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In our previous study, quorum quenching (QQ) bacteria can effectively enhance methane production in an anaerobic membrane bioreactor (AnMBR) while mitigating membrane biofouling. However, the mechanism of such enhancement is unclear. In this study, we analyzed the potential effects from separated hydrolysis, acidogenesis, acetogenesis and methanogenesis steps. The cumulative methane production improved by 26.13%, 22.54%, 48.70% and 44.93% at QQ bacteria dosage of 0.5, 1, 5 and 10 mg strain/g beads, respectively. It was found that the presence of QQ bacteria enhanced acidogenesis step resulting in higher volatile fatty acids (VFA) production, while it had no obvious influence on hydrolysis, acetogenesis and methanogenesis steps. The substrate (glucose) conversion efficiency in acidogenesis step was also accelerated (1.45 folds vs control within first eight hours). The abundance of hydrolytic fermentation gram-positive bacteria and several acidogenic bacteria, such as Hungateiclostridiaceae, was promoted in QQ amended culture, which enhanced VFA production and accumulation. Although the abundance of acetoclastic methanogen Methanosaeta reduced by 54.2% on the 1st day of QQ beads addition, the overall performance of methane production was not affected. This study revealed that QQ had a greater impact on the acidogenesis step in the anaerobic digestion process, though the microbial community in acetogenesis and methanogenesis steps was altered. This work can provide a theoretical basis for using QQ technology to slow down the rate of membrane biofouling in anaerobic membrane bioreactors while increasing methane production and maximizing economic benefits. Nanyang Technological University The authors acknowledge the financial support of Advanced Environmental Biotechnology centre, Nanyang Environment and Water Research Institute (NEWRI), Nanyang Technological University, Singapore.

The pollution of microplastics (MPs) in soil has become a global environmental problem. Due to high sorption capacity and persistence in environment, the MPs exhibit combined effects with organic pollutants in soil, thereby posing a potential risk to soil ecology and human health. However, limited reviews are available on this subject. Therefore, in response to this issue, this review provides an in-depth account of interaction of MPs with organic contaminants in soil and the combined risks to soil environment. The sorption of organic contaminants onto MPs is mainly through hydrophobic and π-π interactions, hydrogen bonding, pore filling and electrostatic and van der Waals forces. The intrinsic characteristics of MPs, organic contaminants and soil are the key factors influencing the sorption of organic pollutants onto MPs. Importantly, the presence of MPs changes the sorption, degradation and transport behaviors of organic contaminants in soil, and affects the toxic effects of organic contaminants on soil organisms including animals, plants and soil microorganisms through synergistic or antagonistic effects. Source control, policy implementation and plastic removal are the main preventive and control measures to reduce soil MPs pollution. Finally, priorities for future research are proposed, such as field investigations of co-pollution, contribution of plastisphere to organic contaminant degradation, and mechanisms of MPs effects on organic contaminant toxicity.

Food waste was used to produce ethanol by yeast fermentation and volatile fatty acids (VFAs) by hydrolytic acidogenesis for chain elongation. Effectiveness of mole ratio of ethanol in yeast fermentation effluent (YFE) to VFAs in hydrolytic acidification effluent (HAE) on chain elongation was examined. The ideal YFE to HAE ratio for chain elongation was 2:1, the highest n-caproate production was 169.76 mg COD/g vS and the food waste utilization was 65.43 %. Electron transfer and carbon distribution did not completely correspond to n-caproate production, suggesting timely product extraction. The abundance of Romboutsia and Clostridium_sensu_stricto_12 increased as chain elongation progressed, which was critical for the chain elongation to n-caproate. The food waste shunting ratio of yeast fermentation to hydrolytic acidogenesis was 6:5, and 572.6 CNY can be created through chain elongation from shunting fermentation of 1 t food waste. This study proposed a new approach for efficient producing n-caproate from food waste.

The quality of groundwater along rivers is greatly affected by long-term infiltration from surface water, especially reclaimed water-receiving rivers. To predict the degree of influence of contaminated river water on groundwater quality, the spatiotemporal distribution and migration evolution prediction of benzo[a]pyrene (B(a)P) was monitored and simulated by Hydrus-coupled Groundwater Modeling Systems (GMS) model in terms of reclaimed water-receiving Liangshui River. The prediction results indicated the goodness-of-fit of this coupled model, according to the model efficiency (E: 0.78-0.93), the mean absolute error (MAE: 0.01-0.32 m) and the root-mean-square error (RMSE: 0.06-0.35 m). The vertical infiltration rate of B(a)P in the vadose zone was 0.102 m

Atrazine has become one of the most popular applied triazine herbicides in the world due to its high herbicidal efficiency and low price. With its large-dosage and long-term use on a global scale, atrazine can cause widespread and persistent contamination of soil and sediment. This review systematically evaluates the toxicological effects, environmental risks, environmental behaviors (adsorption, transport and transformation, and bioaccumulation) of atrazine, and the remediation technologies of atrazine-contaminated soil and sediment. For the adsorption behavior of atrazine on soil and sediment, the organic matter content plays an extremely important role in the adsorption process. Various models and equations such as the multi-media fugacity model and solute transport model are used to analyze the migration and transformation process of atrazine in soil and sediment. It is worth noting that certain transformation products of atrazine in the environment even have stronger toxicity and mobility than its parent. Among various remediation technologies, the combination of microbial remediation and phytoremediation for atrazine-contaminated soil and sediment has wide application prospects. Although other remediation technologies such as advanced oxidation processes (AOPs) can also efficiently remove atrazine from soil, some potential problems still need to be further clarified. Finally, some related challenges and prospects are proposed.

The high salinity of kitchen wastewater might have adverse effects on the production of short-chain fatty acids (SCFAs) in anaerobic fermentation. The effects and mechanisms of salinity on SCFA production in the anaerobic fermentation of kitchen wastewater were studied by varying the salt concentration, as follows: 0 g/L (S0), 2 g/L (S2), 6 g/L (S6), 10 g/L (S10), 15 g/L (S15), and 20 g/L (S20). Experimental results showed that hypersaline conditions (10 g NaCl/L) accelerated the release of soluble proteins at the initial stage of anaerobic fermentation. They also significantly prohibited the hydrolysis and degradation of soluble proteins and carbohydrates. Compared with low salinity tests, the SCFA concentrations under hypersaline conditions (10 g NaCl/L) only reached approximately 43% of the highest concentration on day 10, although the SCFA concentrations in all tests were very close on day 10 (14 g COD/L). High salinity delayed the production of n-butyric acid but did not change the composition of the total SCFAs. High salinity enriched Enterococcus and Bifidobacterium, the relative abundance levels of which reached 27.57% and 49.71%, respectively, before the depletion of substrate. High salinity showed a negative correlation with the relative abundance of the genera Clostridium_sensu_stricto_1, Prevotella and unclassified_f_Oscillospiraceae which are responsible for SCFA production. This study provided a theoretical basis for the fficient utilization of kitchen wastewater.

Anaerobic fermentation of corn straw with rumen microorganisms as inoculum to produce volatile fatty acids (VFAs) is important for biomass valorization. In this study, dynamic variation in bacterial and fungal community composition, carbohydrate-active enzymes (CAZymes) and key functional genes related with VFA production was explored via metagenomic sequencing. Rumen microorganisms efficiently hydrolyzed and acidified corn straw, and VFA concentration reached 8.99 g/L in 72 h. Bacterial and fungal community significantly changed, but the core genera kept stable. Low pH and VFA accumulation were the main factors affecting bacterial and fungal communities. The positive correlations between bacteria were more complex than those between fungi. Most CAZyme abundance significantly decreased after 72 h fermentation, and functional gene abundance participating in VFA generation also decreased. This study provided new insights into dynamic variation of bacteria and fungi during anaerobic ruminal fermentation in vitro, promoting the application of rumen microorganisms in practice.

In recent years, volatile fatty acid (VFA) production through anaerobic fermentation of sewage sludge, instead of methane production, has been regarded as a high-value and promising roadmap for sludge stabilization and resource recovery. This review first presents the effects of some essential factors that influence VFA production and composition. In the second part, we present an extensive analysis of conventional pretreatment and co-fermentation strategies ultimately addressed to improving VFA production and composition. Also, the effectiveness of these approaches is summarized in terms of sludge degradation, hydrolysis rate, and VFA production and composition. According to published studies, it is concluded that some pretreatments such as alkaline and thermal pretreatment are the most effective ways to enhance VFA production from sewage sludge. The possible reasons for the improvement of VFA production by different methods are also discussed. Finally, this review also highlights several current technical challenges and opportunities in VFA production with spectrum control, and further related research is proposed.

Due to complex inherent structure of lignocellulosic biomass, inefficient hydrolysis and acidification limits fermentative volatile fatty acids (VFA) production of mushroom residues. Meanwhile, the mushroom residues present insufficient nutrient with a high C/N ratio. To solve this issue, anaerobic co-fermentation of cellulose-rich Oyster champost and sewage sludge was tested to enhance the VFA production, and the effect of proportion of mixed substrate was investigated in this study. The results indicated that the sewage sludge yielded higher VFAs than the Oyster champost in single-substrate fermentative system. The maximal VFA yield of 595 mgCOD/gVSadded was achieved when the proportion of sewage sludge increased to 50% in the mixed substrate. In the co-fermentation system, the optimal C/N ratio and features of mixed substrate contributed to the enhancement in hydrolysis and acidification in terms of organic solubilization and VFA production, respectively. But the co-fermentation could not increase VFA/SCOD ratio, probably due to the existence of refractory products such as humic-like and protein-like materials. Besides, this co-fermentation system had strong buffer capacity and it was not necessary to dose chemicals to control the system pH for stable VFA production. Acetate was the dominant VFA product in co-fermentation systems. A modified-Logistic model fitted co-fermentation of sludge and Oyster champost well, and presented a faster rate and higher efficiency of VFA production.

Single pretreatment of sewage sludge, either physical, chemical or biological, has its own drawbacks in term of poor sanitization, energy intensity and high operational and capital cost. To tackle these drawbacks, combined high pressure homogenization (HPH) and free nitrous acid (FNA) pretreatment for sludge solubilization and further biodegradation in anaerobic digestion was investigated. Synergistic effect of combined HPH (40 MPa) and FNA (2.49 mg/L) pretreatment (HPH-FNA) for improving anaerobic digestion was evaluated, and its effect on archaeal and bacterial community structure was analyzed. Compared with single HPH and FNA pretreatments, HPH-FNA pretreatment efficiently solubilized wasted activated sludge (WAS), subsequently improved anaerobic digestion. Cumulative biogas production from sewage sludge pretreated with HPH-FNA was 154%, 108% and 284% more than that with single pretreatment of FNA, HPH and raw sludge, respectively. In addition, volumetric biogas production of combined pretreatment system (815 ml) was more than the sum from single pretreatment (710 ml). Methane content in biogas for raw sludge, FNA, HPH and HPH-FNA pretreated sludge was 45%, 51%, 55% and 65%, respectively. Illumina MiSeq sequencing analysis revealed that HPH-FNA pretreatment promoted bacterial growth of phyla Bacteroidetes, Firmicutes and Synergistetes and archaeal genera Methanospirillum and Methanosaeta. Overall, combined HPH-FNA pretreatment of sewage sludge, prior to anaerobic digestion, is an environmentally-friendly and potentially economic technology.

Rumen microorganisms have the ability to efficiently hydrolyze and acidify lignocellulosic biomass. The effectiveness of long-term rumen microorganism fermentation of lignocellulose in vitro for producing volatile fatty acids (VFAs) is unclear. The feasibility of long-term rumen microorganism fermentation of lignocelluose was evaluated in this study, and a stable VFA production was successfully realized for 120 d. Results showed that VFA concentration reached to 5.32-8.48 g/L during long-term fermentation. Hydrolysis efficiency of hemicellulose and cellulose reached 36.5%-52.2% and 29.4%-38.4%, respectively. A stable bacterial community was mainly composed of Prevotella, Rikenellaceae_RC9_gut_group, Ruminococcus, and Succiniclasticum. VFA accumulation led to a pH decrease, which caused the change of bacterial community structure. Functional prediction showed that the functional genes related to hydrolysis and acidogenesis of corn stover were highly expressed during long-term fermentation. The successful long-term rumen fermentation to produce VFAs is of great significance for the practical application of rumen microorganisms.

Microplastics exist widely in water environment. The microplastic distribution in sediments can better reflect the long-term microplastic pollution, especially the vertical distribution. However, the vertical microplastic distribution in sediments is diverse and unclear. This paper is the first study on vertical microplastic distribution in estuary sediment of Fuhe River, the main upstream river flowing to Baiyangdian Wetland in the northern China. The typical feature of Fuhe River is that the effluent of municipal wastewater treatment plants is its main water source. Microplastics in 15 sampling sites and different depths (0–50 cm) were examined. Results showed that the microplastic content decreased with the increase of sediment depth, and the highest content was 1049 ± 462 items/kg in the topmost sediment layer (0–5 cm). The particle size of microplastics was smaller in deeper sediment layers. The proportion of colored microplastics in deeper sediment layers was larger than that in shallower layers. Polyethylene (PE) and polypropylene (PP) were the main plastic polymer types in all sediment samples. The spatial distribution characteristics of microplastics in sediments were closely related to human activities, and the microplastic content was higher in the areas with more intense human activities. This study is helpful to understand the detailed distribution characteristics of microplastics in typical rivers in the northern China, and can provide guidance for reducing microplastic pollution.

Water shortage severely restricts vegetation restoration of mining area in the northwest China. Moderate treatment of reclaimed water is essential for improving the local ecological environment. In this study, relevant water quality standards issued by the states and research results were comprehensively considered to propose a reclaimed water quality standard suitable for vegetation restoration of mining area. The available domestic sewage and mine water was moderately treated by hybrid biological reactor system and nanofiltration membrane system, respectively. The effluent quality meet the requirement of reclaimed water quality standards in this study. This study provides theoretical support for vegetation restoration of mining area.

In order to prolong the effect of CaO2 on improvement of short-chain fatty acids (SCFAs) production in sludge anaerobic fermentation, CaO2 particles were successfully loaded onto the porous surface of steel slag pre-modified with salicylic acid-methanol (SAM-SS). The prepared CaO2/SAM-SS was then characterized and investigated for its effects on anaerobic fermentation. Experimental results revealed that, due to the slow release and reaction of CaO2/SAM-SS, SCFAs concentrations in CaO2/SAM-SS tests were significantly higher than in the control and SAM-SS tests, and high SCFAs concentration was sustained for a longer period than in the CaO2 tests. Since most bacterial indexes were reduced by CaO2/SAM-SS, more supply of "raw materials" from a better disintegration and hydrolysis, which was associated with the alkalinity and •OH radicals released from the reaction of CaO2 with H2O, contribute to the higher SCFAs yields. This study provides a new approach towards a higher and longer SCFAs harvesting.

A lab-scale two-stage Anoxic/Oxic with MBR (AO/AO-MBR) system was operated for 81 days for leachate treatment with different reflux ratio (R). The best system performances were observed with a R value of 150%, and the average removal efficiencies of chemical oxygen demand, ammonia and total nitrogen were 85.6%, 99.1%, and 77.6%, respectively. The microbial community were monitored and evaluated using high-throughput sequencing. Proteobacteria were dominant in all process. Phylogenetic trees were described at species level, genus Thiopseudomonas, Amaricoccus, Nitrosomonas and Nitrobacter played significant roles in nitrogen removal. Co-occurrence analyzing top 20 genera showed that Nitrosomonas-Nitrobacter presented perfect positive relationship, as well as Paracoccus-Brevundimonas and Pusillimonas-Halobacteriovorax.

Photosynthetic bacteria (PSB)-bioconversion is a novel method for wastewater treatment and resource recovery. But fundamental knowledge on effective substrate range, cell proliferation and substrate degradation kinetics are lacking. This paper studied the efficient range of carbon source (in terms of COD) and the fundamental kinetics of COD degradation and cell proliferation of this technology. Results showed that the efficient concentration range of carbon source was 500–40,000 mg·L−1 COD for PSB, which covers most organic wastewaters. Then the substrate degradation and cell proliferation kinetics were studied using Michaelis-Menten equation and Monod equation. The Vmax, Km, μmax and Ks was 4.80 d−1, 7382 mg·L−1, 1.23 d−1 and 7714 mg·L−1 under light-anaerobic condition, and they were 4.27 d−1, 4813 mg·L−1, 0.59 d−1 and 21,295 mg·L−1 under dark-aerobic condition; which fell in the range of conventional biological wastewater technologies. This benchmark study lays foundation for further study and scale-up of this novel technology.

Two-stage anoxic/oxic combined membrane bioreactor (A/O-A/O-MBR) process was used to treat leachate generated from Shenyang Laohuchong landfill, and the effect of hydraulic retention time (HRT) was studied. A long HRT of 9 d and a short HRT of 5 d showed negative effect on the stability of process, resulting in a higher organic concentration of effluent than that with a HRT of 7 d, while the highest removal of chemical oxygen demand (COD), ammonia (NH4+-N) and total nitrogen (TN) were achieved with a HRT of 7 d, which was 82.4%, 99.1% and 75.3% respectively. The analysis of microbial communities by high-throughput sequencing showed that phyla Proteobacteria and Bacteroidetes were the dominant bacteria, which accounted for 36.63–42.39%, 29.21–38.66%, respectively. For genus classification, the most representative of Ferruginibacter, unclassified-Saprospiraceae and Nitrosomonas accounted for 20.76–35.11% totally. The other communities, including Nitrobacter, Planctomyces, Rhodobacteraceae and Nitrospirae, were also developed for organic degradation and denitrification.

Wetlands play an important role in sustaining ecosystems on the earth, which regulate water resources, adjust local climate and produce food for human beings, etc. However, wetlands are facing huge challenges due to human activities and other natural evolution, such as area shrinkage, function weakening and biodiversity decrease, and so on, therefore, some wetlands need to be urgently restored. In this study, the main technology components of close-to-natural restoration of wetlands were summarized. The ecological water requirement and water resource allocation can be optimized for the water balance between social, economy and ecology, which is a key prerequisite for maintaining wetland ecosystem. The pollution of wetland sediments and soils can be assessed by various indicators to provide the scientific basis for natural restoration of wetland base, and suitable strategies should be taken according to the actual conditions of wetland bases. The hydrological connectivity in wetlands and with related water system can be numerically simulated to make the optimal plan for improvement of hydrological connectivity. The ecological restoration of wetlands with the synergetic function of plants, animals and microorganisms was summarized, to improve the quality of wetland water environment and maintain the ecosystem stability. Based on the wetland close-to-natural restoration strategies, a brief ecological restoration plan for a typical wetland, Zaozhadian Wetland, near Xiong'an New Area in the north China was proposed from water resource guarantee, base pollution management, hydrological connectivity improvement and biological restoration. The close-to-natural restoration shows more effective, sustainable and long-lasting and thus a practical prospect.

In this study, a laboratory-scale two-stage anoxic/oxic (A/O) combined membrane bioreactor (MBR) was operated for 113d for the treatment of landfill leachate. The average removal of chemical oxygen demand (COD), ammonia (NH4+-N) and total nitrogen (TN) achieved 80.60%, 99.04% and 74.87%, respectively. A mass balance evaluation suggested that the removal of COD, NH4+-N and TN occurred mainly in the second A/O process, and the total removal capacity of COD, NH4+-N and TN were 125.60g/d, 24.35g/d and 22.40g/d, respectively. High-throughput sequencing analysis indicated that the Proteobacteria (44.57-50.36%), Bacteroidetes (22.09-27.25%), Planctomycetes (6.94-8.47%), Firmicutes (3.31-4.53%) and Chloroflexi (3.13-4.80%) were the dominated phyla in the bacterial community during the operation period. At the genus level, Nitrosomonas, Nitrobacter, Planctomyces, Saprospiraceae and Pseudomonas showed relatively high abundance, which played an important role in the removal of pollutants.

This work studied the effect of total solid (TS) of sewage sludge on VFA production and composition in anaerobic fermentation. Results revealed that VFA concentration reached the highest of 10.16 g/L and the ratio of acetic acid, propionic acid and n-butyric acid was 5:2:2 with the 8% TS sewage sludge. In subsequent chain elongation with sludge fermentation liquid, n-caproic acid concentration reached 43.45 mmol/L. The microbial community analysis indicated that relative abundance of Clostridium_sensu_stricto_12 for n-caproic acid production was high (52.41%). The chain elongation with sludge fermentation liquid had more pathways to produce n-caproic acid, and the chain elongation reactions were thermodynamically possible. The mixed VFAs and high concentration of n-butyric acid benefitted n-caproic acid production. Carbon balance revealed that the VFA composition of sludge fermentation liquid was beneficial to the chain elongation. This study will contribute to wasted sludge minimization and high-value material production.

White rot fungi using P. sajor-caju and T. versicolor was examined to pretreat raw champost (lignin-rich) and oyster champost (cellulose-rich) for enhancement of fermentative volatile fatty acid (VFA) production. Results showed that the efficiency of pretreatment and VFA production was influenced by the fungal strains and substrates. P. sajor-caju pretreatment showed preferential lignin degradation on raw champost and obtained the maximum VFA yield (203 ± 9 mg COD/g VSadded), which increased by 60% and 74% compared to that of control and unpretreated champost, respectively. For cellulose-rich oyster champost, however, fungal pretreatment decreased VFA yield compared to unpretreated champost. Further mechanisms analysis demonstrated the two strains grow and secreted ligninolytic enzymes, which substantially influenced the characteristics of two champosts such as cellulose/lignin ratio and morphology in different extents. P. sajor-caju was highly efficient to lignin-rich champost on selectively degrading lignin and further enhancing digestibility such as VFA production.

A facultative bacterium Microbacterium sp. (QQ strain) was found significantly mitigated membrane biofouling and also increased methane production. It was found genera Nitrospira, norank-c-Bacterodetes vadinHA17, Trichococcus and family Anaerolineaceae were likely responsible for membrane biofouling. The presence of QQ strain increased the total abundance of fermentative and acetogenic genera by 0.61% and 379.61%, respectively, but had a minor effect on the abundance of methanogens. The increased methane production was likely due to the strengthened methanogenic activity and more available substrates. Homo-acetogenic Treponema was enriched (9.01%) in the presence of QQ strain suggesting that apart from hydrogenotrophic methanogenic pathway, extra CH4 could be also produced from the additional acetate synthesized via homo-acetogenic pathway. This study advances knowledge about the effects of QQ strain on microbial communities, microbiota biofouling behavior and anaerobic fermentation process in AnMBRs. Nanyang Technological University The authors acknowledge the financial support of Advanced Environmental Biotechnology Centre, Nanyang Environment and Water Research Institute (NEWRI), Nanyang Technological University. And the authors were grateful to acknowledge the scholarship support from China Scholarship Council (CSC 201706130032).

This study aimed to evaluate the effects and explore the mechanisms of polyethylene (PE), polyurethane sponge (PUS), and granule activated carbon (GAC) on short-chain fatty acids (SCFAs) production from sludge anaerobic fermentation. Results showed that no matter the biocarrier type, addition of biocarriers increased the diversity of SCFAs. In contrast with GAC, addition of PE and PUS considerably facilitated the accumulation of the total SCFAs. Suspended PE and PUS might have stronger frictions with sludge particles which resulted in a better sludge disintegration. Other factors that contributed to the enhancement of PE and PUS include higher hydrolytic and acidogenic enzymes activities, lower methanogenic enzyme activity, more Firmicutes and less Proteobacteria. Consistent with enzymatic and microbial results, the PE and the PUS tests also showed greater abundance in all metabolic functions predicted with PICRUSt. This study provides a novel strategy for sludge anaerobic fermentation by using traditional wastewater biocarriers.

Nitrogen removal from wastewater is a worldwide environmental problem. Photosynthetic bacteria (PSB) were reported to have a great potential in treating varieties of nitrogen-contaminated wastewater. However, their nitrogen metabolic mechanism is still unclear, which was further explored in this work. The results showed that PSB can efficiently utilize NH4+-N, NO3−-N and NO2−-N. Over 90% nitrogen removal efficiencies were obtained under suitable condition. 35 ~ 51% of removed nitrogen was transformed to N2 and N2O. In addition, basically no mutual transformation occurred between NH4+-N, NO3−-N and NO2−-N in PSB, which is different from other biological technologies. Combining with the analysis of functional gene groups, it indicated that there might be a new direct nitrogen transformation pathway, i.e. NH4+ might be directly oxidized to N2/N2O in nitrogen metabolism of PSB, which breaks the limitations of existing technologies, and proposed a new understanding of nitrogen metabolism in PSB.

This work studied preparation of rice husk-based solid acid and its application for efficient hydrolysis and saccharification of corncob. Rice husk-based solid acid (RH-SO3H) was prepared by one-step carbonization and sulfonation method. Analysis demonstrated that RH-SO3H exhibited aromatic carbon sheets structure bearing –SO3H, –COOH and –OH groups. The RH-SO3H was then used to hydrolyse and saccharify corncob. Compared with solid acids made from activated carbon and microcrystalline cellulose, the RH-SO3H showed the highest catalytic efficiency with the maximum reducing sugar yield of 486.53 mg/g and xylose of 253.03 mg/g, which was twice and five times higher than that of control, respectively. Its high efficiency was attributed to –OH and –COOH groups functioned synergistically with –SO3H to hydrolyse lignocellulose by adsorbing β-1,4-glucan in corncob. This study provides a green and effective utilization technology of lignocellulosic biomass.

High pressure homogenization (HPH) pretreatment can effectively enhance anaerobic sludge digestion. In order to understand the corresponding mechanisms, different homogenization pressures were applied on sewage sludge, and solid and liquid fractions were separately digested to clarify contribution of solid and liquid fractions to biogas production. Results showed that the methane was mainly produced from solid fraction, and methane yield was increased with the increase of pretreatment pressure. The biogas and methane production from sludge (digested without solid–liquid separation) was 17% and 45% higher than the sum of that from solid and liquid fractions (digested separately) under a pressure of 40 MPa, respectively. This indicated that the sludge liquid fraction synergistically improved the biodegradation of sludge solids. The improvement of anaerobic digestion was attributed to organic release by sludge disintegration, sludge disruption and further increase of particle surface area. The methane production was linear with effectiveness of HPH pretreatment.

When dual-chamber microbial fuel cell (MFC) is used to detect biochemical oxygen demand (BOD), dissolved oxygen is traditionally used as cathodic electron acceptor. The detection limit of this MFC-based BOD biosensor is usually lower than 200 mg/L. In this paper, the startup of MFC-based BOD biosensor was researched and the external resistor of MFC was optimized. Results showed that the MFC started up with the dissolved oxygen as cathodic electron acceptor within 10 d, and the external resistor was optimized as 500 Ω to ensure the maximum output power of MFC. Dissolved oxygen and potassium permanganate (KMnO4) were used as cathodic electron acceptor to run MFC for detection of wastewater BOD, and the performances of two kinds of BOD biosensors were compared. The MFC-based BOD biosensor using KMnO4 (10 mmol/L) as cathodic electron acceptor exhibited an excellent performance, compared with that using dissolved oxygen. The upper limit of BOD detection was greatly broadened to 500 mg/L, the response time was shortened by 50% for artificial wastewater with a BOD of 100 mg/L, and the relative error of BOD detection was reduced to less than 10%. The MFC-based BOD biosensor using KMnO4 as cathodic electron acceptor showed a better linear relationship (R2 > 0.992) between the electric charge and BOD concentration within a BOD range of 25–500 mg/L. The MFC-based BOD biosensor using the KMnO4 as cathodic electron acceptor is promising with a better application prospect.

Sonication is an effective way for sludge disintegration, which can significantly improve the efficiency of anaerobic digestion to reduce and recycle use of sludge. But high energy consumption limits the wide application of sonication. In order to improve ultrasonic sludge disintegration efficiency and reduce energy consumption, aeration was introduced. Results showed that sludge disintegration efficiency was improved significantly by combining aeration with ultrasound. The aeration flow rate, gas bubble size, ultrasonic density and aeration timing had impacts on sludge disintegration efficiency. Aeration that used in later stage of ultrasonic irradiation with low aeration flow rate, small gas bubbles significantly improved ultrasonic disintegration sludge efficiency. At the optimal conditions of 0.4 W/mL ultrasonic irradiation density, 30 mL/min of aeration flow rate, 5 min of aeration in later stage and small gas bubbles, ultrasonic sludge disintegration efficiency was increased by 45% and one third of ultrasonic energy was saved. This approach will greatly benefit the application of ultrasonic sludge disintegration and strongly promote the treatment and recycle of wastewater sludge.

To improve the reducing sugar production from catalpa sawdust, thermo-chemical pretreatments were examined and the chemicals used including NaOH, Ca(OH)2, H2SO4, and HCl. The hemicellulose solubilization and cellulose crystallinity index (CrI) were significantly increased after thermo-alkaline pretreatments, and the thermo-Ca(OH)2 pretreatment showed the best improvement for reducing sugar production comparing to other three pretreatments. The conditions of thermo-Ca(OH)2 pretreatment and enzymatic hydrolysis were systematically optimized. Under the optimal conditions, the reducing sugar yield increased by 1185.7% comparing to the control. This study indicates that the thermo-Ca(OH)2 pretreatment is ideal for the saccharification of catalpa sawdust and that catalpa sawdust is a promising raw material for biofuel.

A two-stage anoxic/oxic combined membrane bioreactor (A/O-A/O-MBR) was operated for 81 d to treat landfill leachate under different reflux ratios (R). The best performance was found under R = 150%, where the chemical oxygen demand (COD), ammonium (NH4+-N) and total nitrogen (TN) removal was 85.6%, 99.3%, and 80.7%, respectively. Particularly, the highest pollutant removal was achieved in the second-stage A/O, where the COD and TN removal capacity was 78.88 and 11.74 g/d, respectively. Meantime, DOM removal was 83.9%, where the removal of aromatic protein substances I and II, fulvic acids-like compounds, soluble microbial products and humic acids-like compounds was 93.4%, 86.4%, 72.0%, 86.6% and 59.4%, respectively. The gene functions of microbial community in the process showed that amoA, hao, nirK and nosZ, etc. were the core genes for nitrification and denitrification. The carbon source for denitrification might come from the conversion of refractory organic matters in landfill leachate.

Quorum quenching (QQ) is an effective method to control membrane biofouling in aerobic membrane bioreactors (AeMBRs). However, it is not clear if QQ is feasible in an anaerobic membrane bioreactor (AnMBR). In this study, Microbacterium. sp that has QQ capability was embedded in alginate beads, known as QQ beads (QQB), and applied in a lab-scale AnMBR to investigate their potential in fouling control. With the addition of QQB, the operating period of AnMBR-QQB reactor was prolonged by about 8–10 times at constant flux operation before reaching the pre-set maximum transmembrane pressure (TMP). The concentration of Acyl-homoserine lactones (AHLs) in the bulk liquid was significantly higher during the ‘TMP jump’ period compared to QQB and control phases, while AHLs in the membrane foulants were remarkably lower in QQB phase compared to control phase. Furthermore, a much lower level of soluble microbial production (SMP) was observed in QQB phases. Extracellular polymeric substance (EPS), protein in particular, was reduced by 39.73–80.58% in the cake layer of the membrane from QQB phases. Significant changes of organic functional groups were observed in cake layer from QQB membrane as compared with that from control membrane. At the end of operation, bio-polymer (BP), building blocks (BB) and low molecular weight (LMW) organic matters increased in the foulant from control phases but such increase was not observed in QQB phase. After long-term operation, revival of QQB is required due to the declined activity for AHLs degradation. Accepted version The authors were grateful to acknowledge the scholarship support from China Scholarship Council (CSC 201706130032).

Rapid development of livestock industry produces large amount of livestock manure rich in nutrients, organic matters, antibiotics, and heavy metals, thus imposes great harms to human and environment, if the manure is not suitably treated. Biological removal and recovery of nutrients from manure as agriculture fertilizer is attractive due to low cost and simple operation. This review offers an overview of recent development in biological nutrient removal and recovery from livestock manure. Livestock manure is divided into solid manure and liquid manure. Composting and anaerobic digestion of solid manure are fully discussed and important parameters are investigated. Then various processes of nutrient removal and recovery from liquid manure are summarized. Brief economic sustainability and eco-environmental effects are carried out. Finally, current challenges and future prospects in this field are analyzed.

This work aimed to study a pilot-scale sulfur-limestone autotrophic denitrification biofilter (SLADB) to remove nitrogen from municipal tailwater. The capacity of nitrogen removal and spatial distribution of microbial community at low temperature condition were analyzed. Low temperature inhibits nitrogen removal; while prolonging hydraulic retention time (HRT) increased nitrogen removal efficiency. TN and NO3−-N removal efficiency reached 81.1% and 85.3%, respectively, with HRT of 18 h at the temperature ranging from 6.4 to 9.8 °C. Proteobacteria and Chloroflexi were two dominant phyla. Along the reactor, class β-proteobacteria and e-proteobacteria decreased, while γ-proteobacteria and Acidobacteria increased. For genus classification, Thiobacillus, Sulfurimonas, and Ferritrophicum which promote sulfur autotrophic denitrification, decreased significantly. While Anaerolineae promoting heterotrophic denitrification increased obviously. Sphingobacteriia coexisted in SLADB and were beneficial to nitrogen removal. Microbial community spatial distribution patterns were related to nitrogen removal. This study achieved reliable pilot-scale application of SLADB under low temperature for municipal tailwater.

Ultrasound-calcium hydroxide (US-Ca(OH)2) pretreatment effectively enhanced volatile fatty acid (VFA) production from lignocellulosic biomass. In this paper, solid and liquid fraction of pretreated grass clipping was for the first time separately fermented in order to improve organic recovery from liquid fraction and reduce inhibition due to alkaline pretreatment. The total VFA yield and VS removal reached 515 mg/g TS and 59.7% after solid-liquid separation, exhibiting an increase of 116.7% and 91.9% comparing to that of mixture sample. The dominate components of VFAs are acetic and propionate acid, accounting for 80–90% of total VFAs. Kinetic analysis showed that the highest maximum VFA production rate of 690 mg/L·d and the highest cumulative VFA production potential of 3299 mg/L were achieved in the fermentation of solid fraction. Microbial analysis showed that the dominate genera for VFA production were Halocella and Ruminiclostridium, both with a relative abundance of 20.1% in fermentation of solid fraction.

In order to investigate the effect of operational mode, temperature, and planting on the performance of tidal flow constructed wetland (TFCW), four lab-scale units were operated in parallel experiments. They were operated in three cycles d−1 tidal flow mode with planting (3TF+P), three cycles d−1 tidal flow mode without planting (3TF), one cycle d−1 tidal flow mode with planting (1TF+P), and continuous flow mode with planting (CF+P), respectively. The results demonstrated that the multi-cycle tidal flow operational mode promoted the biofilm growth and pollutant removal with the low relative clogging coefficient (RCC) of 21.42% during the whole experimental period. The average COD, -N, and -P area removal rate in 3TF+P reached 18.00, 2.38, and 0.24 g m−2 d−1, respectively. Meanwhile, the influence of low temperature on the performance of TFCW in the winter was partially compensated by the multi-cycle operational mode, which made the performance of TFCW more stable than that of other systems under t...

A novel joint method of bioleaching with Fenton oxidation was applied to condition sewage sludge. The specific resistance to filtration (SRF) and moisture of sludge cake (MSC) were adopted to evaluate the improvement of sludge dewaterability. After 2-day bioleaching, the sludge pH dropped to about 2.5 which satisfied the acidic condition for Fenton oxidation. Meanwhile, the SRF declined from 6.45×10(10) to 2.07×10(10) s2/g, and MSC decreased from 91.42% to 87.66%. The bioleached sludge was further conditioned with Fenton oxidation. From an economical point of view, the optimal dosages of H2O2 and Fe2+ were 0.12 and 0.036 mol/L, respectively, and the optimal reaction time was 60 min. Under optimal conditions, SRF, volatile solids reduction, and MSC were 3.43×10(8) s2/g, 36.93%, and 79.58%, respectively. The stability and settleability of sewage sludge were both improved significantly. Besides, the results indicated that bioleaching-Fenton oxidation was more efficient in dewatering the sewage sludge than traditional Fenton oxidation. The sludge conditioning mechanisms by bioleaching-Fenton oxidation might mainly include the flocculation effects and the releases of extracellular polymeric substances-bound water and intercellular water.

Rumen fluid, formed in rumen of ruminants, includes a complex microbial population of bacteria, protozoa, fungi and archaea, and has high ability to degrade lignocellulosic biomass. In this study, rumen fluid was used to ferment grass clipping for enhancing the hydrolysis and acidification of organic matters. Results showed that strict anaerobic condition, higher grass clipping content and smaller particle size of grass clipping were beneficial to the hydrolysis and acidification of organics. The increase of SCOD and total VFA concentration respectively reached 24.9 and 10.2 g/L with a suitable grass clipping content of 5%, a particle size

In this study, coagulation process was applied to treat the effluent of pharmaceutical wastewater using polymeric ferric sulfate as a coagulant. Three-dimensional excitation-emission matrix fluorescence spectroscopy coupled with parallel factor analysis (EEMs-PARAFAC) was applied to investigate the fluorescent characteristics of dissolved organic matter (DOM) from pharmaceutical wastewater and the reduction of contaminant and fluorescent variations in the coagulation process. It shows that coagulation was effective to remove contaminants in the effluent of pharmaceutical wastewater, and the optimum coagulate dosage was 0.5 g/L, where the removal efficiency of total organic matter (TOC), UV254, turbidity and NH4+-N were achieved 44.2%, 43.3%, 87.0% and 10.27%, respectively. Five fluorescence components were identified by EEMs-PARAFAC, including one fulvic-like component (C1), one xenobiotic-like component (C2), two humic-like components (C3 and C5) and one protein-like component (C4); DOM of pharmaceutical wastewater was dominated by C3, C4 and C2. Under the optimum coagulation condition, the decreasing order of removal efficiencies was C5 (49.92%), C3 (40.95%), C4 (10.58%), C2 (9.68%) and C1 (5.05%). Principal component analysis (PCA) showed C3, C5 had remarkable correlations with TOC and UV254, suggesting that C3 and C5 may be a good indicator for the reduction of TOC and UV254. PCA indicated that the EEM-PARAFAC could be successfully applied to the evaluation of the coagulation efficiency for pharmaceutical wastewater treatment.

Refractory membrane concentrate generated from the membrane bioreactor (MBR) process remains a big challenge. With high pollution loads, high salinity and low biodegradability, membrane concentrates are difficult to be treated by conventional biological treatments. In this work, photosynthetic bacteria (PSB) were employed to handle this problem. The results showed that PSB could simultaneously remove COD, NH3-N, NO3--N, salinity and chroma from the membrane concentrate. The removal efficiency of COD, NH3-N, NO3--N, salinity and chroma reached 24.0%, 78.0%, 81.6%, 57.0% and 60.0% respectively. Dark-aerobic condition was more beneficial for pollutants removal. The tolerance mechanism of PSB in treating membrane concentrate was then analyzed. The contents of protein and carotenoid in PSB increased by 38.7% and 20.7% due to the defense stress effects. The content of bacteriochlorin decreased by 42.9% while the content of coenzyme Q10 was stable at 8.4-8.8%.

Different conductive materials have been employed to stimulate direct interspecies electron transfer (DIET) during methanogenesis, but few studies have been concerned with the interaction between conductive materials and extracellular polymeric substances (EPS) such as the effect on sludge aggregation and redox activity of EPS. This study aims to systematically investigate the role of red mud with 45.46 wt% hematite on methanogenesis during the anaerobic digestion of waste activated sludge. The results showed that the multivalent cations from hematite effectively promoted the formation of large and compact aggregates, which might contribute to the rapid direct electron exchange during the DIET process. Meanwhile, more redox-active mediators including c-type cytochromes (c-Cyts) and humic substances, particularly in tight-bound EPS (TB-EPS), and more redox-active metals such as Fe introduced by red mud could take part in the interspecies electron transfer process between syntrophic bacteria and methanogenic archaea, which also promoted methane production (35.52 ± 2.64% increase compared with the control). This study provided initial scientific evidence to comprehensively assess the role of conductive materials during methanogenesis, with important implications for the biogeochemical redox processes of conductive minerals in natural and engineered environments.

The rumen digested residue of rice straw contains high residual carbohydrates, which makes it a potential cellulosic ethanol feedstock. This study evaluated the feasibility and effectiveness of applying microwave assisted alkali (MAP), ultrasound assisted alkali (UAP), and ball milling pretreatment (BMP) to enhance ethanol production from two digested residues (2.5%-DR and 10%-DR) after rumen fluid digestion of rice straw at 2.5% and 10.0% solid content. Results revealed that 2.5%-DR and 10%-DR had a cellulose content of 36.4% and 41.7%, respectively. MAP and UAP improved enzymatic hydrolysis of digested residue by removing the lignin and hemicellulose, while BMP by decreasing the particle size and crystallinity. BMP was concluded as the suitable pretreatment, resulting in an ethanol yield of 116.65 and 147.42mgg-1 for 2.5%-DR and 10%-DR, respectively. The integrated system including BMP for digested residue at 2.5% solid content achieved a maximum energy output of 7010kJkg-1.

To improve anaerobic digestion efficiency, combination pretreatment of alkaline and high pressure homogenization was applied to pretreat sewage sludge. Effect of alkaline dosage on anaerobic sludge digestion was investigated in detail. SCOD of sludge supernatant significantly increased with the alkaline dosage increase after the combined pretreatment because of sludge disintegration. Organics were significantly degraded after the anaerobic digestion, and the maximal SCOD, TCOD and VS removal was 73.5%, 61.3% and 43.5%, respectively. Cumulative biogas production, methane content in biogas and biogas production rate obviously increased with the alkaline dosage increase. Considering both the biogas production and alkaline dosage, the optimal alkaline dosage was selected as 0.04 mol/L. Relationships between biogas production and sludge disintegration showed that the accumulative biogas was mainly enhanced by the sludge disintegration. The methane yield linearly increased with the DDCOD increase as Methane yield (ml/gVS)=4.66 DDCOD-9.69.

To improve the biogas production from corn stovers, a new bionic reactor was designed and constructed. The bionic reactor simulated the rumen digestion of ruminants. The liquid was separated from corn stovers and refluxed into corn stovers again, which simulated the undigested particles separated from completely digested materials and fed back again for further degradation in ruminant stomach. Results showed that the bionic reactor was effective for anaerobic digestion of corn stovers. The liquid amount and its reflux showed an obvious positive correlation with biogas production. The highest biogas production rate was 21.6 ml/gVS-added d, and the total cumulative biogas production was 256.5 ml/gVS-added. The methane content in biogas ranged from 52.2% to 63.3%. The degradation of corn stovers were greatly enhanced through simulating the animal digestion mechanisms in this bionic reactor.

In-situ remediation of heavy metal-contaminated farmland mainly focuses on acidic soil, however, weak-alkaline farmland widely exists in north China. Meanwhile, fertilization is usually ignored, but it may influence remediation efficiency as well as grain production. In this paper, field experiments were carried out to investigate in-situ simultaneous remediation and fertilization of Cd-contaminated weak-alkaline soil by microbial agent mixed with fulvic acid (MFA), wheat straw biochar, sepiolite and their mixture. Results showed that addition of these conditioners decreased the soil available Cd by 39.86%–71.33% and the wheat Cd by 41.94%–87.10%. The decrease order of soil available Cd followed sepiolite > mixture > biochar > MFA, while the decrease order of wheat Cd was mixture > sepiolite > biochar > MFA. With addition of mixture, the wheat Cd reduced to 0.08 mg/kg, lower than the Cd limit of 0.1 mg/kg in Contaminant Limit in Food of National Food Safety Standards (GB2762-2017), and the highest wheat yield reached 7590 kg/hm2. The MFA had significant effects on improvement of soil organic matters, nutrients and rhizosphere microbes; the biochar was prominent in improving soil organic matters, inhibiting wheat Cd and soil available Cd; the sepiolite had obvious advantages in reducing wheat Cd and soil available Cd; and the mixture had a more balanced effect on soil remediation and fertilization. Correlation study showed that soil available Cd significantly affected the uptake of Cd by wheat, and wheat yield was significantly positively correlated with soil organic matters, available N. Therefore, reducing soil available Cd, increasing soil organic matters and nutrients are the keys to simultaneous remediation and fertilization of Cd-contaminated weak-alkaline soil for wheat production.

Feasibility of bioleaching combining with Fenton-like reaction to remove heavy metals from sewage sludge was investigated. After 5-day bioleaching, the sludge pH decreased from 6.95 to 2.50, which satisfied the acidic conditions for Fenton-like reaction. Meanwhile, more than 50% of sludge-borne heavy metals were dissolved except for Pb. The bioleached sludge was further oxidized with Fenton-like reaction, with an optimal H2O2 dosage of 5 g/L, the Cu, Zn, Pb and Cd removal reached up to 75.3%, 72.6%, 34.5% and 65.4%, respectively, and the residual content of heavy metals in treated sludge meets the requirement of Disposal of Sludge from Municipal Wastewater Treatment Plant - Control Standards for Agricultural Use (CJ/T 309-2009) of China for A grade sludge. Bioleaching combined with Fenton-like reaction was the most effective method for heavy metal removal, compared with 15-day bioleaching and inorganic acid leaching with 10% H2SO4, 10% HCl and 10% HNO3.

The effect of high-pressure homogenization (HPH) treatment on characteristics of dissolved organic matters (DOM) in sewage sludge was investigated. Soluble chemical oxygen demand (SCOD), dissolved organic carbon (DOC), protein and polysaccharide concentration in sludge supernatant significantly increased after HPH treatment. Fourier-transform infrared (FTIR) spectra showed that the main components in the DOM for raw sludge were protein and polysaccharide, while for the treated sludge were protein, polysaccharide and lipid. The spectra of fluorescence excitation-emission matrix (EEM) for DOM showed two protein-like peaks at the excitation/emission wavelengths (Ex/Em) of 225/330–340 nm and 275/310–335 nm. A single broad shoulder representing substances with aromatic structure in range 245–270 nm was found in ultraviolet (UV) spectra of the DOM for the treated sludge. Homogenization pressure and homogenization cycle number affected the content of aromatic carbon per unit DOC. The maximum BOD5/SCOD ratio of 0.48 was achieved at 60 MPa with a single homogenization cycle.

Catalpa sawdust, a promising biofuel production biomass, was pretreated by microwave-water, -NaOH, and -Ca(OH)2 to enhance enzymatic digestibility. After 48h enzymatic hydrolysis, microwave-Ca(OH)2 pretreated sample showed the highest reducing sugar yield. The content of hemicellulose and lignin in catalpa sawdust decreased after microwave-alkali pretreatment. SEM observation showed that the catalpa sawdust surface with microwave-Ca(OH)2 pretreatment suffered the most serious erosion. Crystallinity index of catalpa sawdust increased after all three kinds of pretreatment. The optimum conditions of microwave-Ca(OH)2 pretreatment were particle size of 40mesh, Ca(OH)2 dosage of 2.25% (w/v), microwave power of 400W, pretreatment time of 6min, enzyme loading of 175FPU/g, and hydrolysis time of 96h, and the reducing sugar yield of microwave-Ca(OH)2 pretreated catalpa sawdust reached 402.73mg/g, which increased by 682.15% compared with that of raw catalpa sawdust. The catalpa sawdust with microwave-Ca(OH)2 pretreatment is promising for biofuel production with great potential.

High-pressure homogenization (HPH) technology was applied as a pretreatment to disintegrate sewage sludge. The effects of homogenization pressure, homogenization cycle number, and total solid content on sludge disintegration were investigated. The sludge disintegration degree (DD(COD)), protein concentration, and polysaccharide concentration increased with the increase of homogenization pressure and homogenization cycle number, and decreased with the increase of sludge total solid (TS) content. The maximum DD(COD) of 43.94% was achieved at 80 MPa with four homogenization cycles for a 9.58 g/L TS sludge sample. A HPH sludge disintegration model of DD(COD) = kNaPb was established by multivariable linear regression to quantify the effects of homogenization parameters. The homogenization cycle exponent a and homogenization pressure exponent b were 0.4763 and 0.7324 respectively, showing that the effect of homogenization pressure (P) was more significant than that of homogenization cycle number (N). The value of the rate constant k decreased with the increase of sludge total solid content. The specific energy consumption increased with the increment of sludge disintegration efficiency. Lower specific energy consumption was required for higher total solid content sludge.