to environmental factors in pharmaceutical wastewater treatment plants (PWWTPs) is important for understanding the removal mechanism of these organic pollutants. This study comprehensively investigated 36 activated sludge (AS) samples from 15 PWWTPs in China. The results revealed that Proteobacteria (45.41%) was the dominant phylum in AS samples, followed by Bacteroidetes (19.54%) and Chloroflexi (4.13%). While the dominant genera were similar in both aerobic and anaerobic treatment processes, their relative abundances exhibited significant variations. Genera like HA73, Kosmotoga, and Desulfovibrio were more abundant during anaerobic treatment, while Rhodoplanes, Bdellovibrio, and Hyphomicrobium dominated during aerobic treatment. 13 and 10 core operational taxonomic units (OTUs) were identified in aerobic and anaerobic sludge, respectively. Further analysis revealed that core OTUs belonging to genera Kosmotoga, Desulfovibrio, Thauera, Hyphomicrobium, and Chelativorans, were associated with key functions, including sulfur metabolism, methane metabolism, amino acid metabolism, carbohydrate metabolism, toluene degradation, and nitrogen metabolism. Furthermore, this study highlighted the crucial roles of environmental factors, such as COD, NH4+-N, SO42-, and TP, in shaping both the structure and core functions of bacterial communities within AS of PWWTPs. Notably, these factors indirectly affect functional attributes by modulating the bacterial community composition and structure in pharmaceutical wastewater. These findings provide valuable insights for optimizing the efficiency of biochemical treatment processes in PWWTPs.

Effects of Fe/Fe-Mn oxides loaded biochar on anaerobic degradation of typical phenolic compounds in coal gasification wastewater: Performance and mechanism

In this study, two kinds of magnetic biochar (BC) were synthesized by loading Fe (FeBC) and Fe-Mn oxides (FMBC) and their effects on anaerobic phenolics degradation were investigated. Compared with BC/FMBC, FeBC addition achieved the superior phenolics biodegradation even for 3,5-xylenol. Compared with control, FeBC addition enhanced CH4 production by 100.1 % with the lag time shortened from 9.5 days to 6.6 days while it increased to 11.2 days with FMBC addition. FeBC addition activated adsorption-biodegradation and Fe (III) reduction with the improved electron transfer activity, adenosine triphosphate and cytochrome C concentrations. Abundant phenol degrading bacteria, electroactive bacteria, syntrophic partners could be enriched by FeBC addition, contributing to the enhanced benzoyl-CoA and methanogenesis pathways. However, this enhancement was inhibited by FMBC addition owing to the accumulation of reactive oxygen species. This study provided novel insights into the application of magnetic BC to enhanced anaerobic treatment of phenolic wastewater.

Enhanced anaerobic biodegradation of typical phenolic compounds in coal gasification wastewater (CGW) using biochar: Focusing on the hydrolysis-acidification process and microbial community succession

The aim of this research is to investigate the effects of biochar (BC) on treatment performance (especially hydrolysis-acidification process) and microbial community shifts during anaerobic degradation of typical phenolic compounds in coal gasification wastewater. Compared to the control group, the removal of phenol, p-cresol and 3, 5-xylenol was gradually enhanced when increasing the BC addition within the test dosage (1-5 g/L). The biodegradation of phenol and p-cresol was significantly enhanced by BC addition while limited improvement for 3, 5-xylenol. The addition of BC significantly accelerated the hydrolysis-acidification process with the hydrolytic removal of phenol improved by 69.14%, the microbial activity was enhanced by 57.01%, and the key hydrolase bamA gene was enriched by 117.27%, respectively. Compared to 1-2 g/L dose, more protein-like and humic acid-like substances were secreted with 5 g/L BC, which probably contributed to higher extracellular electron transfer efficiency. In addition, phenol degrading bacteria (Syntrophorhabdus, Dysgonomonas, Holophaga, etc.) and electroactive microorganisms (Geobacter, Syntrophorhabdus, Methanospirillum, etc.) were enriched by BC addition. The functional genes related to carboxylation, benzoylation and ring cleavage processes of benzoyl-CoA pathway were potentially activated by BC.

Microaerobic condition as pretreatment for improving anaerobic digestion: A review

Pretreatment of waste before anaerobic digestion (AD) has been extensively studied during the last decades. One of the biological pretreatments studied is the microaeration. This review examines this process, including parameters and applications to different substrates at the lab, pilot and industrial scales, to guide further improvement in large-scale applications. The underlying mechanisms of accelerating hydrolysis and its effects on microbial diversity and enzymatic production were reviewed. In addition, modelling of the process and energetic and financial analysis is presented, showing that microaerobic pretreatment is commercially attractive under certain conditions. Finally, challenges and future perspectives were also highlighted to promote the development of microaeration as a pretreatment before AD.

Zero-valent iron effectively enhances valuable products generated from wastewater containing 2-bromo-4,6-dinitroaniline during hydrolysis acidification process: Performance and mechanisms

Treatment to remove 2-bromo-4,6-dinitroaniline (BDNA) from wastewater is urgently needed owing to its carcinogenicity, mutagenicity, and teratogenicity. Hydrolysis acidification (HA) is widely used to treat wastewater to improve biodegradability and resource utilization. Thus, a zero-valent iron (ZVI)-coupled HA system was operated to treat BDNA-containing wastewater for the first time, with emphasis on the performance and enhanced mechanisms. The improved results for BDNA removal efficiency and B/C ratio and the decreased acute toxicity suggested that ZVI addition benefited the formation of advantageous products for subsequent biological treatment. The volatile fatty acids (VFAs) ratio (C_HAc:C_HPr:C_HBu) was optimized from 21:5:4 to 29:5:6, which benefited the utilization of wastewater resources for lipid generation. ZVI characterization, density functional theory (DFT) calculations, extracellular polymeric substances (EPS) analysis, molecular ecological network analysis (MENA), and redundancy analysis (RDA) of the microbial community further revealed that the enhanced mechanisms were summarized as beneficial interactions between ZVI and microorganisms. The ZVI was protected from excessive corrosion and lowered the oxidation-reduction potential (ORP), a key environmental factor, resulting in differences in microbial communities. These differences were presented as the enrichment of keystone species (e.g., Lactococcus), which function in BDNA reduction and VFAs generation. Moreover, ZVI promoted electron transfer, as proven by the high electron transfer capacity (ETC) of 0.452 and 0.361 μmol e^-/g VSS in the R_ZVI and blank systems, respectively.

Continuing progress in the field of two-dimensional correlation spectroscopy (2D-COS): Part III. Versatile applications

In this review, the comprehensive summary of two-dimensional correlation spectroscopy (2D-COS) for the last two years is covered. The remarkable applications of 2D-COS in diverse fields using many types of probes and perturbations for the last two years are highlighted. IR spectroscopy is still the most popular probe in 2D-COS during the last two years. Applications in fluorescence and Raman spectroscopy are also very popularly used. In the external perturbations applied in 2D-COS, variations in concentration, pH, and relative compositions are dramatically increased during the last two years. Temperature is still the most used effect, but it is slightly decreased compared to two years ago. 2D-COS has been applied to diverse systems, such as environments, natural products, polymers, food, proteins and peptides, solutions, mixtures, nano materials, pharmaceuticals, and others. Especially, biological and environmental applications have significantly emerged. This survey review paper shows that 2D-COS is an actively evolving and expanding field.

Spatiotemporal distribution and fates of neonicotinoid insecticides during the urban water cycle in the lower reaches of the Yangtze River, China

Neonicotinoid insecticides (NNIs) are the most popular insecticides worldwide, yet their spatiotemporal distribution and fates during the urban water cycle remain limited on a large watershed scale. Thus, we investigated ten kinds of NNIs in surface water from the lower reaches of the Yangtze River and hubs of the urban water cycle in all seasons. In brief, eight out of ten NNIs were detected, and thiamethoxam (THM), imidacloprid (IMI), and dinotefuran (DNT) were the most abundant NNIs in surface water, with concentrations of 0.29-48.15 ng/L, 1.69-20.57 ng/L, and 0.98-25.32 ng/L, respectively. The average concentrations of total NNIs in summer were 1.96-4.41 folds higher than those in other seasons. NNIs in the effluents of municipal wastewater treatment plants (WWTPs) were lower than those in surface water, while the average concentrations of total NNIs in the effluents of industrial WWTPs were 1.56-6.86 folds higher than those in surface water, indicating that insecticide production is an important source for NNIs in surface water. DNT was the most recalcitrant NNI in WWTPs, with an average removal efficiency of 49.89%, while in drinking water treatment plants (DWTPs), the removal efficiencies of most NNIs were limited, except for clothianidin (CLO) (90%). Risk assessment showed that NNIs posed medium or high risks to aquatic life, and DNT contributed 26.86-51.48% to the cumulative risks of detected NNIs. This study investigates the spatiotemporal distribution and risks of NNIs and provides information for the supervision of NNIs in the Yangtze River basin, China.

Effective mechanisms of water purification for nitrogen-modified attapulgite, volcanic rock, and combined exogenous microorganisms

The study tested the water purification mechanism of the combination of microorganisms and purification materials via characteristic, enzymatic, and metagenomics methods. At 48 h, the removal rates of total nitrogen, total phosphorous, and Mn chemical oxygen demand in the combination group were 46.91, 50.93, and 65.08%, respectively. The alkaline phosphatase (AKP) activity increased during all times tested in the volcanic rock, Al@TCAP, and exogenous microorganism groups, while the organophosphorus hydrolase (OPH), dehydrogenase (DHO), and microbial nitrite reductase (NAR) activities increased at 36-48, 6-24, and 36-48 h, respectively. However, the tested activities only increased in the combination groups at 48 h. Al@TCAP exhibits a weak microbial loading capacity, and the Al@TCAP removal is primarily attributed to adsorption. The volcanic rock has a sufficient ability to load microorganisms, and the organisms primarily perform the removal for improved water quality. The predominant genera Pirellulaceae and Polynucleobacter served as the sensitive biomarkers for the treatment at 24, 36-48 h. Al@TCAP increased the expression of Planctomycetes and Actinobacteria, while volcanic rock increased and decreased the expression of Planctomycetes and Proteobacteria. The growth of Planctomycetes and the denitrification reaction were promoted by Al@TCAP and the exogenous microorganisms. The purification material addition group decreased the expression of Hyaloraphidium, Chytridiomycetes (especially Hyaloraphidium), and Monoblepharidomycetes and increased at 36-48 h, respectively. Ascomycota, Basidiomycota, and Kickxellomycota increased in group E, which enhanced the nitrogen cycle through microbial enzyme activities, and the growth of the genus Aspergillus enhanced the phosphorous purification effect.

Enhanced degradation of phenolic compounds in coal gasification wastewater by an iron‑carbon micro-electric field coupled with anaerobic co-digestion

Coal gasification wastewater contains many refractory and toxic pollutants, especially high concentrations of total phenols, which are difficult to degrade by microorganisms. The aim of our study is to explore the anaerobically enhanced degradation of coal gasification wastewater by an iron‑carbon micro-electric field coupled with anaerobic co-digestion. The optimal ratio of activated carbon to iron and the optimal dosage of co-substrate (glucose = 1500 mg/L) were investigated by batch tests. In the long-term operation of the iron‑carbon reactor, 1500 mg/L glucose was added into the influent, and carbon and iron in a ratio of 2:1 were added to the anaerobic sludge. The average effluent COD and total phenols concentrations were kept at approximately 455 and 56.3 mg/L, respectively, and removal rates of both reached 90% after treatment with the iron‑carbon micro-electric field coupled with anaerobic co-digestion in the iron‑carbon reactor. Moreover, compared with the control reactor, the methane production from the iron‑carbon reactor increased to 200 mL/day, with an increase in the methane production rate by 90%. Microbial community analysis indicated that hydrogenotrophic methanogens were enriched, and syntrophic metabolism via interspecies hydrogen transfer was enhanced. Direct interspecies electron transfer might occur between the potential electroactive bacteria Clostridium, Bacteroidetes, and Anaerolinea and the methanogens Methanosaeta, Methanobacterialies, and Methanobacterium for syntrophic metabolism through the iron‑carbon process coupled with anaerobic co-digestion.

Enhanced anaerobic digestion of tar solution from rice husk thermal gasification with hybrid upflow anaerobic sludge-biochar bed reactor

Tar generated as a by-product during biomass gasification contains a high concentration of refractory organic matters. In this study, a hybrid upflow anaerobic sludge-biochar bed reactor was established for tar treatment, and the methane yield was 120-154 NmL-CH₄/g-COD_inf, 20-30% higher than the control reactor. COD removal and methane production significantly decreased in both reactors when the influent tar concentration was doubled from 4954 mg-COD/L to 9964 mg-COD/L. When the influent concentration was reduced, the biochar packed reactor showed a faster recovery. Batch tests confirmed that higher tar concentration inhibited methane production and induced longer lagphase. Biochar addition effectively relieved the inhibition and prolonged the retention of organic matters. SEM observation and 16S rRNA analysis suggested that biochar also acted as the microbe's carrier, and promoted the growth of some microbes. The results of this study provide new ideas for tar treatment.

Electrical selection for planktonic sludge microbial community function and assembly

Electrostimulated hydrolysis acidification (eHA) has been used as an efficient biological pre-treatment of refractory industrial wastewater. However, the effects of electrostimulation on the function and assembly of planktonic anaerobic sludge microbial communities are poorly understood. Using 16S rRNA gene and metagenomic sequencing, we investigated planktonic sludge microbial community structure, composition, function, assembly, and microbial interactions in response to electrostimulation. Compared with a conventional hydrolysis acidification (HA) reactor, the planktonic sludge microbial communities selected by electrostimulation promoted biotransformation of the azo dye Alizarin Yellow R. The taxonomic and functional structure and composition were significantly shifted upon electrostimulation with azo dyes degraders (e.g. Acinetobacter and Dechloromonas) and electroactive bacteria (e.g. Pseudomonas) being enriched. More microbial interactions between fermenters and decolorizing and electroactive bacteria, as well as fewer interactions between different fermenters evolved in the eHA microbial communities. Moreover, the decolorizing bacteria were linked to the higher abundance of genes encoding for azo- and nitro-reductases and redox mediator (e.g. ubiquinone) biosynthesis involved in the transformation of azo dye. Microbial community assembly was more driven by deterministic processes upon electrostimulation. This study offers new insights into the effects of electrostimulation on planktonic sludge microbial community function and assembly, and provides a promising strategy for the manipulation of anaerobic sludge microbiomes in HA engineering systems.

Effects of polyurethane foam carrier addition on anoxic/aerobic membrane bioreactor (A/O-MBR) for coal gasification wastewater (CGW) treatment: Performance and microbial community structure

Coal gasification wastewater (CGW) is a typical toxic and refractory industrial wastewater with abundant phenols contained. Two identical anoxic/aerobic membrane bioreactors (with (R2) and without (R1) polyurethane (PU) foam) were carried out in parallel to investigate the role of PU foam addition in enhancing pollutants removal in CGW. Results showed that both systems exhibited effective removal of chemical oxygen demand (>93%) and total phenols (>97%) but poor ammonia nitrogen removal (<35%) constrained by ammonia oxidation process. GC-MS analysis revealed that aromatic and other refractory intermediates were dramatically reduced in R2. Moreover, the PU addition had negligible influence on the total soluble microbial products and extracellular polymeric substances contents but significantly alleviated membrane fouling with the operating time 33% prolonged. Microbial community revealed that Flavobacterium, Holophaga, and Geobacter were enriched on PU. Influent type might be a main driver for microbial community succession.

N-Doped Biochar as a New Metal-Free Activator of Peroxymonosulfate for Singlet Oxygen-Dominated Catalytic Degradation of Acid Orange 7

In this paper, using rice straw as a raw material and urea as a nitrogen precursor, a composite catalyst (a nitrogen-doped rice straw biochar at the pyrolysis temperature of 800 °C, recorded as NRSBC800) was synthesized by one-step pyrolysis. NRSBC800 was then characterized using XPS, BET, TEM and other technologies, and its catalytic performance as an activator for permonosulfate (PMS) to degrade acid orange 7 (AO7) was studied. The results show that the introduction of N-doping significantly improved the catalytic performance of NRSBC800. The NRSBC800/PMS oxidation system could fully degrade AO7 within 30 min, with the reaction rate constant (2.1 × 10 ^-1 min^-1) being 38 times that of RSBC800 (5.5 × 10^-3 min^-1). Moreover, NRSBC800 not only had better catalytic performance than traditional metal oxides (Co₃O₄ and Fe₃O₄) and carbon nanomaterial (CNT) but also received less impact from environmental water factors (such as anions and humic acids) during the catalytic degradation process. In addition, a quenching test and electron paramagnetic resonance (EPR) research both indicated that AO7 degradation relied mainly on non-free radical oxidation (primarily singlet oxygen (¹O₂)). A recycling experiment further demonstrated NRSBC800's high stability after recycling three times.