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Biochar-assisted anaerobic digestion (AD) remains constrained due to the inefficient decomposition of complex organics, even with the direct interspecies electron transfer (DIET) pathway. The coupling of electrochemistry with the anaerobic biological treatment could shorten lengthy retention time in co-digestion by improving electron transfer rates and inducing functional microbial acclimation. Thus, this work investigated the potential of improving the performance of AD by coupling low-magnitude electric fields with biochar derived from the anaerobically digested biogas residue. Different voltages (0.3, 0.6, and 0.9 V) were applied at various stages to assess the impact on biochar-assisted AD. The results indicate that an external voltage of 0.3 V, coupled with 5 g/L of biochar, elevates CH 4 yield by 45.5% compared to biogas residue biochar alone, and the coupled approach increased biogas production by up to 143% within 10 days. This finding may be partly explained by the enhanced utilization of substrates and the increased amounts of specific methanogens such as Methanobacterium and Methanosarcina . The abundance of the former increased from 4.0 to 11.3%, which enhances the DIET between microorganisms. Furthermore, the coupling method shows better potential for enhancing AD compared to preparing iron-based biochar, and these results present potential avenues for its broader applications., Competing Interests: The authors declare there is no conflict., (© 2024 The Authors This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (CC BY-NC-ND 4.0), which permits copying and redistribution for non-commercial purposes with no derivatives, provided the original work is properly cited (http://creativecommons.org/licenses/by-nc-nd/4.0/).)

Effective separation of volatile fatty acids (VFAs), ammonia (NH 4 + -N) and reactive phosphorous (RP) generated from anaerobic fermentation liquid is critically important for efficient resource recovery. Flow-electrode capacitive deionization (FCDI) is proven to be capable of efficient removal of ions, environmentally friendly and cost-effective in operation. The performances of FCDI system in the separation of NH 4 + -N, RP, and acetate and mechanism of pHs and activated carbon on their performances were investigated. Results showed that a pH of 5.0 promoted the removal of NH 4 + -N (53.1 %) and RP (39.5 %), and 72.0 % of acetate was retained in the solution, which revealed that removal of NH 4 + -N and RP, and retention of acetate were evidently affected by speciation of ions. Furthermore, the recovery of NH 4 + -N and RP was undermined by the adsorption of ions on activated carbon. This study provides a novel insight of ion selective mechanism during the operation of the FCDI system., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Fulvic acids (FAs) belong to inert organic matters in sewage sludge and their influences are often overlooked during convectional anaerobic digestion (AD). Currently, thermal hydrolysis (TH) has been widely applied on sludge pretreatment before AD processes, which makes FAs undergo drastic evolutions and aggressive to sludge AD. Results in the present study indicated that FAs concentration in the liquid was elevated by over incredible 150 folds during sludge TH, from 3.4 mg/L in raw sludge to 590.0 mg/L in hydrolyzed sludge at 180 °C. Moreover, during sludge TH, the chemical structures of FAs, including aromatic condensation degree, elemental composition and functional group, also underwent significant changes, which enhanced FAs electron transfer capability, reduced their biodegradability and promoted their roles on sludge AD. Furthermore, fortunately, the evolutions of FAs were favorable to sludge AD in general. Methane production could be promoted by about 20% under FAs concentration of 0.6 g/L, and the FAs extracted from hydrolyzed sludge presented higher promotion performances than that of the raw FAs, in which 180 °C FAs were particularly conspicuous. Furthermore, FAs evolutions would present differential influences on each phase of sludge AD, promotional to acidogenesis and methanogenesis but inhibitory to hydrolysis. Pearson correlation analysis indicated FAs influences on sludge AD, particularly the hydrolysis phase, were not only related to their concentration, but also chemical structure. The findings of this study demonstrated that FAs influences should not be negligible anymore during sludge AD with TH pretreatment. Meanwhile, since FAs promotion on sludge AD was closely related to their concentration and chemical structure, it would be significant to take FAs evolutions as auxiliary indexes for the regulations of sludge TH., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Medium chain fatty acids (MCFAs) production from excess sludge have recently received great research interest due to higher energy densities, easy-separation capability and high economic benefits. Here, the addition of chain elongation (CE) enrichments with ethanol as electron donor was used to enhance caproate production from one-stage sludge fermentation. Compared with 0.20 g/L of controls, caproate production reached 9.00 g/L by supplementing CE enrichments with ethanol/acetate ratio of 3:1 after 7 days of acidification of organic matter in pretreated sludge fermentation. Clostridium_sensu_stricto_12, that refers to CE, was enriched in the first and second transfer of the sludge microbial consortium. Maintaining the stability of the microbial consortium would be the key that enables stable and efficient caproate production from sludge fermentation by supplementing CE enrichments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Due to the high toxicity of ammonia to organisms and its contribution to eutrophication in surface water, the risk of emission of ammonia and other nitrogenous ions to the environment and ecosystems has aroused wide concerns. Therefore, the discharge criterion on nitrogen in effluent from conventional wastewater treatment plants (WWTP) is very stringent. Furthermore, during the conventional denitrification processes, the relatively costly external carbon source is usually required. Nowadays production of volatile fatty acids (VFAs) from sewage sludge by alkaline anaerobic fermentation has regarded as an attractive carbon source. However, usually ammonia is quite abundant in the fermentation liquid and thus effective mitigation of ammonia in the fermentation liquid is also a significant step for its further utilization. In the present study, the flow electrode capacitive deionization (FCDI) was applied to remove ammonia in the fermentation liquid of sewage sludge. Firstly, response surface method (RSM) was employed to optimize parameters and then the performance of the FCDI in ammonia removal were examined. Results showed that optimal flow rates, carbon content and ammonia concentration were 8.0 mL min -1 , 4.0 wt% and 110 mg N·L -1 and the ammonia removal efficiency (ARE) reached 42.7%, while treating the alkaline fermentation liquid. Seemingly the presence of Na + and polypeptides in the liquid with their average RE of 53.3% and 11.1% substantially compromised ammonia removal probably due to the competition of adsorption sites. This present study serves as a proven concept for the feasibility of the application of the FCDI system in ammonia separation from the VFAs, which could realize economic and ecological benefits., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Thermal hydrolysis has been widely applied to improve organics bioconversion during sludge anaerobic treatment currently, based on which, liquid fermentation to produce volatile fatty acids (VFAs) with high concentration and good purity has been successfully developed by only using hydrolysate as the substrate to avoid the interference of "useless" residual solids. Therefore, obtaining high-quality hydrolysate is the prerequisite for VFAs production via liquid fermentation. However, previous studies on sludge thermal hydrolysis either only focused on organics release or only on sludge dewatering. Actually, the quantity, quality and recovery of the carbon released from sludge are equally important, and a balance between them should be established. Results in the present study indicated that organics concentration in sludge hydrolysate could not be arbitrarily enhanced by increasing thermal hydrolysis intensity or sludge concentration, and interestingly there seemed a threshold of around 32 g/L that the highest concentration the sludge hydrolysate could reach. Moreover, with the increase of hydrolysis intensity, the bioavailability of sludge could be promoted but reached the maximum with BOD 5 /COD of around 0.44 at 180 °C, while sludge dewaterability could be improved but also trended to stable after 160 °C. The findings of this study demonstrate that excessively high hydrolysis intensity would not only waste energy but also induce forms of non-biodegradable organics. The performances of sludge liquid fermentation, including VFAs production and sludge reduce, were closely related to hydrolysis intensity, the choice of which should be based on the balance of the quantity, quality and recovery of the released carbon., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

For preparing high performance biochar to be applicated in persulfate-based oxidation treatment of wastewater, the feasibility of deriving Fe-N biochar from pharmaceutical sludge by endogenous Fe and exogenous N doping was investigated. With exogenous urea doping, Fe x N contained biochar (PZBC800U) was successfully derived from endogenous Fe(OH) 3 contained pharmaceutical sludge. PZBC800U effectively activated peroxymonosulfate (PMS) to remove 80 mg·L -1 levofloxacin (LEV) within 90 min. The main mechanism of PMS activation by PZBC800U for LEV degradation was revealed as non-radical pathways dominated by 1 O 2 generation and direct electron transfer. The formation of Fe x N combined with the increase of pyridinic-N in the biochar changed the electronic structure, improved the electron transfer ability, and thus achieved the excellent PMS activation capacity of the biochar. The vital function of endogenous Fe(OH) 3 was verified by comparing PZBC800U to Fe leached and extra Fe added controls. A total of 18 intermediates in the degradation of LEV were identified, and degradation pathways were proposed. Combined with the average local ionization energy calculation, the priority of piperazine breakage during LEV degradation was experimentally proved and mechanistically elucidated. This study provides a new insight into Fe x N biochar preparation from pharmaceutical sludge and the mechanisms of its excellent PMS activation performance for LEV degradation., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier Ltd.)

To improve the dose efficiency of K 2 FeO 4 in waste activated sludge (WAS) treatment, pH regulation on K 2 FeO 4 pretreatment and acidogenic fermentation was investigated. Four pretreatments were compared, i.e. pH3 + 50 g/kg-TS, pH10 + 50 g/kg-TS, neutral pH + 50 g/kg-TS and neutral pH + 100 g/kg-TS (without pH adjustment). The higher short chain fatty acids (SCFAs) yield and phosphorous dissolution rate was found under the condition of pH 10.0. In pH10 + 50 g/kg-TS, the maximum concentration of SCFAs was 5591 mg-COD/L, which yield was 22.6 times higher than that of the neutral pH + 50 g/kg-TS (237 mg COD/L). The acidogenic fermentation period could be shortened to 5 days and acetic acid accounted for 70 % of SCFAs. Furthermore, PO 4 3- -P in the hydrolysate (346.5 mg/L) accounted for 47.59 % of TP, which is easier to be recovered by chemical precipitation. Therefore, a more economical and feasible utilization mode of potassium ferrate was proposed., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

During the acidogenic fermentation converting waste activated sludge (WAS) into short-chain fatty acids (SCFA), hydrolysis of complex organic polymers is a limiting step and the transformation of harmful substances (such as antibiotics) during acidogenic fermentation is unknown. In this study, potassium ferrate (K 2 FeO 4 ) oxidation was used as a pretreatment strategy for WAS acidogenic fermentation to increase the hydrolysis of sludge and destruct the harmful antibiotics. Pretreatment with K 2 FeO 4 can effectively increase the SCFA production during acidogenic fermentation and change the distribution of SCFA components. With the dosage of 0.2 g/g TS, the maximum SCFA yield was 4823 mg COD/L, which is 28.3 times that of the control group; acetic acid accounts for more than 90% of the total SCFA. The higher dosage (0.5 g/g TS) can further increase the proportion of acetic acid, but inhibit the overall performance of SCFA production. Apart from the promotion of hydrolysis and acidogenesis, K 2 FeO 4 pretreatment can also simultaneously oxidizes and degrades part of the antibiotics in the sludge. When the dosage is 0.5 g/g TS, the degradation efficacy of antibiotics is the most significant, and the contents of ofloxacin, azithromycin, and tetracycline in the sludge are reduced by 69%, 42%, and 50%, respectively. In addition, K 2 FeO 4 pretreatment can also promote the release of antibiotics from sludge flocs, which is conducive to the simultaneous degradation of antibiotics in the subsequent biological treatment process., (Copyright © 2022. Published by Elsevier B.V.)

Effects of biochar on co-digestion of pig manure and dewatered sewage sludge under different total solids (TS) were investigated. Biochar could accelerate the start-up of methanogenesis and shorten the adaptation phase. At TS5%, the methane daily production in biochar group was 60.6% higher than the control; nevertheless, when TS increased, the gap between two groups gradually narrowed. Additionally, the change on antibiotics resistance genes (ARGs) was also affected by TS and the biochar addition. Moreover, biochar was beneficial to reduce ARGs in liquid phase. At TS14%, the total ARGs abundance in the liquid phase of biochar group was 41.4% lower than the control, among which the reduction rates of etB(P), sul1, rpoB2, macA, mupA and mupB were more prominent. These findings could provide useful guidance for developing ARGs elimination strategy before their release into the environment., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Thermal/ultrasonic pre-treatment of sludge has been proven to break the hydrolysis barriers of sewage sludge (SS) and improve the performance of anaerobic digestion (AD). In this study, the objective was to investigate whether the combination of two pre-treatment methods can achieve better results on the AD of SS. The results indicated that, compared with the control group and separate pre-treatment groups, the thermal combined ultrasonic pre-treatment presented more obvious solubilization of soluble proteins, polysaccharides, and other organic matters in SS. The combined method promoted the dissolution of protein-like substances more effectively, with biogas production increased by 19% and the volatile solid (VS) removal rate improved to above 50% compared with the control group. The capillary suction time is reduced by about 85%, which greatly improved the dewatering performance of SS. In addition, the combined method has advantages in degrading sulfonamide antibiotics, roxithromycin and tetracycline. Particularly, by analyzing the interaction between the degradation of different antibiotics and the composition of dissolved organic matters (DOMs), it was found that the composition of DOMs could affect the degradability of different antibiotics. Among them, the high content of tyrosine-like and tryptophan-like was conducive to the degradation of sulfamethoxazole, and the high content of fulvic acid-like and humic acid-like was conducive to the degradation of roxithromycin and tetracycline. This work evaluated the comprehensive effect of thermal combined ultrasonic pre-treatment on SS disposal and provided useful information for its engineering., Competing Interests: Declaration of competing interest The authors have declared no conflict of interest., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Humic-like acids (HAs) are abundant in sewage sludge but mainly bonded with solids. Thus, their influences are often neglected in conventional digestion processes. Currently thermal hydrolysis pretreatment (THP) has been widely adopted in sludge anaerobic digestion (AD) to enhance hydrolysis of complex matters and further to improve methane production. However, the impacts of enhanced release of HAs and the mechanisms involved are not well understood and need to be further investigated because the substantial amounts of HAs present in AD could severely threaten the sludge AD processes. Results in the present study indicated that the concentration of soluble HAs in sludge was elevated by 90 times due to the THP, from 8 mg/L in raw sludge to 727 mg/L in the pretreated sludge hydrolyzed at 180 °C. Moreover, the structural characteristics of soluble HAs, including aromatic condensation degree, elemental composition and functional group, also showed substantial differences with the increased temperature of the THP. Furthermore, the release of HAs presented significant influences on sludge digestion. Acidification rate was inhibited by over 50% with 0.4 g/L of HAs, whereas methanogenesis was improved by nearly 200% with 0.8 g/L HAs and inhibited about 50% with 2.0 g/L. The activities of proteinase and co-enzyme F 420 were decreased by 20% and increased by 19%, respectively, under HAs stress at 0.6 g/L for 5 days. Moreover, molecular structural changes of soluble HAs also contributed to the influences. Especially, the E4/E6 value representing the degree of HAs aromatic condensation and C/N ratio of soluble HAs were closely correlated with their inhibition degree to sludge hydrolysis. The findings of this study demonstrate that the influences of HAs are evident and also vary to the different steps of anaerobic digestion processes, which shall not be negligible during the sludge digestion that is with THP. Due to the rate-limiting step was methanogenesis in the AD process of pretreated sludge by thermal hydrolysis, HAs concentration was recommended at low level, for example around 1.0 g/L, to accelerate or not limit methanogenesis., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Sludge treatment wetlands (STWs) are widely used to treat surplus sludge in recent years. However, the effects of plant species and loading rates on sludge characteristics in earthworm assistant STWs remain unclear. In the current study, six STWs planted with two plant species (Phragmites australis, Typha angustifolia) were investigated under four loading rates (60, 80, 90 and 120 kg DS/m 2 /yr) regarding the influence on sludge characteristics. Furthermore, earthworms were added in three STWs to evaluate their role on sludge stabilization during resting period. Results showed that the best sludge dewatering (dry solids (DS) of 45.0%) and stabilization (volatile solids to total solids (VS/TS) of 40.5%) were determined in the P. australis STWs at the loading rate of 80 kg DS/m 2 /yr. Furthermore, VS/TS and Escherichia coli contents in earthworm STWs were 5.5-11.2% and 12-39% lower than that in the control without earthworm addition. Meanwhile, earthworm also decreased the nutrient contents in STWs. However, earthworms had insignificant effects on heavy metal contents in STWs. Nevertheless, the bioavailability of Cd and Cr in STWs were decreased by earthworm addition, with an acid-soluble fraction of Cd and Cr reduced by 11.2-18% and 2.5-7.5%, respectively. In conclusion, sludge characteristics can be improved by earthworm addition in P. australis STWs., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Most of the developing countries are in need of sanitary toilets due to insufficient supporting facilities and proven technology mainly on disposal of fecal sewage. A microbial fuel cell (MFC)-microbial electrolytic cell (MEC) coupling with an anaerobic baffle reactor (ABR) was used to realize simultaneous removal of nitrogen and carbon in fecal sewage and complete energy recycling. Configuration and rapid start-up of the ABR-MFC-MEC process treating fecal sewage was systematically studied. Results showed that the application of an external voltage of 0.5 V can shorten the start-up time and improve hydrogen production rate to 3.42 × 10 -3  m 3 -H 2 /m 3 /d in the MEC unit, where the double-chamber MFC can drive MEC completing the synchronous coupling start-up. In the single and double chamber systems, bio-electrochemical processes both enhanced shock resistance capacity of the whole ABR-MFC-MEC process during coupled operation, with chemical oxygen demand (COD) removal rates of 99.2% and 98.9% for the single and double chamber systems respectively. Based on results of biological analysis, the coupled system has a distinct selective effect on microbial population and each unit has high microbial diversity to enhance the stability and resistance of the whole system for treatment of feces and urine., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)

A novel strategy of liquid fermentation using anaerobic dynamic membrane reactor (AnDMBR) was proposed to enhance volatile fatty acids (VFAs) production from sewage sludge. Results indicated that liquid sludge fermentation in AnDMBR had the potential in commercial VFAs production. VFAs productivity and concentration as well as substrate conversion rate could reach as high as 7.8 kg VFA-COD/m 3  d, 60 g/L and 0.38 kg VFA-COD/kg VS, respectively. Moreover, dynamic membrane was stably operated for approximately 70 days. During the operational period, membrane flux was increased from 6.25 to 25 L/m 2  d and only once online membrane cleaning was implemented. Results of microbial analyses showed bacterial richness and evenness in AnDMBR were increased by membrane separation and organic loading rate (OLR) increase, but reduced by excessive OLR, which should led the variations in the performances of AnDMBR. Furthermore, the necessity of liquid sludge fermentation for VFAs production was further confirmed by economic assessment and the bioavailability analysis of the residual solids in pretreated sludge. The residual solid was proved to be not conducive to enhance VFAs yield. Conversely, the energy consumption for VFAs production could be reduced from over 100 to below 20 kwh/kg VFAs by avoiding the "useless" residual solids entering into fermenters., (Copyright © 2018 Elsevier B.V. All rights reserved.)

This study investigated the feasibility and performance of simultaneous in-situ CO 2 sequestration and CH 4 production promotion by wollastonite addition in sludge AD. A maximum CH 4 yield increment of 30.8% and maximum methane production rate increment of 64.9% with wollastonite addition at dosage of 16.25 g/L were achieved. CO 2 was efficient sequestered by wollastonite addition and resulted in a higher CH 4 content of 81.7%-82.4%. The mechanism of CO 2 sequestration by wollastonite was confirmed as Ca 2+ release and subsequently carbonation based on cation and precipitates analysis. The results demonstrated that wollastonite could be applied as an effective additive for simultaneous in-situ CO 2 sequestration and CH 4 production promotion of sludge AD., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Volatile fatty acids (VFAs) production from waste activated sludge fermentation could be improved in anaerobic dynamic membrane bioreactor (ADMBR) by retaining residual organics within the reactor and prolonging their reaction time. However, the accumulation of refractory organics made it operate unstably. Therefore, protease catalysis was adopted to deeply exploit those refractory organics in sludge. By combining with dynamic membrane retention, protease catalysis indeed presented a good performance. VFAs yield was further enhanced by over 40% in ADMBR. Membrane fouling was slightly relieved due to protein and polysaccharide degradations in the sludge of dynamic membrane. It was also interestingly found that not only protease activity of sludge was improved from 5 to 21 U/ml, but also β-GLC activity was enhanced from 13 to 20 μmoL/L/h. Microbial community analysis showed protease addition could reduce bacterial richness and evenness in sludge, and accelerate the growth of polysaccharides-hydrolyzing bacteria, as well as inhibit some proteolytic bacteria., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The effect of steam explosion on physicochemical properties of sludge and the performance of anaerobic digestion (AD) was investigated. The steam explosion was conducted under different combinations of temperature and time, ranging 151-198 °C and 4-12 min respectively. The capillary suction time (CST) and viscosity of the sludge was increased with particle size decreased by improved hydrolysis temperature and prolonged hydrolysis time. The best sludge solubilization achieved was 41.3% under pretreatment condition of 198 °C and 4 min. Biogas production was enhanced with the improved sludge solubilization, and a linear correlation was found between biogas production and the severity factor (logR 0 ) of steam explosion. However, the biogas productivity was reduced when the logR 0 was increased from 3.79 to 3.96, probably owing to the generation of refractory organics during the high severity pretreatment. The temperature of 198 °C and the time of 8 min were the recommended operation parameters of steam explosion pretreatment for sludge AD, which could improve biogas production by 99.7 mL/g VS fed . The pH and NH 4 + -N during sludge AD was increased by steam explosion pretreatment; however, no inhibition on biogas production was observed.

Raw sludge was pretreated, and the separated sludge liquid was used as substrate in a continuous operated up-flow anaerobic sludge blanket reactor to produce volatile fatty acids (VFAs). The highest VFA productivity of continuous fermentation with sludge liquid at an organic loading rate (OLR) of 10.0 kg COD/m 3 /d was about 5.0-fold and 4.0-fold higher than batch and semi-continuous fermentation with pretreated sludge slurry, respectively. Moreover, the liquid fermentation with an OLR of 10.0 kg COD/m 3 /d consumed the least energy, which was about 10.57% and 12.12% of batch and semi-continuous sludge fermentation, respectively. When combined with online nitrogen and phosphorus recovery, VFA production further increased by 20.67% and struvite recovery efficiency reached 1.98  ±  0.28 g/g PO 4 3- . The process showed high VFA production, low energy consumption and good nutrients recovery by continuous liquid anaerobic fermentation, significantly increasing the economic potential of VFA production from waste activated sludge., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Based on thermal alkaline hydrolysis (TAH), a novel strategy of stepwise hydrolysis was developed to improve carbon releasing efficiency from waste activated sludge (WAS). By stepwise increasing hydrolysis intensity, conventional sludge hydrolysis (the control) was divided into four stages for separately recovering sludge carbon sources with different bonding strengths, namely stage 1 (60 °C, pH 6.0-8.0), stage 2 (80 °C, pH 6.0-8.0), stage 3 (80 °C, pH 10.0) and stage 4 (90 °C, pH 12.0). Results indicate stepwise hydrolysis could enhance the amount of released soluble chemical oxygen demand (SCOD) for almost 2 times, from 7200 to 14,693 mg/L, and the released carbon presented better biodegradability, with BOD/COD of 0.47 and volatile fatty acids (VFAs) yield of 0.37 g VFAs/g SCOD via anaerobic fermentation. Moreover, stepwise hydrolysis also improved the dewaterability of hydrolyzed sludge, capillary suction time (CST) reducing from 2500 to 1600 s. Economic assessment indicates stepwise hydrolysis shows less alkali demand and lower thermal energy consumption than those of the control. Furthermore, results of this study help support the concepts of improving carbon recovery in wastewater by manipulating WAS composition and the idea of classifiably recovering the nutrients in WAS., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Sewage sludge treatment is becoming one of the most significant challenges for domestic wastewater management. Optimization of sludge management for reducing sludge handling cost in wastewater treatment plant is highly demanded. Sludge treatment reed bed system (STRB) is an eco-environmentally friendly technology which has a low investment input and reduced costs for operation and maintenance. The objective of this study is to evaluate the effect of earthworm assistant STRB in terms of sludge dewatering and stabilization of surplus sludge. The results show that draining and evapotranspiration (ET) take the main role for sludge dewatering; with maximum of 77 and 43 % water was removed through draining and ET, respectively. Plants improved ET rate up to 13.1 % in the planted STRB compare with the unplanted STRB. The combination of plants and earthworms increased ET rate of 20.9 % more than the control STRB (unplanted without earthworms). The planted STRB with earthworm reached the lowest water content in accumulated sludge of 46 %. There was a systematic increase of total solids (TS) concentration from 0.5 % in the influent to 25-54 % in the accumulated sludge. Earthworms enhanced the sludge stabilization dramatic with the ratio of volatile solids (VS)/TS decreased from 49 % in the influent to 18 % in the accumulated sludge in the earthworm assistant STRB. The results demonstrated a good efficiency for sludge dewatering and stabilization with the assistant of earthworms in STRBs, which can be an alternative technology for sludge treatment in wastewater treatment plants.

The real cause to the low yield of volatile fatty acids (VFAs), from inhibition or low biodegradation, is uncertain in sludge anaerobic fermentation. In this study, poor biodegradability of proteins and fast decrease of the indigenous hydrolase activity in the residual post-fermented sludge were found to be the major reasons. With the addition of trypsin or alkaline protease in residual post-fermented sludge after primary alkaline fermentation, degradation efficiency of refractory protein increased by 33.6% and 34.8%, respectively. Accordingly, the VFAs yields were improved by 69.7% and 106.1%, respectively. Furthermore, the activities of added trypsin and alkaline protease could maintain at 13.52 U/mL and 19.11 U/mL in the alkaline fermentation process. This study demonstrated that exploiting the refractory proteins in residual post-fermented sludge by protease addition seems to be a very promising way for improving VFAs yield of conventional alkaline fermentations with waste activated sludge., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

In this study, the anaerobic fermentation was carried out for volatile fatty acids (VFAs) production at different pH (between 7.0 and 10.0) conditions with untreated sludge and heat-alkaline pretreated waste activated sludge. In the fermentation with untreated sludge, the extent of hydrolysis of organic matters and extent of acidification at alkaline pH are 54.37% and 30.37%, respectively, resulting in the highest VFAs yield at 235.46mg COD/gVS of three pH conditions. In the fermentation with heat-alkaline pretreated sludge, the acidification rate and VFAs yield at neutral pH are 30.98% and 240.14mg COD/gVS, respectively, which are higher than that at other pH conditions. With the glucose or bovine serum albumin as substrate for VFAs production, the neutral pH showed a higher VFAs concentration than the alkaline pH condition. The results of terminal restriction fragment length polymorphism (T-RFLP) analysis indicated that the alkaline pH caused low microbial richness. Based on the results in this study, we demonstrated that the alkaline pH is favor of hydrolysis of organic matter in sludge while neutral pH improved the acidogenesis for the VFAs production from sludge. Our finding is obvious different to the previous research and helpful for the understanding of how heat-alkaline pretreatment and alkaline fermentation influence the VFAs production, and beneficial to the development of VFAs production process., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Homoacetogens are a group of microorganisms with application potential to produce chemicals and biofuels by the bioconversion of synthesis gas. In this study, we collected waste activated sludge samples to screen homoacetogens by Hungate anaerobic technique, and studied the effect of pH on acetate and alcohol production from H2/CO2 gas. The mixed culture contained Clostridium ljungdahlii, Lysinibacillus fusiformis and Bacillus cereus. Acetate concentration achieved 31.69 mmol/L when the initial pH was 7. The mixed culture containing homoacetogen could converting H2/CO2 to acetate, which provides an efficient microbial resource for the bioconversion of synthesis gas.

The occurrence and reactivation of viable but non-culturable (VBNC) Escherichia coli after different anaerobic digestions and the subsequent dewatering and storage were evaluated and compared. Culturable E. coli in digested sludge increased by two to four orders of magnitudes immediately after dewatering. However, counts of both the total and viable E. coli indicated that the increase of E. coli was attributed to its reactivation from the VBNC state to the culturable state. The VBNC pathogen incidences of thermophilic digestion were two to three orders of magnitude higher than those of mesophilic digestion. Accordingly, culturable E. coli in thermophilic, digested sludge after storage were one order of magnitude higher than mesophilic digestion. Anaerobic digestion thus mainly alters the culturable state of pathogens rather than killing them; therefore the biological safety of digested sludge, especially temperature-phased anaerobic digestion, should be carefully assessed.

A novel continuous-flow bioreactor with aerobic granular sludge and self-forming dynamic membrane (CGSFDMBR) was developed for efficient wastewater treatment. Under continuous-flow operation, aerobic granular sludge was successfully cultivated and characterized with small particle size of about 0.1-1.0mm, low settling velocity of about 15-25 m/h, loose structure and high water content of about 96-98%. To maintain the stability of aerobic granular sludge, strategies based on the differences of settling velocity and particle-size between granular and flocculent sludge were implemented. Moreover, in CGSFDMBR, membrane fouling was greatly relieved. Dynamic membrane was just cleaned once in more than 45 days' operation. CGSFDMBR presented good performance in treating septic tank wastewater, obtaining average COD, NH(4)(+)-N, TN and TP removal rates of 83.3%, 73.3%, 67.3% and 60%, respectively, which was more efficient than conventional bioreactors since that carbon, nitrogen and phosphorus were simultaneously removed in a single aerobic reactor., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

An innovative adsorption/nitrification/denitrification/sludge-hydrolysis wastewater treatment process (ENRS) characterized by carbon source manipulation with a biological adsorption unit and a sludge hydrolysis unit was developed to enhance nitrogen removal and reduce sludge production for municipal wastewater treatment. The system presented good performance in pollutants removal, yielding the effluent with average COD, NH(4)(+)-N, TN and TP of 48.5, 0.6, 13.2 and 1.0 mg/L, respectively. Sixty percent of the total carbon source in the influent was concentrated and separated by the quick adsorption of activated sludge, providing the possibilities of reusing waste carbon source in the denitrification tank and accumulating nitrobacteria in the nitrification tank. Low temperature of 6-15 °C and high hydraulic loading rate of 3.0-15.0 m(3)/d did not affect NH(4)(+)-N removal performance, yielding the NH(4)(+)-N of lower 1.0 mg/L in the effluent. Furthermore, 50% of the residual sludge in the ENRS system could be transformed into soluble COD (SCOD) by alkaline thermal hydrolysis with temperature of 60 °C and pH of 11, and the hydrolyzed carbon could completely substitute methanol as a good quality carbon to support high efficient denitrification., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The mass concentration of molybdenum in ammonium molybdate wastewater is usually 0.5~2.0 g/L, which has a high recovery value, but the impurity of iron and aluminum in wastewater seriously affect the recovery rate of molybdenum. The separation and extraction of Mo, Fe and Al from ammonium molybdate wastewater by "impurity removal + ion exchange adsorption" process was studied. By analyzing the existence forms of molybdenum, iron and aluminum at different pH, the precipitation removed the iron and aluminum impurities, and then adsorbed molybdenum in wastewater with ZJ-32 macroporous weak basic anion exchange resin, and the molybdenum resin was desorbed by 12% ammonia water to obtain ammonium molybdate solution. The results show that molybdenum can be separated from Fe and Al under suitable conditions. The filtrate after impurity removal is adsorbed by ion exchange resin, the average recovery rate of molybdenum is 96.47%, and the average desorption rate of molybdenum-bearing resin can reach 99.46% after desorption by ammonia water. The process can effectively avoid the influence of iron and aluminum colloid on molybdenum adsorption, and realize the double resource utilization of molybdenum and iron and aluminum. [ABSTRACT FROM AUTHOR]

Industrial parks have been important to China's rapid economic development. The wastewater generated by these industrial parks tends toward large volumes, varied compositions, high pollutant concentrations, and it generally is toxic and difficult to biodegrade. The abilities of treatment plants to effectively treat industrial wastewater are greatly influenced by the upstream treatment step that occurs at the source in the industrial park. Based on the notion of the water footprint, a wastewater treatment assessment index was developed and tested to evaluate and enhance the centralized wastewater treatment plants of two industrial parks. The treatment performance of a plant in a comprehensive industrial park was compared to that of a chemical industrial park. The former scored significantly higher than the latter. Because of its low scores in the evaluation, the treatment problems of the chemical industrial park were diagnosed and enhancement measures were implemented. After the enhancements were in place, the plant was re-evaluated. Its post-enhancement scores on the index's primary indicator for process advancement and its dependent performance regarding the downstream environment greatly increased, indicating that the wastewater treatment performance had significantly improved. Therefore, the index developed by this study successfully evaluated and determined effective enhancements for wastewater treatment in China's industrial parks, which contributes to industrial wastewater pollution control. Image 1 • Upstream and downstream wastewater treatments in industrial parks are interrelated. • An effective wastewater treatment assessment index was developed. • Wastewater treatment was comparatively evaluated for two Chinese industrial parks. • Post-evaluation enhancements significantly improved treatment performance. [ABSTRACT FROM AUTHOR]

The aim of our research was to investigate the enhanced anaerobic degradation process of coal gasification wastewater (CGW) by conductive material activated carbon and Fe 3 O 4 nanoparticles (Fe 3 O 4 NPs) with the assistance of co-substrate. The optimal ratio of activated carbon to Fe 3 O 4 NPs (3:1) and the optimal addition of co-substrate (glucose concentration =1500 mg/L) were explored through batch tests. During the long-run reactor experiments, 1500 mg/L glucose was mixed into the influent, and activated carbon-Fe 3 O 4 NPs in a ratio of 3:1 were mixed into the anaerobic sludge. The concentration of total phenols in the effluent was kept around 50 mg/L, with a removal rate of 96% and an increase in methane production to 226 mL/day in the experimental reactor. Compared with the control reactor, the methane yield was increased by 64.6%. Toxicity analysis indicated that the toxicity of CGW can be greatly alleviated by conductive material activated carbon and Fe 3 O 4 NPs coupled with anaerobic co-digestion conditions. Microbial community analysis demonstrated that direct interspecies electron transfer (DIET) may have occurred between exoelectrogens (Clostridium, Anaerolinea, Mesotoga, Synergistia) and methanogenic endoelectrogens (Methanobacterium , Methanothrix) for syntrophic metabolism through activated carbon-Fe 3 O 4 nanoparticles coupled with anaerobic co-metabolism. [Display omitted] • Anaerobic degradation of phenols by activated carbon-Fe 3 O 4 NPs coupled with co-metabolism was investigated. • Total phenols removal reached 96% and methane production increased to 226 mL/day. • DIET might occur between exoelectrogens and methanogenic endoelectrogens for syntrophic metabolism. [ABSTRACT FROM AUTHOR]

Wastewater microbial fuel cells (MFCs) can transform the chemical energy into electricity; however, little is known on the effect of circuit modes on start-up and performance of wastewater MFCs. Here we have investigated the effect of four circuit modes on start-up, performance and membrane fouling of MFCs systematically. Besides shortening the start-up period and improving the performance of MFCs, applying anodic negative potential also balances pH of the system and thus enhances COD removal. The open-circuit constant potential mode (OC-MFC) presents the shortest start-up period of 5 days, with the highest voltage output of 810 mV and the slightest membrane fouling, which provides an effectively strategy to accelerate the start-up of wastewater MFCs. The circuit mode applied to start up wastewater MFC not only affects the degree of membrane fouling, but also causes significant differences in anode microbial communities. The total abundance of exoelectrogens in the closed-circuit intermittent potential (CI-MFC) mode was the highest up to 54.70%, but the performance of CI-MFC inferiors to OC-MFC, indicating that performance of the wastewater MFC is not solely determined by the dominant bacteria. Overall, the OC-MFC provides a new strategy to accelerate the start-up period and enhance performance of wastewater MFC simultaneously. [Display omitted] • Negative potential accelerates the start-up speed and enhances the performance of MFCs. • The higher effluent pH of the MFCs corresponds to a higher COD removal. • The OC-MFC mode produces the slightest membrane fouling during start-up. • The abundance of exoelectrogens under the CI-MFC mode is as high as 54.7%. [ABSTRACT FROM AUTHOR]

Coal gasification wastewater (CGW) has a complex composition and exhibits significant concentration and toxicity. In practical engineering, a single treatment technique may not always produce the best results. In this paper, iron-carbon multi-micro-electric field coupling anaerobic co-digestion treatment is adopted with synthetic CGW as the research object. By using single factor analysis and response surface methodology, the optimum operating conditions: the activated carbon/zero-valent iron (ZVI) (C/Fe) ratio of 2:1 and a carboxymethyl cellulose (CMC) concentration of 0.8 mg/L were achieved. According to the reactor's operation findings, methane production grew to 200 mL/d, and the average removal efficiencies of total phenol and quinoline could reach 52.8 ± 5.6% and 94.9 ± 6.8%, respectively, under optimal operating conditions. The iron-carbon multi-micro-electric field coupling anaerobic co-digestion can significantly lower the toxicity of CGW during optimal operation, according to an investigation of effluent toxicity. The microbial community in the granular sludge of the anaerobic system was analyzed using metagenomic sequencing technology. Direct interspecies electron transfer (DIET) was promoted by the coupling system with enriched electroactive bacteria like Syntrophorhabdus and Geobacter. This study can serve as a guide for engineering applications that promote anaerobic improved treatment of refractory wastewater. • Anaerobic degradation of CGW by iron-carbon micro-electric field coupled with co-digestion was investigated. • The optimum dosage for C: Fe= 2:1, CMC concentration was 0.8 mg/L. • The coupling system can significantly reduce the toxicity of CGW. • The coupling system enriched Syntrophorhabdus and electroactive bacteria Geobacter. [ABSTRACT FROM AUTHOR]

Formation process and fouling characteristics of the dynamic membrane were studied in a modified self-forming dynamic membrane bioreactor (SF-DMBR) for recovering the organic matters in wastewater, and the performance of this SF-DMBR was investigated. Results indicated that 80% of the organic matters in wastewater could be quickly recovered under continuous operation. Furthermore, the evolutions of the fouling components were determined during the formation and development processes of dynamic membrane. After the long-term operation, the decreases of protein concentration, accompanying with the increases of polysaccharides and microorganisms contents due to special operating conditions, were interestingly observed in the sludge of membrane surface. This could explain why membrane fouling was much weak. Therefore, though high membrane fluxes at 50–150 L/(m 2 ·h) were adopted in this study, the reactor can still obtain a long-term stable operation and the operating cycle reached as long as 8 days. Finally, membrane fouling process was described by combined models. [ABSTRACT FROM AUTHOR]

This study explored the impact of pyrolysis parameters and modification methods on the characteristics of pharmaceutical sludge biochar, and investigated its capacity and mechanisms for levofloxacin (LEV), a typical fluoroquinolone antibiotics, adsorption. The results showed that S BET of the biochar was improved with temperature increase, but decreased when temperature reached 900 °C. Under the optimal pyrolysis condition of 800 °C and 90 min, the biochar possessed the highest S BET of 264.05 m2 g−1, excellent iodine value of 401.41 ± 3.84 mg∙g−1 and phenol adsorption of 57.36 ± 3.39 mg∙g−1. Among KOH, ZnCl 2 , and CO 2 modifications, ZnCl 2 modification achieved the highest phenol adsorption of 123.40 ± 4.65 mg g−1, with a significantly improved S BET of 534.91 m2 g−1. The maximum LEV adsorption capacity of ZnCl 2 modified biochar, PZBC800, reached 159.26 mg g−1, which overwhelmed the reported sludge biochars. BET, zeta potential, FT-IR, XPS, and Raman analysis, along with quantum chemistry calculation, revealed that pore filling, hydrogen bonding, π-π interaction, surface complexation, and electrostatic interaction were the main mechanisms for the excellent LEV adsorption performance of PZBC800. Deep removal (99.9%) of Fluoroquinolones (FQs) from pharmaceutical wastewater was also achieved by PZBC800 adsorption. The study promoted the development of pharmaceutical sludge biochar preparation and its application in advanced treatment of FQs pharmaceutical wastewater. [Display omitted] • High quality pharmaceutical sludge biochar with S BET of 534.91 m2 g−1 was prepared. • Capacity of sludge biochar for levofloxacin (LEV) adsorption reached 159.26 mg g−1. • DFT calculation revealed the electrostatic mechanism influencing LEV adsorption. • π-π, H-bond, surface complexation, pore filling involved in LEV-biochar adsorption. • Biochar adsorption removed 99.9% of antibiotics from pharmaceutical wastewater. [ABSTRACT FROM AUTHOR]