Search

A manganese–nitrogen co-doped porous carbon with high nitrogen content was prepared to improve the contribution rate of non-radical pathways to the degradation process of organic pollutants.

Developing green and high-efficient pyrometallurgy processes to recycle precious metals from spent lithium-ion batteries (LIBs) is of great importance for resource sustainability and environmental protection. Herein, a novel reduction roasting approach relying on spent LIB separator to refine the spent cathode is proposed. The efficiency of repurposing separator as a reductant for roasting the spent LiCoO

This study investigated the performance of anaerobic co-digestion (AcoD) of pig manure and food waste on the reduction of antibiotic resistomes under wet and dry AcoD conditions. High-throughput quantitative PCR technology was utilized for a comprehensive assessment of the performances of the two processes. The results show that dry AcoD with a total solids (TS) content of 20% effectively reduced total antibiotic resistance genes (ARGs) by 1.24 log copies/g wet sample, while only 0.54 log copies/g wet sample was reduced in wet AcoD with a TS content of 5%. Dry AcoD was more efficient in reduction of aminoglycosides, multidrug and sulfonamide resistance genes compared with the reduction of other classes of ARGs. Dry AcoD caused a significant reduction of ARGs with resistance mechanisms of efflux pump and antibiotic deactivation. In contrast, there was no obvious difference in reductions of ARGs with different resistance mechanisms in wet AcoD. Network analysis showed that ARGs were significantly correlated with mobile genetic elements (MGEs) (Spearman's r 0.8, P 0.05), as well as microbial communities. Enrichment of ARGs and MGEs was found at the early period of AcoD processes, indicating some ARGs and MGEs increased during the hydrolysis and acidogenesis stages. But after a long retention time, their abundances were effectively reduced by dry AcoD in the subsequent stages.

Phenol and ammonia are common pollutants in many industrial wastewaters. The partial nitritation and anammox process is a very promising technology for treating phenol-ammonia wastewater. This study was the first time to rapidly achieve the start-up and operation of the single-stage partial nitritation /anammox reactor treating phenol-ammonia wastewater. The optimized ratio of phenol and nitrogen (phenol/NH4+ -N=0.3) was set to start-up the reactor. After 60 days of operation, the total nitrogen and COD removal efficiencies were around 73.0% and 79.5%, respectively. The activity of ammonium-oxidizing bacteria was291.1 ± 3.0 mg NH4+ -N g-1 MLVSS d-1 and the specific anammox activity was 20.9 ± 1.0 mg NH4+ -N g-1 MLVSS d-1 . The results indicated that the anammox bacteria had adapted to phenol condition and remained stable activity after the 60 days' operation in the reactor. The sequence analysis of 16SrRNA showed that the microbial community structure evolved to a balanced distribution that the removals of phenol and ammonia could be achieved simultaneously. PRACTITIONER POINTS: Phenol/N ratio of 0.3 was set to start up the single-stage partial nitritation/anammox reactor. The single-stage partial nitritation /anammox reactor was rapidly started up when treating the phenol-ammonia wastewater. Total nitrogen removal rate and COD removal efficiencies could achieve to 73.0% and 79.5%, respectively. Microbial community structure evolved to stable distribution of which AOB, anammox bacteria, denitrification bacteria and heterotrophic nitrification bacteria coexisted.

High salinity in phenolic wastewater inhibited anaerobes' metabolic activity, thereby affecting the anaerobic biotransformation of phenol. In this study, granular activated carbon (GAC) coupled with exogenous hydrogen (H

Nonylphenol ethoxylate-n (NPnEO) is a nonionic surfactant, and can be degraded in chemical and biological ways for short-chain NPnEO with n ≤ 10. However, when n is >10, the degradation of NPEO in ...

Roxarsone (ROX) is widely used in animal farms, thereby producing organoarsenic-bearing manure/wastewater. ROX cannot be completely degraded and nor can its arsenical metabolites be effectively immobilized during anaerobic digestion, potentially causing arsenic contamination upon discharge to the environment. Herein, we designed and tested a sulfate-mediated bioelectrochemical system (BES) to enhance ROX degradation and in situ immobilization of the released inorganic arsenic. Using our BES (0.5 V voltage and 350 μM sulfate), ROX and its metabolite, 4-hydroxy-3-amino-phenylarsonic acid (HAPA), were completely degraded within 13-22 days. In contrast, the degradation efficiency of ROX and HAPA was

Dry anaerobic digestion (AD) has advantages over wet AD in treating high-solid organic wastes like livestock and food wastes, but an elevated total solids (TS) content would affect the AD performances. In this study, methane production of digesters co-digesting pig manure (PM) and food waste (FW) at different TS contents (R1, TS 5%; R2, TS 10%; R3, TS 15%; and R4, TS 20%) was assessed. The results showed the specific methane yield had no significant difference with the increase of TS contents from 5% to 15% (278.8-291.7 NmL/g VSadded), while it was reduced at a 20% TS content (259.8 NmL/g VSadded). Two peaks of total volatile fatty acids and daily methane production were observed in the high-solid digesters (R2-R4), while only one peak occurred in wet AD (R1). A new kinetics model was developed to describe the two-peak methane production behavior at high TS contents. The analysis on the microbial community structure clearly showed the different evolutions of methanogenic pathways in low and high solids content systems. In dry AD (R4), there was a general shifting from the acetoclastic pathway, to mixotrophic pathway and hydrogenotrophic pathway, with the dominance of mixotrophic and hydrogenotrophic methanogens.

Anaerobic ceramic membrane bioreactor (AnCMBR) is an attractive alternative for the treatment of high-strength phenol wastewater, but the effects of sludge retention time (SRT) on the performance and membrane fouling are still unclear. The results indicated that the AnCMBR was successfully employed to treat high-strength wastewater containing 5 g phenol L-1. The removal efficiencies of phenol and chemical oxygen demand (COD) reached over 99.5% and 99%, respectively, with long SRT and short SRT. SRT had no obvious effect on the performance of the AnCMBR treating high-strength phenol wastewater with long time operation. The strong performance robustness of AnCMBR benefited from the enrichment of hydrogenotrophic methanogens and syntrophic phenol-degrading bacteria. However, the decline of SRT led to a more severe membrane fouling in the AnCMBR, which was caused by the small size of sludge flocs and high concentration of protein in the biopolymers. Therefore, this work presented a comprehensive insight to the feasibility and robustness of the AnCMBR for treating high-strength phenol wastewater.

Membrane fouling is still the main obstacle that hinders the development and implementation of anaerobic membrane bioreactor (AnMBR). In conventional upflow anaerobic reactors, sludge at different height usually presents certain differences in characteristics in terms of particle size, etc. The immersion depth of membrane modules in anaerobic reactors can also influence the fouling of membrane. Thus, it is of great interest to investigate the fouling mechanism with the membrane installed at different heights in reactors. The filtration performance and sludge properties were investigated at different heights of AnMBR. The fouling of membrane in the middle position was severer than that in the top and bottom positions. The total resistance of membrane in the top, middle, and bottom positions was 27.31 × 1011 m−1, 34.67 × 1011 m−1, and 25.29 × 1011 m−1, respectively. By comparing the characteristics and structure of bulk sludge and cake layer at three heights, the bulk sludge in the middle position presented higher content of soluble microbial products (SMP) and finer flocs, and the cake layer was also denser. The results obtained in this study indicated that small size of sludge flocs as well as adhesion of SMP might be the major factors governing membrane fouling at different height in the AnMBR.

Roxarsone (3-nitro-4-hydroxyphenylarsonic acid) is an extensively used organoarsenic feed additive. The effective removal of arsenic from roxarsone degradation before discharging is of great importance for controlling artificial arsenic pollution in aquatic environment. In this study, a bifunctional TiO2/ferrihydrite (TiO2/FeOOH) hybrid was synthesized by a hydrothermal method for the simultaneously photocatalytic degradation of roxarsone and adsorption removal of released arsenic. The analysis of the prepared TiO2/FeOOH by field-emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), Raman spectra, X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), and X-ray photoelectron spectroscopy (XPS) confirmed the successful formation of the hybrid of crystalline TiO2 and no crystalline FeOOH. TiO2/FeOOH hybrid had better adsorption capacity for As(V) than roxarsone. Compared to TiO2, the TiO2/FeOOH hybrid exhibited much superior UV-driven photocatalytic activities for roxarsone degradation. After 12 h irradiation, more than 96% of roxarsone was degraded by 1:1 TiO2/FeOOH hybrid, and the released As(V) was simultaneously removed from the solution. The residual As(V) concentration was lower than 0.02 mg L−1. The reusability test indicated that TiO2/FeOOH hybrid had excellent stability and reliability. The possible mechanism of roxarsone degradation and released inorganic arsenics removal by this hybrid was also proposed. These results clearly indicated that the TiO2/FeOOH hybrid could be used for the removal of roxarsone and its degradation product.

In this study, a combined corncob-based fixed bed bioreactor and sequencing batch reactor system (CCF-SBR) was developed to treat low-temperature (3-12 °C) and low carbon/nitrogen ratio (C/N = 2) wastewater with a single SBR as the control. Results showed similarly low COD concentration of CCF-SBR (20.4 ± 3.7 mg·L

Zero-valent iron (ZVI) can enhance anaerobic digestion, and has great potential to alleviate/eliminate methanogenesis inhibition. Little is known about the feasibility of utilizing ZVI to alleviate methanogenesis inhibition that is caused by typical animal feed additive roxarsone in livestock wastewater. In this study, the role of ZVI on alleviating roxarsone-induced methanogenic inhibition and its mechanisms were investigated. With the increase of roxarsone concentration from 5.0 to 50.0 mg/L, the inhibition of methanogenesis increased from 3.0% to 65.7%. This inhibition was alleviated by 80.7% and 57.2% when 1.0 and 10.0 g/L ZVI were added, respectively. Due to ZVI addition, an efficient arsenic immobilization onto ZVI (45.4–85.8%) was achieved mainly through the formation of FeAsO4 precipitate and adsorption by ZVI. Under the function of ZVI, hydrogenotrophic methanogenic activity was obviously restored. The microbial community analysis indicates that the ZVI-regulated alleviation on the methanogenesis inhibition was attributed to the enrichment of Methanobacterium and Methanosarcina. The findings from this study demonstrate that ZVI addition is an effective way for treatment of organoarsenic-contaminated wastewater.

For the upgradation and building of wastewater treatment plants in limited areas, biological wastewater treatment processes with a high pollutant removal loading rate are required. Biofilm or membrane-based systems can achieve a high pollutant removal loading rate through high microbial biomass concentrations and/or activities. The sludge separation is the primary bottleneck for achieving high biomass concentrations inside the biological reactors. In addition, low growers including anaerobic ammonia oxidation bacteria and methanogens are usually easier to form granules and induce high nutrient removal loading rates. The possible granule formation mechanisms should be clarified through physical, chemical and biological aspects, including hydraulic control, microbial extracellular polymeric substances formation, biological energy utilization control, microbial interactions and also other microbial processes. In future, the possible mechanisms should be further clarified, and then high-efficient bioreactors, new microbial ecology control strategy and novel biofilm carriers should be developed for advancing biological wastewater treatment processes with high pollutant removal loading rates.

Biofilm carriers play an important role in attached growth systems for wastewater treatment processes. In this study, to establish a more robust and efficient anammox system, corncobs were used as ...

Poly-aluminium chloride (PAC) is often used to enhance phosphorus removal and control membrane fouling in membrane bioreactors (MBRs). However, the influence of aluminium accumulation on the biological nitrification and phosphorus removal of MBRs has not been well assessed. In the present study, the effects of accumulated aluminium on sludge activity and morphology were investigated in a lab-scale anoxic–oxic membrane bioreactor. The reasonably high removal efficiencies of NH4+-N, TN, and COD, i.e. 94.9%, 84.8%, and 92.8%, respectively, were achieved in the reactor when the percentage of atomic aluminium on sludge surface increased to 14.2%. However, the decreases in the ammonia oxidation rate, nitrite oxidation rate, and specific oxygen uptake rate of sludge by 82.1%, 79.8%, and 46.4%, respectively, were observed. Meanwhile, the activity of phosphate-accumulating organisms was completely inhibited. Furthermore, the protein content in the extracellular polymeric substances of sludge decreased substantially, and the sludge became more dispersed due to the alum accumulation, compared with that of the initial phase. Therefore, long-term dosing of PAC in the MBR should be managed to avoid excessive aluminium accumulation in the sludge.

Roxarsone and sulfadiazine are typical feed additives and often occur in manure and livestock wastewater. Anaerobic digestion is a common technique for the treatment of manure and livestock wastewater. However, the influence of roxarsone and sulfadiazine on anaerobic digestion and their degradation are still unclear. In this study, the effect of roxarsone and sulfadiazine on the anaerobic digestion of synthetic wastewater and their degradation were investigated. During 70-day incubation, the presence of 200 mg L−1 sulfadiazine exhibited little influence on hydrolysis and acidification, but resulted in a temporary inhibition on methanogenesis, whereas 120 mg L−1 of roxarsone resulted in nearly complete inhibition on methanogenesis. Further, the co-existence of 100 mg L−1 sulfadiazine and 60 mg L−1 roxarsone significantly exacerbated the inhibition on anaerobic digestion. Sulfadiazine exhibited high resistance to the adsorption and biodegradation, while roxarsone was nearly completely degraded during anaerobic digestion. Nearly half of total arsenic was transferred from solution to anaerobic granular sludge. The predominant arsenic species was 4-hydroxy-3-aminophenylarsonic acid in the solution and As3+ in the sludge. These results will provide valuable information for anaerobic treatment of livestock wastewater simultaneously contaminated by roxarsone and sulfadiazine.

Membrane technologies are challenged by severe membrane fouling when treating animal manure digestate due to high turbidity and high concentrations of organic and inorganic matter. In this study, a bench-scale electrodialysis reversal (EDR) was carried out to assess its feasibility for nutrient recovery from pig manure digestate. Pretreatment consisted of acidification for releasing phosphorus to the liquid phase and low-speed centrifugation for removing large particles. Results showed complete removal of NH4+ and removal of phosphate up to 84% from the feed solution, with their concentrations in the product reaching 4.2 and 0.7 g/L at a volumetric ratio of 6/2, respectively. During the semi-continuous operation, particle and chemical deposition were significantly mitigated. Despite periodical HCl cleaning, tyrosine-like and humic-like substances fouled anion-exchange membranes (AM) gradually. Nevertheless, this fouling ceased after treating the digestate at a capacity of 330 L/m2 membrane when the conductivity and ion-exchange capacity of AM decreased by 18.5% and 13.3% compared with the virgin membrane, respectively. Based on infrared spectra, these organic foulants existed in the fouling area around the membrane surface, rather than migrating deeper into the interior of the membrane. This study reveals a potential of long-term operation of EDR for treating pig manure digestate.

Microalgae have great potential for biofuel production and wastewater treatment, but the high cost of harvesting hinders their practical application. In this study, economical harvesting of hydrophobic microalgae by electro-flotation without coagulation was assessed. The harvesting performance of this method for selected species of freshwater microalgae with different degrees of hydrophobicity (Tribonema sp., highly hydrophobic; Scenedesmus sp., moderately hydrophobic; and Pandorina sp., hydrophilic) were compared. It was found that microalgal hydrophobicity played a critical role in electro-flotation. Under the same condition (current 0.3 A, velocity gradient 200 s

Roxarsone (ROX) is an organoarsenic feed additive, and can be discharged into aquatic environment. ROX can photodegrade into more toxic inorganic arsenics, causing arsenic pollution. However, the photodegradation behavior of ROX in aquatic environment is still unclear. To better understand ROX photodegradation behavior, this study investigated the ROX photodegradation mechanism and influencing factors, and modeled the photodegradation process. The results showed that ROX in the aquatic environment was degraded to inorganic As(III) and As(V) under light irradiation. The degradation efficiency was enhanced by 25 % with the increase of light intensity from 300 µW/cm2 to 800 µW/cm2 via indirect photolysis. The photodegradation was temperature dependence, but was only slightly affected by pH. Nitrate ion (NO3−) had an obvious influence, but sulfate, carbonate, and chlorate ions had a negligible effect on ROX degradation. Dissolved organic matter (DOM) in the solution inhibited the photodegradation. ROX photodegradation was mainly mediated by reactive oxygen species (in the form of single oxygen 1O2) generated through ROX self-sensitization under irradiation. Based on the data of factors affecting ROX photodegradation, ROX photodegradation model was built and trained by an artificial neural network (ANN), and the predicted degradation rate was in good agreement with the real values with a root mean square error of 1.008. This study improved the understanding of ROX photodegradation behavior and provided a basis for controlling the pollution from ROX photodegradation.

Extensive use of organoarsenic feed additives such as roxarsone has caused organoarsenicals to occur in livestock wastewater and further within anaerobic wastewater treatment systems. Currently, information on the long-term impacts of roxarsone on anaerobic granular sludge (AGS) activity and the underlying mechanisms is very limited. In this study, the response of AGS to long-term loading of roxarsone was investigated using a laboratory up-flow anaerobic sludge blanket reactor spiked with 5.0 mg L−1 of roxarsone. Under the effect of roxarsone, methane production decreased by ∼40% due to the complete inhibition on acetoclastic methanogenic activity on day 260, before being restored eventually. Over 30% of the influent arsenic was accumulated in the AGS and the capability of AGS to prevent intracellular As(III) accumulation increased with time. The AGS size was reduced by ∼30% to 1.20‒1.26 mm. Based on morphology and confocal laser scanning microscopy analysis, roxarsone exposure stimulated the excretion of extracellular polymeric substances and the surface spalling of AGS. High-throughput sequencing analysis further indicated roxarsone initially altered the acidogenic pathway and severely inhibited the acetoclastic methanogen Methanothrix. Acetogenic bacteria and Methanothrix were finally enriched and became the main contributor for a full restoration of the initial methane production. These findings provide a deeper understanding on the effect of organoarsenicals on AGS, which is highly beneficial for the effective anaerobic treatment of organoarsenic-bearing wastewater.

Food waste fermentation liquid (FWFL) can be used as carbon source to enhance nitrogen removal in wastewater treatment. However, the influence of lipid, a common component of food waste, on denitrification remains unclear. In this study, the effect of oil and fat on denitrification process and the underlying mechanisms were investigated using synthetic oil- and fat-bearing carbon source and verified with real FWFL. In the batch experiment, oil and fat had no obvious influence on denitrification, but in the semi-continuous experiment, the denitrification rate in the oil- and fat-added assays decreased to 44% and 38% of that in the control, respectively, after 45 batches. Oil and fat caused sludge floatation, and the floating sludge thickness increased with the continuous operation. Oil/fat-sludge aggregates were observed in the floating sludge and limited gas release. Microbial community analysis indicated that oil and fat did not affect denitrifying bacteria abundance. Limitation of mass transfer might be the main reason for the inhibition of oil and fat on denitrification. In the real FWFL experiment, the denitrification rate in the original and emulsified oil-bearing FWFL decreased to 24% and 56% of that in the demulsifying FWFL, respectively, after 45 batches. These findings indicate the necessity of removing lipids when FWFL is used as denitrification carbon source.

Nitrogen removal is often limited in municipal wastewater treatment due to the insufficiency of carbon source, and using food wastes fermentation liquid as carbon source could cut down the cost of operating and recycle food wastes. Food wastes fermentation liquid production and application as external carbon source were explored in the laboratory and full-scale system in this study. In the laboratory scale, lactic acid and VFAs were the main components of fermentation liquid, and the highest total chemical oxygen demand (TCOD) production was obtained with activated sludge as inoculum. The yield of TCOD was around 794.5 mg/g TSfed and NH4+-N was 3.5 mg/g TSfed. The denitrification rate with fermentation liquid was slightly lower than acetic acid and butyric acid, but higher than lactic acid and starch. In the full-scale investigation, the TCOD concentration in fermentation liquid was in the range of 6.9–12.8 g/L and the ratio of TCOD/inorganic nitrogen was 210.5–504.5:1. NO3−-N removal increased from 52.1% to 94.2% after fermentation liquid addition, confirming the potentiality of food wastes fermentation liquid replace the commercial carbon source in wastewater treatment plants.

Ciprofloxacin (CIP) is a widely used third generation fluoroquinolone antibiotics, and has been often detected in wastewater treatment plants. Finding an effective way to remove them from wastewater is of great concern. Ultraviolet (UV)/chlorine advanced oxidation process (AOP) has many advantages in micropollutant removal. In this study, CIP degradation in UV/chlorine process was investigated. Only 41.2% of CIP was degraded by UV photolysis and 30.5% by dark chlorination in 30 min, while 98.5% of CIP was degraded by UV/chlorine process in 9 min. HCO3− had markedly inhibition, NO3− and SO42- had slight inhibition, and Cl− had a marginal inhibition on CIP degradation in UV/chlorine system. The degradation of CIP in UV/chlorine process was mainly attributed to the attack of reactive species. The relative contributions of hydrated electrons (eaq ), hydroxyl radicals (HO ), chlorine atoms (Cl ), and UV photolysis were investigated. Under neutral condition in aqueous solution, CIP degradation had highest pseudo first-order reaction rate constant, in which eaq had the highest contribution, followed by Cl , HO , and UV photolysis. The intermediates and byproducts were identified and the degradation pathway was proposed. The total organic chlorine (TOCl) and biotoxicity were further assessed. CIP and natural organic matters (NOMs) were removed efficiently in real water. UV/chlorine showed the potential for the wastewater treatment containing CIP.

Roxarsone, an extensively used organoarsenical feed additive, is often pooled in livestock wastewater. Sulfate exists ubiquitously in livestock wastewater and is capable for arsenic remediation. However, little is known about impacts of sulfate on roxarsone biotransformation during anaerobic digestion of livestock wastewater. In this study, the biodegradation of 5.0 mg L−1 roxarsone, and the accumulation and volatilization of the generated arsenical metabolites in a sulfate-spiked upflow anaerobic granular blanket reactor were investigated. Based on the analysis of degradation products, the nitro and arsenate groups of roxarsone were successively reduced to amino and arsenite groups before the C–As bond cleavage. Effluent arsenic concentration was ∼0.75 mg L−1, of which 82.9–98.5% were organoarsenicals. The maximum arsenic volatilization rate reached 32.6 μg-As kg−1-VS d−1. Adding 5.0 mg L−1 sulfate enabled 66.7% and 45.9% decrease in inorganic arsenic concentration and arsenic volatilization rate, respectively. Arsenic content in the anaerobic granular sludge (AGS) was accumulated to 1250 mg kg−1 within 420 days. Based on the results of FESEM-EDS and XPS, sulfate addition induced arsenic precipitation in the AGS through the formation of orpiment. Arsenic in the effluent, biogas and AGS accounted for 52.9%, 0.01% and 47.1% of the influent arsenic when the reactor operated stably. The findings from this study suggest that sulfate has effectively regulatory effects on arsenic immobilization and volatilization during anaerobic digestion of organoarsenic-contaminated livestock wastewater.

Roxarsone (ROX) is a typical organoarsenic feed additive, and most of ROX is excreted unchanged in manure and wastewater. The stability and mobility of ROX result in the environmental risk of arsenic contamination spreading. The degradation of ROX to arsenate (As(V)) can reduce the mobility and environmental risk. Riboflavin is a photosensitizer and can catalyze ROX to As(V), but it is not stable in water environment. In this study, riboflavin-derivative 2′,3′,4′,5′-tetraacetylriboflavin (RTA) was used to replace riboflavin as photosensitizer. The possibility of ROX photodegradation using riboflavin-derivative (RTA) as photosensitizer was investigated. The results showed that RTA was more stable than riboflavin in water environment. ROX was degraded to arsenite (As(III)) by RTA in 90 min under simulated sunlight irradiation and 50 min under natural sunlight irradiation, and further to As(V). The degradation was inhibited under acidic or alkaline pH conditions, while was favorable under neutral pH conditions. The mechanisms of ROX degradation by RTA were further explored. 1O2, O2 − and excited RTA played important role in the RTA-sensitized ROX photodegradation. The photocatalytic degradation of roxarsone by RTA can reduce mobility of arsenic and the environmental risk caused by organoarsenicals.

Although anaerobic membrane bioreactor (AnMBR) has been proposed for the treatment of phenolic wastewater, the membrane fouling is still a major obstacle. The effects of dosing of granular activated carbon (GAC) and polyaluminum chloride (PACl) on the treatment performance and membrane fouling of anaerobic ceramic membrane bioreactor were investigated for treating phenol- and quinoline-containing wastewater. The results suggested that the one-off dosing of GAC resulted in a decrease of protein/carbohydrate ratio, which might account for the aggravation of membrane fouling alongside with the decreased flocs size. Nevertheless, the substrate uptake rates (SUR) of phenol and quinoline, and the specific methanogenic activity of sludge at the GAC dosing stage of experimental reactor (R1) were 8.79 ± 0.63 mg phenol g−1 MLVSS d−1, 7.01 ± 0.09 mg quinoline g−1 MLVSS d−1 and 0.27 ± 0.01 g CODCH4 g−1 MLVSS d−1, which were 1.69, 3.59 and 1.93 times higher than that of the control reactor (R2). The dosing of PACl reduced the membrane fouling rate by changing the floc structure of sludge, as well as the component of SMP and EPS. However, the substrate uptake rate of quinoline was declined. This work provides a comprehensive evaluation on the effect of GAC and PACl dosing on membrane fouling and performance of anaerobic ceramic membrane bioreactor treating phenol-and quinoline-containing wastewater.

In response to the shortage of water resources, multiple processes have been applied to turn wastewater secondary effluent (SE) into potable water. However, trace organic contaminants (TOrCs) and high concentrations of organic matter contained in SE pose a significant challenge to the reclamation. In this manuscript, combined UV-based and biofilm processes were used to treat the SE spiked with ibuprofen (IBU) and clofibric acid (CA). The efficiency of these sequential treatments was characterized in terms of changes in dissolved organic carbon (DOC), absorbance at 254 nm (A254), fluorescence excitation-emission matrix (FEEM), the concentration of IBU and CA, and molecular weight of SE. Parallel factor (PARAFAC) was applied as the analysis method for FEEM of the samples and two fluorescent components were successfully identified: humic-like substances (C1) and protein-like matter (C2). Large reductions in A254, C1, C2, IBU, and CA were observed during the UV-based processes, especially with the addition of H2O2. Nearly 50% of A254, 80% of the component C1 were decreased and almost complete removal of the component C2 and TOrCs was achieved by UV/2.0 mM H2O2 after 90-min treatment. During the oxidation processes, the formation of lower molecular weight (LMW) compounds was detected, and the biodegradability of the organic matters was greatly increased. Although no significant DOC reduction was obtained in UV-based processes, an obvious further DOC reduction (30~60%) was achieved by biofilm treatment following UV-based processes, especially after UV/H2O2 treatments. In the meantime, large amounts of LMW were removed in the biofilm treatment process. This manuscript provides an effective advanced treatment of SE for the removal of DOC and TOrCs, facilitating the wastewater reclamation.

The long start-up time and large demand of Anammox seed sludge limit the practical application of Anammox process. In this study, the seeding strategy of fast start-up of Anammox process using 2.0 g VSS L−1 of anaerobic granular sludge (AGS) or activated sludge (AS) with various low concentration of Anammox sludge as inoculum was investigated. In laboratory scale, the start-up (achieving 70% TN removal) was shortened from 21 days to 5 days when Anammox sludge concentration increased from 0.02 g VSS L−1 to 0.2 g VSS L−1 with 2 g VSS L−1 AS as inoculum, and 16S rDNA analysis indicated the enrichment of Anammox bacteria, while the start-up failed with AGS. In pilot scale, the start-up was achieved in 10 days using 0.02 g VSS L−1 of Anammox sludge and 2.0 g VSS L−1 of AS, confirming the fast start-up of Anammox process with low concentration of Anammox sludge.

Carbon nanotubes (CNTs) could be directly used as metal-free catalysts for the reduction of nitroaromatics by sulfide in water, but their catalytic ability need a further improvement. This study evaluated the feasibility of surface modification through thermal and radiation pretreatments to enhance catalytic activity of CNTs on nitrobenzene reduction by sulfide. The results show that thermal treatment could effectively improve the catalytic behaviors of CNTs for the reduction of nitrobenzene by sulfide, where the optimum annealing temperature was 400 °C. However, plasma radiation pretreatment didn’t result in an obvious improvement of the CNTs catalytic activity. Moreover, the possible reasons have been explored and discussed in the study. Additionally, the impacts of various operational parameters on nitrobenzene reduction catalyzed by the CNTs after an optimized surface modification were also evaluated. It was found that the rate of nitrobenzene removal by sulfide was positively correlated with CNTs doses in a range of 0.3–300 mg L−1; the optimum pH was around 8.0; higher temperature and sulfide concentration facilitated the reaction; and the presence of humic acid exhibited a negative effect on nitrobenzene reduction.

Anammox process is considered as a promising technology for removing total nitrogen from low-strength ammonium and phenol-containing wastewater. However, it is still a challenge for the anammox process to treat high-strength ammonium and phenol-containing wastewater. A completely separated partial nitritation and anammox (CSPN/A) process was developed to remove total nitrogen from high-strength phenol-containing wastewater. About 92% of COD, 100% of phenol, and 82.4% of total nitrogen were successfully removed at a NH4+-N concentration of 200 mg L−1 with a phenol/NH4+-N mass ratio of 0.5 in the CSPN/A process. Furthermore, a shock loading of 300 mg phenol L−1 with a phenol/NH4+-N mass ratio of 1.5 led to a complete failure of partial nitritation, but the performance was rapidly recovered by the increase of NH4+-N concentration. Although the activities of ammonium-oxidizing bacteria and anammox bacteria were severely inhibited at a phenol/NH4+-N mass ratio of 1.5, the enrichment of efficient phenol degraders in the CSPN stage could strengthen the performance robustness of partial nitritation and anammox process. Therefore, this study presented a new insight on the feasibility of the anammox process for treating high-strength ammonium and phenol-containing wastewater.

Membrane fouling has been the primary challenge limiting the application of electrodialysis (ED) technologies in wastewater treatment, particularly the wastewater containing abundant dissolved organic matter, such as the digested sludge centrate. This study proposed an electro-ion substitution modified electrodialysis (EIS-ED) system that can recover NH4+ from the sludge centrate in coastal wastewater treatment plants (WWTPs), with negligible membrane fouling and scaling formed. In this system, the sludge centrate flowed between two cation-exchange membranes (CM), alongside the seawater providing Na+ as the substitution of NH4+. According to the experimental data and modeling, EIS-ED recovered more than 70% of NH4+ from the sludge centrate with an energy consumption of 2.03 kWh/kg NH4+-N, which was 14% lower than the conventional ED. Membranes, solutions and electrodes were the three major contributors of the linear ohmic resistance in the EIS-ED process. EIS-ED significantly resisted membrane fouling by means of electrostatic repulsion between the CM and negatively charged compounds, including particles and dissolved organic matter, and membrane scaling was also mitigated. After a treatment of 20 L sludge centrate, no significant decrease of membrane ion-exchange capacity was observed in the EIS-ED, while a decrease of 5.3% was found in the conventional ED. Accordingly, the potential application prospect of EIS-ED was proposed, which can recover at least 70% of NH4+ from the sludge centrate and reduce 10–20% of the NH4+ loading to the mainstream processes in coastal WWTPs.

Introducing reductive species into heterogeneous catalysts can improve their catalytic efficiency in Fenton-like processes. Iodide ions (I−), a typical reductive species with good reducibility, might enhance the catalytic performance of H2O2 activation when doped in heterogeneous catalysts. In this study, the iodine-doped Bi2WO6 (IX-Bi2WO6) nanosheets were synthesized with a facile hydrothermal method and used to activate H2O2 to degrade bisphenol A (BPA). Compared with Bi2WO6, which was almost inactive, the IX-Bi2WO6 exhibited great improvement for BPA degradation. Among the fabricated catalysts, the I0.50-Bi2WO6 with an iodine content of 0.50 mmol was found to be most effective and could work efficiently in a wide pH range from 4.0 to 10.0. Moreover, with a low consumption of H2O2 (H2O2 : pollutant molar ratio = 10:1), 78% BPA was degraded within 10 min at initial pH 7.0. Unlike the conventional H2O2 activation mechanism, the direct electron transfer was verified to be the main mechanism for the BPA degradation based on the results of electron paramagnetic resonance (EPR) analysis, radical quenching, and electrochemical experiments in this work. Furthermore, the activation of H2O2 by iodine-doped BiVO4 and Bi2MoO6 was also conducted to validate the applicability of such an iodine doping approach. These results indicate that the introduction of reductive species I− is a promising and effective method to develop highly efficient Bi-based catalysts for H2O2 activation.

Animal manure is often anaerobically digested for the purpose of producing biogas. The digested manure, namely digestate, can be applied onto farmlands to enhance crop yields as it is abundant in nutrients. However, intensive livestock farming brings about manure exceeding the carrying capacity of lands nearby. Technologies focused on nutrient recovery from digestate have been studied recently, while many problems and challenges still remain unsolved. In this article, these recovery technologies are reviewed and compared, and challenges are deliberated. Ammonia stripping and struvite formation are easily operated technologies in comparison with membrane technologies. Amongst membrane technologies, electrodialysis reversal and forward osmosis are promising due to their high resistance to membrane fouling. Further studies should be focused on the operational cost, disposal of solid and liquid residuals and marketization of the recovered products.

Animal manure should be regarded as a resource rather than a waste as it contains abundant nutrients (nitrogen and phosphorus) and organic matter. In this study, a laboratory-scale bipolar membrane electrodialysis (BMED) system was set up to assess the recovery of ammonium (NH4+), phosphate (PO43−) and volatile fatty acids (VFAs) from both synthetic and real pig manure hydrolysate for the first time. Synthetic hydrolysate was used as feed first to investigate the ionic migrations in the BMED system. After 5.5 h of operation, 52% of NH4+ migrated to the base compartment, and 98% of PO43− and 95% of VFAs migrated to the acid compartment. A BMED model was established to quantify the ion flux balance in the membrane stack. It substantiated that the low recovery efficiencies of NH4+ and the impurity of acid solution were primarily caused by the undesired diffusion of ions through bipolar membranes. Subsequently, a novel two-stage BMED operation based on the “inflection point” of voltage was developed to minimize the NH4+ loss and separate PO43− and VFAs from the acid compartment. Through this operation, the recovery efficiency of NH4+ increased to 78%, and 75% of PO43− and 87% of VFAs were separated from Cl− and SO42− in the acid compartment. Finally, real pig manure hydrolysate was tested and the variations of ions in the BMED were consistent as those using synthetic wastewater. This study demonstrates that it is feasible to recover valuable nutrients and VFAs from pig manure hydrolysate using two-stage BMED technology.