Jun 2022, Volume 16 Issue 6
    

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  • RESEARCH ARTICLE
    Zecong Yu, Keke Xiao, Yuwei Zhu, Mei Sun, Sha Liang, Jingping Hu, Huijie Hou, Bingchuan Liu, Jiakuan Yang

    • ORP value from −278.71 to −379.80 mV showed indiscernible effects on methane yield.

    • Fe(II) and Fe(III) promoted more degradation of proteins and amino acids than Fe0.

    • The highest enrichment of Geobacter was noted in samples added with Fe0.

    • Cysteine was accumulated during iron enhanced anaerobic sludge digestion.

    • Both iron content and valence were important for methane production.

    This study compared effects of three different valent iron (Fe0, Fe(II) and Fe(III)) on enhanced anaerobic sludge digestion, focusing on the changes of oxidation reduction potential (ORP), dissolved organic nitrogen (DON), and microbial community. Under the same iron dose in range of 0−160 mg/L after an incubation period of 30 days (d), the maximum methane production rate of sludge samples dosed with respective Fe0, Fe(II) and Fe(III) at the same concentration showed indiscernible differences at each iron dose, regardless of the different iron valence. Moreover, their behavior in changes of ORP, DON and microbial community was different: (1) the addition of Fe0 made the ORP of sludge more negative, and the addition of Fe(II) and Fe(III) made the ORP of sludge less negative. However, whether being more or less negative, the changes of ORP may show unobservable effects on methane yield when it ranged from −278.71 to −379.80 mV; (2) the degradation of dissolved organic nitrogen, particularly proteins, was less efficient in sludge samples dosed with Fe0 compared with those dosed with Fe(II) and Fe(III) after an incubation period of 30 d. At the same dose of 160 mg/L iron, more cysteine was noted in sludge samples dosed with Fe(II) (30.74 mg/L) and Fe(III) (27.92 mg/L) compared with that dosed with Fe0 (21.75 mg/L); (3) Fe0 particularly promoted the enrichment of Geobacter, and it was 6 times higher than those in sludge samples dosed with Fe(II) and Fe(III) at the same dose of 160 mg/L iron.

  • RESEARCH ARTICLE
    Malan Yi, Yao Fang, Guoping Hu, Shufeng Liu, Jinren Ni, Tang Liu

    • Season and landform influenced spatiotemporal patterns of abundant and rare taxa.

    • Different stochastic processes dominated abundant and rare subcommunity assembly.

    • River flow and suspended solids regulated assembly processes of rare taxa.

    The rare microbial biosphere provides broad ecological services and resilience to various ecosystems. Nevertheless, the biogeographical patterns and assembly processes of rare bacterioplankton communities in large rivers remain uncertain. In this study, we investigated the biogeography and community assembly processes of abundant and rare bacterioplankton taxa in the Yangtze River (China) covering a distance of 4300 km. The results revealed similar spatiotemporal patterns of abundant taxa (AT) and rare taxa (RT) at both taxonomic and phylogenetic levels, and analysis of similarities revealed that RT was significantly influenced by season and landform than AT. Furthermore, RT correlated with more environmental factors than AT, whereas environmental and spatial factors explained a lower proportion of community shifts in RT than in AT. The steeper distance–decay slopes in AT indicated higher spatial turnover rates of abundant subcommunities than rare subcommunities. The null model revealed that both AT and RT were mainly governed by stochastic processes. However, dispersal limitation primarily governed the AT, whereas the undominated process accounted for a higher fraction of stochastic processes in RT. River flow and suspended solids mediated the balance between the stochastic and deterministic processes in RT. The spatiotemporal dynamics and assembly processes of total taxa were more similar as AT than RT. This study provides new insights into both significant spatiotemporal dynamics and inconsistent assembly processes of AT and RT in large rivers.

  • RESEARCH ARTICLE
    Di Zhang, Rong Hou, Wenbo Wang, He Zhao

    • The feasibility of facile fabrication of capacitor from floc sludge is discussed.

    • The porous carbon composites are obtained by acidification and KOH activation.

    • The as-prepared 3D structure has large surface area and optimal pore size.

    • Admirable specific capacitance and outstanding cycling stability are obtained.

    In this paper, floc sludge was transformed into porous carbon matrix composites by acidification and KOH activation at high temperature and used as an electrode material for application in capacitors. The effects of different treatment processes on the electrochemical properties of sludge materials were compared. The results of electrochemical tests showed that the sludge electrode exhibited excellent energy storage performance after HNO3 acidification and KOH activation with a mass ratio of 3:1 (KOH/C). The specific capacitance of the sludge electrode reached 287 F/g at a current density of 1 A/g. In addition, the sludge electrode material showed excellent cycle stability (specific capacity retained at 93.4% after 5000 cycles at 5 A/g). Based on XRD, FTIR, SEM, TEM, and BET surface analysis, the morphology of sludge electrode materials can be effectively regulated by chemical pretreatment. The best-performing material showed a 3D porous morphology with a large specific surface area (2588 m2/g) and optimal pore size distribution, improving ion channels and charge conductivity. According to the life cycle assessment of floc sludge utilization, it reduced the resource consumption and toxicity risk by more than 90% compared with ordinary sludge disposal processes. This work provided a cost-effective and eco-friendly sludge reuse method and demonstrated the application potential of sludge-based materials in high-performance supercapacitors.

  • REVIEW ARTICLE
    Lihui Gao, Yijun Cao, Lizhang Wang, Shulei Li

    • The sustainable approaches related to Fenton sludge reuse systems are summarized.

    • Degradation mechanism of Fenton sludge heterogeneous catalyst is deeply discussed.

    • The efficient utilization directions of Fenton sludge are proposed.

    The classical Fenton oxidation process (CFOP) is a versatile and effective application that is generally applied for recalcitrant pollutant removal. However, excess iron sludge production largely restricts its widespread application. Fenton sludge is a hazardous solid waste, which is a complex heterogeneous mixture with Fe(OH)3, organic matter, heavy metals, microorganisms, sediment impurities, and moisture. Although studies have aimed to utilize specific Fenton sludge resources based on their iron-rich characteristics, few reports have fully reviewed the utilization of Fenton sludge. As such, this review details current sustainable Fenton sludge reuse systems that are applied during wastewater treatment. Specifically, coagulant preparation, the reuse of Fenton sludge as an iron source in the Fenton process and as a synthetic heterogeneous catalyst/adsorbent, as well as the application of the Fenton sludge reuse system as a heterogeneous catalyst for resource utilization. This is the first review article to comprehensively summarize the utilization of Fenton sludge. In addition, this review suggests future research ideas to enhance the cost-effectiveness, environmental sustainability, and large-scale feasibility of Fenton sludge applications.

  • RESEARCH ARTICLE
    He Zhao, Ching-Hua Huang, Chen Zhong, Penghui Du, Peizhe Sun

    • 2,6-DCBQ and TCBQ generated THMs differently in chlorine and UV/chlorine processes.

    • UV significantly enhanced hydroxylation of 2,6-DCBQ and CHCl3 formation.

    • THMs formation of DCBQ was enhanced due to UV benefitting excited DCBQ* hydrolysis.

    • Hydroxylation and UV were both important for TCBQ in promoting THMs formation.

    • High pH promoted hydroxylation of HBQs and CHCl3 formation, especially for TCBQ.

    Halobenzoquinones (HBQs) are highly toxic disinfection byproducts (DBPs) and are also precursors of other DBPs such as trihalomethanes (THMs). The formation of THMs from HBQs during chlorine-only and UV/chlorine processes with or without bromide was investigated experimentally. Density functional theory (DFT) reactivity descriptors were also applied to predict the nucleophilic/electrophilic reactive sites on HBQs and intermediates. The results were combined to explain the different behaviors of 2,6-dichloro-1,4-benzoquinone (2,6-DCBQ) and tetrachloro-1,4-benzoquinone (TCBQ) and to propose mechanism for the promoting roles of UV and hydroxylation of HBQs in THMs formation. Under UV/chlorine, UV significantly enhanced THMs formation from 2,6-DCBQ compared to chlorine-only, mainly due to the production of OH-DCBQ*. Excited 2,6-DCBQ* by UV benefited nucleophilic hydrolysis to produce OH-DCBQ*, which favored electrophilic attack by chlorine, thereby inducing more THMs formation. UV/chlorine modestly promoted THMs formation from TCBQ compared to chlorine-only. Hydroxylation of TCBQ and UV irradiation were both important in promoting THMs formation due to the high electrophilic property of OH-TCBQ and TCBQ*. Meanwhile, hydroxylation of HBQs and CHCl3 formation were enhanced at higher pH. This work suggested that enhanced formation of THMs from HBQs should be considered in the application of combined UV and chlorine processes.

  • RESEARCH ARTICLE
    Zicong Zhao, Jing Yang, Zigeng Zhang, Sheping Wang, Zhiqiang Zhang, Jinsuo Lu

    • The combination of NaOH and nitrite was used to control harmful gas in sewers.

    • Hydrogen sulfide and methane in airspace were reduced by 96.01% and 91.49%.

    • Changes in sewage quality and greenhouse effect by chemical dosing were negligible.

    • The strong destructive effects on biofilm slowed down the recovery of harmful gases.

    • The cost of the method was only 3.92 × 10−3 $/m3.

    An innovative treatment method by the combination of NaOH and nitrite is proposed for controlling hydrogen sulfide and methane in gravity sewers and overcome the drawbacks of the conventional single chemical treatment. Four reactors simulating gravity sewers were set up to assess the effectiveness of the proposed method. Findings demonstrated hydrogen sulfide and methane reductions of about 96.01% and 91.49%, respectively, by the combined addition of NaOH and nitrite. The consumption of NaNO2 decreased by 42.90%, and the consumption rate of NaOH also showed a downward trend. Compared with a single application of NaNO2, the C/N ratio of wastewater was increased to about 0.61 mg COD/mg N. The greenhouse effect of intermediate N2O and residual methane was about 48.80 gCO2/m3, which is far lower than that of methane without control (260 gCO2/m3). Biofilm was destroyed to prevent it from entering the sewage by the chemical additives, which reduced the biomass and inhibited the recovery of biofilm activity to prolong the control time. The sulfide production rate and sulfate reduction rate were reduced by 92.32% and 85.28%, respectively. Compared with conventional control methods, the cost of this new method was only 3.92 × 10−3 $/m3, which is potentially a cost-effective strategy for sulfide and methane control in gravity sewers.

  • PERSPECTIVES
    Lei Li, Shijie Yuan, Chen Cai, Xiaohu Dai

    Methanogenesis is the last step in anaerobic digestion, which is usually a rate-limiting step in the biological treatment of organic waste. The low methanogenesis efficiency (low methane production rate, low methane yield, low methane content) substantially limits the development of anaerobic digestion technology. Traditional pretreatment methods and bio-stimulation strategies have impacts on the entire anaerobic system and cannot directly enhance methanogenesis in a targeted manner, which was defined as “broad-acting” strategies in this perspective. Further, we discussed our opinion of methanogenesis process with insights from the electron transfer system of syntrophic partners and provided potential targeted enhancing strategy for high-efficiency electron transfer system. These “precise-acting” strategies are expected to achieve an efficient methanogenesis process and enhance the bio-energy recovery of organic waste.

  • REVIEW ARTICLE
    Kehui Liu, Xiaojin Guan, Chunming Li, Keyi Zhao, Xiaohua Yang, Rongxin Fu, Yi Li, Fangming Yu

    • The overall global perspective of the PHMCS field was obtained.

    • PHMCS research has flourished over the past two decades.

    • In total, 8 clusters were obtained, and many new hot topics emerged.

    • “Biochar,” “Drought,” “Nanoparticle,” etc., may be future hot topics.

    • Five future directions are proposed.

    In total, 9,552 documents were extracted from the Web of Science Core Collection and subjected to knowledge mapping and visualization analysis for the field of phytoremediation of HM-contaminated soil (PHMCS) with CiteSpace 5.7 R3 software. The results showed that (1) the number of publications increased linearly over the studied period. The top 10 countries/regions, institutions and authors contributing to this field were exhibited. (2) Keyword co-occurrence cluster analysis revealed a total of 8 clusters, including “Bioremediation,” “Arsenic,” “Biochar,” “Oxidative stress,” “Hyperaccumulation,” “EDTA,” “Arbuscular mycorrhizal fungi,” and “Environmental pollution” clusters (3) In total, 334 keyword bursts were obtained, and the 25 strongest, longest duration, and newest keyboard bursts were analyzed in depth. The strongest keyword burst test showed that the hottest keywords could be divided into 7 groups, i.e., “Plant bioremediation materials,” “HM types,” “Chelating amendments,” “Other improved strategies,” “Bioremediation characteristics,” “Risk assessment,” and “Other.” Almost half of the newest topics had emerged in the past 3 years, including “biochar,” “drought,” “health risk assessment,” “electrokinetic remediation,” “nanoparticle,” and “intercropping.” (4) In total, 9 knowledge base clusters were obtained in this study. The studies of Ali et al. (2013), Blaylock et al. (1997), Huang et al. (1997), van der Ent et al. (2013), Salt et al. (1995), and Salt (1998), which had both high frequencies and the strongest burst scores, have had the most profound effects on PHMCS research. Finally, future research directions were proposed.

  • RESEARCH ARTICLE
    Weiying Li, Yu Tian, Jiping Chen, Xinmin Wang, Yu Zhou, Nuo Shi

    • The early corrosion process in the cast iron pipes was investigated.

    • The increase of NaOCl (<0.75 mg/L) accelerated the cast iron corrosion.

    • Biocorrosion caused by IOB could be divided into three stages in the early stage.

    • Synergistic and antagonistic effects exist between residual chlorine and IOB.

    Corrosion in drinking water distribution systems (DWDSs) may lead to pipe failures and water quality deterioration; biocorrosion is the most common type. Chlorine disinfectants are widely used in DWDSs to inhibit microorganism growth, but these also promote electrochemical corrosion to a certain extent. This study explored the independent and synergistic effects of chlorine and microorganisms on pipeline corrosion. Sodium hypochlorite (NaOCl) at different concentrations (0, 0.25, 0.50, and 0.75 mg/L) and iron-oxidizing bacteria (IOB) were added to the reaction system, and a biofilm annular reactor (BAR) was employed to simulate operational water supply pipes and explain the composite effects. The degree of corrosion became severe with increasing NaOCl dosage. IOB accelerated the corrosion rate at an early stage, after which the reaction system gradually stabilized. When NaOCl and IOB existed together in the BAR, both synergistic and antagonistic effects occurred during the corrosion process. The AOC content increased due to the addition of NaOCl, which is conducive to bacterial regrowth. However, biofilm on cast iron coupons was greatly influenced by the disinfectant, leading to a decrease in microbial biomass over time. More research is needed to provide guidelines for pipeline corrosion control.

  • RESEARCH ARTICLE
    Qiong Guo, Zhichao Yang, Bingliang Zhang, Ming Hua, Changhong Liu, Bingcai Pan

    • Fungi enable the constant UASB operation even at OLR of 25.0 kg/(m3×d).

    • The COD removal of 85.9% and methane production of 5.6 m3/(m3×d) are achieved.

    • Fungi inhibit VFAs accumulation and favor EPS generation and sludge granulation.

    • Fungi enrich methanogenic archaea and promote methanogenic pathways.

    Anaerobic digestion is widely applied in organic wastewater treatment coupled with bioenergy production, and how to stabilize its work at the high organic loading rate (OLR) remains a challenge. Herein, we proposed a new strategy to address this issue via involving the synergetic role of the Aspergillus sydowii 8L-9-F02 immobilized beads (AEBs). A long-term (210-day) continuous-mode operation indicated that the upflow anaerobic sludge bed (UASB) reactor (R1, with AEBs added) could achieve the OLR as high as 25.0 kg/(m3×d), whereas the control reactor (R0, with AEBs free) could only tolerate the maximum OLR of 13.3 kg/(m3×d). Remarkably, much higher COD removal (85.9% vs 23.9%) and methane production (5.4 m3/(m3×d) vs 2.2 m3/(m3×d)) were achieved in R1 than R0 at the OLR of 25.0 kg/(m3×d). Such favorable effect results from the facts that fungi inhibit VFAs accumulation, favor the pH stabilization, promote the generation of more extracellular polymeric substance, and enhance the sludge granulation and settleability. Moreover, fungi may enhance the secretion of acetyl-coenzyme A, a key compound in converting organic matters to CO2. In addition, fungi are favorable to enrich methanogenic archaea even at high OLR, improving the activity of acetate kinase and coenzyme F420 for more efficient methanogenic pathway. This work may shed new light on how to achieve higher OLR and methane production in anaerobic digestion of wastewater.

  • REVIEW ARTICLE
    Mengtian Li, Ge Song, Ruiping Liu, Xia Huang, Huijuan Liu

    • Diversity and detection methods of pathogenic microorganisms in sludge.

    • Control performance of sludge treatment processes on pathogenic microorganisms.

    • Risk of pathogen exposure in sludge treatment and land application.

    The rapid global spread of coronavirus disease 2019 (COVID-19) has promoted concern over human pathogens and their significant threats to public health security. The monitoring and control of human pathogens in public sanitation and health facilities are of great importance. Excessive sludge is an inevitable byproduct of sewage that contains human and animal feces in wastewater treatment plants (WWTPs). It is an important sink of different pollutants and pathogens, and the proper treatment and disposal of sludge are important to minimize potential risks to the environment and public health. However, there is a lack of comprehensive analysis of the diversity, exposure risks, assessment methods and inactivation techniques of pathogenic microorganisms in sludge. Based on this consideration, this review summarizes the control performance of pathogenic microorganisms such as enterovirus, Salmonella spp., and Escherichia coli by different sludge treatment technologies, including composting, anaerobic digestion, aerobic digestion, and microwave irradiation, and the mechanisms of pathogenic microorganism inactivation in sludge treatment processes are discussed. Additionally, this study reviews the diversity, detection methods, and exposure risks of pathogenic microorganisms in sludge. This review advances the quantitative assessment of pathogenic microorganism risks involved in sludge reuse and is practically valuable to optimize the treatment and disposal of sludge for pathogenic microorganism control.

  • RESEARCH ARTICLE
    Quanli Man, Peilian Zhang, Weiqi Huang, Qing Zhu, Xiaoling He, Dongsheng Wei

    H. venusta TJPU05 showed excellent HN-AD ability at high salinity.

    • Successful expression of AMO, HAO, NAR and NIR confirmed the HN-AD ability of TJPU05.

    H. venusta TJPU05 could tolerate high salt and high nitrogen environment.

    H. venusta TJPU05 is a promising candidate for the bio-treatment of AW.

    A novel salt-tolerant heterotrophic nitrification and aerobic denitrification (HN-AD) bacterium was isolated and identified as Halomonas venusta TJPU05 (H. venusta TJPU05). The nitrogen removal performance of H. venusta TJPU05 in simulated water (SW) with sole or mixed nitrogen sources and in actual wastewater (AW) with high concentration of salt and nitrogen was investigated. The results showed that 86.12% of NH4+-N, 95.68% of NO3-N, 100% of NO2-N and 84.57% of total nitrogen (TN) could be removed from SW with sole nitrogen sources within 24 h at the utmost. H. venusta TJPU05 could maximally remove 84.06% of NH4+-N, 92.33% of NO3-N, 92.9% of NO2-N and 77.73% of TN from SW with mixed nitrogen source when the salinity was above 8%. The application of H. venusta TJPU05 in treating AW with high salt and high ammonia nitrogen led to removal efficiencies of 50.96%, 47.28% and 43.19% for NH4+-N, NO3-N and TN respectively without any optimization. Furthermore, the activities of nitrogen removal–related enzymes of the strain were also investigated. The successful detection of high level activities of ammonia oxygenase (AMO), hydroxylamine oxidase (HAO), nitrate reductase (NAR) and nitrite reductase (NIR) enzymes under high salinity condition further proved the HN-AD and salt-tolerance capacity of H. venusta TJPU05. These results demonstrated that the H. venusta TJPU05 has great potential in treating high-salinity nitrogenous wastewater.

  • RESEARCH ARTICLE
    Yanlin Li, Bo Wang, Lei Zhu, Yixing Yuan, Lujun Chen, Jun Ma

    • LDHs and MMOs was synthesized by ultrasound-assisted one-step co-precipitation.

    • MMOs performs the best for Cr(VI) and E. coliNDM-1 simultaneous removal.

    • Possible antibacterial pathways of Cr-MMOs were proposed.

    Herein we provide a novel high-efficiency nanocomposite for bacterial capture based on mixed metal oxides (MMOs) with deleterious chromium properties. With both the layer structure of layered double hydroxides (LDHs) and the magnetic properties of Fe, MMOs enrich the location of ionic forms on the surface, providing a good carrier for adsorption of the heavy metal Cr(VI). The capacity for adsorption of Cr(VI) by MMOs can be as high as 98.80 mg/g. The prepared Cr(VI)-MMOs achieved extremely expeditious location of gram-negative antibiotic-resistant E. coliNDM-1 by identifying lipid bilayers. Cr-MMOs with a Cr loading of 19.70 mg/g had the best bactericidal effect, and the concentration of E. coliNDM-1 was decreased from ~108 to ~103 CFU/mL after 30 min of reaction. The binding of nitrogen and phosphorus hydrophilic groups to chromate generated realistic models for density functional theory (DFT) calculations. The specific selectivity of MMOs toward bacterial cells was improved by taking Cr(VI) as a transferable medium, thereby enhancing the antibacterial activity of Cr-MMOs. Under the combined action of chemical and physical reactions, Cr(VI)-MMOs achieved high capacity for inactivation of bacteria. Moreover, the metallic elements ratio in Cr-MMOs remained stable in their initial valence states after inactivation. This guaranteed high removal efficiency for both heavy metals and bacteria, allowing recycling of the adsorbent in practical applications.