Microbial community compositions in different functional zones of Carrousel oxidation ditch system for domestic wastewater treatment

Comparative assessment of microbiome and resistome of influent and effluent of sewage treatment plant and common effluent treatment plant located in Delhi, India using shotgun approach

Antimicrobial resistance (AMR) is a significant threat that demands surveillance to identify and analyze trends of the emerging antibiotic resistance genes (ARGs) and potential microbial carriers. The influent of the wastewater treatment plants (WWTPs) reflects the microbes derived from the population and effluent being the source of dissemination of potential pathogenic microbes and AMR. The present study aimed to monitor microbial communities and antibiotic resistance genes in WWTPs employing a whole metagenome shotgun sequencing approach. The samples were collected from a sewage treatment plant (STP) and a common effluent treatment plant (CETP) in Delhi, India. The results showed the influent of STP to be rich in Bifidobacterium, Bacteroides, Escherichia, Arcobacter, and Pseudomonas residents of gut microbiota and known to cause diseases in humans and animals; whereas the CETP sample was abundant in Aeromonas, Escherichia, and Shewanella known to be involved in the degradation of different compounds. Interestingly, the effluent samples from both STPs and CETP were rich in microbial diversity, comprising organic and xenobiotic compound degrading and disease-causing bacteria, indicating the effluent being the source of dissemination of concerning bacteria to the environment. The functional profile at both sites displayed similarity with an abundance of housekeeping function genes as analyzed by Clusters of Orthologous Genes (COG), KEGG Orthology (KO), and subsystem databases. Resistome profiling by MEGARes showed the dominance of ARGs corresponding to beta-lactams having relative abundance ranging from 16% to 34% in all the metagenome datasets, followed by tetracycline (8%-16%), aminoglycosides (7%-9%), multi-drug (5%-9%), and rifampin (3%-9%). Also, AMR genes oxa, ant3-DPRIME, and rpoB, which are of clinical importance were predominantly and most prevalently present in all the samples. The presence of AMR in effluents from both types of treatment plants indicates that wastewater from both sources contributes to the spread of pathogenic bacteria and resistance genes, increasing the environmental AMR burden and therefore requires tertiary treatment before discharge. This work will facilitate further research towards the identification of suitable biomarkers for monitoring antibiotic resistance.

Elucidating biofouling development and succession in membrane distillation using treated effluent

Biofouling in membrane distillation (MD) has several repercussions, including reduced efficiency of the MD process and limiting membrane life. Additionally, the evaluation of MD biofouling using treated effluents from wastewater treatment plants remains an unexplored area. Thus, biofouling formation and development in a long term MD process (15 days) using treated effluent from a wastewater treatment plant was explored in this study. The results revealed that flux decline occurred in four phases: i) initial decline (0-1 d), ii) gradual decline (1-5 d), iii) progressive decline (5-10 d), and iv) rapid decline (10-15 d). Liquid Chromatography-Organic Carbon Detection (LC-OCD) analysis demonstrated that the treated effluent contained humic-like substances, which deposited on the membrane surface in phase 1. Whereas biopolymers development on the membrane surface in phase 2 and 3 was linked to biofouling. Microbial community analysis revealed that the initial colonisers were predominantly thermophilic bacteria, which were different from the microbial community of the treated effluent. The biofilm-forming bacteria included Schlegelella, Meiothermus, and Vulcaniibacterium. These microorganisms proliferate and release excessive extracellular polymeric substances (EPS), leading to the development of mature biofilm on membrane surface. This helped in the deposition of organics and inorganics from the bulk feed, which led to microbial community succession in phase 4 with the emergence of the Kallotenue genus. The results suggested that organic substances and microbial communities on membrane surface at different stages in a long-term MD process had a significant influence on MD performance for high-quality wastewater reuse.

A comprehensive comparison of microbial communities between aerobic granular sludge and flocculent sludge for nutrient removal in full-scale wastewater treatment plants

Understanding the microbial community structure of sludge is crucial for improving the design, operation and optimisation of full-scale wastewater treatment plants (WWTPs). This study aimed to have a comprehensive comparison of microbial communities between aerobic granular sludge and flocculent sludge from two full-scale sequential batch reactors-based WWTPs with nutrient removal for the first time. To better understand key functional bacteria such as polyphosphate accumulating bacteria (PAOs), competitive bacteria such as glycogen accumulating bacteria (GAOs) and nitrifying bacteria for both nitrogen and phosphorus removal, another two full-scale WWTPs with only carbon (C) removal and C and nitrogen (N) removal were compared too. It was found that the richness and diversity of the microbial population in sludge increased with pollutant removal from only C, C and N, to C,N, P removal. For C, N P removal, granule structure led to a more diverse and rich microbial community structure than flocculent structure. Although more abundant nitrifying bacteria were enriched in granular sludge than flocculent sludge, the abundance of total putative PAOs was equivalent. However, the most typical putative PAOs such as Tetrasphaera and Candidatus Accumulibacter seemed to be more correlated with biological phosphorus removal performance, which might be more proper to be used as an indication for P removal potential. The higher abundance of GAOs in flocculent sludge with better phosphorus removal performance might suggest that further investigation is needed to understand the functions of GAOs. In addition, the equivalent abundances of PAOs in the WWTPs with only C removal and with C, N, and P removal, respectively, indicate that many newly reported putative PAOs might not contribute to P removal. This study provides insight into the microbial communities and functional bacteria in aerobic granular sludge and flocculent sludge in full-scale SBRs, which can provide microbes-informed optimisation of reactor operation for better nutrient removal.

Effects of a co-bacterial agent on the growth, disease control, and quality of ginseng based on rhizosphere microbial diversity

BACKGROUND

The ginseng endophyte Paenibacillus polymyxa Pp-7250 (Pp-7250) has multifaceted roles such as preventing ginseng diseases, promoting growth, increasing ginsenoside accumulation, and degrading pesticide residues, however, these effects still have room for improvements. Composite fungicides are an effective means to improve the biocontrol effect of fungicides, but the effect of Pp-7250 in combination with its symbiotic bacteria on ginseng needs to be further investigated, and its mechanism of action has not been elucidated. In this study, a series of experiments was conducted to elucidate the effect of Paenibacillus polymyxa and Bacillus cereus co-bacterial agent on the yield and quality of understory ginseng, and to investigate their mechanism of action.

RESULTS

The results indicated that P. polymyxa and B. cereus co-bacterial agent (PB) treatment improved ginseng yield, ginsenoside accumulation, disease prevention, and pesticide degradation. The mechanism is that PB treatment increased the abundance of beneficial microorganisms, including Rhodanobacter, Pseudolabrys, Gemmatimonas, Bacillus, Paenibacillus, Cortinarius, Russula, Paecilomyces, and Trechispora, and decreased the abundance of pathogenic microorganisms, including Ellin6067, Acidibacter, Fusarium, Tetracladium, Alternaria, and Ilyonectria in ginseng rhizosphere soil. PB co-bacterial agents enhanced the function of microbial metabolic pathways, biosynthesis of secondary metabolites, biosynthesis of antibiotics, biosynthesis of amino acids, carbon fixation pathways in prokaryotes, DNA replication, and terpenoid backbone biosynthesis, and decreased the function of microbial plant pathogens and animal pathogens.

CONCLUSION

The combination of P. polymyxa and B. cereus may be a potential biocontrol agent to promote the resistance of ginseng to disease and improve the yield, quality, and pesticide degradation.

Enhanced methane production from waste activated sludge by potassium ferrate combined with thermal hydrolysis pretreatment

Anaerobic digestion of waste activated sludge (WAS) was one of the directions of sludge treatment, but how to effectively improve the production of methane as a resource product of anaerobic digestion of sludge still needs further research. The study examined how the combination of potassium ferrate (PF) and thermal hydrolysis (TH) pretreatment affected methane production from sludge. The results demonstrated a positive synergistic effect on methane production with PF-TH pretreatment. Specifically, by employing a 0.05 g/g TSS (total suspended solids) PF in conjunction with TH at 80 °C for 30 min, the methane yield increased from 170.66 ± 0.92 to 232.73 ± 2.21 mL/g VSS (volatile suspended solids). The co-pretreatment of PF and TH has been substantiated by mechanism studies to effectively enhance the disintegration and biodegradability of sludge. Additionally, the variation of microbial community revealed an enrichment of active microorganisms associated with anaerobic digestion after treated with PF + TH, resulting in a total abundance increase from 11.87 to 20.45% in the PF + TH group.

Microbial community and antimicrobial resistance niche differentiation in a multistage, surface flow constructed wetland

Free-living (FL) and particulate-associated (PA) communities are distinct bacterioplankton lifestyles with different mobility and dissemination routes. Understanding spatio-temporal dynamics of PA and FL fractions will allow improvement to wastewater treatment processes including pathogen and AMR bacteria removal. In this study, PA, FL and sediment community composition and antimicrobial resistance gene (ARG; tetW, ermB, sul1, intI1) dynamics were investigated in a full-scale municipal wastewater free-water surface polishing constructed wetland. Taxonomic composition of PA and FL microbial communities shifted towards less diverse communities (Shannon, Chao1) at the CW effluent but retained a distinct fraction-specific composition. Wastewater treatment plant derived PA communities introduced the bulk of AMR load (70 %) into the CW. However, the FL fraction was responsible for exporting over 60 % of the effluent AMR load given its high mobility and the effective immobilization (1-3 log removal) of PA communities. Strong correlations (r2>0.8, p < 0.05) were observed between the FL fraction, tetW and emrB dynamics, and amplicon sequence variants (ASVs) of potentially pathogenic taxa, including Bacteroides, Enterobacteriaceae, Aeromonadaceae, and Lachnospiraceae. This study reveals niche differentiation of microbial communities and associated AMR in CWs and shows that free-living bacteria are a primary escape route of pathogenic and ARG load from CWs under low-flow hydraulic conditions.

Different microbial communities in paddy soils under organic and nonorganic farming

Organic agriculture is a farming method that provides healthy food and is friendly to the environment, and it is developing rapidly worldwide. This study compared microbial communities in organic farming (Or) paddy fields to those in nonorganic farming (Nr) paddy fields based on 16S rDNA sequencing and analysis. The predominant microorganisms in both soils were Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteria, and Nitrospirota. The alpha diversity of the paddy soil microbial communities was not different between the nonorganic and organic farming systems. The beta diversity of nonmetric multidimensional scaling (NMDS) revealed that the two groups were significantly separated. Distance-based redundancy analysis (db-RDA) suggested that soil pH and electrical conductivity (EC) had a positive relationship with the microbes in organic paddy soils. There were 23 amplicon sequence variants (ASVs) that showed differential abundance. Among them, g_B1-7BS (Proteobacteria), s_Sulfuricaulis limicola (Proteobacteria), g_GAL15 (p_GAL15), c_Thermodesulfovibrionia (Nitrospirota), two of f_Anaerolineaceae (Chloroflexi), and two of g_S085 (Chloroflexi) showed that they were more abundant in organic soils, whereas g_11-24 (Acidobacteriota), g__Subgroup_7 (Acidobacteriota), and g_Bacillus (Firmicutes) showed differential abundance in nonorganic paddy soils. Functional prediction of microbial communities in paddy soils showed that functions related to carbohydrate metabolism could be the major metabolic activities. Our work indicates that organic farming differs from nonorganic farming in terms of microbial composition in paddy soils and provides specific microbes that might be helpful for understanding soil fertility.

Changes in the transformation of nitrogen and phosphorus under different microbial communities in sewage pipes

Microbial communities living in different environments can affect the transformation of nitrogen and phosphorus in sewage pipes. Two different environments were simulated to investigate the differences in the transformation of nitrogen and phosphorus under different microbial communities in the pipe. Results showed that the concentration of nitrogen and phosphorus changed greatly in the first 25-33 days and the first 21 days, respectively, and then remained stable. The decrease in amino acid nitrogen (AAN) concentration and the increase in ammonia nitrogen (NH4 + -N) concentration in the sediments were evident in the contrast group. The concentrations of total phosphorus (TP), dissolved total phosphorus (DTP), and dissolved reactive phosphorus (DRP) in the overlying water and interstitial water decreased, and that of TP in the sediment increased. Some microorganisms in the sediments of both groups are related to the transformation of nitrogen and phosphorus, such as Clostridium_sensu_stricto_1, Sporacetigenium, Norank_f__Anaerolineaceae, Norank_f__norank_o__PeM15, and Caldisericum. The relative abundance of these microorganisms was remarkably differed between the two groups, which partly caused the difference in nitrogen and phosphorus transformation among overlying water, interstitial water, and sediment in the two environments. PRACTITIONER POINTS: The concentration of N and P changed greatly in the first 20-30 days. AAN and NH4 + -N in sediments had greater concentration variation in contrast group. In two groups, TP, DTP, and DRP of water decreased, and TP of sediment increased. Microbe related to the transformation of N and P differed between the two groups.

Machine learning modeling for the prediction of phosphorus and nitrogen removal efficiency and screening of crucial microorganisms in wastewater treatment plants

The effectiveness of wastewater treatment plants (WWTPs) is largely determined by the microbial community structure in their activated sludge (AS). Interactions among microbial communities in AS systems and their indirect effects on water quality changes are crucial for WWTP performance. However, there is currently no quantitative method to evaluate the contribution of microorganisms to the operating efficiency of WWTPs. Traditional assessments of WWTP performance are limited by experimental conditions, methods, and other factors, resulting in increased costs and experimental pollutants. Therefore, an effective method is needed to predict WWTP efficiency based on AS community structure and quantitatively evaluate the contribution of microorganisms in the AS system. This study evaluated and compared microbial communities and water quality changes from WWTPs worldwide by meta-analysis of published high-throughput sequencing data. Six machine learning (ML) models were utilized to predict the efficiency of phosphorus and nitrogen removal in WWTPs; among them, XGBoost showed the highest prediction accuracy. Cross-entropy was used to screen the crucial microorganisms related to phosphorus and nitrogen removal efficiency, and the modeling confirmed the reasonableness of the results. Thirteen genera with nitrogen and phosphorus cycling pathways obtained from the screening were considered highly appropriate for the simultaneous removal of phosphorus and nitrogen. The results showed that the microbes Haliangium, Vicinamibacteraceae, Tolumonas, and SWB02 are potentially crucial for phosphorus and nitrogen removal, as they may be involved in the process of phosphorus and nitrogen removal in sewage treatment plants. Overall, these findings have deepened our understanding of the relationship between microbial community structure and performance of WWTPs, indicating that microbial data should play a critical role in the future design of sewage treatment plants. The ML model of this study can efficiently screen crucial microbes associated with WWTP system performance, and it is promising for the discovery of potential microbial metabolic pathways.

Enhanced biological wastewater treatment supplemented with anaerobic fermentation liquid of primary sludge

The wastewater treatment performance in an inverted A2/O reactor supplemented with fermentation liquid of primary sludge was explored comparing to commercial carbon sources sodium acetate and glucose. Similar COD removal rate was observed with the effluent COD stably reaching the discharge standard for those 3 carbon sources. However, the fermentation liquid distributed more carbon source in the anaerobic zone. Fermentation liquid and sodium acetate tests achieved better nitrogen removal rate than glucose test. The fermentation liquid test showed the best biological phosphorus removal performance with the effluent phosphorus barely reaching the discharge standard. The microbial community characterization revealed that the fermentation liquid test was dominated by phylum Proteobacter in all the anoxic, anaerobic and aerobic zones. Denitrifying phosphorus accumulating organisms (PAOs) (i.e., genera Dechloromonas and unclassified_f__Rhodocyclaceae) were selectively enriched with high abundances (over 20%), which resulted in improved phosphorus removal efficiency. Moreover, the predicted abundances of enzymes involved in nitrogen and phosphorus removal were also enhanced by the fermentation liquid.

Sugarcane straw returning is an approaching technique for the improvement of rhizosphere soil functionality, microbial community, and yield of different sugarcane cultivars

Sugarcane straw returned to the field has rapidly increased due to the bane on straw burning in China. Straw returning of new sugarcane cultivars has been practiced in the fields. Still, its response has not been explored on soil functionality, microbial community and yield of different sugarcane cultivars. Therefore, a comparison was made between an old sugarcane cultivar ROC22 and a new sugarcane cultivar Zhongzhe9 (Z9). The experimental treatments were: without (R, Z), with straw of the same cultivar (RR, ZZ), and with straw of different cultivars (RZ, ZR). Straw returning improved the contents of soil total nitrogen (TN by 73.21%), nitrate nitrogen (NO3—N by 119.61%), soil organic carbon (SOC by 20.16%), and available potassium (AK by 90.65%) at the jointing stage and were not significant at the seedling stage. The contents of NO3—N was 31.94 and 29.58%, available phosphorus (AP 53.21 and 27.19%), and available potassium (AK 42.43 and 11.92%) in RR and ZZ were more than in RZ and ZR. Straw returning with the same cultivar (RR, ZZ) significantly increased the richness and diversity of the rhizosphere microbial community. The microbial diversity of cultivar Z9 (treatment Z) was greater than that of cultivar ROC22 (Treatment R). In the rhizosphere, the relative abundance of beneficial microorganisms Gemmatimonadaceae, Trechispora, Streptomyces, Chaetomium, etc., increased after the straw returned. Sugarcane straw enhanced the activity of Pseudomonas and Aspergillus and thus increased the yield of sugarcane., The richness and diversity of the rhizosphere microbial community of Z9 increased at maturity. In ROC22, bacterial diversity increased, and fungal diversity decreased. These findings collectively suggested that the impact of Z9 straw returning was more beneficial than ROC22 on the activity of rhizosphere microorganism’s soil functionality and sugarcane production.

Characteristics of groundwater microbial communities' structure under the impact of elevated nitrate concentrations in north China plain

In groundwater environments, the interaction between microbial communities and the hydrogeochemical parameters have been investigated extensively in the past years. However, little is known whether the maximum contamination level (MCL) is a threshold value that dictates the microbial composition. In this study, we analyzed 10 groundwater samples for their nitrate, nitrite, COD and sulfate concentrations, and characterized their microbial compositions using 16 S rRNA based high-throughput sequencing methods. All the 10 samples had oxygen demands higher than the corresponding MCL of China (10 mg L^-1); moreover, 4 out of 10 samples also had nitrate concentrations higher than the corresponding MCL, which indicated that the groundwater quality was negatively impacted by anthropogenic activities. Comparing the microbial composition of groundwater that had higher-than-MCL nitrate concentrations to those that had lower-than-MCL nitrate concentrations, no significant differences were detected in communities' richness and diversity. However, the non-metric multi-dimensional analysis suggested that the 4 groundwater samples whose nitrate concentration exceed MCL are distinctly different from those of the rest 6 samples, indicating that MCL does have a significant impact on microbial structures. Pearson's correlation analysis suggested that none of the four analyzed hydrochemical parameters had significant impact on microbial communities' richness and diversity; however, at the genus level, the correlation results suggested that JG30-KM-CM45, Sphingomonas and Rhodococcus are closely correlated with nitrate concentration. The findings of this study deepened our understanding with respect to the relationships between the environmental quality indices and the microbial compositions of groundwater.

Transformation trend of nitrogen and phosphorus in the sediment of the sewage pipeline and their distribution along the pipeline

Microorganisms transform nitrogen and phosphorus in the sediment of sewage pipelines. When the sediment was scoured by water flow, these elements migrate. This work studied the changes in biofilm morphology and microbial community structure, and focused on the differences in the transformation of nitrogen and phosphorus along the pipeline. The results showed that the nitrogen and phosphorus concentrations varied systematically with time and space (the front, middle, and posterior segments of the pipe). With time, amino acid nitrogen (AAN) concentration in the sediment gradually decreased, NH₄⁺-N concentration slowly increased, NO₃^--N concentration began to increase after 25 days, and TP concentration continued to increase after 9 days. The AAN, NH₄⁺-N, and TP concentrations were highest in the posterior segment of the pipe and lowest in the front segment. However, NO₃^--N showed two stages: its concentration was highest in the front segment and lowest in the posterior segment during the first 17 days, after which the opposite was observed. Changes in the nitrogen and phosphorus concentrations were related to the microbial communities in the sediments. The abundances of Rhodobacter (0.001 <p ≤ 0.01), Trichococcus (p ≤ 0.001), Nakamurella (0.01 <p ≤ 0.05), and norank_f__norank_o__PeM15 (0.001 <p ≤ 0.01) in the terminal sediments were significantly higher than those in the initial sediments. Meanwhile, the abundances of Clostridium_sensu_stricto_1, Rhodobacter, norank_f__norank_o__PeM15, and Brevundimonas were different in the front, middle, and posterior segments. Furthermore, nitrogen and phosphorus were easily adsorbed on the small particles and were scoured and re-deposited on the posterior segment of the pipe, resulting in enrichment. The temporal variation in nitrogen and phosphorus and its spatial distribution along the pipeline were due to the combination of biotransformation and migration.

The importance of rest phase and pollutant removal mechanism of tidal flow constructed wetlands (TFCW) in rural grey water treatment

This paper explored the effects of the rest phase of tidal flow constructed wetlands (TFCW) on pollutant removal and microbial communities, and further analyzed the mechanism of TFCW removal of pollutants from grey water. The results showed that the removal rate of organic matter was 69.91 ± 2.44% in the control group (NR-TFCW) without the rest phase, 94.95 ± 1.17% in the experimental group (TFCW), and 96.95 ± 2.43% in the control group (P-TFCW) with the ventilation pipe enhanced rest phase. Limiting and enhancing the oxygen supply in the emptying stage of TFCW will enhance the overlap rate of microorganisms in the upper, middle and lower layers of the reactor. Enhancing the rest phase of TFCW leaded to better aerobic removal of organic matter in the microbial community, while limiting the rest phase of TFCW results in the opposite. In addition, the species overlap rate of the top, middle and bottom layers of NR-TFCW (69.98%) and P-TFCW (54.29%) was higher than that of TFCW (11.34%). The removal of organic matter by TFCW mainly relied on the adsorption of biochar in the flood phase, and the microorganisms aerobic degraded the organic matter adsorbed on the biochar in the rest phase. And thus form a continuous cycle of adsorption and biological regeneration. The microbial community in TFCW did not have the ability to nitrify, but had the ability to remove phosphorus. Ammonia nitrogen in the influent was adsorbed by biochar or converted into cytoplasm. While the phosphorus in the influent was adsorbed by the biochar, it was also being biologically removed.

Deciphering the microbial community structures and functions of wastewater treatment at high-altitude area

Introduction: The proper operation of wastewater treatment plants is a key factor in maintaining a stable river and lake environment. Low purification efficiency in winter is a common problem in high-altitude wastewater treatment plants (WWTPs), and analysis of the microbial community involved in the sewage treatment process at high-altitude can provide valuable references for improving this problem. Methods: In this study, the bacterial communities of high- and low-altitude WWTPs were investigated using Illumina high-throughput sequencing (HTS). The interaction between microbial community and environmental variables were explored by co-occurrence correlation network. Results: At genus level, Thauera (5.2%), unclassified_Rhodocyclaceae (3.0%), Dokdonella (2.5%), and Ferribacterium (2.5%) were the dominant genera in high-altitude group. The abundance of nitrogen and phosphorus removal bacteria were higher in high-altitude group (10.2% and 1.3%, respectively) than in low-altitude group (5.4% and 0.6%, respectively). Redundancy analysis (RDA) and co-occurrence network analysis showed that altitude, ultraviolet index (UVI), pH, dissolved oxygen (DO) and total nitrogen (TN) were the dominated environmental factors (p < 0.05) affecting microbial community assembly, and these five variables explained 21.4%, 20.3%, 16.9%, 11.5%, and 8.2% of the bacterial assembly of AS communities. Discussion: The community diversity of high-altitude group was lower than that of low-altitude group, and WWTPs of high-altitude aeras had a unique microbial community structure. Low temperature and strong UVI are pivotal factors contributing to the reduced diversity of activated sludge microbial communities at high-altitudes.

Using molecular weight-based fluorescent detector to characterize dissolved effluent organic matter in oxidation ditch with algae

Implementation of microalgae has been considered for enhancing effluent wastewater quality. However, it can cause environmental issues due to the release of extracellular and algal organic matter in the biological process. This study aimed to investigate the characteristics of dissolved effluent as algae- and bacteria-derived organic matter during the oxidation ditch process. Furthermore, experiments were conducted under three combinations filled by Spirulina platensis, Chlorella vulgaris, and without microalgae. The results showed that dissolved effluent organic matter was more aromatic and hydrophobic than before treatment. Fluorescence spectroscopy identified two components-aromatic protein-like and soluble microbial product-like components-at excitation/emission of 230/345 nm and 320/345 nm after treatment, instead of fulvic acid-like at 230/420 nm and humic acid-like at 320/420 nm in raw wastewater. These components were fractionated based on the average of molecular weight cut-offs (MWCOs), and high (MWCOs > 50,000 Da), medium (MWCOs 50,000-1650 Da), and low molecular weights (MWCOs < 1650 Da) were reported. Biological oxidation ditch under symbiosis algal bacteria generated humic and fulvic acid with a higher MWCOs than the process without algal. The quality and quantity of dissolved effluent organic matter in an oxidation ditch reactor were significantly affected by algal-bacteria symbiotic.

Molecular microbiological approaches reduce ambiguity about the sources of faecal pollution and identify microbial hazards within an urbanised coastal environment

Urbanised beaches are regularly impacted by faecal pollution, but management actions to resolve the causes of contamination are often obfuscated by the inability of standard Faecal Indicator Bacteria (FIB) analyses to discriminate sources of faecal material or detect other microbial hazards, including antibiotic resistance genes (ARGs). We aimed to determine the causes, spatial extent, and point sources of faecal contamination within Rose Bay, a highly urbanised beach within Sydney, Australia's largest city, using molecular microbiological approaches. Sampling was performed across a network of transects originating at 9 stormwater drains located on Rose Bay beach over the course of a significant (67.5 mm) rainfall event, whereby samples were taken 6 days prior to any rain, on the day of initial rainfall (3.8 mm), three days later after 43 mm of rain and then four days after any rain. Quantitative PCR (qPCR) was used to target marker genes from bacteria (i.e., Lachnospiraceae and Bacteroides) that have been demonstrated to be specific to human faeces (sewage), along with gene sequences from Heliobacter and Bacteriodes that are specific to bird and dog faeces respectively, and ARGs (sulI, tetA, qnrS, dfrA1 and vanB). 16S rRNA gene amplicon sequencing was also used to discriminate microbial signatures of faecal contamination. Prior to the rain event, low FIB levels (mean: 2.4 CFU/100 ml) were accompanied by generally low levels of the human and animal faecal markers, with the exception of one transect, potentially indicative of a dry weather sewage leak. Following 43 mm of rain, levels of both human faecal markers increased significantly in stormwater drain and seawater samples, with highest levels of these markers pinpointing several stormwater drains as sources of sewage contamination. During this time, sewage contamination was observed up to 1000 m from shore and was significantly and positively correlated with often highly elevated levels of the ARGs dfrA1, qnrS, sulI and vanB. Significantly elevated levels of the dog faecal marker in stormwater drains at this time also indicated that rainfall led to increased input of dog faecal material from the surrounding catchment. Using 16S rRNA gene amplicon sequencing, several indicator taxa for stormwater contamination such as Arcobacter spp. and Comamonadaceae spp. were identified and the Bayesian SourceTracker tool was used to model the relative impact of specific stormwater drains on the surrounding environment, revealing a heterogeneous contribution of discrete stormwater drains during different periods of the rainfall event, with the microbial signature of one particular drain contributing up to 50% of bacterial community in the seawater directly adjacent. By applying a suite of molecular microbiological approaches, we have precisely pinpointed the causes and point-sources of faecal contamination and other associated microbiological hazards (e.g., ARGs) at an urbanised beach, which has helped to identify the most suitable locations for targeted management of water quality at the beach.

Shifts of bacterial community and molecular ecological network in activated sludge system under ibuprofen stress

The major objectives of this study were to explore the long-term effects of ibuprofen (IBP) on nutrient removal, community compositions, and microbial interactions of the activated sludge system. The results showed that 1 mg/L IBP had no inhibitory effects on the removal of organic matters and nutrients. IBP significantly reduced the microbial diversity and changed the bacterial community structure. Some denitrifiers (Denitratisoma and Hyphomicrobium) increased significantly, while NOB (Nitrospira) significantly decreased under IBP stress (P < 0.05). Furthermore, molecular ecological network analysis indicated that IBP reduced the overall network size and links, but led to a closer network with more efficient communication, which might be the strategy of microbes to survive under the stress of IBP and further maintain the performance stability. Different phylogenetic populations had different responses to IBP, as a closer subnetwork with more synergistic relations was observed in Chloroflexi and a looser subnetwork with more competitive relationships was detected in Proteobacteria. The topological roles of nodes significantly changed, and the putative keystone species decreased under the stress of IBP. This study broadens our knowledge of the long-term effects of IBP on the microbial community structure and the interactions between species in the activated sludge system.

Performance and bacterial community profiles of sequencing batch reactors during long-term exposure to polyethylene terephthalate and polyethylene microplastics

Microplastics (MPs) are ubiquitous in wastewater treatment plants (WWTPs), but much remains to be learned about their roles in WWTPs. Herein, polyethylene terephthalate (PET) and polyethylene (PE) particles were added into sequencing batch reactors (SBRs), and the sole impacts and co-impacts of MPs with other pollutants (phenol and Cu²⁺) on wastewater treatment processes were evaluated. Results indicated that MPs did not significantly affect SBR performance, either alone or co-occurrence with phenol, but the co-exposure to MPs and Cu²⁺ severely suppressed COD removal efficiency by 37.02%-64.70%. The functional groups of activated sludge had no changes after receiving MPs, but the MPs-Cu²⁺ co-exposure could greatly promote the secretion of extracellular polymeric substances. Furthermore, MPs had no negative impacts on diversity, richness and structure of bacterial communities, and PET and PE showed different preferences for enrichment of bacterial populations. Moreover, the MPs-Cu²⁺ co-exposure obviously reduced the overall abundances of Cu-related genes in SBRs.

Acute exposure effects of tetracycline, ampicillin, sulfamethoxazole, and their mixture on nutrient removal and microbial communities in the activated sludge of air-scouring and reciprocation membrane bioreactors

The fate of antibiotics, their effects on non-target species, and the spread of antibiotic resistance in wastewater treatment systems have been of concern in recent years. Despite its importance, the effects of these antibiotics on biological nutrient removal in WWTPs have not been completely elucidated. To evaluate the effects of antimicrobial compounds on nutrient removal performance and microbiome, batch experiments were performed using activated sludge samples taken from two distinct membrane bioreactor systems (reciprocation MBR vs. air-scouring MBR). We exposed the activated sludge to 0 mg/L, 0.1 mg/L, and 1.0 mg/L of tetracycline (TET), ampicillin (AMP), sulfamethoxazole (SUL), and their mixture. The mixture of antibiotics significantly decreased ammonia removal efficiency in the reciprocation MBR (rMBR) and air-scouring MBR (AS MBR) by 5% and 12%, respectively. A significant reduction (p < 0.05) in the amoA-AOB gene was observed in AS MBR, while this gene remained unaffected in the rMBR. Interestingly, the gene abundance of amoA from comammox Nitrospira increased from 2.8 × 10⁸ gene copies per gram sludge (0 mg/L) to 5.0 × 10⁸ gene copies per gram sludge (1.0 mg/L) in the setup with antibiotics in the mixture. Correlation analysis of the relative abundance of prevalent taxa and antibiotic concentrations showed that the microbial communities of the AS MBR were more susceptible to TET and MXD antibiotics than the rMBR microbiome.

Microbial characteristics in anaerobic membrane bioreactor treating domestic sewage: Effects of HRT and process performance

Two anaerobic membrane bioreactors (AnMBRs) equipped with different membrane pore size (0.4 or 0.05 µm) were operated at 25˚C and fed with domestic wastewater. The hydraulic retention time (HRT) of the reactors was shortened. The microbial communities of the two AnMBRs were investigated by 16S rRNA gene amplicon sequencing to see the effects of HRT. The predominant Archaea was an aceticlastic methanogen Methanosaeta. The composition of hydrogenotrophic methanogens changed with the HRTs: the population of Methanobacterium was higher for longer HRTs, whereas the population of unclassified Methanoregulaceae was higher for shorter HRTs. The Anaerolineae, Bacteroidia and Clostridia bacteria were dominant in both of the reactors, with a combined relative abundance of over 55%. The relative abundance of Anaerolineae was proportional to the biogas production performance. The change in the population of hydrogenotrophic methanogens or Anaerolineae can be used as an indicator for process monitoring. The sum of the relative abundance of Anaerolineae and Clostridia fluctuated slightly with changes in the HRT in both AnMBRs when the reactor was stably operated. The co-occurrence analysis revealed the relative abundance of the operational taxonomic units belonging to Anaerolineae and Clostridia was functionally equivalent during the treatment of real domestic sewage. A principal coordination analysis revealed that the changes in the microbial community in each reactor were consistent with the change of HRT. In addition, both the HRT and the stability of the process are important factors for maintaining microbial community structures.

In-situ fermentation coupling with partial-denitrification/anammox process for enhanced nitrogen removal in an integrated three-stage anoxic/oxic (A/O) biofilm reactor treating low COD/N real wastewater

Mainstream partial-denitrification with anammox (PD-anammox) process faced the challenge of complex organics involved in real sewage. Herein, PD-anammox coupled with in-situ fermentation was successfully achieved in a full biofilm system formed by three-stage anoxic/oxic reactor to treat real wastewater with low COD/N of 3.6. The total nitrogen (TN) removal efficiency was enhanced to 78.4% ± 3.6% with average TN and ammonium concentrations in effluent of 10.6 and 0.5 mg N/L, respectively. Batch tests confirmed that partial-denitrification was the major nitrite provider for anammox in the anoxic biofilm, while in-situ fermentation could decompose the complex organics to readily-biodegradable organics for full- or partial-denitrification. Additionally, a significant anammox bacteria (Candidatus Brocadia) population was detected in the second (3.53%) and third (4.46%) anoxic zones, while denitrifiers and fermentative bacteria were mainly enriched in the first anoxic zone. This study presents a feasible approach for PD-anammox process in practical application under mainstream condition.

Pilot-scale microaerobic hydrolysis-acidification and anoxic-oxic processes for the treatment of petrochemical wastewater

Microaerobic hydrolysis and acidification (MHA), as a promising pre-treatment method of industrial wastewater, is drawing increasing attention to enhance the hydrolysis-acidification rate and inhibit the production of toxic gas H₂S. In the present work, a pilot-scale MHA reactor coupled with anoxic-oxic (A/O) processes for treating the petrochemical wastewater was established and the mechanism and application of the MHA reaction were explored. The results showed that the ratio of VFA/COD was increased by 43-90% and low effluent S^2- concentration (less than 0.2 mg/L) was obtained after MHA treatment with 5.5-13.8 L air m^-3 h^-1 supply. The MHA sludge exhibited a good settleability, a higher protease activity and plentiful community diversity. In addition to the dominant anaerobic bacteria responsible for hydrolysis and acidification such as Clostridiales uncultured, Anaerovorax, Anaerolineaceae uncultured and Fastidiosipila, the sulfate reducing bacteria involving Desulfobacter, Desulfomicrobium and Desulfobulbus, the sulphur oxidizing bacteria involving Thiobacillus, Arcobacter and Limnobacter, the nitrifies such as Nitrosomonadaceae uncultured and Nitrospira, and denitrifies Thauera were also identified. MHA pre-treatment guaranteed the efficacy and stability of the following A/O treatment. The removal efficiency of COD and ammonium of the MHA-A/O system remained at around 78.3% and 80.8%, respectively, although the organic load fluctuated greatly in the influent.

Transformations from specialists to generalists cause bacterial communities are more stable than micro-eukaryotic communities under anthropogenic activity disturbance

Different microbial components have different responses to environmental disturbances. Here, we found that the planktonic bacterial and micro-eukaryotic communities had different responses to anthropogenic activity disturbance in a subtropical river, because they had different survival strategies (generalist and specialist). We used nutrients (nitrogen and phosphorus) as indicators of anthropogenic activities. We found that river stretch 1 showed low nutrient concentrations from October 2018 to September 2019. However, a nutrient disturbance was observed in river stretch 2. The nutrient concentrations increased largely in December and January but recovered to low values in June. Bacterial communities had higher resilience under this disturbance than micro-eukaryotic communities in river stretch 2. The bacterial community composition were quite different between the two river stretches in December and January but were similar in June and July. However, the differences of micro-eukaryotic community composition between the two river stretches were always high during the study period. The bacterial communities in river stretch 2 contained more generalists and nutrient tolerant specialists. The bacterial nutrient tolerant specialists rapidly decreased in the low nutrient months and were replaced by the generalists. Bacteria which were involved in this shifts accounted for 29.3% of the total abundance. However, the micro-eukaryotic communities in river stretch 2 contained more moderate generalists. These moderate generalists were insensitive to the variation of nutrients and only 19.56% of the micro-eukaryotes had significant responses to the disturbance. The survival strategies caused bacterial communities had higher adaptability than eukaryotes to environmental fluctuation.

Distribution patterns of microbial community and functional characteristics in full-scale wastewater treatment plants: Focusing on the influent types

The impacts of the influent type in wastewater treatment plants (WWTPs) on the distribution patterns of the microbial community and functional characteristics were investigated. The obtained results indicated that the influent types exhibited evident influences on the microbial distribution patterns. The diversity and richness of functional microbes in HI-WWTP (with a ratio of >30% industrial wastewater in influents) were evidently decreased compared with those in HM- (with 70-90% municipal wastewater in influents) and M-WWTPs (with >90% municipal wastewater in influents). The core functional bacteria included denitrifiers, anaerobic fermentation bacteria (AFB), organic degrading bacteria (ODB), phosphorus accumulating organisms (PAO) and nitrite oxidizing bacteria (NOB), but they exhibited distinct abundances in WWTPs receiving different categories of wastewater. The denitrifiers in HI-WWTPs was 15.6-32.5% higher than that in other WWTPs, while PAOs had higher abundances in M - and HI-WWTPs (28.9% and 39.3%, respectively) compared with HM-WWTPs. Clear co-occurrence relationships were found among the main functional microbes with similar metabolic characteristics. Moreover, information on functional genes related to carbon, nitrogen and phosphorus metabolism, which is closely associated with pollutant removal efficiency, was obtained. M-WWTPs had higher abundances of genetic expressions for organic matters degradation (i.e. amino acid (10.42%) and carbohydrate (9.86%) metabolisms). Nar, Nir and Nor showed lowest abundances in HM-WWTPs, causing the low nitrogen removal (63.04-65.79%). However, influent type had little effect on genetic expression related with phosphorus removal. This work provided new insights into the interrelationship among bacterial co-occurrence, microbial activity and pollutant removal in WWTPs with different influent types.

Removal behaviour of residual pollutants from biologically treated palm oil mill effluent by Pennisetum purpureum in constructed wetland

The reason for such enormous efforts in palm oil mill effluent research would be what has been singled out as one of the major sources of pollution in Malaysia, and perhaps the most costly and complex waste to manage. Palm oil mill final discharge, which is the treated effluent, will usually be discharged to nearby land or river since it has been the least costly way to dispose of. Irrefutably, the quality level of the treated effluent does not always satisfy the surface water quality in conformity to physicochemical characteristics. To work on improving the treated effluent quality, a vertical surface-flow constructed wetland system was designed with Pennisetum purpureum (Napier grass) planted on the wetland floor. The system effectively reduced the level of chemical oxygen demand by 62.2 ± 14.3%, total suspended solid by 88.1 ± 13.3%, ammonia by 62.3 ± 24.8%, colour by 66.6 ± 13.19%, and tannin and lignin by 57.5 ± 22.3%. Heat map depicted bacterial diversity and relative abundance in life stages from the wetland soil, whereby bacterial community associated with the pollutant removal was found to be from the families Anaerolineaceae and Nitrosomonadaceae, and phyla Cyanobacteria and Acidobacteria.

Anthropogenic activities change the relationship between microbial community taxonomic composition and functional attributes

Functional redundancy is considered common in microbial systems, but recent studies have challenged this idea. The mechanism for this contradictory result is not clear. However, in this study, we hypothesize that strong environmental filtering which links to the anthropogenic activities is able to weaken microbial functional redundancy. We used metagenome and 16S rRNA gene high-throughput sequencing to investigate planktonic microbial communities in a subtropical river. We found that the weak anthropogenic activities might result in a low selection pressure in the river upstream area. Therefore, the microbial community functional attributes were stable although the community composition changed with the water temperature and NO₃ -N in upstream area (this indicates functional redundancy). However, the strong anthropogenic activities in river downstream area selected pollutant-degraded functions (e.g. nitrogen metabolism, toluene, xylenes and ethylbenzene degradation) and potentially pollutant-degraded (tolerant) microbes, and therefore caused the microbial community composition synchronously changed with the variation of community functional attributes. Our results reveal that strong environmental filtering which associates with the anthropogenic activities not only has effects on microbial community composition and community functional attributes but also on their relationships. These results provide a new insight to refine the functional redundancy idea.

Versatility of nitrite/nitrate-dependent anaerobic methane oxidation (n-DAMO): First demonstration with real wastewater

Nitrite/nitrate-dependent anaerobic methane oxidation (n-DAMO) processes have been proven effective for nitrogen removal from synthetic wastewater. However, the demonstration using real wastewater has not been achieved yet. To this end, this study investigated the versatile applications of n-DAMO process in real wastewater treatment for the first time. Two methane-based membrane biofilm reactors (MBfRs) were employed to combine anammox and n-DAMO microorganisms, targeting nitrogen removal in mainstream (i.e., domestic sewage) and sidestream (i.e., anaerobic digestion liquor), respectively. Considering various technologies in sewage treatment, three different technical routes, including nitritation + methane-based MBfR, partial nitritation + methane-based MBfR and partial nitritation + anammox + methane-based MBfR, were investigated comprehensively, all producing effluent quality with total nitrogen (TN) at 5 mg N/L or less. Regarding the sidestream treatment, the methane-based MBfR also removed up to 96% TN from the partially nitrified anaerobic digestion liquor at a practically useful rate of 0.5 kg N/m³/d. Microbial communities revealed by 16S rRNA gene amplicon sequencing indicated the dominance of n-DAMO archaea in both reactors, along with the existence of anammox bacteria and n-DAMO bacteria. As the first demonstration of n-DAMO process in real wastewater, this study comprehensively confirmed the applicability of using methane as carbon source to remove nitrogen from both mainstream and sidestream wastewater, supporting their adoption by industries in practice.

Jianqu fermentation with the isolated fungi significantly improves the immune response in immunosuppressed mice

ETHNOPHARMACOLOGICAL RELEVANCE

Jianqu, a classical formula of traditional Chinese medicine, is used clinically to treat symptoms like chill and fever headache, diarrhea and loss of appetite and act on patients with low immunity. However, the quality control of Jianqu fermentation is not well established, and its function in regulating the body's immunity still remains unclear.

AIM OF THE STUDY

The present study firstly assesses the structure and diversity of fungal community during Jianqu fermentation and then investigates the immune regulating function of Jianqu extract in mouse model.

MATERIALS AND METHOD

The high-throughput sequencing is conducted to analyze the diversity and distribution of fungal community during the fermentation process of Jianqu, and then fungi with a high frequency and relative abundance are isolated. The immunosuppressed mice are induced by using cyclophosphamide (CTX) and used to evaluate the immune regulating function of Jianqu extract from natural fermentation or directed fermentation, respectively.

RESULTS

With the fermentation, the diversity and distribution of fungal community significantly changed. The number of OTU (operational taxonomic unit) was gradually decreased from 223 ± 1 in the early phase to 201 ± 11 in the middle phase and to 175 ± 32 in the later phase of Jianqu fermentation. Generally, in genus level, Millerozyma, Debaryomyces and Rhizomucor showed a significant increase and became dominant in the mid or later phase of fermentation, while the Aspergillus displayed a decrease following the fermentation. However, Saccharomycopsis is a dominate species in surveyed samples. Next, six fungi strains with a high frequency and relative abundance, including Saccharomycopsis fibuligera, Millerozyma farinose, Hyphopichia burtonii, Rhizomucor pusillus, Lichtheimia ramosa, and Monascus purpureus, are isolated successfully. Interestingly, directed fermentation for Jianqu with the six isolated fungi strains could achieve similar morphological characteristics with the natural fermentation. Consistently, Jianqu extract from directed fermentation demonstrated a similar therapeutic effect on immune response as that of naturally fermented Jianqu.

CONCLUSIONS

We firstly showed the significant change of structural profiles of fungal communities during Jianqu fermentation, and successfully isolated six dominate fungi strains in Jianqu. Interestingly, directed fermentation for Jianqu with these isolated strains could achieve a similar morphological characteristics and immune-modulating function as natural fermentation. It was suggested that Jianqu fermentation with functional fungi instead of natural microbes provide a new approach for the improvement of the production and quality control of the traditional Chinese medicine of Jianqu.

Mechanistic insights into the effect of poly ferric sulfate on anaerobic digestion of waste activated sludge

Poly ferric sulfate (PFS), one of the typical inorganic flocculants widely used in wastewater management and waste activated sludge (WAS) dewatering, could be accumulated in WAS and inevitably entered in anaerobic digestion system at high levels. However, knowledge about its impact on methane production is virtually absent. This study therefore aims to fill this gap and provide insights into the mechanisms involved through both batch and long-term tests using either real WAS or synthetic wastewaters as the digestion substrates. Experimental results showed that the maximum methane potential and production rate of WAS was respectively retarded by 39.0% and 66.4%, whereas the lag phase was extended by 237.0% at PFS of 40 g per kg of total solids. Mechanism explorations exhibited that PFS induced the physical enmeshment and disrupted the enzyme activity involved in anaerobic digestion, resulting in an inhibitory state of the bioprocess of hydrolysis, acidogenesis, and methanogenesis. Furthermore, PFS's inhibition to hydrogenotrophic methanogenesis was much severer than that to acetotrophic methanogenesis, which could be supported by the elevated abundances of Methanosaeta sp and the dropped abundances of Methanobacterium sp in PFS-present digester, and probably due to the severe mass transfer resistance of hydrogen between the syntrophic bacteria and methanogens, as well as the higher hydrogen appetency of PFS-induced sulfate reducing bacteria. Among the derivatives of PFS, "multinucleate and multichain-hydroxyl polymers" and sulfate were unveiled to be the major contributors to the decreased methane potential, while the "multinucleate and multichain-hydroxyl polymers" were identified to be the chief buster to the slowed methane-producing rate and the extended lag time.

Metagenomics approach and canonical correspondence analysis of novel nitrifiers and ammonia-oxidizing archaea in full scale anaerobic-anoxic-oxic (A2/O) and oxidation ditch processes

Various microorganisms are involved in nitrogen removal, and their group compositions depend closely on operating parameters. The structures and functions of nitrification microorganisms in full-scale anaerobic-anoxic-oxic (A2/O) and oxidation ditch processes were analyzed using metagenomics and canonical correspondence analysis. The community structure of ammonia-oxidizing archaea in the oxidation ditch was 3.8 (winter) - 6.3 (summer) times higher than in A2/O, and the complete ammonia oxidizer was only found in the oxidation ditch process. The canonical correspondence analysis of various environmental variables showed that Nitrosomonadales, Crenarchaeota, and Nitrospira inopinata correlate highly with nitrification, and Nitrospira was involved in NO₂^--N oxidation rather than Nitrobacter. The longer solid and hydraulic retention times in the oxidation ditch were more effective in achieving a wider range of novel nitrification than A2/O. This result indicates that microbial communities of novel nitrifiers and ammonia-oxidizing archaea improved in the oxidation ditch process, significantly contributing to stable nitrogen removal.

Analysis of Microbial Communities and Pathogen Detection in Domestic Sewage Using Metagenomic Sequencing

Wastewater contains diverse microbes, and regular microbiological screening at wastewater treatment plants is essential for monitoring the wastewater treatment and protecting environmental health. In this study, a metagenomic approach was used to characterize the microbial communities in the influent and effluent of a conventional domestic sewage treatment plant in the metropolitan city of Jeddah. Bacteria were the prevalent type of microbe in both the influent and effluent, whereas archaea and viruses were each detected at <1% abundance. Greater diversity was observed in effluent bacterial populations compared with influent, despite containing similar major taxa. These taxa consisted primarily of Proteobacteria, followed by Bacteroidetes and Firmicutes. Metagenomic analysis provided broad profiles of 87 pathogenic/opportunistic bacteria belonging to 47 distinct genera in the domestic sewage samples, with most having <1% abundance. The archaea community included 20 methanogenic genera. The virus-associated sequences were classified mainly into the families Myoviridae, Siphoviridae, and Podoviridae. Genes related to resistance to antibiotics and toxic compounds, gram-negative cell wall components, and flagellar motility in prokaryotes identified in metagenomes from both types of samples. This study provides a comprehensive understanding of microbial communities in influent and effluent samples of a conventional domestic sewage treatment plant and suggests that metagenomic analysis is a feasible approach for microbiological monitoring of wastewater treatment.

Bacterial community colonization on tire microplastics in typical urban water environments and associated impacting factors

Only limited information is available on bacterial communities' dynamics on tire microplastics in urban water environments. This study exploited 16S rDNA high-throughput sequencing to characterize bacterial communities on tire microplastics, using three different tire brands and tire sizes, in two typical urban water environments, including an influent pond of constructed wetland (CW) and its subsequent effluent into a landscape river (LR) during three different periods, namely, 1 month, 3 and 6 months. Results showed that the abundance of bacterial colonization on tire microplastics will increase over time. Proteobacteria, Bacteroidetes were the dominant bacteria at a phylum level, although they exhibited dynamic changes. At a genus level, the identifiable bacteria found in tire microplastics was generally the common bacteria in wastewater discharge, such as Aquabacterium and Denitratisoma. Additionally, alpha diversity showed no significant differences in bacterial communities at the same locations. While beta diversity showed that the bacterial communities on the tire microplastics in the two locations was different. BugBase revealed that tire microplastics could support pathogenic bacteria in urban water environments. PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) indicated that the abundance of microorganisms associated with metabolism and degradation increased with time. Moreover, the ambient environmental factors were the main influencing factors of bacterial communities on tire microplastics. Herein, the contribution rate of nutrient salts (NO₂-N, NO₃-N, NH₄-N, CODcr) was approximately 63%, and that of environmental physical factors of T and pH was 50%. While physicochemical factors, including particle size, contact angle, element content only had a slight impact. Accordingly, tire microplastics, as an emerging environmental pollutant, can act as carries for bacterial colonization and propagation, particularly harmful microorganisms. Therefore, the obtained findings can provide new insight into potential risks of harmful microorganisms that colonize tire microplastics in urban water environments.

The differential proliferation of AOB and NOB during natural nitrifier cultivation and acclimation with raw sewage as seed sludge

Nitrifier immigration from sewers to wastewater treatment systems is attracting increasing attention for understanding nitrifier community assembly mechanisms, and improving process modeling and operation. In this study, nitrifiers in raw sewage were cultivated and acclimated in a sequencing batch reactor (SBR) for 90 days to investigate the characteristics of the influent nitrifiers after immigration. During the experiment, specific nitrite utilization rate (SNUR) exceeded specific ammonia utilization rate (SAUR) when floc size reached 224 ± 46 μm, and nitrogen loss occurred at the same time. The ratio of nitrite oxidizing bacteria (NOB) to ammonia oxidizing bacteria (AOB) increased from 0.84 to 2.14 after cultivation. The Illumina MiSeq sequencing showed that the dominant AOB was Nitrosomonas sp. Nm84 and unidentified species, and the three most abundant Nitrospira were Nitrospira defluvii, Nitrospira calida, and unidentified Nitrospira spp. in both raw sewage and cultivated activated sludge. The shared reads of raw sewage and activated sludge were 48.76% for AOB and 89.35% for Nitrospira. These indicated that nitrifiers, especially NOB, immigrated from influent can survive and propagate in wastewater systems, which may be a significant hinder to suppress NOB in the application of advanced nitrogen remove process based on partial nitrification in the mainstream.

Biodiversity of organisms inhabiting the water supply network of Wroclaw. Detection of pathogenic organisms constituting a threat for drinking water recipients

The objective of the article was to present the diversity of organisms inhabiting the water supply network with particular consideration of pathogenic organisms that can cause an epidemiological threat, with the application of high throughput sequencing (HTS). The study material was water sampled from 15 points in the water supply system. High species diversity of bacteria was evidenced, as well as the presence of microorganisms from genus Clostridium and family Enterobacteriaceae. No presence of bacteria Clostridium perfringens was recorded, which suggests proper performance of water treatment processes. Owing to advanced techniques of molecular biology, the article also presents species very similar to pathogenic bacteria the detection of which is not possible by means of standard water analysis (plate culture). Based on literature data and very high similarity of the genome of the bacteria to that of pathogenic bacteria, the species are considered to potentially show the same negative character towards the recipient, and cause a serious epidemiological threat. Therefore, the performed analyses show that classic methods of assessment of sanitary quality of water are not fully sufficient, and HTS analysis should be performed as an auxiliary tool to provide the complete image of the community in the existing network.

Efficient municipal wastewater treatment by oxidation ditch process at low temperature: Bacterial community structure in activated sludge

Temperature is a key element affecting the activity of microorganisms in activated sludge. Low water temperature generally leads to decreasing wastewater treatment efficiency and destroying sludge settleability. In this study, activated sludge samples from a municipal wastewater treatment plant (WWTP) implementing oxidation ditch process was used to investigate the bacterial community characteristics of a system that operates well in a cold region (Xinjiang, China) by high-throughput 16S rRNA gene sequencing. The results showed that the influent temperature was 7-12 °C in winter and 13-17 °C in summer, while the sludge volume index (SVI) of samples was between 51 and 74 mL/g. The average removal efficiencies for chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), suspended solid (SS), ammonia nitrogen (NH₄⁺-N), total nitrogen (TN), and total phosphorus (TP) were 94%, 95%, 95%, 91%, 73% and 89%, respectively. The bacteria were distributed in 32 phyla and 559 genera. The dominant phyla were Proteobacteria (28.85-48.45%), Bacteroidetes (20.00-31.22%), Chloroflexi (3.59-12.23%), Actinobacteria (1.58-15.54%) and Firmicutes (1.38-10.49%). The dominant genera were Saprospiraceae_norank (4.41-12.23%), Comamonadaceae_unclassified (3.82-8.83%), Anaerolineaceae_norank (1.39-9.35%), Dokdonella (1.13-11.26%), Candidatus_Microthrix (0.26-7.50%), Flavobacterium (0.32-8.14%), Ferribacterium (0.36-5.19%) and Nitrospira (0.084-5.37%), which were different from those found in warm-region WWTPs. Contrary to previous studies, the relative abundance of ammonia-oxidizing bacteria (AOB; Nitrosomonas and Nitrosomonadaceae) and nitrite-oxidizing bacteria (NOB; Nitrospira) increased when the temperature decreased. The successful operation of this WWTP suggests that cold-region WWTPs can achieve good pollutants removal efficiency by simultaneously maintaining an ultra-low sludge load and high dissolved oxygen concentration in the oxidation ditch. The findings of this study provide fundamental knowledge required for an efficient and stable operation of WWTPs in cold regions.

pH control and microbial community analysis with HCl or CO2 addition in H2-based autotrophic denitrification

H₂-based autotrophic denitrification is promising to remove nitrate from water or wastewater lacking organic carbon sources, and pH is one of its most important process parameters. HCl and CO₂ addition are known as adequate pH control methods for practical purposes. However, because of H₂, added CO₂ may participate in microbial metabolisms and affect denitrification mechanisms. Here, a combined micro-electrolysis and autotrophic denitrification (CEAD) reactor, in which H₂ is generated based on galvanic-cell reactions between zero-valent iron and carbon, was optimized and continuously operated for 233 days by adding HCl or CO₂ to control pH in the range of 7.2-8.2. Microbial communities were compared between the two pH-control methods through high-throughput sequencing of 16S rRNA, nirS, and nirK genes. Under a low COD/N ratio of 0.5 in the influent (with ∼36 mgNO₃^--N/L), when adding HCl, the total nitrogen (TN) removal efficiency reached 91.4% ± 0.9% with a 28-h hydraulic retention time (HRT). When adding CO₂, the TN removal efficiency was improved to 96.5% ± 1.7% with 24-h HRT. Significant differences of 16S rRNA and nirS genes between the two pH-control stages indicated the variation of microbial communities and nirS-type denitrifiers. With HCl addition, Thiobacillus, unclassified Comamonadaceae, Arenimonas, Limnobacter, and Thermomonas, which were reported previously as likely autotrophic or heterotrophic denitrifiers, were most dominant in the biofilms. With CO₂ addition, the biofilms became dominated by Anaerolineaceae and Methylocystaceae (related to organic carbon metabolism), Denitratisoma (likely heterotrophic denitrifier), and uncultured bacteria TK10 and AKYG587. The results suggest that the added CO₂ not only contributed to pH control but also participated in microbial metabolisms. This study provides useful insights into microbial mechanisms and further optimization of H₂-based autotrophic denitrification in water and wastewater treatment.

Nitrogen removal mechanism and microbial community changes of bioaugmentation subsurface wastewater infiltration system

Limited nitrogen removal capacity (mainly nitrate, NO₃^--N) remains a major challenge for subsurface wastewater infiltration system (SWIS). Two nitrogen-removing strains have been isolated from SWIS and inoculated to SWIS to investigate the effect of bioaugmentation on nitrogen removal performance and mechanism. The results showed bioaugmentation improved the removal efficiencies of NH₄⁺-N from 86.81% to 92.86% and TN from 74.90% to 86.55% and running stability compared to unbioaugmentation SWIS. 16 s rRNA amplicon sequencing results of the bacterial indicated that bioaugmentation altered the microbial community structure especially at 150 cm depth and increased the relative abundance of bacteria associated with nitrogen removal, significantly increasing the abundance of Rhizobiales_Incertae_Sedis and Lachnospiraceae. Furthermore, the relation between internal microbial characteristics and operational factors indicated that Hyphomicrobiaceae and Gemmatimonadaceae were also closely related to nitrogen removal. Predicted function profiles revealed that bioaugmentation enhanced the activity of nitrogen removal enzymes (Hao, NorBC, NasAB, NarGHI, NirBD and NosZ).

The microbial community in filamentous bulking sludge with the ultra-low sludge loading and long sludge retention time in oxidation ditch

Sludge bulking is a major problem that restricts the development of the activated sludge process. The microbial community responsible for sludge bulking varies depending on water quality and operational conditions. This study analysed the microbial community of bulking sludge in oxidation ditch with ultra-low sludge loading and long sludge retention time using high-throughput sequencing. The study found that the relative abundance of bacterial genus Saprospiraceae_norank was the highest in bulking sludge, reaching 13.39-28.83%, followed by Comamonadaceae_unclassified, Ardenticatenia_norank and Tetrasphaera, with the relative abundance of 4.59-11.08%, 0.52-16.60% and 0.17-8.92% respectively. In contrast, the relative abundance of bacteria that easily caused sludge bulking including Microthrix (0.54-2.47%), Trichococcus (0.32-1.71%), Gordonia (0.14-1.28%), and Thiothrix (0.01-0.06%) were relatively low. Saprospiraceae_norank was predominant and induced sludge bulking in oxidation ditch. The relative abundance of fungal genus Trichosporon was the highest in bulking sludge, reaching 16.95-24.98%, while other fungal genera were Saccharomycetales_unclassified (5.59-14.55%), Ascomycota_norank (1.45-13.51%), Galactomyces (5.23-11.23%), and Debaryomyces (7.69-9.42%), whereas Trichosporon was the dominant fungal genus in bulking sludge. This study reported that excessive Saprospiraceae_norank can induce sludge bulking for the first time, which provides important knowledge to control sludge bulking.

Streptophyta and Acetic Acid Bacteria Succession Promoted by Brass in Slow Sand Filter System Schmutzdeckes

Macro- and microorganism activities are important for the effectiveness of the slow sand filtration (SSF), where native microorganisms remove contaminants mainly by substrate competition, predation, and antagonism. The aim of the present study was to evaluate the addition of the oligodynamic metals iron, copper, and brass, inserted separately into SSF to enhance pollutant removal in water samples. Four laboratory-scale SSFs were built and tested: control, iron, copper, and brass. Water analysis included physicochemical evaluation, total and fecal coliform quantification. An analysis on microbial communities in the SSFs schmutzdecke was achieved by using 16S rRNA amplification, the Illumina MiSeq platform, and the QIIME bioinformatics software. The results demonstrated that inorganic and organic contaminants such as coliforms were removed up to 90%. The addition of metals had no significant effect (p > 0.05) on the other parameters. The microbial community analysis demonstrated different compositions of the SSF with brass-influent, where the eukaryote Streptophyta was predominant (31.4%), followed by the acetic acid bacteria Gluconobacter (24.6%), and Acetobacteraceae (7.7%), these genera were absent in the other SSF treatments. In conclusion, the use of a SSF system can be a low cost alternative to reduce microbial contamination in water and thus reduce gastrointestinal diseases in rural areas.

Assessing the spatial and temporal variability of bacterial communities in two Bardenpho wastewater treatment systems via Illumina MiSeq sequencing

Next generation sequencing provides new insights into the diversity and ecophysiology of bacteria communities throughout wastewater treatment plants (WWTP), as well as the fate of pathogens in wastewater treatment system. In the present study, we investigated the bacterial communities and human-associated Bacteroidales (HF183) marker in two WWTPs in North America that utilize Bardenpho treatment processes. Although, most pathogens were eliminated during wastewater treatment, some pathogenic bacteria were still observed in final effluents. The HF183 genetic marker demonstrated significant reductions between influent and post-Bardenpho treated samples in each WWTP, which coincided with changes in bacteria relative abundances and community compositions. Consistent with previous studies, the major phyla in wastewater samples were predominantly comprised by Proteobacteria (with Gammaproteobacteria and Alphaproteobacteria among the top two classes), Actinobacteria, Bacteroidetes, and Firmicutes. Dominant genera were often members of Proteobacteria and Firmicutes, including several pathogens of public health concern, such as Pseudomonas, Serratia, Streptococcus, Mycobacterium and Arcobacter. Pearson correlations were calculated to observe the seasonal variation of relative abundances of gene sequences at different levels based on the monthly average temperature. These findings profile how changes in bacterial communities can function as a robust method for monitoring wastewater treatment quality and performance for public and environmental health purposes.

Thiothrix eikelboomii interferes oxygen transfer in activated sludge

This study revealed that, Thiothrix eikelboomii, a well-known filamentous bacterium that causes sludge bulking, could also interfere oxygen transfer during wastewater treatment. The volumetric oxygen transfer coefficient (K_La) in filamentous-bulking sludge (FBS) was found to be 43% lower than that in floc-forming sludge (FFS) at similar biomass concentrations, partially because the filamentous bacteria had increased the sludge apparent viscosity. The K_La value for FBS, however, was still significantly lower than that for FFS even if both sludges had similar apparent viscosity. Numerous tiny and free-swimming filaments were observed to attach on the air bubble surface, presumably reducing the liquid film renewal and increasing the liquid film thickness. Moreover, the filaments were co-coated with extracellular polymeric substances of protein and polysaccharide, which could make them performing like "amphiphilic molecules" of surfactants to hinder oxygen transfer. Therefore, the particular surface property of filaments and their interaction with air bubbles could also impact oxygen transfer. Thiothrix eikelboomii was identified to be the responsible filamentous bacterium that lowered the K_La value, while other filamentous bacteria with short filaments did not interfere oxygen transfer. This study implies that controlling sludge bulking benefits not only sludge settling but also oxygen transfer.

The link between nitrous oxide emissions, microbial community profile and function from three full-scale WWTPs

Few attempts have been made in previous studies to link the microbial community structure and function with nitrous oxide (N₂O) emissions at full-scale wastewater treatment plants (WWTPs). In this work, high-throughput sequencing and reverse transcriptase-qPCR (RT-qPCR) was applied to activated sludge samples from three WWTPs for two seasonal periods (winter and summer) and linked with the N₂O emissions and wastewater characteristics. The total N₂O emissions ranged from 7.2 to 937.0 g N-N₂O/day, which corresponds to an emission factor of 0.001 to 0.280% of the influent NH₄-N being emitted as N₂O. Those emissions were related to the abundance of Nitrotoga, Candidatus Microthrix and Rhodobacter genera, which were favored by higher dissolved oxygen (DO) and nitrate (NO₃^-) concentrations in the activated sludge tanks. Furthermore, a relationship between the nirK gene expression and N₂O emissions was verified. Detected N₂O emission peaks were associated with different process events, related to aeration transition periods, that occurred during the regular operation of the plants, which could be potentially associated to increased emissions of the WWTP. The design of mitigation strategies, such as optimizing the aeration regime, is therefore important to avoid process events that lead to those N₂O emissions peaks. Furthermore, this study also demonstrates the importance of assessing the gene expression of nosZ clade II, since its high abundance in WWTPs could be an important key to reduce the N₂O emissions.

Geographical Patterns of nirS Gene Abundance and nirS-Type Denitrifying Bacterial Community Associated with Activated Sludge from Different Wastewater Treatment Plants

Denitrifying bacteria is a driver of nitrogen removal process in wastewater treatment ecosystem. However, the geographical characteristics of denitrifying bacterial communities associated with activated sludge from diverse wastewater treatment plants (WWTPs) are still unclear. Here, quantitative PCR and next-generation sequencing of the nirS gene were applied to characterize the abundance and denitrifying bacterial communities from 18 geographically distributed WWTPs. The results showed that the nirS abundance ranged from 4.6 × 10² to 2.4 × 10³ copies per ng DNA, while nirS-type denitrifying bacterial populations were diverse and distinct from activated sludge communities. Among WWTPs, total nitrogen removal efficiencies varied from 25.8 to 84%, which was positively correlated with diversity indices, whereas abundance-based coverage estimator index decreased with an increase in latitude. The dominant phyla across all samples were proteobacteria, accounting for 46.23% (ranging from 17.98 to 87.07%) of the sequences. Eight of the 22 genera detected were dominant: Thauera sp., Alicycliphilus sp., and Pseudomonas sp., etc. Based on network analysis, the coexistence and interaction between dominant genera may be vital for regulating the nitrogen and carbon removal behaviors. Multivariate statistical analysis revealed that both geographic location and wastewater factors concurrently govern the distribution patterns of nirS-type denitrifying bacterial community harbored in WWTPs. Taking together, these results from the present study provide novel insights into the nirS gene abundance and nirS-type denitrifying bacterial community composition in geographically distributed WWTPs. Moreover, the knowledge gained will improve the operation and management of WWTPs for nitrogen removal.

Drip irrigation biofouling with treated wastewater: bacterial selection revealed by high-throughput sequencing

Clogging of drippers due to the development of biofilms weakens the advantages and impedes the implementation of drip irrigation technology. The objective of this study was to characterise the bacterial community of biofilms that develop in a drip irrigation system supplied with treated wastewater. High-throughput sequencing of 16S rRNA gene amplicons indicated that the bacterial community composition differed between drippers and pipes, mainly due to changes in the abundance of the genus Aquabacterium. Cyanobacteria were found to be involved in the biological fouling of drippers. Moreover, bacterial genera including opportunistic pathogenic bacteria such as Legionella and Pseudomonas were more abundant in dripper and pipe biofilms than in the incoming water. Some genera such as Pseudomonas were mostly recovered from drippers, while others (ie Bacillus, Brevundimonas) mainly occurred in pipes. Variations in the hydraulic conditions and properties of the materials likely explain the shift in bacterial communities observed between pipes and drippers.

Profiling the diversity of Cryptosporidium species and genotypes in wastewater treatment plants in Australia using next generation sequencing

Wastewater recycling is an increasingly popular option in worldwide to reduce pressure on water supplies due to population growth and climate change. Cryptosporidium spp. are among the most common parasites found in wastewater and understanding the prevalence of human-infectious species is essential for accurate quantitative microbial risk assessment (QMRA) and cost-effective management of wastewater. The present study conducted next generation sequencing (NGS) to determine the prevalence and diversity of Cryptosporidium species in 730 raw influent samples from 25 Australian wastewater treatment plants (WWTPs) across three states: New South Wales (NSW), Queensland (QLD) and Western Australia (WA), between 2014 and 2015. All samples were screened for the presence of Cryptosporidium at the 18S rRNA (18S) locus using quantitative PCR (qPCR), oocyst numbers were determined directly from the qPCR data using DNA standards calibrated by droplet digital PCR, and positives were characterized using NGS of 18S amplicons. Positives were also screened using C. parvum and C. hominis specific qPCRs. The overall Cryptosporidium prevalence was 11.4% (83/730): 14.3% (3/21) in NSW; 10.8% (51/470) in QLD; and 12.1% (29/239) in WA. A total of 17 Cryptosporidium species and six genotypes were detected by NGS. In NSW, C. hominis and Cryptosporidium rat genotype III were the most prevalent species (9.5% each). In QLD, C. galli, C. muris and C. parvum were the three most prevalent species (7.7%, 5.7%, and 4.5%, respectively), while in WA, C. meleagridis was the most prevalent species (6.3%). The oocyst load/Litre ranged from 70 to 18,055 oocysts/L (overall mean of 3426 oocysts/L: 4746 oocysts/L in NSW; 3578 oocysts/L in QLD; and 3292 oocysts/L in WA). NGS-based profiling demonstrated that Cryptosporidium is prevalent in the raw influent across Australia and revealed a large diversity of Cryptosporidium species and genotypes, which indicates the potential contribution of livestock, wildlife and birds to wastewater contamination.

Bacterial diversity and community in Qula from the Qinghai-Tibetan Plateau in China

Qula is a cheese-like product usually prepared with unpasteurized yak milk under open conditions, with both endogenous and exogenous microorganisms involved in the fermentation process. In the present study, 15 Qula samples were collected from five different regions in China to investigate the diversity of microbial communities using high-throughput sequencing targeting the V3–V4 region of 16S rRNA gene. The bacterial diversity significantly differed among samples of different origins, indicating a possible effect of geography. The result also showed that microbial communities significantly differed in samples of different origin and these differences were greater at the genus than the phylum level. A total of six phyla were identified in the samples, and Firmicutes and Proteobacteria had a relative abundance >20%. A total of 73 bacterial genera were identified in the samples. Two dominant genera (Lactobacillus and Acetobacter) were common to all samples, and a total of 47 operational taxonomic units at different levels significantly differed between samples of different origin. The predicted functional genes of the bacteria present in samples also indicated differences in bacterial communities between the samples of different origin. The network analysis showed that microbial interactions between bacterial communities in Qula were very complex. This study lays a foundation for further investigations into its food ecology.

Activated sludge bacterial communities of typical wastewater treatment plants: distinct genera identification and metabolic potential differential analysis

To investigate the differences in activated sludge microbial communities of different wastewater treatment plants (WWTPs) and understand their metabolic potentials, we sampled sludge from every biological treatment unit of 5 full-scale waste water treatment systems in 3 typical Chinese municipal WWTPs. The microbial communities and overall metabolic patterns were not only affected by influent characteristics but also varied between different biological treatment units. Distinct genera in different wastewater treatment systems were identified. The important microorganisms in domestic sewage treatment systems were unclassified SHA-20, Caldilinea, Dechloromonas, and unclassified genera from Rhodospirilaceae and Caldilineaceae. The important microorganisms in dyeing wastewater treatment systems were Nitrospira, Sphingobacteriales, Thiobacillus, Sinobacteraceae and Comamonadaceae. Compared with the obvious differences in microbial community composition, the metabolic potential showed no significant differences.