Enhanced biodegradation of coal gasification wastewater with anaerobic biofilm on polyurethane (PU), powdered activated carbon (PAC), and biochar

Treatment of eutrophic water in pyrite-filled constructed wetland integrated with microelectrolysis driven by iron/sulfur cycle: Performance and mechanism

This study developed a microelectrolysis-integrated constructed wetland with pyrite filler around the cathode (e-PCW) to treat eutrophic water. Results indicated that e-PCW effectively enhanced pyrite dissolution, converting solid-phase electron donors into bioavailable forms, thereby facilitating the enrichment of various denitrifying bacteria on pyrite surfaces. Importantly, iron-reducing and sulfur-reducing bacteria attached to the pyrite surfaces enhanced the conversion of ferric iron and sulfate, thereby driving iron and sulfur cycles and promoting electron transfer. Therefore, synergistic effects of pyrite and microelectrolysis made e-PCW achieve higher total nitrogen (TN) and total phosphorus (TP) removal efficiencies. With a hydraulic retention time of 24 h, the highest removal efficiencies of TN and TP achieved 78% and 75%, respectively. Furthermore, when eutrophic water containing high concentration of algae was fed into e-PCW, it consistently demonstrated superior TN and TP removal capabilities. This work provides a valuable approach to optimizing constructed wetland technology for treating eutrophic water.

Effects of carrier surface hydrophilic modification on sludge granulation: From sludge characteristics, extracellular polymeric substances, and microbial community

Aerobic granular sludge (AGS) is a powerful biotechnological tool capable of treating multiple pollutants simultaneously. However, the granulation process and pollutant removal efficiency still need to be further improved. In this study, Fe2O3- and MnO2-surface-modified straw foam-based AGS (Fe2O3@SF-AGS and MnO2@SF-AGS), with an average particle size of 3 mm, were developed and evaluated. The results showed that surface modification reduced the hydrophobic groups of carriers, facilitating the attachment and proliferation of microorganisms. Notably, MnO2@SF-AGS showed excellent granulation performance, reaching a stable state about one week earlier than the unmodified SF-AGS. The polymeric substance content of MnO2@SF-AGS was found to be 1.28 times higher than that of the control group. Furthermore, the removal rates for NH4+-N, TN, and TP were enhanced by 27.28%, 12.8%, and 32.14%, respectively. The bacterial communities exhibited significant variations in response to different surface modifications of AGS, with genera such as Saprospiraceae, Terrimonas, and Ferruginibacter playing a crucial role in the formation of AGS and the removal of pollutants specifically in MnO2@SF-AGS. The charge transfer of metal ions of MnO2@SF promotes the granulation process and pollutant removal. These results highlight that MnO2@SF-AGS is an effective strategy for improving nitrogen and phosphorus removal efficiency from wastewater.

Enhancing nitrogen removal performance using immobilized aerobic denitrifying bacteria by modified polyvinyl alcohol/sodium alginate (PVA/SA)

Aerobic denitrification has emerged as a promising and efficient method for nitrogen removal from wastewater. However, the direct application of aerobic denitrifying bacteria has faced challenges such as low nitrogen removal efficiency, bacterial loss, and poor stability. To address these issues, this study developed a novel microbial particle carrier using NaHCO3-modified polyvinyl alcohol (PVA)/sodium alginate (SA) gel (NaHCO3-PVA/SA). This carrier exhibits several advantageous properties, including excellent mass transfer efficiency, favorable biocompatibility, convenient film formation, abundant biomass, and exceptional pollutant treatment capacity. The carrier was modified with 0.3% NaHCO3, 8.0% PVA, and 1.0% SA, resulting in a remarkable 3.4-fold increase in the average pore diameter and a 12.8% improvement in mass transfer efficiency. This carrier was utilized to immobilize the aerobic denitrifying bacterium Stutzerimonas stutzeri W-2 to enhance nitrogen removal (NaHCO3-PVA/SA@W-2), resulting in a NO3--N removal efficiency of 99.06%, which was 21.39% higher than that without modification. Compared with the non-immobilized W-2, the degradation efficiency was improved by 43.70%. After five reuses, the NO3--N and TN removal rates remained at 99% and 93.01%, respectively. These results provide a solid foundation for the industrial application of the modified carrier as an effective tool for nitrogen removal in large-scale wastewater treatment processes.

Biotoxicity dynamic change and key toxic organics identification of coal chemical wastewater along a novel full-scale treatment process

It is particularly important to comprehensively assess the biotoxicity variation of industrial wastewater along the treatment process for ensuring the water environment security. However, intensive studies on the biotoxicity reduction of industrial wastewater are still limited. In this study, the toxic organics removal and biotoxicity reduction of coal chemical wastewater (CCW) along a novel full-scale treatment process based on the pretreatment process-anaerobic process-biological enhanced (BE) process-anoxic/oxic (A/O) process-advanced treatment process was evaluated. This process performed great removal efficiency of COD, total phenol, NH4+-N and total nitrogen. And the biotoxicity variation along the treatment units was analyzed from the perspective of acute biotoxicity, genotixicity and oxidative damage. The results indicated that the effluent of pretreatment process presented relatively high acute biotoxicity to Tetrahymena thermophila. But the acute biotoxicity was significantly reduced in BE-A/O process. And the genotoxicity and oxidative damage to Tetrahymena thermophila were significantly decreased after advanced treatment. The polar organics in CCW were identified as the main biotoxicity contributors. Phenols were positively correlated with acute biotoxicity, while the nitrogenous heterocyclic compounds and polycyclic aromatic hydrocarbons were positively correlated with genotoxicity. Although the biotoxicity was effectively reduced in the novel full-scale treatment process, the effluent still performed potential biotoxicity, which need to be further explored in order to reduce environmental risk.

Overview of enhancing biological treatment of coal chemical wastewater: New strategies and future directions

Coal chemical wastewater (CCW) is a type of refractory industrial wastewater, and its treatment has become the main bottleneck restricting the sustainable development of novel coal chemical industry. Biological treatment is considered as an economical, effective and environmentally friendly technology for CCW treatment. However, conventional biological process is difficult to achieve the efficient removal of refractory organics because of CCW with the characteristics of composition complexity and high toxicity. Therefore, seeking the novel enhancement strategy appears to be a favorable solution for enhancing biological treatment efficiency of CCW. This review focuses on presenting a comprehensive picture about the exogenous enhancement strategies for CCW biological treatment. The performance and potential application of exogenous enhancement strategies, including co-metabolic substrate enhancement, biofilm filler enhancement, adsorption material enhancement and conductive mediator enhancement, were expounded. Meanwhile, the enhancing mechanisms of different strategies were comprehensively discussed from a biological perspective. Furthermore, the prospects of enhancement strategies based on the engineering performance, economic cost and environmental impact (3E) evaluation were introduced. And novel enhancement strategy based on "low carbon emissions", "resource recycling" and "water environment security" in the context of carbon neutrality was proposed. Taken together, this review provides technical reference and new direction to facilitate the regulation and optimization of typical industrial wastewater biological treatment.

Pilot study on ceramic flat membrane bioreactor in treatment of coal chemical wastewater

Some toxic and refractory pollutants in coal chemical wastewater can penetrate the biochemical treatment systems and cause high concentrations of suspended solids in the effluent, which may obstruct the subsequent advanced treatment. In this project, a submerged ceramic plate membrane system was integrated to the last oxic corridor of an existing multistage anoxic/oxic tank. In the ceramic flat membrane bioreactor, the influent chemical oxygen demand (COD) was 102.24-178.88 mg/L, with a removal ratio of approximately 30%. The NH3-N concentration in the effluent was relatively stable with an average value of 1.76 mg/L. The turbidity of the effluent was in the range of 0.235-0.852 NTU and was stable below 1 NTU. A flux of 30 L m-2·h-1 could meet the requirements of the pilot test. A gas-water ratio of 50:1 was found optimal. When the concentration of mixed liquor suspended solids (MLSS) was >3769 mg/L, the extracellular polymeric substance in the mixed solution was utilized by microorganisms as a substrate. High MLSS decreased membrane fouling rate. NaClO backwashing can effectively remove pollutants without adversely affecting the treatment efficiency of membrane bioreactors.

A review of application of combined biochar and iron-based materials in anaerobic digestion for enhancing biogas productivity: Mechanisms, approaches and performance

Strengthening direct interspecies electron transfer (DIET), via adding conductive materials, is regarded as an effective way for improving methane productivity of anaerobic digestion (AD). Therein, the supplementation of combined materials (composition of biochar and iron-based materials) has attracted increasing attention in recent years, because of their advantages of promoting organics reduction and accelerating biomass activity. However, as far as we known, there is no study comprehensively summarizing the application of this kind combined materials. Here, the combined methods of biochar and iron-based materials in AD system were introduced, and then the overall performance, potential mechanisms, and microbial contribution were summarized. Furthermore, a comparation of the combinated materials and single material (biochar, zero valent iron, or magnetite) in methane production was also evaluated to highlight the functions of combined materials. Based on these, the challenges and perspectives were proposed to point the development direction of combined materials utilization in AD field, which was hoped to provide a deep insight in engineering application.

Sustained degradation of phenol under extreme conditions by polyurethane-based Bacillus sp. ZWB3

Phenol is a serious pollutant to the environment, therefore, it is urgent to find a rapid and effective method for its removal. In this study, Bacillus cereus ZWB3 immobilized on a polyurethane (PUF) carrier was studied. The PUF-ZWB3 required only 20 h for the degradation of 1,500 mg L-1 of phenol, shortened by 8 h than the free bacteria. In addition, the PUF-ZWB3 could increase the degradation concentration of phenol from 1,500 to 2,000 mg L-1, and the complete degradation of 2,000 mg L-1 phenol only used 44 h. In addition, the PUF-ZWB3 showed much higher removal of phenol than the free bacteria at different pH values, salt concentrations, and heavy metal ions. Particularly, the PUF-ZWB3 could still completely remove phenol in a strongly alkaline environment, such as pH 10 and 11. In addition, the removal efficiency of phenol by PUF-ZWB3 was still 100% after 10 cycles. This study showed that the PUF immobilization system had great potential in the field of remediation of organic pollution.

Conductive biofilms in up-flow anaerobic sludge blanket enhanced biomethane recovery from municipal sewage under ambient temperatures

The feasibility of municipal sewage treatment in laboratory-scale up-flow anaerobic sludge blankets was investigated in this work. Unlike previous studies, granular activated carbon (conductive) or sponge (non-conductive) was introduced to hollow plastic balls as carriers and suspended in the middle and upper layers of the reactors. The two bioreactors were operated at four different hydraulic retention times (stepwise reduced from 24 h to 8 h) for 100 days at ∼18 °C. The conductive-amended treatment was more effective than the non-conductive treatment in enhancing reactor performance. Interestingly, in the reactor containing conductive carriers, microorganisms enriched in the conductive biofilm were also dominant in the suspended sludge. In the reactor containing sponge carriers, the dominant microorganisms differed between the non-conductive biofilm and the suspended sludge. This study underlines that the enrichment of functional microbial communities and the positive impacts of biofilm on suspended sludge are the keys to improving biomethane recovery.

Innovative Coating-Etching Method of Biocarrier Fabrication for Treating Wastewater with a Low C/N Ratio

A novel method was used to fabricate the bio-carrier with both a high specific surface area and good compatibility. The results of monitoring the growth of biofilms at a low C/N ratio (0.83) showed that resulting carrier-PLA-cavity offered certain advantages for biofilm growth by providing an appropriate microenvironment for bacterial growth in wastewater treatment. The biofilm on carrier-PLA-cavity grew and updated faster than the naked-carrier. The biomass and thickness of biofilms growing on carrier-PLA-cavity were 10 kg/m³ and 500 μm, respectively. From the wastewater tests, 90% of the total nitrogen was removed via simultaneous nitrification and denitrification (SND) by the biofilm biomass attached to carrier-PLA-cavity, compared to 68% for the naked-carrier. The COD removal efficiency values of the carrier-PLA-cavity and naked-carrier were 94% and 86%, respectively. The microbial community analysis of carrier biofilms showed that Halomonas was the most abundant genus, and heterotrophic nitrification and denitrification were responsible for nitrogen removal in both reactors. Notably, this method does not require any complicated equipment or structural design. This novel method might be a promising strategy for fabricating biocarriers for treating wastewater with a low C/N ratio.

An assessment of the purification performance and resilience of sponge-based aerobic biofilm reactors for treating polluted urban surface waters

Pollutants are continuously released into surface waters, which decrease the dissolved oxygen (DO) concentration and leads to the formation of black-odorous water, especially in slow-flowing urban lakes and enclosed small ponds. In situ treatment by artificial aeration or water cycling, coupled with biofilm, can address this problem without occupying large amounts of land. In this study, we designed a novel sponge-based aerobic biofilm reactor (SABR) and evaluated its performance in purifying urban surface water under different conditions. In the urban lake water treatment, the continuous inflow results revealed that the NH₄⁺-N and NO₂^--N concentrations in the effluent were stable and remained lower than 0.10 mg/L and 0.05 mg/L, respectively. Abrupt increases in the NH₄⁺-N and NO₂^--N concentrations in the influent and sudden increases in the NH₄⁺-N and NO₂^--N concentrations in the effluent were observed, and only 4 to 8 days were required for the concentrations to decline below 0.10 mg/L and 0.05 mg/L, respectively. Increases in the polyurethane sponge filling ratios in the SABRs can reduce the DO concentration but do not affect NH₄⁺-N removal. When no biodegradable organic matter was present in the enclosed surface water, the degradation time of NH₄⁺-N from 14.22 to 0.10 mg/L was only 9 days when SABRs were combined with water cycling, which was shorter than the time needed by water cycling alone (16 days), and most of the NH₄⁺-N was converted to NO₃^--N. When massive amounts of biodegradable organic matter were present in the enclosed surface water, 22 days were required to remove the NH₄⁺-N when SABRs were combined with water cycling. Our results indicated that organic matter could be used as a carbon source to eliminate the produced NO₃^--N in SABRs. Therefore, the newly developed bioreactor provides an effective approach for treating N-polluted urban surface waters.

Study of nitrogen removal efficiency of the filled bed reactors using alkali-treated corncobs-sulfur (mixotrophic) for treating the effluent from simulated urban wastewater plants

China's urban wastewater treatment plants' nitrogen discharge standards have become more stringent in recent years. In this experiment, the filled bed denitrification system with corncob-sulfur as fillers were constructed for the secondary effluent of the wastewater. The optimum operating conditions of the denitrification reactor with different fillers as electron donors were investigated by varying the operating parameters. According to the experiment, the alkali pretreated corncobs could maintain long-term denitrification effect. The optimum HRT for the mixotrophic denitrification reactor with alkali-treated corncob-sulfur as filler was 1.5 h, with a minimum effluent NO₃^--N concentration of 0.31 mg/L and a removal rate of 98.62%, and effluent nitrite nitrogen, NH₄⁺-N, and sulfate accumulation of 0.03 mg/L, 0.71 mg/L and 72.4 mg/L. The reactor with mixed nutrient type had the most abundant species community structure by high-throughput sequencing analysis.

Influence of cosubstrate and hydraulic retention time on the removal of drugs and hygiene products in sanitary sewage in an anaerobic Expanded Granular Sludge Bed reactor

Diclofenac (DCF), ibuprofen (IBU), propranolol (PRO), triclosan (TCS) and linear alkylbenzene sulfonate (LAS) can be recalcitrant in Wastewater Treatment Plants (WWTP). The removal of these compounds was investigated in scale-up (69 L) Expanded Granular Sludge Bed (EGSB) reactor, fed with sanitary sewage from the São Carlos-SP (Brazil) WWTP and 200 mg L^-1 of ethanol. The EGSB was operated in three phases: (I) hydraulic retention time (HRT) of 36±4 h; (II) HRT of 20±2 h and (III) HRT of 20±2 h with ethanol. Phases I and II showed no significant difference in the removal of LAS (63 ± 11-65 ± 12 %), DCF (37 ± 18-35 ± 11 %), IBU (43 ± 18-44 ± 16 %) and PRO (46 ± 25-51 ± 23 %) for 13±2-15 ± 2 mg L^-1, 106 ± 32-462 ± 294 μg L^-1, 166 ± 55-462 ± 213 μg L^-1 and 201 ± 113-250 ± 141 μg L^-1 influent, respectively. Higher TCS removal was obtained in phase I (72 ± 17 % for 127 ± 120 μg L^-1 influent) when compared to phase II (51 ± 13 % for 135 ± 119 μg L^-1 influent). This was due to its greater adsorption (40 %) in the initial phase. Phase III had higher removal of DCF (42 ± 10 % for 107 ± 26 μg L^-1 influent), IBU (50 ± 15 % for 164 ± 47 μg L^-1 influent) and TCS (85 ± 15 % for 185 ± 148 μg L^-1 influent) and lower removal of LAS (35 ± 14 % for 12 ± 3 mg L^-1 influent) and PRO (-142 ± 177 % for 188 ± 88 μg L^-1 influent). Bacteria similar to Syntrophobacter, Smithella, Macellibacteroides, Syntrophus, Blvii28_wastewater-sludge_group and Bacteroides were identified in phase I with relative abundance of 3.1 %-4.7 %. Syntrophobacter was more abundant (15.4 %) in phase II, while in phase III, it was Smithella (12.7 %) and Caldisericum (15.1 %). Regarding the Archaea Domain, Methanosaeta was more abundant in phases I (84 %) and II (67 %), while in phase III it was Methanobacterium (86 %).

Environmental contamination by heterocyclic Polynuclear aromatic hydrocarbons and their microbial degradation

Heterocyclic polynuclear aromatic hydrocarbons (PAHs) have been detected in all environmental matrices at few ppb to several ppm concentrations and they are characterized by high polarity. Some heterocyclic PAHs are mutagenic and carcinogenic to humans and various organisms. Despite being potent environmental pollutants, these compounds have received less attention. This paper focuses on the sources and occurrence of these compounds and their microbial degradation using diverse species of bacteria, fungi, and algae. Complete removal of 1.8 to 2614 mg/L of nitrogen heterocyclic PAH (PANH), 0.27 to 184 mg/L of sulfur heterocyclic PAH (PASH), and 0.6 to 120 mg/L of oxygen heterocyclic PAH (PAOH) compounds by various microbial species was observed between 3 h and 18 days, 8 h to 6 days, and 4 h to 250 h, respectively under aerobic condition. Strategies for enhancing the removal of heterocyclic PAHs from aquatic systems are also discussed along with the challenges.

Valorization of hydrothermal carbonization products by anaerobic digestion: Inhibitor identification, biomethanization potential and process intensification

Integrating hydrothermal carbonization (HTC) and anaerobic digestion for biorefinery-oriented full utilization of wet organic wastes is a promising emerging technology. The objectives of this study were to identify the potential inhibitory substances, evaluate the biomethane potential of mixed and aqueous products and explore process intensifying strategies. The results indicated that the high HTC temperature of 240 °C resulted in a significantly low methane yield of 60 ± 5 mL/g COD and a high Short chain fatty acid (SCFAs) accumulation of 4174 ± 76 mg/L. GC-MS analysis showed that the contents of inhibitory pyrazines, pyridines and ketones in aqueous fraction at 240 °C substantially increased from 13.14%, 0.4%, 0.55% at 180 °C to 23.34%, 2.89%, 5.13%, respectively. When the aqueous products obtained from 240 °C-HTC was supplemented or pretreated by carbonaceous material, the methane yields were greatly improved and increased to 1.3-fold and 1.8-fold, respectively. These finding could provide some valuable technical information for HTC based biorefinery of organic waste.

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.

Enhancing methane production from anaerobic digestion of waste activated sludge with addition of sodium lauroyl sarcosinate

In this study, sodium lauroyl sarcosinate (SLS) was used to promote anaerobic digestion of waste activated sludge for producing methane. It was found maximum cumulative methane production increased from 98.1 ± 3.1 to 166.0 ± 4.3 mL/g Volatile Suspended Solids (VSS) with dosage increasing from 0 (control) to 40 mg SLS/g TSS. But the addition of SLS (>10 mg SLS/g Total Suspended Solids (TSS)) resulted in prolonged lag phase time. Microbiological analysis showed that Syntrophobacter and Syntrophomonas both got enriched in reactors fed with SLS. Furthermore, hydrogenotrophic methanogens genus got more enrichment in contrast to acetoclastic methanogens. Mechanism analysis indicated that addition SLS could decrease surface tension, and promote release of organic matters as well as improve activities of hydrolytic enzymes. Besides, SLS could be nearly degraded completely within 3 days, and its degradation intermediates could be further transformed into methane gradually, thus enhancing methane production eventually.

The effect of step-feeding distribution ratio on high concentration perchlorate removal performance in ABR system with heterotrophic combined sulfur autotrophic process

In a lab-scale anaerobic baffled reactor (ABR) with eight compartments, the heterotrophic and sulfur autotrophic processes were combined to remove perchlorate. And then, the step-feeding distribution ratio of the heterotrophic perchlorate reduction unit (HPR unit) was optimized to achieve efficient removal of high concentration perchlorate. Under the optimized step-feeding distribution ratio, the perchlorate removal efficiency reached to 99.8% with the influent concentration of 1300 mg/L, indicating that the removal performance of step-feeding was better than that of normal-feeding. A mass balance results showed that the perchlorate removal capacity of the C1-C5 compartments were 11.8 ± 0.6, 13.2 ± 0.2, 11.7 ± 1.0, 8.8 ± 0.2 and 9.8 ± 1.0 g/d during the stage VIII, indicating that the step-feeding can effectively relieve pollutant loading of C1 compartment and improve the perchlorate removal capacity of the C2-C5 compartments. Moreover, the high-throughput sequencing analysis showed that bacterial community was significant difference between the HPR and sulfur autotrophic perchlorate removal (SAPR) units. Principal component analysis (PCA) showed that perchlorate removal was more positive correlation with the forward compartments than the posterior compartments of HPR unit. The study confirms that the optimized step-feeding ratio is beneficial to remove the high concentration perchlorate via combining heterotrophic and sulfur autotrophic processes.

Enhanced phenols removal and methane production with the assistance of graphene under anaerobic co-digestion conditions

Coal gasification wastewater (CGW) contains high concentration phenols which lead to poor anaerobic biodegradability and resource utilization. In this paper, new insights to improve synthetic CGW anaerobic degradation with the help of graphene under co-digestion conditions were investigated. Batch tests showed that with the addition of graphene dosage of 10 g/L and glucose as a co-substrate with chemical oxygen demand (COD) concentration of 2000 mg/L, the average COD concentration decreased from 3995 mg/L on day 1 to 983 mg/L on day 12. The average total phenol (TP) concentration decreased from 431 mg/L on day 1 to 23 mg/L on day 12. The cumulative methane production for 12 days was about 200 mL. Long-term experiments showed the average effluent COD and total phenol reached 1137 mg/L and 200 mg/L, respectively. While methane production stabilized at 500 mL/d. In addition, the coenzyme F₄₂₀ concentration increased from 1.075 μmol/g/VSS to 2.3 μmol/g/VSS. The analysis of microbial community structure indicated that the performance of phenols removal and methane production was related to the main microbial flora. The enriched Clostridium, Pseudomonas and species from Firmicutes and Chloroflexi participated in the stages of hydrolysis and acidogenesis. The electrogens Pseudomonas and archaea Methanosaeta were likely the major groups taking part in the direct interspecies electron transfer (DIET). The results obtained in this paper provide a theoretical basis for high-efficiency anaerobic degradation of CGW in practical engineering applications.

Decomposition process of cefotaxime sodium from antibiotic wastewater by Up-flow Blanket Filter (UBF) reactor: Reactor performance, sludge characteristics and microbial community structure analysis

In this study, a novel Up-flow Blanket Filter (UBF) reactor was applied to the degradation of antibiotic wastewater. The experiments showed that when the hydraulic retention time (HRT) was 24 h and the ratio of volatile fatty acids (VFA) to alkalinity (ALK) was 0.3, the best removal efficiency was achieved in the combined packing UBF reactor, and the COD removal efficiency reached 80.1%-84.6%, exhibiting a significant difference in reaction performance from the other two reactors (P < 0.05) and a good efficiency of cefotaxime sodium removal. Moreover, the microstructure and surface characteristics of the reactor fillers were studied through scanning electron microscope (SEM) analysis, which showed that three fillers all had biofilm adhesion, but the combined packing gave best performance. Energy dispersive spectrometer (EDS) tests indicated abundant element components in the combined packing. The particle size distribution of sludge was also considered in the experiment, and the result showed the particle size of sludge increased with the operation of the reactor. In addition, microbial community structures of sludge and biofilm with the combined packing were analyzed. High-throughput sequencing confirmed the existence of Pseudomonas, which had good adaptability to antibiotic wastewater and became the dominant bacteria. Decomposition process of cefotaxime sodium after hydrolysis and anaerobic treatment was analyzed through Fourier transform infrared spectroscopy (FTIR). The reactor, which is economical, exhibited favorable performance in degrading the pollutions in the antibiotic wastewater.

Optimization of a novel single air-lift sequencing bioreactor for raw piggery wastewater treatment: Nutrients removal and microbial community structure analysis

In this study, a sequencing batch and intermittent air-lift bioreactor (SBIAB) was evaluated under the three independent variables to treat raw piggery wastewater. The effects of hydraulic retention time (HRT), air flow rate and sludge retention time (SRT) on the nutrients removal of SBIAB were researched. The optimum values of HRT, air flow rate and SRT were 8 d, 2 l/min and 20 d, respectively. Meanwhile, the removal rates of chemical oxygen demand (COD), NH₄⁺-N, total nitrogen (TN) and total phosphorus (TP) were up to 89.5%, 93.5%, 61.1% and 57.3%, respectively. Generally, the nutrients removal performance could be enhanced with increasing HRT from 6 to 10 d, while it was inhibited at air flow rate of 3 l/min. Higher air flow rate caused the alkaline pH and high free ammonia concentration, which imposed restrictions on the process of wastewater treatment. In the SBIAB, a coupling of aerobic/anoxic/anaerobic zone was formed according to the changes of oxidation-reduction potential (ORP) values at the optimum condition. Microbial community structure analysis indicated that the functional microbes including Brachymonas, Prokaryote, Giesbergeria, Comamonadaceae bacterium, Clostridiales bacterium, Comamonas, Tissierella, Aequorivita were enriched in the SBIAB, which played a significant role in the removal of complex organics and nitrogen.

Powdered activated carbon (PAC) amendment enhances naphthalene biodegradation under strictly sulfate-reducing conditions

Capping represents an efficient and well-established practice to contain polycyclic aromatic hydrocarbons (PAHs) in sediments, reduce mobility, and minimize risks. Exposure to PAHs can encourage biodegradation, which can improve the performance of capping. This study investigates biodegradation of naphthalene (a model PAH) in highly reducing, sediment-like environments with amendment of different capping materials (PAC and sand). Microcosms were prepared with sediment enrichments, sulfate as an electron acceptor, and naphthalene. Results show that PAC stimulates naphthalene biodegradation and mineralization, as indicated by production of ¹⁴CO₂ from radiolabeled naphthalene. Mineralization in PAC systems correlates with the enrichment of genera (Geobacter and Desulfovirga) previously identified to biodegrade naphthalene (Spearman's, p < 0.05). Naphthalene decay in sand and media-free systems was not linked to biodegradation activity (ANOVA, p > 0.05), and microbial communities were correlated to biomass yields rather than metabolites. Naphthalene decay in PAC systems consists of three stages with respect to time: latent (0-88 days), exponential decay (88-210 days), and inactive (210-480 days). This study shows that PAC amendment enhances naphthalene biodegradation under strictly sulfate-reducing conditions and provides a kinetic and metagenomic characterization of systems demonstrating naphthalene decay.

Performance, mechanism and stability of nitrogen-doped sewage sludge based activated carbon supported magnetite in anaerobic degradation of coal gasification wastewater

In current study, the UASB reactor was enhanced by nitrogen-doped sewage sludge based activated carbon supported Fe₃O₄ (Fe₃O₄/N-SBAC) for coal gasification wastewater treatment. The results showed that COD removal efficiency was increased to 64.4% with Fe₃O₄/N-SBAC assistance and the corresponding methane production rate achieved up to 1093.6 mL/d. Fe₃O₄/N-SBAC promoted microbial growth and enzymatic activity, leading to high extracellular polymeric substances and coenzyme F₄₂₀ concentrations. Fe₃O₄/N-SBAC also facilitated the sludge granulation process with high particle size, substantial interspecific signal molecules and low diffusible signal factor. Microbial community analysis revealed that Fe₃O₄/N-SBAC might support direct interspecies electron transfer process, in which the enriched Geobacter was likely to communicate with Methanothrix via electrical connection, improving anaerobic degradation of coal gasification wastewater. Total phenols shock and pH impact revealed that reactor stability was enhanced in the Fe₃O₄/N-SBAC-supplemented system.

Enhanced anaerobic degradation of quinoline, pyriding, and indole with polyurethane (PU), Fe3O4@PU, powdered activated carbon (PAC), Fe(OH)3@PAC, biochar, and Fe(OH)3@biochar and analysis of microbial succession in different reactors

The study was to explore the feasibility of polyurethane (PU), Fe₃O₄@PU, powdered activated carbon (PAC), Fe(OH)₃@PAC, biochar, and Fe(OH)₃@biochar as biological carriers in strengthening anaerobic degradation of quinoline, pyridine, and indole. When the concentrations of pollutants were 25 mg/L and 50 mg/L, reactors based on PAC and Fe(OH)₃@PAC had higher degradation ratios than the other reactors. However, when the concentrations of pollutants were 75 mg/L and 100 mg/L, with the addition of PU and Fe₃O₄@PU, reactors began to show their superiority in the degradation of the selected NHCs. Among these, the reactor based on Fe₃O₄@PU had the optimal degradation ratio on quinoline, pyridine, and indole. PU, PAC, Fe(OH)₃@PAC, biochar, and Fe(OH)₃@biochar benefited the enrichment of Acinetobacter, Comamonas, Levilinea, Longilinea, and Desulfomicrobium. The reactor with the carrier of Fe₃O₄@PU had some specificity, which benefited the enrichment of Zoogloea, Thiobacillus, Anaeromyxobacter, Sphingobium, Terrimonas, Parcubacteria genera incertae sedis, Bdellovibrio, Rhizobium, and Acidovorax.

Shift of Sediments Bacterial Community in the Black-Odor Urban River during In Situ Remediation by Comprehensive Measures

The phenomenon of black-odor urban rivers with rapid urbanization has attracted extensive attention. In this study, we investigated the water quality and composition of sediment-associated bacteria communities in three remediation stages (before remediation, 30 days after remediation, and 90 days after remediation) based on the in situ remediation using comprehensive measures (physical, chemical, and biological measures). The results show that the overlying water quality was notably improved after in situ remediation, while the diversity and richness of sediment-associated bacterial communities decreased. A growing trend of some dominant genus was observed following the remediation of a black-odor river, such as Halomonas, Pseudomonas, Decarbonamis, Leptolina, Longilina, Caldiseericum, Smithella, Mesotoga, Truepera, and Ralstonia, which play an important role in the removal of nitrogen, organic pollutants and hydrogen sulfide (H2S) during the sediment remediation. Redundancy analysis (RDA) showed that the bacterial community succession may accelerate the transformation of organic pollutants into inorganic salts in the sediment after in situ remediation. In a word, the water quality of the black-odor river was obviously improved after in situ remediation, and the bacterial community in the sediment notably changed, which determines the nutrients environment in the sediment.