Characterization of aerobic granular sludge used for the treatment of petroleum wastewater

Responses of microbial communities in coastal sediments exposed to triclocarban and triclosan

Triclocarban (TCC) and triclosan (TCS) are applied in a wide range of pharmaceutical and personal care products to prevent or reduce bacterial growth. Due to their extensive application, they are frequently detected in marine environments. In this study, marine sediment systems exposed to different concentrations of TCC and TCS were established to evaluate their effects on microbial communities. It was found that TCC and TCS increased catalase and protease activities on Day 1, but inhibited after 15 days. Microbial activity, as indicated by increased dehydrogenase activity and polysaccharide production, should be enhanced after a 15-day adaptation period. High-throughput sequencing revealed resilient α-diversity but significant shifts in community structures were observed, particularly on Day 15. Function prediction analysis confirmed that most functional profiles remained stable, and network analysis indicated that TCC and TCS enhanced the complexity of the microbial community. This study provides new insights into the impacts and risks of TCC and TCS on the marine environment.

Catalytic ozone oxidation of chemical RO membrane concentrate wastewater by a Cu-Ce@γ-Al2O3 ozone catalyst

A Cu-Ce@γ-Al₂O₃ catalyst was developed for the efficient treatment of chemical reverse osmosis (RO) membrane concentrate wastewater. The working conditions and reaction mechanisms of Cu-Ce@γ-Al₂O₃ catalytic ozonation were systematically investigated, and its application in the catalytic ozonation of chemical RO membrane concentrate wastewater was explored. The catalyst was comprehensively characterized using scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), and Fourier-transform infrared (FTIR) spectroscopy, revealing its microstructure, elemental composition, and crystal structure. The optimal reaction conditions were identified as follows: ozone dosage of 8 mg/L/min, initial pH of 9.0, catalyst filling ratio of 10%, and a reactor height-to-diameter ratio of 5:1. Under these conditions, the catalytic ozonation achieved a chemical oxygen demand (COD) removal rate of 63.4%. Free-radical quenching experiments confirmed that hydroxyl radicals (·OH) played a dominant role in the catalytic ozonation system. Kinetic analysis revealed that the catalytic ozonation of chemical RO membrane concentrate wastewater with Cu-Ce@γ-Al₂O₃ followed second-order kinetics. The degradation mechanisms of organic matter in the wastewater were further analyzed using ultraviolet-visible (UV-Vis) spectroscopy and three-dimensional fluorescence spectroscopy. Additionally, a weighted rank sum ratio (WRSR) evaluation model was developed to provide a comprehensive assessment of the process performance. PRACTITIONER POINTS: Cu-Ce@γ-Al2O3 catalysts with excellent catalytic performance were prepared. Efficient catalytic ozonation of chemical RO membrane concentrate with high salinity was realized. Degradation mechanism of organic pollutants by catalytic ozonation is clarified. Evaluation model for catalytic ozonation of chemical RO membrane concentrate was established.

Mechanism of molecular communication and bacterial community succession in microalgal bacterial biofilms under different photoperiods

Microalgal-bacterial biofilms are a competitive wastewater treatment technology. This study investigated the impact of photoperiod on the characteristics and performance of these biofilms in treating pig farm wastewater. Under continuous lighting (L-24h), we observed optimal NH4+-N removal efficiency, minimal chlorophyll levels, and peak concentrations of polysaccharides and c-di-GMP. The concentration of c-di-GMP, strongly correlated with the dominant genera Brevundimonas, Devosia, and Comamonas, modulated the maturation of microalgal-bacterial biofilms. The formation of these biofilms promoted NH4+-N removal. SEM imaging under L-24h conditions revealed microalgae and bacteria intimately bound by extracellular polymeric substances. Overall, this study unveiled the mechanisms of molecular communication and bacterial community succession within microalgal-bacterial biofilms under varying photoperiods.

Enhancing nitrogen removal in combined sewage overflows by using bio-fluidized bed with ceramic waste powder carriers: effects and mechanisms

Micron-size ceramic waste powder (< 75 μm and 75-150 μm) was used as the carrier in a high-concentration powder carrier bio-fluidized bed (HPB) to treat simulated overflow sewage (CSOs). The sludge extracellular polymers (EPS), electron transfer capacity of EPS, nitrogen removal pathways, and microbiological characteristics were analyzed to gain insights into the nitrogen removal pathways and mechanisms. The results showed that only the effluent from the HPB (< 75 μm) could meet the stringent pollutant discharge standards in China of 50 mg/L for CODCr and 15 mg/L for total nitrogen from beginning to end. Meanwhile, the electrochemical performance tests indicated that the electron accepting and donating capacities of the sludge EPS in the HPB (< 75 μm) were 42.75% and 32.73% higher than those in the conventional activated sludge, meaning that ceramic powder carriers can increase the extracellular electron transfer capacity of the sludge and accelerate the denitrification process. Also, metagenomics analysis results showed that the relative abundances of the denitrification-related Nor genes were 28-39% higher in the HPB (< 75 μm) and HPB (75-150 μm) than in the conventional activated sludge (CAS). These results show that ceramic waste powders have the potential to be used as carriers in HPB systems to treat CSOs.

Potential effects of Cu2+ stress on nitrogen removal performance, microbial characteristics, and metabolism pathways of biofilm reactor

Sequencing batch biofilm reactors (SBBR) were utilized to investigate the impact of Cu2+ on nitrogen (N) removal and microbial characteristics. The result indicated that the low concentration of Cu2+ (0.5 mg L-1) facilitated the removal of ammonia nitrogen (NH4+-N), total nitrogen (TN), nitrate nitrogen (NO3--N), and chemical oxygen demand (COD). In comparison to the average effluent concentration of the control group, the average effluent concentrations of NH4+-N, NO3--N, COD, and TN were found to decrease by 40.53%, 17.02%, 10.73%, and 15.86%, respectively. Conversely, the high concentration of Cu2+ (5 mg L-1) resulted in an increase of 94.27%, 55.47%, 22.22%, and 14.23% in the aforementioned parameters, compared to the control group. Low concentrations of Cu2+ increased the abundance of nitrifying bacteria (Rhodanobacter, unclassified-o-Sacharimonadales), denitrifying bacteria (Thermomonas, Comamonas), denitrification-associated genes (hao, nosZ, norC, nffA, nirB, nick, and nifD), and heavy-metal-resistant genes related to Cu2+ (pcoB, cutM, cutC, pcoA, copZ) to promote nitrification and denitrification. Conversely, high concentration Cu2+ hindered the interspecies relationship among denitrifying bacteria genera, nitrifying bacteria genera, and other genera, reducing denitrification and nitrification efficiency. Cu2+ involved in the N and tricarboxylic acid (TCA) cycles, as evidenced by changes in the abundance of key enzymes, such as (EC:1.7.99.1), (EC:1.7.2.4), and (EC:1.1.1.42), which initially increased and then decreased with varying concentrations of Cu2+. Conversely, the abundance of EC1.7.2.1, associated with the accumulation of nitrite nitrogen (NO2--N), gradually declined. These findings provided insights into the impact of Cu2+ on biological N removal.

Achieving partial nitrification by sludge treatment using sulfide: Optimal conditions determination, long-term stability evaluation and microbial mechanism exploration

This study proposes an innovative strategy for achieving PN in synthetic domestic wastewater by side-stream sludge treatment using sulfide as the sole control factor. By conducting controllable batch experiments and response surface analysis, optimal sulfide treatment conditions were firstly determined as 90 mg/L of sulfide, 7.5 of pH, 100 rpm of rotation and 12 h of treatment time. After treatment, half of ammonia oxidizing bacteria (AOB) activity remained, but nitrite oxidizing bacteria (NOB) activity was barely detected. Nitrite accumulation rate of long-term running PN steadily reached 83.9 % with 99.1 % of ammonia removal efficiency. Sulfide treatment increased community diversity and facilitated stability of microbiota functioning with PN phenotype, which might be sustained by the positive correlation between ammonia oxidation gene (amoA) and sulfur oxidation gene (soxB). Correspondingly, the network analysis identified the keystone microbial taxa of persistent PN microbiota as Nitrosomonas, Thauera, Truepera, Defluviimonas and Sulitalea in the later stage of long-term reactor.

Ultra-rapid development of 'solid' aerobic granular sludge by stable transition/filling of inoculated 'hollow' mycelial pellets in hypersaline wastewater

To overcome the long start-up period in cultivating aerobic granular sludge (AGS) under hypersaline environment, mycelial pellets (MPs) of halotolerant fungus Cladosporium tenuissimum NCSL-XY8 were inoculated to try to realize the ultra-rapid development of salt-tolerant AGS by stable transition of 'hollow' MPs into 'solid' AGS without apparent fragmentation. The granules directly met the standard of AGS after inoculating MPs (Day 0), and it basically satisfied relatively strict standards of AGS (SVI30 < 50 mL/g, D50 > 300 μm, D10 > 200 μm and SVI30/SVI5 > 0.9) under anaerobic/aerobic mode during whole cultivation processes. Microstructure of the granular cross section clarified that MPs with hollow/loose inner layer transitioned into solid/dense AGS under anaerobic/aerobic mode within 7 days, while formed skin-like floating pieces and unstable double-layer hollow granules under aerobic mode. Organics removal reached relatively stable within 13 days under anaerobic/aerobic mode, 6 days faster than aerobic mode. This study provided a strategy for ultra-rapid and stable development of AGS, which showed the shortest granulation period in various AGS-cultivation strategies.

A pilot-scale anoxic-anaerobic-anoxic-oxic combined with moving bed biofilm reactor system for advanced treatment of rural wastewater

Rural domestic poses a significant challenge to treatment technologies due to significant fluctuations in both water quality, particularly in terms of carbon concentration, and quantity. Conventional biological technology, such as anaerobic-anoxic-oxic (A2O) systems, is inefficient. In this work, a continuous pilot-scale anoxic-anaerobic-anoxic-oxic (A3O) reactor with a moving bed biofilm reactor (MBBR) system was constructed and optimized to improve the treatment efficiency of rural domestic wastewater. The sludge return ratio, volume ratio of the oxic-to-anoxic zone (Voxi/Vano), step-feeding and hydraulic retention time (HRT) at low temperature were considered the main parameters for optimization. Microbial analysis was performed on both the mixed liquor and carrier of the A3O-MBBR system under initial and post-optimized conditions. The results indicated that the A3O-MBBR improved the treatment efficiency of rural domestic wastewater, especially for total phosphorus (TP), which increased by 20 % compared with that of the A2O-MBR. In addition, the removal efficiencies of nitrogen and phosphorus were further optimized, and the average concentrations of total nitrogen (TN) and TP in the effluent reached 2.46 and 0.364 mg/L, respectively, at a sludge reflux ratio of 100 or 150 %, Voxi/Vano =200 %, step-feeding of 0.5Q/0.5Q (anaerobic/anoxic) and HRT of 15 h at low temperature in the A3O-MBBR, which met standard A of GB18918-2002, China (TN < 15 mg/L, TP < 0.5 mg/L). The average rate of attaining the standard increased by 58.63 % (post optimization). The microbial analysis showed an increase in species diversity and richness after the parameters were optimized. Moreover, compared to the microbial community structure before optimization, the post-optimization exhibited a more stable microbial structure with a significant enrichment of functional bacteria. Defluviimonas, Novosphingobium and Bifidobacterium, considered as the dominant nitrification or denitrifying bacteria, were enriched in the suspended sludge of the MBBR reactor, which the relative abundance increased by 3.11 %, 3.84 %, and 3.24 %, respectively. Further analysis of the microbial community in the carrier revealed that the abundance of Nitrospira and the denitrifying bacteria carried by the carrier were much greater than those in the suspended sludge. Consequently, the microorganism cooperation between suspended sludge and biofilm might be responsible for the improved performance of the optimized A3O-MBBR.

The potential effects of N-Acyl homoserine lactones on aerobic sludge granulation during phenolic wastewater treatment

The formation of aerobic granular sludge (AGS) is relatively difficult during the treatment of refractory wastewater, which generally shows small granular sizes and poor stability. The formation of AGS is regulated by N-Acyl homoserine lactones (AHLs)-mediated quorum sensing (QS). However, the potential role of AHLs in AGS formation under the toxic stress of refractory pollutants and the heterogeneity in the distribution and function of AHLs across different aggregates are not well understood. This study investigated the potential effects of AHLs on the formation of AGS during phenolic wastewater treatment. The distribution and succession of AHLs across varying granular sizes and development stages of AGS were investigated. Results showed that AGS was successfully formed in 13 days with an average granular size of 335 ± 39 μm and phenol removal efficiency of >99%. The levels of AHLs initially increased and then decreased. C4-HSL and 3-oxo-C10-HSL were enriched in large granules, suggesting they may play a pivotal role in regulating the concentration and composition of extracellular polymeric substances (EPS). The content of EPS constantly increased to 149.4 mg/gVSS, and protein (PN) was enriched in small and large granules. Luteococcus was the dominant genus constituting up to 62% after the granulation process, and exhibited a strong association with C4-HSL. AHLs might also regulate the bacterial community responsible for EPS production, and pollutant removal, and facilitate the proliferation of slow-growing microorganisms, thereby enhancing the formation of AGS. The synthesis and dynamics of AHLs were mainly governed by AHLs-producing bacterial strains of Rhodobacter and Pseudomonas, and AHLs-quenching strains of Flavobacterium and Comamonas. C4-HSL and 3-oxo-C10-HSL might be the major contributors to promoting sludge granulation under phenol stress and play critical roles in large granules. These findings enhance our understanding of the roles that AHLs play in sludge granulation under toxic conditions.

Shifts in structure and dynamics of the soil microbiome in biofuel/fuel blend-affected areas triggered by different bioremediation treatments

The use of biofuels has grown in the last decades as a consequence of the direct environmental impacts of fossil fuel use. Elucidating structure, diversity, species interactions, and assembly mechanisms of microbiomes is crucial for understanding the influence of environmental disturbances. However, little is known about how contamination with biofuel/petrofuel blends alters the soil microbiome. Here, we studied the dynamics in the soil microbiome structure and composition of four field areas under long-term contamination with biofuel/fossil fuel blends (ethanol 10% and gasoline 90%-E10; ethanol 25% and gasoline 75%-E25; soybean biodiesel 20% and diesel 80%-B20) submitted to different bioremediation treatments along a temporal gradient. Soil microbiomes from biodiesel-polluted areas exhibited higher richness and diversity index values and more complex microbial communities than ethanol-polluted areas. Additionally, monitored natural attenuation B20-polluted areas were less affected by perturbations caused by bioremediation treatments. As a consequence, once biostimulation was applied, the degradation was slower compared with areas previously actively treated. In soils with low diversity and richness, the impact of bioremediation treatments on the microbiomes was greater, and as a result, the hydrocarbon degradation extent was higher. The network analysis showed that all abundant keystone taxa corresponded to well-known degraders, suggesting that the abundant species are core targets for biostimulation in soil remediation processes. Altogether, these findings showed that the knowledge gained through the study of microbiomes in contaminated areas may help design and conduct optimized bioremediation approaches, paving the way for future rationalized and efficient pollutant mitigation strategies.

Discovery of a novel potential polyphosphate accumulating organism without denitrifying phosphorus uptake function in an enhanced biological phosphorus removal process

Enhanced biological phosphorus removal (EBPR) is an effective process for phosphorus removal from wastewater. In this study, two lab-scale sequencing batch reactors (SBR) were used to perform EBPR process, in which genus Propioniciclava was unexpectedly accumulated and its relative abundance was over 70 %. A series of tests were conducted to explore the role of Propioniciclava in the two EBPR systems. The two systems performed steadily throughout the study, and the phosphorus removal efficiencies were 96.6 % and 93.5 % for SBR1 and SBR2, respectively. The stoichiometric analysis related to polyphosphate accumulating organisms (PAOs) indicated that polyphosphate accumulating metabolism (PAM) was achieved in the anaerobic phase. It appeared that the Propioniciclava-dominated systems could not perform denitrifying phosphorus removal. Instead, phosphorus was released under anoxic conditions without carbon sources. According to the genomic information from Integrated Microbial Genomes (IMG) database, Propioniciclava owns ppk1, ppk2 and ppx genes that are associated with phosphorus release and uptake functions. By phylogenetic investigation of communities by reconstruction of unobserved states 2 (PICRUSt2) analysis, the abundance of genes related to phosphorus metabolism was much higher than that of genes related to denitrification. Therefore, Propioniciclava was presumed to be a potential PAO without denitrifying phosphorus uptake function. In addition to Propioniciclava, Tessaracoccus and Thiothrix were also enriched in both systems. Overall, this study proposes a novel potential PAO and broadens the understanding of EBPR microbial communities.

The influence of different nitrate concentrations on aerobic sludge granulation and the role of extracellular polymeric substances

This study investigated the influence of nitrate on aerobic granular sludge (AGS) granulation. The introduction of nitrate at 5, 15 and 20 mg L-1 promoted AGS granulation, and the promoting effect was positively correlated with nitrate concentrations. Meanwhile, exogenous nitrate significantly increased denitrification rate in the AGS system. However, granular disintegration appeared at a long-term addition of nitrate. An in-deep analysis showed that nitrate stimulated the secretion of extracellular polymeric substances (EPS), especially the content of proteins, which might be the main reason for the AGS granulation. However, the rapid and excessive increase in EPS might cause granular disintegration, as excessive EPS blocked the transmission of substrates, leading to the increase of dead cells in the granules. Besides, nitrate also altered the hydrophobicity of EPS and the content of α-helix, 3-turned helix and polymeric chain that favored aggregation, which also affected AGS granulation. From the microbial community level, nitrate induced the enrichment of denitrifying bacteria, including those that also functioned as EPS producers, such as Micropruina and Flavobacterium, resulting in the rapid increase of functional enzymes associated with amino acid synthesis, thereby promoting the secretion of proteins in EPS. Conversely, disintegration caused by mass transfer blockage might lead to the loss of EPS producing bacteria and subsequent decrease in EPS content, further accelerating granular disintegration.

Evaluating the inhibitory effects of Nitrobenzene short-term stress on denitrification performance: Electron behaviors, bacterial and fungal community

Denitrifying system is a feasible way to remove nitro-aromatic compounds (NACs) in wastewater. However, the toxicity and mechanisms of NACs to denitrification remain unknown. This study investigated effects of nitrobenzene (NB, a typical NAC) on denitrification in short term. Results showed that NB in 10-50 mg/L groups decreased NO3--N removal efficiency by 9%-24%, but increased nitrous oxide (N2O) generation by 6-17fold. Mechanistic research indicated that NB could deteriorate electron behaviors and disturbed enzyme activities of microbial metabolism and denitrification, leading to a decline in denitrification performance. Structural equation modeling revealed that N2O reductase activity was the core factor in predicting denitrification performance at exposure of NB, with the indirect effects of NADH and electron transport system activity. High-throughput sequencing analysis demonstrated that NB had made an alteration on both bacterial and fungal community structure, as well as their interactions.

Performance and mechanism of glycerol-driven denitrifying phosphorus removal from low organic matter sewage

The performance and mechanism of the glycerol-driven denitrifying phosphorus removal (DPR) process were investigated in low organic matter wastewater treatment using the modified anaerobic-anoxic-oxic (MAAO) system. The results revealed that denitrifying bacteria preferentially utilized glycerol, reducing nitrate interference on anaerobic phosphate release. Fermentation bacteria converted excess glycerol into available carbon sources, which were utilized by denitrifying phosphorus-accumulating organisms (DPAOs). Optimize glycerol dosage (calculated in chemical oxygen demand) could be estimated based on 6 times the effluent NO3--N of the anoxic zone. As glycerol dosage increased, the relative abundance of fermentation bacteria surged from 8.2% to 17.7%, subsequently boosting the DPR rate from 34.6% to 77.2%. Notably, denitrifying glycogen-accumulating organisms (DGAOs) decreased from 0.5% to 0.2% but remained instrumental in nitrogen removal. The collaborative actions of fermentation bacteria, DPAOs, and DGAOs were vital in upholding the stability of nutrient removal in the glycerol-driven DPR process.

Roles of high/low nucleic acid bacteria in flocs and probing their dynamic migrations with respirogram

Bacterial migration is crucial for the stability of activated sludge but rarely reported. The static distribution was explored by changes in bacteria concentration with extracellular polymeric substances (EPS) extractions. Next, denitrification and aeration were conducted as normal running conditions for examining the bacterial migration between floc-attached and dispersed growth. Above observations were further explored by conducting copper ion (Cu2+) shock as an extreme running condition. After extracting EPS, low nucleic acid (LNA) bacteria migrated from the sludge to the supernatant primarily, and high nucleic acid (HNA) bacteria remained in the residual sludge, suggesting that HNA bacteria mainly distributed inside the sludge while LNA bacteria outside the sludge. During the denitrification process, LNA bacteria migrated out of flocs, which increased by 6.94 × 106 events/mL in the supernatant. During the feast phase of aeration, LNA bacteria grew attached to flocs, causing the increased flocs diameter from 45.60 to 47.40 μm. During the following aerobic famine phase, LNA bacteria grew dispersedly, but HNA bacteria remained unchanged. However, a further severe famine phase drove HNA bacteria to be dispersed, breaking flocs with the decreased diameter from 48.10 to 46.50 μm. When the Cu2+ shock was employed, LNA and HNA bacteria increased but the LNA/HNA ratio decreased in the supernatant, indicating more HNA bacteria migrating to the dispersed phase. From a structural perspective, HNA bacteria distributed inside the sludge and functioned as the backbone of flocs, undertaking the maintenance of flocs stability primarily; while LNA bacteria distributed outside the sludge and functioned as filling materials, having a secondary influence on flocs stability. These processes were also probed by respirogram exactly, correlating the system-scale measurement and microscale migrations and providing an early warning signal under abnormal circumstances. The processed HNA-backbone theory is promising for regulating the stability of activated sludge based on bacterial migrations.

The shock of benzalkonium chloride on aerobic granular sludge system and its microbiological mechanism

Quaternary ammonium compounds (QACs) are a kind of biocides and surfactants widely used around the world and wastewater treatment systems were identified as its largest pool. QACs could significantly inhibit microbial activity in biological treatment. Aerobic granular sludge (AGS) is an emerging wastewater biological treatment technology with high efficiency and resistance, but it is still unclear if AGS system could tolerate QACs shock. In this study, a typical QAC (benzalkonium chloride (BACC12)) was selected to investigate its effect on AGS system. Results indicate that BAC could inhibit the pollutants removal performance of AGS system, including COD, NH4+-N and PO43- in the short term and the inhibition ratio had positive correlation with BAC concentration. However, AGS system could gradually adapt to the BAC stress and recover its original performance. BAC shock could destroy AGS structure by decreasing its particle size and finally leading to particle disintegration. Although AGS could secret more EPS to resist the stress, BAC still had significant inhibition on cell activity. Microbial community analysis illustrated that after high BAC concentration shock in short term, Thauera decreased significantly while Flavobacterium became the dominant genus. However, after the performance of AGS system recovered the dominant genus returned to Thauera and relevant denitrifiers Phaeodactylibacter, Nitrosomonas and Pseudofulvimonas also increased. The typical phosphorous removal microorganism Rubrivivax and Leadbetterella also showed the similar trend. The variation of denitrification and phosphorus removal microbial community was consistent with AGS system performance indicating the change of functional microorganism played key role in the AGS response to BAC stress.

Anaerobic-aerobic treatment of high-strength and recalcitrant textile dyeing effluents

Eco-friendly treatment of complex textile and dyeing wastewaters poses a pressing environmental concern. An approach adopting different treatment paths and integrated anaerobic-aerobic processes for high-strength and recalcitrant textile dyeing wastewater was examined. The study demonstrated that over 97% of suspended solids (SS) and more than 70% of chemical oxygen demand (COD) were removed by polyaluminum chloride pre-coagulation of suede fabric dyeing stream. Up to 58% of COD and 83% of SS were removed through hydrolysis pretreatment of other low-strength streams. Notable COD removal of up to 99% from a feed of 20,862 mg COD/L was achieved by integrated anaerobic-aerobic treatment of high strength stream. Besides achieving high COD removal of 97%, the anaerobic granular sludge process demonstrated multi-faceted attributes, including high feed loading, smaller footprint, little sludge production, and good stability. The integrated anaerobic-aerobic treatment offers a robust and viable option for highly contaminated and recalcitrant textile dyeing wastewater.

Sulfamethoxazole impact on pollutant removal and microbial community of aerobic granular sludge with filamentous bacteria

In this study, sulfamethoxazole (SMX) was employed to investigate its impact on the process of aerobic granule sludge with filamentous bacteria (FAGS). FAGS has shown great tolerance ability. FAGS in a continuous flow reactor (CFR) could keep stable with 2 μg/L of SMX addition during long-term operation. The NH₄⁺, chemical oxygen demand (COD), and SMX removal efficiencies kept higher than 80%, 85%, and 80%, respectively. Both adsorption and biodegradation play important roles in SMX removal for FAGS. The extracellular polymeric substances (EPS) might play important role in SMX removal and FAGS tolerance to SMX. The EPS content increased from 157.84 mg/g VSS to 328.22 mg/g VSS with SMX addition. SMX has slightly affected on microorganism community. A high abundance of Rhodobacter, Gemmobacter, and Sphaerotilus of FAGS may positively correlate to SMX. The SMX addition has led to the increase in the abundance of the four sulfonamide resistance genes in FAGS.

Long-term comparison of the performance of biostimulation and phytoextraction in soil contaminated with diesel and heavy metals

The long-term remediation performance under the natural conditions is required to establish the appropriate remediation strategy for contaminated soil. The objective of this study was to compare the long-term remediation efficiency of biostimulation and phytoextraction in contaminated soil containing petroleum hydrocarbons (PHs) and heavy metals. Two types of contaminated soil (soil contaminated with diesel only and co-contaminated with diesel and heavy metals) were prepared. For the biostimulation treatments, the soil was amended with compost, whereas maize, a representative phytoremediation plant, was cultivated for the phytoextraction treatments. There was no significant difference in remediation performance of biostimulation and phytoextraction in the diesel-contaminated soil, in which the maximum total petroleum hydrocarbon (TPH) removability was 94-96% (p < 0.05). However, phytoextraction exhibited the higher removability for TPH and heavy metals than biostimulation in the co-contaminated soil. There was no considerable change in the TPH removal in biostimulation (16-25%), while phytoextraction showed a 75% of TPH removal rate in the co-contaminated soil. Additionally, no significant changes were observed in heavy metals concentration of biostimulation, whereas the removability of heavy metals was 33-63% in phytoextraction. Meanwhile, maize, which is a suitable plant for phytoextraction, showed a translocation factor (translocating efficiency from roots to shoots) value of >1. Correlation analysis revealed that soil properties (pH, water content, and organic content) negatively correlated with pollutants removal. Additionally, the soil bacterial communities were changed over the investigated period, and the types of pollutants exerted a significant influence on the bacterial community dynamics. This study performed a pilot-scale comparison of two types of biological remediation technologies under natural environmental conditions and provided information on changes in the bacterial community structures. This study can be useful for establishing appropriate biological remediation methods to restore soil contaminated with PHs and heavy metals.

Environmentally relevant level of perfluorooctanoic acid affect the formation of aerobic granular sludge

The growing increasing occurrence of perfluorooctanoic acid (PFOA) in wastewater has raised concerns about its potential impact on the environment. Nevertheless, the impact of PFOA at environmentally relevant level on the formation of aerobic granular sludge (AGS) is still a 'black box'. This study thus aims to fill this gap by comprehensive investigation of sludge properties, reactor performance and microbial community during the formation of AGS. It was found that 0.1 mg/L PFOA delayed the formation of AGS, causing relatively lower proportion of large size AGS at the end of operation process. Interestingly, the microorganisms contribute to the reactor's tolerance to PFOA by secreting more extracellular polymeric substances (EPS) to slow or block the entry of toxic substances into the cells. During the granule maturation period, the reactor nutrient removal especially chemical oxygen demand (COD) and total nitrogen (TN) were affected by PFOA, decreasing the corresponding removal efficiencies to ∼81.2% and ∼69.8%, respectively. Microbial analysis further revealed that PFOA decreased the abundances of Plasticicumulans, Thauera, Flavobacterium and Cytophagaceae_uncultured, but it has promoted Zoogloea and Betaproteobacteria_unclassified growth, which maintained the structures and functions of AGS. The above results revealed that the intrinsic mechanism of PFOA on the macroscopic representation of sludge granulation process was revealed, and it is expected to provide theoretical insights and practical support for direct adoption of municipal or industrial wastewater containing perfluorinated compounds to cultivate AGS.

Response of aerobic activated sludge to edible oil exposure: Extracellular polymeric substance (EPS) characteristics and microbial community

Aerobic activated sludge is widely used to degrade edible oil wastewater in wastewater treatment plants. During this process, the observed poor organics removal performance might be caused by poor sludge settling performance, which might be influenced by extracellular polymeric substances (EPS) and the structure of the microbial community. However, this hypothesis was not confirmed. Thus, this study investigated the response of activated sludge to 50% and 100% edible oil exposure in comparison to glucose, focusing on organics removal performance, characteristics of sludge, EPS, and microbial community structure. Results showed that both concentrations of edible oil influenced the systems' performance, although 100% edible oil showed more significant negative effects than 50% edible oil. The mechanisms behind the influence of edible oil on the aerobic activated sludge system and the differences between the different concentrations of edible oil were revealed. The worse system performance in the edible oil exposure system was due to the worse sludge settling performance, which was significantly affected by edible oil (p < 0.05). The sludge settling performance was mainly inhibited by promoting the formation of floating particles and the enrichment of filamentous bacteria in the 50% edible oil exposure system; biosurfactant secretion was also speculated as the reason, in addition to the above factors, in the 100% edible oil exposure system. The macroscopic largest floating particles, highest total relative abundance of foaming bacteria and biosurfactant production genera (34.32%), lowest surface tension (43.7 mN/m), and highest emulsifying activity (E₂₄ = 25%) of EPS in 100% edible oil exposure systems provide strong evidence.

Bioaugmentation and enhanced formation of biogranules for degradation of oil and grease: Start-up, kinetic and mass transfer studies

Biogranulation technology is an emerging biological process in treating various wastewater. However, the development of biogranules requires an extended period of time when treating wastewaters with high oil and grease (O&G) content. A study was therefore conducted to assess the formation of biogranules through bioaugmentation with the Serratia marcescens SA30 strain, in treating real anaerobically digested palm oil mill effluent (AD-POME), with O&G of about 4600 mg/L. The biogranules were developed in a lab-scale sequencing batch reactor (SBR) system under alternating anaerobic and aerobic conditions. The experimental data were assessed using the modified mass transfer factor (MMTF) models to understand the mechanisms of biosorption of O&G on the biogranules. The system was run with variable organic loading rates (OLR) of 0.69-9.90 kg/m³d and superficial air velocity (SAV) of 2 cm/s. After 60 days of being bioaugmented with the Serratia marcescens SA30 strain, the flocculent biomass transformed into biogranules with excellent settleability with improved treatment efficiency. The biogranules showed a compact structure and good settling ability with an average diameter of about 2 mm, a sludge volume index at 5 min (SVI₅) of 43 mL/g, and a settling velocity (SV) of 81 m/h after 256 days of operation. The average removal efficiencies of O&G increased from 6 to 99.92%, respectively. The application of the MMTF model verified that the resistance to O&G biosorption is controlled via film mass transfer. This research indicates successful bioaugmentation of biogranules using the Serratia marcescens SA30 strain for enhanced biodegradation of O&G and is capable to treat real AD-POME.

Anaerobic-anoxic-oxic biological treatment of high-strength, highly recalcitrant polyphenylene sulfide wastewater

This paper outlines an integrated anaerobic-anoxic-oxic (A2O) treatment scheme for high-strength, highly recalcitrant wastewater from the production of polyphenylene sulfide (PPS) resins and their composite chemicals. An integrated anaerobic granular sludge blanket (GSB) and anoxic-oxic (AO) reactor indicated that the A2O removed chemical oxygen demand (COD) of up to 7,043 mg/L with no adverse impact from high total dissolved solids (25,000 mg/L) on the GSB COD removal and effluent suspended solids. At a Total Kjeldahl Nitrogen (TKN) nitrification load of 0.11 g TKN/L.d and 400 mg NH₃/L, almost 99 % of the NH₃ was degraded with effluent NH₃ < 5 mg/L, meeting the limit of 35 mg/L. High S^2- levels of up to 1470 mg/L can be transformed through aerobic microbial degradation to meet a limit of 1.0 mg/L. With proper microbial acclimation and process designs, the integrated A2O scheme offers a resilient and robust treatment for high-strength recalcitrant PPS wastewater.

Enhancement of biogranules development using magnetized powder activated carbon

Biogranulation has emerged as a viable alternative biological wastewater treatment approach because of its strong biodegradability potential, toxicity tolerance, and biomass retention features. However, this process requires a long duration for biogranules formation to occur. In this study, magnetic powder activated carbon (MPAC) was used as support material in a sequencing batch reactor to enhance biogranules development for wastewater treatment. Two parallel SBRs (designated R1 and R2) were used, with R1 serving as a control without the presence of MPAC while R2 was operated with MPAC. The biodegradability capacity and biomass properties of MPAC biogranules were compared with a control system. The measured diameter of biogranules for R1 and R2 after 8 weeks of maturation were 2.2 mm and 3.4 mm, respectively. The integrity coefficient of the biogranules in R2 was higher (8.3%) than that of R1 (13.4%), indicating that the addition of MPAC improved the structure of the biogranules in R2. The components of extracellular polymeric substances were also higher in R2 than in R1. Scanning electronic microscopy was able to examine the morphological structures of the biogranules which showed there were irregular formations compacted together. However, there were more cavities situated in R1 biogranules (without MPAC) when compared to R2 biogranules (with MPAC). Dye removal reached 65% and 83% in R1 and R2 in the post-development stage. This study demonstrates that the addition of MPAC could shorten and improve biogranules formation. MPAC acted as the support media for microbial growth during the biogranulation developmental process.

Aerobic granular sludge development using diatomite for low-strength wastewater treatment

This paper presents an assessment of the start-up performance of aerobic granular sludge (AGS) for the treatment of low-strength (chemical oxygen demand, COD < 200 mg/L) domestic wastewater by the application of a diatomite carrier. The feasibility was evaluated in terms of the start-up period and stability of the aerobic granules as well as COD and phosphate removal efficiencies. A single pilot-scale sequencing batch reactor (SBR) was used and operated separately for the control granulation and granulation with diatomite. Complete granulation (granulation rate ≥ 90%) was achieved within 20 days for the case of diatomite with an average influent COD concentration of 184 mg/L. In comparison, control granulation required 85 days to accomplish the same feat with a higher average influent COD concentration (253 mg/L). The presence of diatomite solidifies the core of the granules and enhances physical stability. AGS with diatomite recorded the strength and sludge volume index of 18 IC and 53 mL/g suspended solids (SS) which is superior to control AGS without diatomite (19.3 IC, 81 mL/g SS). Quick start-up and achievement of stable granules lead to an efficient COD (89%) and phosphate removal (74%) in 50 days of bioreactor operation. Interestingly, this study revealed that diatomite has some special mechanism in enhancing the removal of both COD and phosphate. Also, diatomite has a significant influence on microbial diversity. The result of this research implies that the advanced development of granular sludge by using diatomite can provide promising low-strength wastewater treatment.

A study on the efficiency of the sequential batch reactor on the reduction of wastewater pollution from oil washing

Industrial pollution discharges from washing fuel oils pose severe problems for the environment, particularly for the marine environment receiving these discharges. This work evaluates the biological treatment performance of wastewater (90 m³/h) rich in organic matter with low biodegradability using a sequential batch reactor (SBR) on a laboratory scale. The test using SBR was carried out for 25 days on a continuous cycle of 24 h (30 min of filling, 17 h of aeration, 4 h of anoxia, 2 h of settling, and 30 min of emptying). The feasibility of alternative sources of microorganisms from urban wastewater. The performance of the batch sequencing reactor was evaluated using turbidity, total suspended solids, chemical oxygen demand (COD), biological oxygen demand (BOD), ammonium, nitrate, and phenol as indicators. The results obtained showed that the COD/BOD ratio and the pollutant load vary from one campaign to another. The removal efficiency of COD, BOD, TSS (Total suspended solids), ammonium, nitrate, and phenol varies from 81%, 91%, 72%, 100%, 52%, and 63%. Thus, SBR-type treatment could be an interesting way to reduce pollution due to its simplicity, less space occupation, low energy consumption, and not requiring highly qualified personnel.

Challenges of aerobic granular sludge utilization: Fast start-up strategies and cationic pollutant removal

Aerobic granular sludge (AGS) is a self-aggregated microorganism consortium with pollutant removal properties. The aim of this work is to study and review the application of aerobic granules for water treatment with special focus on new applications and methodologies. Carbon-nitrogen containing pollutants are the classic targets of AGS technology. Carbon and nitrogen removal of AGS are classified as a biodegradation process. More recently, the AGS granules have been studied as sorbent materials for wastewater treatment. In particular, the sorption of cationic pollutants has been studied through biosorption and bioaccumulation mechanisms without distinguishing when one or the other process is involved. AGS conformation made them suitable for complex wastewater treatment. Indeed, several studies have demonstrated the removal of polyvalent cationic pollutants even with higher capacity than conventional sorbent materials. However, this was achieved almost exclusively for synthetic substrates, with single cation evaluation and using in some cases only qualitative measures. For successful industrial AGS application in complex substrates, it is necessary to evaluate and demonstrate the technology in real industrial conditions and reduce the currently long start-up times which limits its utility. Two new strategies have been proposed: autoinducer molecules and the production of artificial granular from common active sludge with commercial alginate. Finally, the increase of research on AGS cations assimilation properties will allow a new point of view, where granules will be materials for the recovery of valuable metals from industrial wastewater streams.

Low-temperature-resistance granulation of activated sludge and the microbial responses to the granular structural stabilization

Completely loss of granular structural stability and reliable start-up of aerobic granular sludge (AGS) system are considered as the biggest challenges for its engineering application under seasonal temperature variation, especially extremely low temperatures. In this study, two identical sequencing batch reactors (SBR) were successfully start-up at 10 °C (R1) and 25 °C (R2), respectively, and then operated under a strategy of stepwise change of temperatures to investigate the stability of the granular sludge by examining its microbial characteristics, bis (3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP), extracellular polymeric substance (EPS) and sludge physiochemical properties. The results showed that AGS formed under the low temperature preferentially secrete EPS and c-di-GMP for stable granulation and improvement of its resistance to temperature changes. Meanwhile, R1 successfully obtained aerobic granulation with high biomass concentration and superior settleability, as well as high pollutant removal performance. In comparison, R2 took a longer time for granulation and was subjected to serious disintegration of AGS. The matrix structure partially formed by filamentous bacteria during the start-up stage in R1 was one of major reasons for its own superiority beyond R2 in granulation. Slow-growing organisms such as autotrophic nitrifying and Anammox bacteria, phosphorus accumulation organisms, EPS-producing genera, and c-di-GMP pathway-dependent genera, were exclusively enriched in the R1 and resulted in higher pollutants removal efficiencies and stable structure, whereas Sphaerotilus dominated in R2 that related closely with its unstable performance. Therefore, the strategy based on the stepwise change of temperatures from extremely low temperatures may be one feasible way for the sustainable application of AGS system, which is of significance to address the challenging problems of AGS applications.

Evaluating the role of algae in algal-bacterial granular sludge: Nutrient removal, microbial community and granular characteristics

Algal-bacterial granular sludge (ABGS) and bacterial granular sludge (BGS, control group) were operated over 240 days to investigate the role of algae in treating synthetic municipal wastewater. The results showed that algae significantly improved the removal efficiency of total nitrogen (TN). The nitrogen removal load of ABGS was 2.6 mg-N/g-VSS/day (22.8 %, light) and 1.1 mg-N/g-VSS/day (9.6 %, dark) higher than that of BGS, respectively, which was attributed to algae enhanced NH₃-N removal capacity in the anaerobic stage and increased the utilization efficiency of organics in denitrification. Algae increased the relative abundance of denitrifying bacteria, and ABGS (28.83 %) was higher than BGS (14.28 %). Moreover, the dominant phylum of algae was Chlorophyta (98.39 %), the chlorophyll-a was sustained at 1.28 ± 0.26 mg/g-VSS. Algae significantly increased the content of extracellular polymeric substances (EPS), and the increased polysaccharide came from the tightly bound EPS. This study expands the understanding of the role of algae in ABGS.

Formation mechanisms and assembly patterns of anammox biofilm induced by carrier type: Novel insights based on low-strength wastewater treatment

The morphological structure, properties, microbial community and function of anammox biofilms induced by large-pore carriers (Bls), small-pore carriers, filament carriers and non-carriers (Bn) in low-strength wastewater were comprehensively studied. The carriers promoted biomass accumulation and agglomeration, with Bls demonstrating the highest biomass proportion of 0.76, the highest specific anammox activity (0.41 kgN/(kgVSS·d)^-1) and the largest aggregates. Hydraulic shearing stimulated Bn to secrete most extracellular polymeric substances and capture more inorganic ions for enhanced strength. Metagenomic sequencing showed that the four biofilms shared a common core flora, but differed in cross-metabolism. The proportion of the functional bacterium Candidatus Brocadia was highest in Bls, while the increase in heterotrophic bacteria in Bn supported stronger metabolic capacity. Finally, the proposed anisotropic or isotropic carrier structure was identified as the key to generating "uniform development" and "central development" models. This study is helpful for understanding the anammox aggregation mechanism and carrier optimization.

Nitrogen removal intensification of aerobic granular sludge through bioaugmentation with "heterotrophic nitrification-aerobic denitrification" consortium during petroleum wastewater treatment

The bioaugmentation potential of aerobic granular sludge (AGS) was investigated using heterotrophic nitrification-aerobic denitrification (HN-AD) bacterial consortium to improve nitrogen removal during petroleum wastewater treatment. An efficient HN-AD consortium was constructed by mixing Pseudomonas mendocina K0, Brucella sp. K1, Pseudomonas putida T4 and Paracoccus sp. T9. AGS bioaugmented by immobilized HN-AD consortium enhanced nitrogen removal, which showed NH₄⁺-N and TN removal efficiency of 92.4% and 79.8%, respectively. The immobilized consortium addition facilitated larger AGS formation, while granules > 2.0 mm accounted for 16.7% higher than that of control (6.7%). Further, the abundance of napA gene was 4-times higher in the bioaugmented AGS as compared to the control, which demonstrated the long-term stability of HN-AD consortium in the bioreactor. The bioaugmented AGS also showed a higher abundance of xenobiotics biodegradation and nitrogen metabolism. These results highlight that bioaugmentation of AGS technology could be effectively used for enhanced denitrification of petroleum wastewater.

Clostridium weizhouense sp. nov., an anaerobic bacterium isolated from activated sludge of petroleum wastewater

A Gram-stain-positive, anaerobic, spore-forming, rod-shaped (0.4–0.6 µm×2.5–3.2 µm), flagellated bacterium, designated strain YB-6T, was isolated from activated sludge of an anaerobic tank at Weizhou marine oil mining wastewater treatment plant in Beihai, Guangxi, PR China. The culture conditions were 25–45 °C (optimum, 37 °C), pH 4–12 (pH 7.0) and NaCl concentration of 0–7 % w/v (0%). Strain YB-6T grew slowly in petroleum wastewater and removed 68.2 % of the total organic carbon in petroleum wastewater within 10 days. Concentrations of naphthalene, anthracene and phenanthrene at an initial concentration of 50 mg l−1 were reduced by 32.8, 40.4 and 14.6 %, respectively, after 7 days. Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain YB-6T belongs to Clostridium cluster I and is most closely related to Clostridium uliginosum CK55T (98.5 % similarity). The genome size of strain YB-6T was 3.96 Mb, and the G+C content was 26.5 mol%. The average nucleotide identity value between strain YB-6T and C. uliginosum CK55T was 81.9 %. The major fatty acids in strain YB-6T were C14 : 0 FAME, C16 : 0 FAME and summed feature 4 (unknown 14.762 and/or C15 : 2 FAME). The main polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, five unidentified aminophospholipids, one unidentified glycolipid and one unidentified aminolipid. Diaminopimelic acid was not detected in the strain YB-6T cell walls. Whole-cell sugars mainly consisted of ribose and galactose. Based on the results of phenotypic and genotypic analyses, strain YB-6T represents a novel species of the genus Clostridium , for which the name Clostridium weizhouense sp. nov. is proposed. The type strain is YB-6T (=GDMCC 1.2529T=JCM 34754T).

Efficiency and bacterial diversity of an improved anaerobic baffled reactor for the remediation of wastewater from alkaline-surfactant-polymer (ASP) flooding technology

Alkaline-surfactant-polymer (ASP) flooding technology is used to maximize crude oil recovery. However, the extensive use of alkaline materials makes it difficult to treat the water used. Here, an improved multi-zone anaerobic baffled reactor (ABR) using FeSO₄ as electron acceptor was employed to treat the wastewater from ASP flooding technology, and the effects on major pollutants (hydrolyzed polyacrylamide, petroleum substances, surfactants suspended solids) and associated parameters (chemical oxygen demand, viscosity) were evaluated. Gas chromatography-mass spectrometry (GC-MS) was used to follow the degradation and evolution of organic compounds while high-throughput DNA sequencing was used to determine the bacterial diversity in the ABR. The results obtained after 90 d of operation showed decreases in all parameters measured and the highest mean removal rates were obtained for petroleum substances (98.8%) and suspended solids (77.0%). Amounts of petroleum substances in the ABR effluent could meet the requirements of a national standard for oilfield reinjection water. GC-MS analysis showed that a wide range of chemicals (e.g. aromatic hydrocarbons, esters, alcohols, ketones) could be sequentially removed from the influent by each zone of ABR. The high-throughput DNA sequencing showed that the bacteria Micropruina, Saccharibacteria and Synergistaceae were involved in the degradation of pollutants in the anaerobic and anoxic reaction zones, while Rhodobacteraceae and Aliihoeflea were the main functional microorganisms in the aerobic reaction zones. The results demonstrated that the improved ABR reactor had the potential for the treatment of wastewater from ASP flooding technology.

Effects of combined 4-chlorophenol and Cu2+ on functional genes for nitrogen and phosphorus removal and heavy metal resistance genes in sequencing batch bioreactors

The effects of combined 4-chlorophenol (4-CP) and Cu²⁺ on microbial community structures, functional genes for nitrogen and phosphorus removal, and heavy metal resistance genes (HMRGs) were explored in wastewater treatment using sequencing batch bioreactors (SBRs). Compared to influent 4-CP (2.3-4.5 mg/L), the removal of pollutants including chemical oxygen demands (COD), NH₄⁺-N, PO₄^3--P, and 4-CP was inhibited under Cu²⁺ stress (5 mg/L). The effects of Cu²⁺ on microbial community structures were more significant than those of 4-CP with respect to operational time, while the dominant function from gene information was not affected with or without influent 4-CP and Cu²⁺ via sequencing analysis. The influent 4-CP and Cu²⁺ largely influenced the dynamic changes of functional genes and HMRGs, and the abundance of partial HMRGs was correlated to the functional genes and dominant genera. This study provides insights into the treatment of combined chlorophenols and Cu²⁺ in wastewater.

Response of extracellular polymeric substances and microbial community structures on resistance genes expression in wastewater treatment containing copper oxide nanoparticles and humic acid

The extracellular polymeric substances (EPS) and microbial community structures were investigated in wastewater treatment containing copper oxide nanoparticles (CuO NPs) (reactor R1) and CuO NPs and humic acid (HA) (reactor R2) using both sequencing batch bioreactors (SBRs), and their response on resistance genes expression was analyzed. The removal of influent chemical oxygen demands (COD) and NH₄⁺-N was moderately influenced under CuO NPs (5 mg/L) stress, while the function of HA (10 mg/L) was not reflected. However, the EPS production and microbial community were affected by the HA addition. The expression of different antibiotic resistance genes (ARGs), metal-resistance genes (MRGs), and intI1 was related to the primary compositions of polysaccharides and proteins in EPS and different microbial communities at the genus level. Furthermore, the expression of resistance genes was not stimulated under CuO NPs stress, and supplying HA was suggested to reduce their expression in wastewater treatment.

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

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

Effectively stimulating partial denitrification to utilize dissolved slowly-biodegradable organic matter by introducing in-situ biosorption and hydrolytic acidification

In this study, partial denitrification (PD, nitrate → nitrite) using dissolved slowly-biodegradable organic matter (DSBOM) was effectively established by introducing biosorption and hydrolytic acidification (HA) as a pretreatment for carbon capture and conversion. After 119 days of optimized operation, an efficient nitrate to nitrite transformation of 80% was achieved, with an influent nitrate level of 40 mg/L and DSBOM level of 183.8 mg/L. There was a significant shift from exogenous PD to endogenous PD, with energy supplied by HA products of captured DSBOM, i.e., acetate, saccharide and intracellular poly-hydroxyalkanoates (PHAs), jointly facilitating nitrite production. This was well explained by that genera Dechloromonas (26.7%), possibly responsible for carbon HA and nitrite production, were enriched; while abundant enzymes for glycolysis, acetate fermentation and PHAs storage, and 2.6 times more nitrate reductases than nitrite reductases were identified. These results highlight a novel carbon capture reuse and PD-based anammox strategy to cost-effectively treat nitrogen.

Comparison of different cultures and culturing conditions for the biological deterioration of organic load from real saline bilge wastewater: microbial diversity insights and ecotoxicity assessment

Bilge wastewater is a high strength, typically saline wastewater, originating from operation of ships. In this study, the treatment of real bilge wastewater was tested using pure isolated aerobic strains and mixed cultures (aerobic and anaerobic). The Chemical Oxygen Demand (COD) and ecotoxicity decrease were monitored over time, while the microbial dynamics alterations in mixed cultures were also recorded. The isolated strains Pseudodonghicola xiamenensis, Halomonas alkaliphila and Vibrio antiquaries were shown to significantly biodegrade bilge wastewater. Reasonable COD removal rates were achieved by aerobic mixed cultures (59%, 9 days), while anaerobic mixed cultures showed lower performance (34%, 51 days). The genus Pseudodonghicola was identified as dominant under aerobic conditions both in the mixed cultures and in the control sample (raw wastewater), after exposure to bilge wastewater, demonstrating natural proliferation of the genus and potential contribution to COD reduction. Biodegradation rates were higher when initial organic load was high, while the toxicity of raw wastewater partially decreased after treatment.

Rapid domestication of autotrophic nitrifying granular sludge and its stability during long-term operation

The nitrifying granular sludge process is a prospective technology for the efficient treatment of rare earth mine wastewater in southern Jiangxi, China. However, the long formation time of nitrifying granular sludge greatly restricted its application. In the present study, nitrifying granules were domesticated in a pilot-scale sequencing batch reactor by using heterotrophic granular sludge as carriers and adding exogenous nitrifying bacteria concentrate. According to variations of granular properties and ammonia removal, autotrophic nitrifying granules were successfully domesticated within 38 days using the strategy. It was found that the process involved secondary nucleation and microbial community evolution of the seed heterotrophic granules, and Nitrosomonas replaced most heterotrophic bacteria and became the dominant species with the largest relative abundance. During the subsequent 168 days of operation, the domesticated autotrophic nitrifying granules were stable, and their structures were denser than those of the inoculated granules. The ammonia nitrogen removal rate of the reactor was greater than 90% for a long period of time, and persistent partial nitrification was once achieved. However, severe fluctuation of influent ammonia nitrogen during the 120th to 206th day significantly inhibited the activity of nitrifying bacteria, which gradually led to the decrease of the ammonia nitrogen removal rate.

Effects of anaerobic granular sludge towards the treatment of flowback water in an up-flow anaerobic sludge blanket bioreactor: Comparison between mesophilic and thermophilic conditions

Cost-effective treatment of flowback water remains a challenge for the sustainability of shale gas development. This study evaluated the efficiency of anaerobic granular sludge (AnGS) technology for flowback water treatment under mesophilic and thermophilic conditions. The granule characteristics and metagenomic characterization were also investigated. Thermophilic AnGS achieved 70.9% of COD removal and 362 NmL/d of methane production, higher than those for mesophilic AnGS (60.0% and 241 NmL/d). Thermophilic AnGS had higher extracellular polymeric substances content but low granular size and settleability. Metagenomic analysis revealed the genes related to hydrolysis acidification and carbohydrate metabolism were upregulated during thermophilic condition. Thermophilic condition most likely improved the hydrolysis of complex organics in the flowback water such as guar gum and hydrolyzed polyacrylamide, and led to higher COD removal and methane production. These results suggest that AnGS technology is a promising alternative for the treatment of flowback water, particularly when operated at thermophilic condition.

A Bioreactor Designed for Restricting Oversize of Aerobic Granular Sludge

Aerobic granular sludge (AGS) with oversized diameter commonly affects its stability and pollutant removal. In order to effectively restrict the particle size of AGS, a sequencing batch reactor (SBR) with a spiny aeration device was put forward. A conventional SBR (R1) and an SBR (R2) with the spiny aeration device treating tannery wastewater were compared in the laboratory. The result indicates that the size of the granular sludge from R2 was smaller than that from R1 with sludge granulation. The spines and air bubbles could effectively restrict the particle size of AGS by collision and abrasion. Nevertheless, there was no significant change in mixed liquor suspended solids (MLSS) and the sludge volume index (SVI) in either bioreactors. The removal (%) of chemical oxygen demand (COD) and ammonia nitrogen (NH4+-N) in these two bioreactors did not differ from each other greatly. The analysis of biological composition displays that the proportion of Proteobacteria decreased slightly in R2. The X-ray fluorescence (XRF) analysis revealed less accumulation of Fe and Ca in smaller granules. Furthermore, a pilot-scale SBR with a spiny aeration device was successfully utilized to restrict the diameter of granules at about 300 μm.

Immobilization of Rhodococcus qingshengii strain FF on the surface of polyethylene and its adsorption and biodegradation of mimic produced water

Low pH and high salinity characteristic of produced water (PW) posed a big challenge for the direct biological treatment. The immobilization of R. qingshengii strain FF, which degraded petroleum effectively under low pH, and application of immobilized R. qingshengii strain FF in treating mimic PW was studied in this work. The immobilization of R. qingshengii strain FF on the surface of polyethylene foam (PEF), one type of waste packaging materials, was optimized using the response surface methodology. Under optimum conditions, cell density of R. qingshengii strain FF immobilized on the surface of PEF reached 388 mg (cells)/g(PEF). In addition, a few factors, including hydraulic retention time (HRT), pH and salinity, were studied for treating mimic PW using immobilized R. qingshengii strain FF. The result of this study demonstrated that TPH degradation efficiency of PW by immobilized R. qingshengii strain FF reached above 90% when HRT was longer than 8 h. Weak acid and high salinity conditions only moderately decreased TPH. Asphalt, alkanes and aromatic hydrocarbon contained in petroleum can be degraded to some extent. These results indicated that immobilized R. qingshengii strain FF can be used as a highly efficient strain which could be used in biological treatment of real PW.

Impact of hydraulic retention time on swine wastewater treatment by aerobic granular sludge sequencing batch reactor

In this study, the effect of hydraulic retention time (HRT) on the performance of aerobic granular sludge (AGS) treating swine wastewater (SW) in sequencing batch reactor (SBR) was investigated. The HRT was set at 4.8, 6, 8, 12, and 16 h and performed in five parallel aerobic granular sludge sequence batch reactors (AGSBRs), respectively. The results showed that sedimentation performance and biomass concentration were improved by decreasing the HRT from 16 to 8 h. However, when further decreasing HRT from 8 to 4.8 h, the AGS performance became worse. The AGS process with HRT of 8 h exhibited high pollutant removal efficiency, and an abundant microbial community and a stable microbial community structure were observed. High-throughput 16S rRNA analysis revealed that there were significant differences between the microorganisms in AGS samples with HRT of 8 h at the phylum level and that the dominant microbes changed as the process proceeded. At the genus level, the species and relative abundance of microorganisms gradually evolved for AGS stability in all cases.

Tailoring the distribution of microbial communities and gene expressions to achieve integrating nitrogen transformation in a gravity-driven submerged membrane bioreactor

A pilot-scale upgraded gravity-driven submerged membrane (GDSM) reactor was constructed to enhance nitrogen removal. It was artificially formed multiple stratified environments (dissolved oxygen (DO) and substrate supply (TOC, TN, COD, NH₄⁺-N, NO₂^--N, and NO₃^--N)) by embedding moving water baffles to control water-flow process in bulk liquid with slow-flowing liquid state. Significant diversity and relative abundance of microorganisms associated with nitrogen transformation paths (i.e., ammonia-oxidizing archaea, ammonia-oxidizing bacteria, nitrite oxidizing bacteria, and denitrifying bacteria) were tailored to distribute on different spatial and temporal regions, and performed their dominant functions. The process simultaneously integrated diverse and effective nitrogen transformation paths (i.e., nitrification, partial nitrification, denitrification, anammox, and dissimilatory nitrate reduction) to achieve high nitrogen removal, with NH₄⁺-N, TN, and COD eliminated by 94.68 ± 2.55%, 55.16 ± 5.53%, and 80.17 ± 6.75%, respectively. Gene expressions involved in the nitrogen transformations were estimated by qPCR to explore the shifts of dominant nitrogen transforming bioreactions in multiple stratified environments. Pearson correlation coefficients supported that the functional genes had more stable and active ability by complementing each other. As a result, an endogenous integration of diverse nitrogen transformation paths was achieved in a single system by artificially tailoring the distributions of microbial communities and gene expressions with enhanced nitrogen removal.

Granulation enhancement and microbial community shift of tylosin-tolerant aerobic granular sludge on the treatment of tylosin wastewater

To reduce the environment pollution from the extensive use of tylosin (TYL), in this study, an antibiotic adaptive strategy was used to enhance the TYL tolerance of aerobic granular sludge (AGS) for the treatment of TYL wastewater. The results showed that the granulation process was enhanced after 30 days of operation. The TYL-tolerant AGS gradually formed and maintained a diameter of 1.2 mm, with the mixed liquor suspended solids (MLSS) of 6810 mg⋅L^-1 and sludge volume index (SVI) of 26 mL⋅g^-1. Meanwhile, the chemical oxygen demand (COD), NH₄⁺-N, and total N removal effiencies could reach up to 92.9%, 91.7%, 88.5%, respectively. The average TYL removal rate was 85.5% with the effuent TYL of 1.45 mg⋅L^-1. In addition, the microbial communities shifted significantly that Bacteroidetes and Proteobacteria dominated the phylm, and the Macellibacteroides was the major genus which might possess the anitibiotic resistance genes of TYL.

Effect of carbon source on pollutant removal and microbial community dynamics in treatment of swine wastewater containing antibiotics by aerobic granular sludge

Aerobic granular sludge sequencing batch reactor (AGSBR) is a promising approach for wastewater treatment. In the paper, the effects of methanol, starch and sucrose as carbon sources on the treatment of swine wastewater (SW) containing antibiotics by aerobic granular sludge (AGS) were studied. The results revealed that the carbon sources could affect the morphology, biomass, and settleability of AGS, and AGS could maintain a better sludge performance when sucrose was used as carbon source. The pollutants (ammonium nitrogen (NH+ 4-N), organic matter and total phosphorus (TP)) in SW also had a good removal effect, and the removal rates reached 81.14%, 96.83% and 97.37% respectively. The removal efficiencies of tetracycline (TC) and oxytetracycline (OTC) from SW were the best when sucrose as co-metabolic matrix by microorganisms. The analysis of miseq pyrosequencing demonstrated that carbon sources with methanol, starch and sucrose improved the diversity of microbial community in AGS, and the dominant bacteria also changed. The dominant groups involved in TC and OTC, removal at different classification levels suggested that the formation of bacterial communities was determined by carbon sources.

Improvement in nitrogen removal and changes in community structure in a sequencing batch reactor bioaugmented with P. stutzeri strain XL-2

The aim of this work was to study the bioaugmentation of P. stutzeri strain XL-2 in activated sludge to improve nitrogn removal from wastewater with the guide of growth kinetics. When 4250 mg/L COD and 80 mg/L NH₄⁺-N were applied, the TN removal efficiency in a bioaugmented sequencing batch reactor (SBR_XL) achieved 95%, while that in the control reactor (SBR_C) without strain XL-2 was only 84% (P < 0.05). The microbial community analysis demonstrated that strain XL-2 was successfully bioaugmented in SBR_XL, and increasing influent COD concentration promoted its abundance. Influent COD concentration played a dominant role in affecting community structure, while the bioaugmentation of strain XL-2 had much less impact on the community structure. Combined with principal coordinates analysis, redundancy analysis and FAPROTAX, the improvement of TN removal was mainly achieved by the bioaugmentation of strain XL-2, which played a major role in promoting aerobic denitrification.

Simultaneous carbon reutilization for primary sludge and stable nitrite production in a hydrolytic acidification coupled with partial denitrification system to treat nitrate contaminant

Partial denitrification (PD, nitrate → nitrite) is a promising process for the hazardous nitrate removal by producing nitrite for Anammox. In this study, the startup and performance of PD using slowly biodegradable organic matter in primary sludge was explored by combining with in-situ hydrolytic acidification (HA). Results showed that efficient PD was established with 61.3% nitrite production at an influent nitrate level of 50 mg/L, with a simultaneous 23.1% reduction in volatile sludge mass. Efficient electron donors including acetate (13.2%), dissolved saccharide (11.9%), and intracellular poly-hydroxyalkanoates (22.5%) were generated from sludge HA, jointly promoting desirable nitrite production. Microbial analysis revealed that adding primary sludge significantly increased community diversity; however, the specific genera Dechloromonas (11.9%) and Thauera (10.5%) remained stably enriched to facilitate the efficient sludge reduction and nitrite production. These findings provide a novel strategy for simultaneously treating primary sludge, nitrate contaminant, and domestic wastewater using a HAPD and Anammox process.