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Cation exchange resin (CER) has been reported to promote sludge fermentation. However, previous studies have typically focused on the effects of CER on sludge properties to enhance fermentation, and the role of CER as a biocarrier for anaerobic consortia during fermentation has been overlooked. Thus, in this study, the potential of gel-type and macro-reticular type CERs to serve as biocarriers in fermentation was investigated. A significant number of anaerobes appeared to be attached to the surfaces of CER during 2-day fermentation. However, an extended fermentation time negatively affected the attachment of anaerobic consortia, suggesting that CER may be a suitable carrier for short-term fermentation processes, such as biohydrogen fermentation. Electrochemical analyses revealed that the electron transfer capacities of CER with attached anaerobes were enhanced after both 2-day and 28-day fermentation periods, with the macro-reticular type CER exhibiting higher electron transfer capacity than the gel-type CER. Fermentation experiments using mixing model substrates with macro-reticular and gel-type CERs with attached anaerobes showed that the macro-reticular type CER was more beneficial for biohydrogen fermentation than the gel-type CER. Further analyses of microbial communities revealed that hydrogen-producing bacteria (i.e., Caloramator, unclassified_f_Caloramatoraceace, and Sporanaerobacter) were more likely to adhere to the macro-reticular type CERs. This outcome confirmed that macro-reticular type CERs have significant potential as a carrier for anaerobic consortia to promote the generation of hydrogen and volatile fatty acids. These findings are expected to provide a reference for using materials as biocarriers to enhance the biohydrogen fermentation of sludge. [ABSTRACT FROM AUTHOR]

Heavy metal pollution in rivers and lakes arising due to rapid economic development has been extensively studied by various countries due to its direct impact on ecological health and human well-being. However, there is a lack of comprehensive and systematic reviews addressing the current research status of this subject. In this study, we conducted a visual metrological analysis of the literature from 2001 to 2021 using the Web of Science (WoS) and China National Knowledge Infrastructure (CNKI) citation databases. The results show that studies conducted in other countries initially outnumbered those in China; after 2010, China emerged as the foremost contributor. Furthermore, both the WoS and CNKI databases indicate active engagement of Chinese researchers through a significant proportion of published papers on metal research, with prominent contributions coming from institutions such as the Chinese Academy of Sciences (CAS) and University CAS. Nevertheless, Chinese research institutions still have relatively low total paper citation numbers and have yet to establish themselves as key players in international scientific research efforts. Additionally, core authors from different countries share substantial similarities in their research directions and focuses. Consistent research hotspots regarding heavy metals in rivers and lakes were identified across both databases, including heavy metal pollution, adsorption, human activities, water quality, and sediment. [ABSTRACT FROM AUTHOR]

A novel heart-cutting two-dimensional liquid chromatography coupled with tandem mass spectrometry (2D-LC-MS/MS) was developed for the qualitative and quantitative analysis of methomyl residue in tobacco. Compared to traditional methodologies, fairly high sensitivity and stability were achieved, and the sample procedure was simplified in the two-dimensional liquid chromatography (2D-LC) method. Although methomyl had poor retention performance in most of the reversed-phase liquid chromatography (RPLC) columns, an effective RP/RP strategy was successfully facilitated. An XB-Phenyl column was employed in the first dimension to effectively remove thousands of interference compounds in the matrix. In the second dimension, an ADME column was applied for further separation. After optimization of the separation conditions, a six-way valve was utilized for direct transformation of the target fraction from the 1st column to the 2nd column. A dynamic range of 2.5 ng/mL to 500 ng/mL was achieved with correlation coefficient (r2) greater than 0.9995. The limit of detection and limit of quantification were determined to be 0.69 and 2.30 ng/mL, respectively. The 2D-LC method shows high sensitivity, good reproducibility, and recovery for methomyl in tobacco samples. Therefore, the new method was quite suitable for routine analysis. [ABSTRACT FROM AUTHOR]

A novel heart‐cutting two‐dimensional liquid chromatography coupled with tandem mass spectrometry method was developed for quantitative analysis of pendimethalin residue in tobacco. The strategy of reversed phase liquid chromatography coupled with another reversed‐phase liquid chromatography was employed for high column efficiency and excellent compatibility of mobile phase. In the first dimensional chromatography, a cyano column with methanol/water as the eluent was applied to separate pendimethalin from thousands of interference components in tobacco. By heart‐cutting technique, which effectively removed interference components, the target compound was cut to the second dimensional C18 column for further separation. The pendimethalin residue was finally determined by the tandem mass spectrometry under multiple reaction monitoring reversed‐phase liquid chromatography mode. Sample pretreatment of the new method was simplified, involving only extraction and filtration. Compared with traditional methodologies, the new method showed fairly high selectivity and sensitivity with almost no matrix interference. The limit of quantitation for pendimethalin was 1.21 ng/mL, whereas the overall recoveries ranged from 95.7 to 103.3%. The new method has been successfully applied to non‐stop measure of 200 real samples, without contamination of ion source. Detection results of the samples agreed well with standard method. [ABSTRACT FROM AUTHOR]

Byline: Feng Wang, Siqing Xia, Dianhai Yang The group-specific primers were applied to investigate microbial communities in Chem-Bioflocculation (CBF) reactor by PCR-DGGE method. α-proteobacteria, β-proteobacteria, actinomycetes and acidobacterium, were analysed by using diversity index at different dosage of Polyaluminium Ferric Chloride (PAFC) based on DGGE patterns. Clustering analysis showed that community structure of specific bacteria groups changed when flocculant dosage was adjusted, but flocculant dosage had dissimilar effect on the community structure of different bacteria group. α-proteobacteria possibly was the most influential populations relative to biological function in CBF reactor. The biological function should be inhibited when the flocculant dosage exceeded 80 mg/L.

• VS reduction showed exponential decrease as sludge age extended from 5 to 40 d. • Decline in protein degradation accounted for 80.4% of the decrease of VS conversion. • Changed amount and components of EPS correlated little to degradability of sludge. • Increased molecular weight of EPS strongly correlated to the declined degradability. • More stable secondary structure of protein in EPS determined decreased degradation. Long sludge age (10 ~ 30 d) is prevalent in the operation of wastewater treatment plants of China, leading to big challenge to subsequent anaerobic digestion of sewage sludge because of low degradability and poor methane production. In order to overcome the low sludge degradability and promote the directional enhancement, the effects of sludge age on anaerobic digestion performance, especially the corresponding influencing mechanism in terms of distribution, occurrence state and structure of organic compounds in sludge driven by different sludge age were investigated. It was found that when the sludge age during wastewater treatment extended from 5 d to 40 d, the VS reduction of sludge showed an "exponential" decrease, and the degradability of protein, polysaccharides and lipids in sludge all declined. Among them, the degradation of protein was the most affected (down-regulated by 35.8%), and the decrease in degradation of protein accounted for 80.4% of the decrease of VS conversion. Sludge age during wastewater treatment impact the distribution, occurrence state and structure of organic compounds in activated sludge. And it was clarified that instead of the changed amount and components of EPS, the increased molecular weight of EPS and more stable secondary structure of protein driven by α-helix and β-turn in EPS were mainly responsible for the declined degradability of protein and sludge. [ABSTRACT FROM AUTHOR]

Effects of sludge age on volatile fatty acids (VFAs) production and Phosphorus (P) release during anaerobic acidification of waste activated sludge (WAS) were investigated. Sequencing batch reactors (SBR) fed with simulating domestic sewage were applied to produce WAS of different sludge ages, and batch tests were used for anaerobic acidification. The maximum dissolved total organic carbon, release of PO 4 3 + − P , and accumulation of acetate (C2), propionate (C3), butyrate (C4), and valerate (C5) decreased by 56.2%, 55.8%, 52.6%, 43.7%, 82.4% and 84.8%, respectively, as the sludge age of WAS increased from 5 to 40 days. Limited degradation of protein played a dominating role in decreasing DTOC and VFAs production. Moreover, the increase in molecular weight of organics and organic nitrogen content in the supernatant after acidification suggested that the refractory protein in WAS increased as sludge age extended. Although the production of C2, C3, C4, and C5 from WAS decreased as the sludge age increased, the proportions of C2 and C3 in VFAs increased, which might be due to the declined production of C5 from protein and the faded genus Dechlorobacter. Keeping sludge age of WAS at a relatively low level (<10 days) is more appropriate for anaerobic acidification of WAS as internal carbon sources and P resource. [Display omitted] [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Oxygen or ammonia limited condition was adverse to achieve nitrite accumulation. • Different AOB with similar oxygen sensitivity were enriched in the two reactors. • Nitrospira defluvii dominated both reactors but had different oxygen affinity. • Ammonia and nitrite levels were the key factors for selection of the nitrifiers. Abstract For understanding the potential of achieving nitritation under different oxygen and ammonia levels, two activated sludge reactors with high (R H) and low (R L) dissolved oxygen (DO) were parallelly operated. During over two months continuous operation, rare nitrite accumulation was observed in both reactors. K -strategists Nitrosomonas oligotropha and r -strategists Nitrosomonas europaea were enriched in the R H and R L , respectively, yet their response to DO variations was almost identical. Although K -strategists Nitrospira defluvii dominated both reactors, species cultured with low-DO exhibited higher oxygen affinity. Instead of DO, ammonia and nitrite availability should be the key factor for the selective enrichment of these nitrifiers. Taken together, the limiting ammonia for ammonia oxidizing bacteria and the better oxygen-uptake capacity of nitrite oxidizing bacteria was respectively responsible for the failure of nitrite accumulation in the R H and R L. This study supported that high DO coupled with excess ammonia would favor the achievement of mainstream nitritation. [ABSTRACT FROM AUTHOR]

l Fast formation of micro-granules realized in a modified continuous-flow reactor. l Nitritation could be achieved within 6 days using the micro-granule (ca. 100 µm). l Maintaining ammonia in-excess was the key for NOB repression with micro-granules. l The micro-granules possessed ammonium oxidation potential of 59.3 ± 1.9 mg/g VSS/h. In this study, a modified continuous-flow nitrifying reactor was successfully operated for rapid cultivation of micro-granules and achieving robust nitritation. Results showed that sludge granulation with mean size of ca. 100 µm was achieved within three weeks by gradually increasing settling velocity-based selection pressure from 0.48 to 0.9 m/hr. Though Nitrospira like nitrite-oxidizing bacteria (NOB) were enriched in the micro-granules with a ratio between ammonia-oxidizing bacteria (AOB) and NOB of 5.7%/6.5% on day 21, fast nitritation was achieved within one-week by gradually increasing of influent ammonium concentration (from 50 to 200 mg/L). Maintaining ammonium in-excess was the key for repressing NOB in the micro-granules. Interestingly, when the influent ammonium concentration switched back to 50 mg/L still with the residual ammonium of 15–25 mg/L, the nitrite accumulation efficiency increased from 90% to 98%. Experimental results suggested that the NOB repression was intensified by both oxygen and nitrite unavailability in the inner layers of micro-granules. Unexpectedly, continuous operation with ammonium in excess resulted in overproduction of extracellular polysaccharides and overgrowth of some bacteria (e.g., Nitrosomonas, Arenimonas , and Flavobacterium), which deteriorated the micro-granule stability and drove the micro-granules aggregation into larger ones with irregular morphology. However, efficient nitritation was stably maintained with extremely high ammonium oxidation potential (> 50 mg/g VSS/hr) and nearly complete washout of NOB was obtained. This suggested that smooth and spherical granule was not a prerequisite for achieving NOB wash-out and maintaining effective nitritation in the granular reactor. Overall, the micro-granules exhibited a great practical potential for high-rate nitritation. Graphical Abstract [Display omitted]. [ABSTRACT FROM AUTHOR]

Abstract: 2-Methylquinoline is a common organic contaminant in environment. Its degradation in wastewater treatment system has not been fully explored. In this study, batch experiments were conducted to investigate the biodegradation of 2-methylquinoline by activated sludge under both aerobic and denitrifying conditions. The results showed that 2-methylquinoline was degraded under both conditions, but the degradation under aerobic condition was significantly faster than that under denitrifying condition. Total organic carbon (TOC) residues were detected in the final effluent under both conditions, indicating the formation of recalcitrant metabolites. Further analysis identified 1,2,3,4-tetrahydro-2-methylquinoline, N,N-diethyl-benzenamine, and 4-ethyl-benzenamine as common metabolites under both conditions. 4-Butyl-benzenamine and 2,6-diethyl-benzenamine were additional metabolites under the aerobic condition, whereas 2-methyl-4-quinolinol was exclusive to the denitrifying condition. Most of these metabolites were further degraded during the treatment process. 1,2,3,4-Tetrahydro-2-methylquinoline, however, remained in the final effluent under both conditions, implying its persistence in the environment. It can be concluded that 2-methylquinoline undergoes the similar degradation pathway under both treatment conditions. [Copyright &y& Elsevier]