Subsequent Biological Treatment Research Articles

Coagulation/Flocculation of Slaughterhouse Effluent Using Pac and Tanfloc as Coagulants

Objective: In this context, this research aimed to evaluate the influence of different types of coagulants, one inorganic and one natural (PAC and Tanfloc), in the treatment of an effluent from a pig slaughterhouse. Method/design/approach: Both coagulants were prepared in aqueous solution at the time of the test, 1% (v/v) for PAC and 0.5% (m/v) for Tanfloc. To assess the effect of the coagulants on the effluent, coagulation/flocculation tests were carried out using the jar-test apparatus. The dosages evaluated for both coagulants were 50, 100, 150, 200, 250 and 300 mg/L. The parameters analyzed were color and turbidity. Results and conclusion: According to the results of the statistical analysis, the optimum dosages obtained for both coagulants was 250 mg/L. With these dosages, removal of the parameters analyzed was observed (> 94% for turbidity and > 85% for color) with residuals (< 40 NTU for turbidity and < 400 uH for color), showing better results at this optimum dosage when Tanfloc is used as a coagulant. Implications of the research: The growing awareness that effluent treatment is of fundamental importance to public health and environmental pollution control has led us to look for low-cost alternatives to treat these effluents, using a vegetable organic coagulant based on tannin as an alternative to aluminum polychloride (PAC). Originality/value: Due to the growing need for low-cost, easily accessible treatments that do not require large areas, physical-chemical treatment of slaughterhouse effluent can be used as a pre-treatment, with the use of alternative coagulants, being a viable way to reduce organic matter for subsequent biological treatment, or in some cases replace the biological process.

Optimisation, modelling and mechanism of photocatalytic degradation of sofosbuvir antiviral by TiO2 nanoparticles coupled with biological treatment

ABSTRACT The overarching objective of this research endeavour was to develop an integrated approach to the complete removal and breakdown of the antiviral compound sofosbuvir. To accomplish this, a two-fold strategy was employed, involving a heterogeneous photocatalysis process coupled with subsequent biological treatment. Leveraging the versatile TiO2-P25 nanoparticles, a meticulous optimisation was carried out using the Box-Behnken methodology, strategically considering the interplay of three pivotal independent variables: pH, initial molecule concentration, and catalyst concentration. This optimisation aimed not only to augment the degradation of sofosbuvir but also to enhance its COD removal. The complex influence of these factors was mathematically encapsulated in a second-order polynomial equation, offering valuable insights into the process dynamics. COD removal and optimal parameters for degradation were a pH of 6.8, a catalyst dosage of 1 g L−1, and an initial molecule concentration of 0.1 mM under a 125 W high-pressure mercury lamp. The efficiency of elimination for the degradation was 100% at 120 min and for the COD removal extinguished 99.44% at 6 h. Sofosbuvir has a rapid degradation, COD removal degree is lower, which means the presence of intermediate compounds more difficult to treat by photocatalysis. Thus, the viability of implementing a link between the nanoparticles TiO2-photocatalysis as a biodegradability improvement pretreatment with the biological process has been studied as an essential activity to enhance treatment efficiency while reducing energy use and treatment times. combination of photocatalysis with a biological treatment improves the treatment. The density functional theory (DFT) approach was applied to better understand the mechanism of sofosbuvir degradation and to examine the impact of different degradation sites. Mechanism Analysis of the photoproducts and photoproduct intermediates was identified by HPLC-MS. However, a 120 min BOD5/COD ratio (COD, chemical oxygen demand; BOD, biochemical oxygen demand) of ≥0.4 results from the degradation of sofosbuvir by TiO2.

Peroxymonocarbonate activation via Co nanoparticles confined in metal-organic frameworks for efficient antibiotic degradation in different actual water matrices.

Traditional advanced oxidation processes suffer from low availability of ultrashort lifetime radicals and declining stability of catalysts. Co nanoparticles in hollow bimetallic metal-organic frameworks (Co@MOFs) were synthesized via a solvothermal method. Nanoconfinement and peroxymonocarbonate (PMC) degradation system endows Co@MOFs with high catalytic activity and stability even in the actual water matrices. The nanocomposites exhibited 100-200nm polyhedron structure with irregular nanocavity between the 20nm shell and multicores. Co nanoparticles were completely encapsulated by the FeIII-MOF-5 shell according to the X-ray diffraction and photoelectron spectra. Both 0.8nm micropores and 3.6nm mesopores were proven to be present. The yolk-shell Co@MOFs exhibited higher catalytic performance than that of Co nanoparticles, hollow FeIII-MOF-5 and its core-shell counterpart toward PMC activation during sulfamethoxazole degradation. The catalytic activities of Co@MOFs for the activation of unsymmetrical peroxides (PMC and peroxymonosulfate) were much higher than those for the symmetrical peroxides (H2O2 and persulfate) and the heterogeneous catalysis was dominant in the Co@MOFs activated H2O2 and PMC systems. The MOF stability was the highest and metal leakages were the least in the activated PMC system among the four peroxides because of mild reaction conditions and the alkalescent solution (pH=8.3-8.4). Furthermore, the high removal efficiencies (>94%) and degradation rates could be maintained in the different actual water matrices due to the confinement effects. The contributions of carbonate and hydroxyl radicals were primary for sulfamethoxazole degradation, and superoxide anion and singlet oxygen also played essential roles according to scavenging experiments and time-series spin-trapping electron spin resonance spectra. Six degradation pathways were proposed according to 26 intermediate identification and the pharmacophores of more than 80% intermediates were destroyed, which would benefit subsequent biological treatment. Successful combination of nanoconfinement and PMC might provide a new effective solution for pollution remediation.

Systematical comparison of antibiotic degradation in the activated peroxymonocarbonate and Fenton systems: Kinetics, matrix influence, mechanisms and intermediate toxicities

The degradation of representative antibiotics and their mechanisms in the activated peroxymonocarbonate (PMC) and Fenton systems were systematically investigated and compared in this work. The PMC can exist and be reliable at high ratios for 1 h according to the 13C nuclear magnetic resonance spectra. The activated PMC system was proven to be more efficient than the Fenton system for the degradation of sulfamethoxazole, ciprofloxacin and ceftriaxone under same experiment conditions. The activated PMC system exhibited higher sulfamethoxazole removal performance in different actual water matrices due to the insignificant effect of coexisting substances, while the impurities had an adverse impact on the Fenton system. The pH of the activated PMC system was relatively stable and ranged from 7.8 to 8.2, while the pH of the Fenton system dropped from 5.2 to 4.1. The slight decreases of sulfamethoxazole removal efficiencies were observed after bubbling O2, N2 and CO2 in the Fenton system, while removal rates in the activated PMC system were greatly prohibited and the inhibition ratios increased with gas solubility. The selective 1O2 and CO3− played primary roles in the activated PMC system according to scavenging experiments and time-series spin-trapping electron spin resonance spectra, which resulted in higher removal efficiencies and lower oxidation degree. The non-selective OH contribution was dominant in the Fenton system. The activated PMC system was more suitable for subsequent biological treatment and friendlier to the ecosystem than the Fenton system according to intermediate pharmacophore removal and toxicity comparisons. The activated PMC system showed apparent advantages over the Fenton system in most cases, which might encourage more researchers to devote their interest and time on this promising degradation system.

Preparation of cationic aggregates derived from sewage sludge for efficient capture of organic matter

Capturing the abundant organic matter residing in wastewater can not only reduce the emission of CO2 from the source, but the enriched organics can also be used for anaerobic fermentation to generate and offset energy consumption in wastewater treatment processes. The key is to find or develop low-cost materials that can capture organic matter. Herein, sewage sludge-derived cationic aggregates (SBC-g-DMC) were successfully prepared via a hydrothermal carbonization process coupled with a graft copolymerization reaction for recovering organic matter from wastewater. Based upon preliminary screening of synthesized SBC-g-DMC aggregates regarding grafting rate, cationic degree, and flocculation performance, SBC-g-DMC2.5 aggregate prepared with 60 mg of initiator, DMC-to-SBC mass ratio of 2.5:1, 70 °C, and 2 h of reaction time was selected for further characterization and evaluation. Results showed that SBC-g-DMC2.5 aggregate has a positively-charged surface over a wide pH range of 3–11 and a hierarchical micro-/nano-structure, endowing it with an excellent organic matter capture efficiency (97.2% of pCOD, 68.8% of cCOD, and 71.2% of tCOD). Meanwhile, SBC-g-DMC2.5 exhibits inappreciable trapping ability for the dissolved COD, NH3–N, and PO43−, guaranteeing the regular running of subsequent biological treatment units. Electronic neutralization, adsorption bridging, and sweep coagulation between cationic aggregates surface and organic matter were identified as the primary mechanisms for SBC-g-DMC2.5 to capture organics. This development is expected to provide a theoretical reference for sewage sludge disposal, carbon reduction, and energy recovery during municipal wastewater treatment.

Improving organic matter and nutrients removal and minimizing sludge production in landfill leachate pre-treatment by Fenton process through a comprehensive response surface methodology approach

Landfill leachate (LL) represents a very complex effluent difficult to treat and to manage which usually requires a chemical pre-treatment. In this study, response surface methodology (RSM) was used to identify the optimum operating conditions of the Fenton process as a pre-treatment of LL in order to reduce the high organic content and simultaneously optimize the BOD5:TN:TP ratio. The dosages of Fenton process reagents, namely Fe2+ and H2O2, were used as variables for the implementation of RSM. Chemical oxygen demand (COD), five-days biochemical oxygen demand (BOD5), total nitrogen (TN), total phosphorus (TP) removals (and simultaneously BOD5:TN:TP ratio), sludge-to-iron ratio (SIR) and organic removal-to-sludge ratio (ORSR) were selected as target responses. This approach considered the SIR and ORSR parameters which are a useful tool for assessing sludge formation during the process along with organic matter removal. The variables (H2O2 and Fe2+ concentrations) significantly affected the responses, as the role of oxidation mechanism is dominant with respect to coagulation one. The pH for the process was fixed to 2.8 while the treatment time was set to 2 h. The optimum operational conditions obtained by perturbation and 3D surface plot, were found to be 4262 mg/L and 5104 mg/L for Fe2+ and H2O2, respectively (H2O2/Fe2+ molar ratio = 2) with COD, BOD5, TN and TP removals of 70%, 67%, 84% and 96% respectively, while SIR and ORSR final values were 1.15 L/mol and 33.79 g/L respectively, in accordance with models-predicted values. Moreover, the initial unbalanced BOD5:TN:TP ratio (9:1:1) was significantly improved (100:6:1), making the effluent suitable for a subsequent biological treatment. The investigated approach allowed to optimize the removal of organic load and nutrients as well as to minimize the sludge formation in Fenton process, providing a useful tool for the operation and management of LL pre-treatment.

Pretreatment of herbal waste using sonication

The effect of hydrodynamic cavitation (HC) and the manner it affects the biodegradability of herbal waste suspended on municipal wastewater subjected to mechanical pre-treatment was examined in this paper. The HC was performed at an optimal inlet pressure equal to 3.5 bar and with the cavitation number of 0.11; the number of recirculation passes through the cavitation zone amounted to 30.5. The BOD5/COD ratio was enhanced by more than 70% between the 5th and 10th minute of the process, indicating the enhanced biodegradability of herbal waste shortly. Fiber component analysis, FT-IR/ATR, TGA and SEM analysis were conducted to check the findings and to demonstrate changes in the chemical and morphological structure of herbal waste. It confirmed that hydrodynamic cavitation visibly influenced the herbal composition and their structural morphology, decreased hemicellulose, cellulose and lignin content, but did not form the by-products affecting the subsequent biological treatment of herbal waste.

Effective and mechanistic insights into reverse osmosis concentrate of landfill leachate treatment using coagulation-catalytic ozonation-bioaugmentation-based AnMBR

Landfill leachate membrane concentrates containing high concentrations of organics pose a major threat to the environment, and efficient treatment methods are urgent issue. In this study, a coagulation-catalytic ozonation-bioaugmentation-based anaerobic membrane bioreactor (CCOB-AnMBR) process was applied to treat reverse osmosis concentrate (ROC) of landfill leachate. Compared with polyaluminum ferric chloride (PAFC) and prefrontal cortex (PFC), coagulation using polyferric sulfate (PFS) effectively removed refractory contaminants including macro molecular organics (MMOs), benzene ring compounds (BRCs), humic acid (HA), and fulvic acid (FvA) in ROC of landfill leachate, with average 78.3%, 53.5%, 34.7% and 34.3%, respectively. Catalytic ozonation with MnOx-CeOx-Al2O3 increased the biodegradability index by degrading refractory organic compounds, which facilitated subsequent biological treatment of ROC. The oxidation of mostly occurs at the solid–liquid interface and the presence of MnOx-CeOx-Al2O3 nanocatalyst enhanced ozone decay and increased generation of hydroxyl radical (•OH) and singlet oxygen (1O2) in ROC. In addition, bioaugmentation using recombinant genetically engineered Desulfovibrio vulgaris expressing Sat and dsrAB (rGEDEV-sds) promoted metabolism of sulfate by driving transfer sulfate from the environment into the cell and sulfate dissimilation reduction process. Bioaugmentation-based AnMBR (Bio-AnMBR) caused complete degradation of the total organic carbon (TOC), enhanced degradation of leachate pollutions, and decreased the concentration of sulfate in ROC. The macro molecular organics, refractory organic contaminants, the residual coagulation-resistant substances (CRS), and heavy metal were effectively degraded in the Bio-AnMBR system. Furthermore, CCOB-AnMBR exhibits high processing efficiency in the degradation of the contaminants in ROC of landfill leachate. Overall, this excellent performance proves the feasibility and elucidates the mechanism of CCOB-AnMBR process for the removal of contaminants in ROC of landfill leachate.

Sonochemical advanced oxidation process for the degradation of furosemide in water: Effects of sonication’s conditions and scavengers

The intensive consumption of pharmaceuticals and drugs in the last decades has led to their increased concentrations in wastewaters from industrial sources. The present paper deals, for the first time, with the sonochemical degradation and mineralization of furosemide (FSM) in water. FSM is a potent loop diuretic used to treat fluid build-up due to heart failure, liver scarring, or kidney disease. The influence of several operating parameters such as acoustic intensity, ultrasonic frequency, initial FSM concentration, solution’s pH, nature of the dissolved gas (Ar, air and N2) and radical scavengers (2-propanol and tert-butanol) on the oxidation of FSM was assessed. The obtained results showed that the degradation rate of the drug increased significantly with the increase of the acoustic intensity in the range of 0.83 to 4.3 W cm−2 and decreased with the augmentation of the frequency in the range of 585–1140 kHz. It was also found that the initial rate of the sonolytic degradation of FSM increased with the increase of its initial concentration (2, 5, 10, 15 and 20 mg/L). The most significant degradation was achieved in acidic conditions at pH 2, while in terms of saturating gas, the rate of FSM degradation decreased in the order of Ar > air > N2. The FSM degradation experiments with radical scavengers showed that the diuretic molecule degraded mainly at the interfacial region of the bubble by hydroxyl radical attack. Additionally, in terms of acoustic conditions, the sono-degradation of 30.24 µmol L-1 of FSM solution demonstrate an optimal performance at 585 kHz and 4.3 W/cm2, the results indicated that even if the ultrasonic action eliminated the total concentration of FSM within 60 min, a low degree of mineralization was obtained due to the by-products formed during the sono-oxidation process. The ultrasonic process transforms FSM into biodegradable and environmentally friendly organic by-products that could be treated in a subsequent biological treatment. Besides, the efficiency of the sonolytic degradation of FSM in real environmental matrices such as natural mineral water and seawater was demonstrated. Consequently, the sonochemical advanced oxidation process represent a very interesting technique for the treatment of water contaminated with FSM.

Response Surface Optimization and Floc Structure Analysis of Magnetic Flocculation Technology for Anaerobic Digestion Reject Water

In order to improve the removal efficiencies of SS and Fe3+ in anaerobic digestion reject water for the subsequent biological treatment process, on the basis of the single factor test in the early stage, the response surface method was used, and the structure of the formed floc was analyzed by magnetic flocculation. The optimum amounts of magnetic powder, polyaluminum chloride (PAC) and polyacrylamide (PAM) were 40.51 mg/L, 31.31 mg/L and 4.05 mg/L, respectively. At this time, the removal efficiencies of SS and Fe3+ were 97.84% and 98.35%. The effects of floc particle size, scanning electron microscopy, infrared spectroscopy and two-dimensional fractal dimension of flocs on the flocculation ability showed that: compared with conventional coagulation, the average particle size of flocs treated by magnetic flocculation was 76.56 μm, the Fe-O-Al absorption peak appeared at 984 cm−1, the flocculation ability was significantly improved, the surface of the floc was rough and porous, and the structure was dense, and the sedimentation performance was significantly improved also.

NAMPT and NAPRT serum levels predict response to anti-TNF therapy in inflammatory bowel disease.

Nicotinamide phosphoribosyltransferase (NAMPT) and nicotinic acid phosphoribosyl transferase (NAPRT) are key intracellular enzymes that participate in the biosynthesis on NAD but have also been shown to be released as proinflammatory cytokines. A number of reports have shown that circulating NAMPT is increased in serum of patients with inflammatory disorders, including inflammatory bowel diseases (IBD), while nothing is known regarding circulating NAPRT and the presence of both cytokines in IBD patient stools. In the present study, we evaluated eNAMPT and eNAPRT levels in a large cohort of IBD patients not on biological therapy and in a subset that then was prescribed biologics. We conducted a retro-perspective study on 180 patients, of which 111 underwent subsequent biological treatment (adalimumab, vedolizumab, and ustekinumab). We analyzed eNAMPT and eNAPRT concentrations in serum and faces of IBD patients, correlating them with response to biologics. We now report that eNAMPT and eNAPRT are significantly increased in both serum and stools of IBD patients. NAMPT and NAPRT levels correlate with disease severity, with C reactive protein and with serum IL-6 levels. Importantly, levels of NAMPT in patients starting treatment with adalimumab correlate with response failure at three months: patients with levels above 4 ng/ml were significantly less likely to obtain benefit. Serum NAMPT as a biomarker of response yields a sensitivity of 91% and a specificity of 100%. The present work strongly suggests that a prospective trial evaluating eNAMPT and eNAPRT levels in relation to response to biologicals in IBD should be initiated.

The effect of pH/PAC on the coagulation of anionic surfactant wastewater generated in the cosmetic production

The wastewater generated from the production of cosmetic raw materials contained a large number of anionic surfactants, which could hardly meet the wastewater discharge standards in China when biological technology was employed as a sole treatment strategy. Coagulation pretreatment was one of important operation units of wastewater treatment, and it could greatly reduce the burden of subsequent biological treatment and improve the efficiency of wastewater treatment. The pH value of the wastewater directly affected the hydrolysis intermediates of the coagulants, thereby influencing the performance of the flocculation reaction. In this study, the effects of adjusting the pH value of raw wastewater on the removal efficiencies of the pollutants, dissolved organic matter and sludge morphology were discussed. The changes of coagulation performance and group structure and thermal stability of flocculated sludge under the coupling action of pH/polyaluminum chloride (PAC) were studied. The results showed that only adjusting the pH of raw wastewater could promote removal efficiencies of chemical oxygen demand (COD) and linear alkylbenzene sulfonate sodium (LAS) and enhance the conductivity of actual cosmetic wastewater, but could not remove the aromatic proteins. The highest coagulation efficiency was achieved under PAC concentration of 2.6 g/L and the pH value of 6. The molecular weight distribution of organics after coagulation was mainly concentrated in the range of> 100 kDa and< 3 kDa, and medium molecular weight organics were mainly removed. It was expected to provide strategies for improving the coagulation performance of actual cosmetic wastewater.

Application of partial ozonation on tank truck cleaning concentrate and the influence on biodegradability and ecotoxicity: a pilot-scale study.

This study investigates the pilot-scale ozone treatment of reverse osmosis concentrate (ROC), originating from variable tank truck cleaning wastewater. The influence of ozonation on short- and long-term biodegradation potential was examined through respirometry and Zahn-Wellens, respectively. Ecotoxicity was also examined for several concentrate batches and ozonation steps. Chemical oxidation through ozone had a beneficial effect on chemical oxygen demand removal, with a removal efficiency up to 56%. Formation of short-term biochemical oxygen demand (BODst) was induced for several, but not all batches, showing the potential of subsequent biological treatment of ozonated ROC. An increase in the inherent biodegradability through Zahn-Wellens was observed for all tested samples after ozonation, rising to a maximum of 68% after 3 hours of ozonation, highlighting the importance of sludge adaptation. Ecotoxicity, tested with Artemia franciscana and the saltwater algae P. tricornutum, showed initial decreases in algae inhibition after short ozonation periods. An increase in algae inhibition was, however, seen after prolonged ozonation for all tested ROC samples, pointing to the formation of ecotoxic by-products. Artemia showed no significant toxicity effects. When applying biological treatment through Zahn-Wellens, a decrease in ecotoxicity was observed for several samples, likely through biological oxidation of the produced degradation products.

Impacts of steam explosion pretreatment on semi-continuous anaerobic digestion of lignin-rich submerged macrophyte

This study evaluated the impacts of steam explosion pretreatment of lignin-rich macrophyte (Potamogeton maackianus) on semi-continuous anaerobic digestion. The pretreatment accelerated hydrolysis efficiency from 9% to 19% (untreated) to 38%–48% (pretreated), which considerably enhanced the methane yield from 108 ± 31 to 200 ± 36 mL g-VS−1. As a negative impact, the soluble COD concentration in the effluent in the pretreatment condition was high (10,000–12,000 mg L−1) due to the accumulation of steam explosion by-products (soluble lignin and phenolic compounds). This high concentration of by-products in the digestate can destabilise subsequent biological treatment processes; therefore, their removal from the digestate will be necessary. Although the concentration of inhibitory phenolic compounds in the pretreated P. maackianus was high, it was continuously removed (38 ± 10%) in the reactor, which ensured process stability. As a result, this study demonstrated for the first time the effectiveness of direct anaerobic digestion treatment of steam-exploded lignocellulose biomass over a long-term continuous operation. By summarising the results of previous studies and our study, we found that the improvement in CH4 production (y, %) by steam explosion pretreatment is regulated by lignin content in the untreated biomass (x, %-TS) and expressed by the equation, y = 18.1 e0.071x (p = 0.0001). This empirical formula indicates that the effectiveness of steam explosion pretreatment increases exponentially with an increase in the lignin content.

Zero-valent iron effectively enhances valuable products generated from wastewater containing 2-bromo-4,6–dinitroaniline during hydrolysis acidification process: Performance and mechanisms

Treatment to remove 2-bromo-4,6-dinitroaniline (BDNA) from wastewater is urgently needed owing to its carcinogenicity, mutagenicity, and teratogenicity. Hydrolysis acidification (HA) is widely used to treat wastewater to improve biodegradability and resource utilization. Thus, a zero-valent iron (ZVI)-coupled HA system was operated to treat BDNA-containing wastewater for the first time, with emphasis on the performance and enhanced mechanisms. The improved results for BDNA removal efficiency and B/C ratio and the decreased acute toxicity suggested that ZVI addition benefited the formation of advantageous products for subsequent biological treatment. The volatile fatty acids (VFAs) ratio (CHAc:CHPr:CHBu) was optimized from 21:5:4 to 29:5:6, which benefited the utilization of wastewater resources for lipid generation. ZVI characterization, density functional theory (DFT) calculations, extracellular polymeric substances (EPS) analysis, molecular ecological network analysis (MENA), and redundancy analysis (RDA) of the microbial community further revealed that the enhanced mechanisms were summarized as beneficial interactions between ZVI and microorganisms. The ZVI was protected from excessive corrosion and lowered the oxidation-reduction potential (ORP), a key environmental factor, resulting in differences in microbial communities. These differences were presented as the enrichment of keystone species (e.g., Lactococcus), which function in BDNA reduction and VFAs generation. Moreover, ZVI promoted electron transfer, as proven by the high electron transfer capacity (ETC) of 0.452 and 0.361 μmol e–/g VSS in the RZVI and blank systems, respectively.

Fenton-like reaction of glucose oxidase-glucose@Kaolin coupled with green rust: A framework triggering FeⅣ=O in refractory pollutants degradation

Fenton reaction has been widely applied with fast reaction speed and strong oxidation capacity, but it also has some noticeable defects of acid-alkali reagents over-consumption and strong tendency of H2O2 self-decomposition under high concentration. In order to overcome these shortcomings, this study proposed a green rust/Kaolin fixed glucose oxidase (GR/Glu-Kaolin@GOD) Fenton system. The production of H2O2 from Glu-GOD@Kaolin system was catalyzed by GR to generate oxidizing species and degrade aniline organic wastewater. Results showed that the enzymatic reaction could produce H2O2 at a gradual incremental pace in situ, avoiding active agent quenching and heightening its utilization rate. Furthermore, this system was proved to have an excellent removal effect under neutral and weak-acid conditions, which was superior to the traditional homogeneous Fenton with a narrow pH range. In this study, diversified active substances in the system were detected including hydroxyl radicals, FeIV=O and superoxide radicals, whose real-time degradation contribution changes were calculated and analyzed. On basis of the results, the roles of these active agents and the interactional principles among them were explored. Furthermore, the close correlation between Fe2+ in GR and GlcA and degradation mechanisms upon 3, 4-DMA were set forth in detail. Especially, in the middle and later stage of the reaction, the contribution of FeIV=O, generated through the complexes between Fe(Ⅱ) and GlcA, would continue to increase due to the gradually benign pH environment and FeIV=O gave full play to advantages in decarboxylating those intermediate products containing methyl, etc, which consequently enhanced both the oxidation efficiency and effluent biodegradability. In addition, the optimal operational conditions were determined through response surface data analysis. Moreover, the residual Glu and small molecular acids in the water could be fully exploited as suitable microbial carbon sources, and elevate the efficiency of the subsequent biological treatment.

Bio-Fenton-Assisted Biological Process for Efficient Mineralization of Polycyclic Aromatic Hydrocarbons from the Environment

The intensive production of fossil fuels has led to serious polycyclic aromatic hydrocarbon (PAH) contamination in water and soil environments (as PAHs are typical types of emerging contaminants). Bio-Fenton, an alternative to Fenton oxidation, which generates hydrogen peroxide at a nearly neutral pH condition, could ideally work as a pretreatment to recalcitrant organics, which could be combined with the subsequent biological treatment without any need for pH adjustment. The present study investigated the performance of a Bio-Fenton-assisted biological process for mineralization of three typical types of PAHs. The hydrogen peroxide production, PAH removal, overall organic mineralization, and microbial community structure were comprehensively studied. The results showed that the combined process could achieve efficient chemical oxygen demand (COD) removal (88.1%) of mixed PAHs as compared to activated sludge (33.1%), where individual PAH removal efficiencies of 99.6%, 83.8%, and 91.3% were observed for naphthalene (NAP), anthracene (ANT), and pyrene (PYR), respectively, with the combined process.

Recirculation of activated sludge for coagulant synthesis under hydrothermal conditions.

A hypothesis was proposed that the activated sludge was converted into hydrochar full of phenolic hydroxyl and then was made into coagulant by graft copolymerization. The results show that under the addition of HCl, the content of phenolic hydroxyl on the surface of hydrochar (SBC) under hydrothermal conditions increased sharply, up to 1.586mmol/g, showing that HCl dosage of 0.10g/g dry sludge and holding time of 4h was recommended. Under graft copolymerization with the addition of DMC, the coagulant was synthesized. Based on the analysis by FTIR, XPS, zeta potential, etc., the possible synthesis route of coagulant from SBC was that phenolic hydroxyl on SBC was activated by the initiator and then the polymerization between SBC and DMC was triggered. The optimal grafting conditions are gotten. It was named as SBCHCl0.10g, 4h-g-DMC0.7. The removal by SBCHCl0.10g, 4h-g-DMC0.7 on COD and turbidity in domestic wastewater is up to 69% and 93%, respectively. The component of COD indicated that almost all particulate COD and most of colloidal COD are removed. On the contrary, the removal on dissolved COD can be neglected. Most of NH3-N and P is kept in the wastewater. This is in favor of subsequent reuse and biological treatment.

Feasibility study on produced water oxidation as a pretreatment at offshore platform

Produced water (PW) generated worldwide has lately become an issue of environmental concern. PW has a complex composition and a suitable treatment at offshore oil and gas platforms is required to achieve zero harmful discharge into the sea. The feasibility of electrochemical oxidation, heat-activated persulfate and ozonation was investigated as PW pretreatment. For comparison purposes, a common oxidant dosage level of 5% and 10% treatment equivalent chemical oxygen demand(COD) removal were established. Aiming to access PW biodegradability, an assay for biological oxygen demand(BOD) for high salinity matrix was also developed as a tool to characterize treatment efficiency. Electrochemical oxidation was largely independent on the anode materials, and controlled by the applied charge passed through the system. Heat-activated persulfate reaction was time-consuming and dependent on activation temperature, as well as initial oxidant concentration. Both methods reduced COD and BOD without significantly improving PW biodegradability, probably due to by-products generation. Ozonation had the most promising results applying doses ranging from 3.5 to 151mgO3/L. The benzene in PW after ozonation reduced up to 71% alongside with> 70% toxicity reduction for tested doses. Ozonation also showed to marginally improve PW biodegradability, which underline the potential of ozone to facilitate a subsequent biological treatment.

Potassium ferrate pretreatment promotes short chain fatty acids yield and antibiotics reduction in acidogenic fermentation of sewage sludge

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 (K2FeO4) oxidation was used as a pretreatment strategy for WAS acidogenic fermentation to increase the hydrolysis of sludge and destruct the harmful antibiotics. Pretreatment with K2FeO4 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, K2FeO4 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, K2FeO4 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.