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Plastic pollution and antibiotic resistance are two emerging environmental and human health crises today. Although it was revealed that microplastics can serve as vectors for the dissemination of antibiotic resistance, it is still unclear how the nanoplastics influence the horizontal transfer of antibiotic resistance genes (ARGs). Herein, we firstly compared the effect of polystyrene (PS) micro/nanoplastics on the transformation of plasmid-borne ARG, using a transformation model consisting of plasmid pUC19 (amp

Nowadays, metal-organic framework (MOF) materials are used in the application of sustained release of drugs. Because of high efficiency, good stability and varied properties, MOFs have shown great potential and a promising future in terms of delivery. In this article, many factors which can have a significant impact on the release during the slow release of a drug were introduced, such as temperature, pH, permeability and toxicity. This article also analyses the performance of different types of MOF in the study of different drugs, including coordination complexes, coordination polymers, and microscale coordination polymers. With an in-depth understanding of the different conditions, the process of designing and producing sophisticated MOF materials can be promised.

Conditioning can drastically improve the dewaterability of sewage sludge and is widely practiced in most wastewater treatment plants (WWTPs). Sludge conditioning was also reported as a crucial step in sludge treatment to attenuate antibiotic resistance, but it remains unclear whether the attenuated antibiotic resistance by conditioning treatments would guarantee low abundance of antibiotic resistance genes (ARGs) in the compost products of municipal sewage sludge. Herein, the impacts of three conditioning treatments, including bioleaching and chemical conditioning using Fe[III]/CaO or polyacrylamide (PAM), on the abundances of 20 ARGs and 4 mobile genetic elements (MGEs) during conventional aerobic composting of dewatered sludge were investigated. It was found that the absolute and relative abundances of total ARGs in compost product of bioleached sludge accounted for only 13.8%-28.8% of that in compost products of un-conditioned, Fe[III]/CaO-conditioned, or PAM-conditioned sludges. Besides, bioleaching conditioning resulted in the lowest abundances of ARG subtypes and ARG-associated bacteria in the sludge compost product. The shift of ARG profiles in the bioleached sludge composting can be mainly ascribed to the ARG-associated bacteria, while the MGEs drove the ARG profiles during conventional composting of un-conditioned sludge and the two chemically conditioned sludge. Thus, bioleaching conditioning is superior to the chemical conditioning using Fe[III]/CaO or PAM in mitigating antibiotic resistance in sludge compost products, which was contributed by the pre-removal of ARGs prior to composting treatment and the potential limitation of ARGs transfer during conventional composting.

Sludge reuse and utilization is one of important routines of disseminating fecal pollution to surface water and groundwater. However, it remains unclear the spatial distribution of fecal pollution indicators in sludge flocs and their reductions during sludge treatment processes. In this study, the abundances of fecal pollution indicators including cross-assembly phage (crAssphage), JC and BK polyomavirus (JCPyV, BKPyV), human adenovirus (HAdV), the human-specific HF183 Bacteroides (HF183) and Escherichia coli (EC) in soluble extracellular polymeric substances (S-EPS), loosely-bound EPS (LB-EPS), tightly-bound EPS (TB-EPS), and pellets of sludge flocs were determined, and the effect of potassium ferrate (PF) treatment on their removal and inactivation was investigated by using both qPCR and viability-qPCR. Results showed that all investigated indicators were detected in each fraction of sludge flocs. The PF treatment led to a great migration of indicators from sludge pellets to sludge EPS and some extent of their inactivation in each fraction of sludge flocs. The overall reductions of human fecal indicators in sludge determined by qPCR were 0-1.30 logs, which were 0-2 orders of magnitude lower than those of 0.69-2.39 logs detected by viability-qPCR, implying their inactivation by PF treatment to potentially alleviate the associated human health risks.

Fenton conditioning processes have been recently employed to improve the dewaterability of sewage sludge. However, it remains unclear whether the conditioning with Fenton's reagent would simultaneously attenuate antibiotic resistance genes (ARGs) in sludge and improve sludge dewaterability. It was found in the present study that sludge pre-acidification played a pivotal role in simultaneously removing ARGs and improving sludge dewaterability by conditioning with Fenton's reagent. When the sewage sludge was pre-acidified to pH = 3.0 and was then conditioned using Fenton's reagent, the absolute abundances of the total ARGs and the total mobile genic elements (MGEs) in conditioned sludge were reduced by 1.85-2.10 and 2.84-3.12 log units, respectively. Additionally, sludge capillary suction time (CST) and specific resistance to filtration (SRF) were drastically reduced, and the moisture content (MC) in dewatered sludge cake was reduced to only 60.61-69.95%. Such effective attenuation of ARGs and MGEs in conditioned sludge led to their removal in both the dewatered sludge cakes and dewatering filtrate. However, only the improvement of sludge dewaterability was attained by sludge conditioning with Fenton's reagent but without sludge pre-acidification. During the conditioning treatment, the removal of loosely bound extracellular polymeric substance (EPS) and tightly bound EPS in conditioned sludge contributed to the improvement of sludge dewaterability, and the damage of sludge microbial cells was highly correlated with the attenuation of antibiotic resistance. Thus, sludge pre-acidification combined with conditioning using Fenton's reagent can be employed to simultaneously attenuate the antibiotic resistance in sewage sludge and improve sludge dewaterability.

UV-based advanced oxidation processes (UV-AOPs) have been recommended to disinfect wastewater treatment plant (WWTP) effluents to control the dissemination of antibiotic resistance, but the mechanism of intracellular antibiotic resistance genes (i-ARGs) degradation by UV-AOPs is still poorly understood. Here we compared the efficacies of UV, UV/H

Fecal contamination in wastewater treatment system may pose severe threats to human health, but the detailed contamination of fecal bacterial and viral pathogens in municipal sewage sludge remains unclear. In addition, it is also unclear how sludge conditioning treatments would impact the distribution of fecal markers in conditioned sewage sludge. Before addressing these two issues, the possible polymerase chain reaction (PCR) inhibition effect when determining the abundances of fecal markers in both sludge solids and sludge supernatants should be solved, and methods of effectively concentrating fecal markers from sludge supernatant should also be developed. In the present study, we found that the serial tenfold dilution effectively reduced the PCR inhibition effect when determining the abundances of fecal markers including cross-assembly phages (CrAssphage), JC polyomavirus (JCPyV), human-specific HF183 bacteroides (HF183), human BK polyomavirus (BKPyV), human adenovirus (HAdV) and Escherichia coli (EC), while the utilization of negatively charged HA membrane was effective to recover fecal markers from sludge supernatant. The results of a six-month monitoring revealed that gene markers of CrAssphage, JCPyV, HF183, BKPyV, HAdV, and EC can be detected in municipal sewage sludge collected from a local wastewater treatment plant. Among the investigated four chemical conditioning methods, i.e., chemical conditioning with polyacrylamide (PAM), Fe[III]/CaO, or Fenton's reagent, and chemical acidification conditioning, chemical conditioning with Fenton's reagent was much more effective than the other three conditioning methods to reduce the abundances of fecal markers in the supernatant and solid of conditioned sewage sludge. Furthermore, the investigated fecal markers in the conditioned sewage sludge can be simultaneously attenuated by employing suitable conditioning methods, consequently reducing the associated environmental risks.

Mine waters often contain selenate, which needs to be removed to avoid harmful human and environmental health impacts. This study evaluated the performance of a laboratory-scale inverse fluidised bed reactor (IFBR) for biological selenate reduction at 30°C. The IFBR with floating biomass carriers was fed with synthetic mine water (pH 6.0–7.0) containing ∼10 mM (1.4 g L−1) selenate, nutrients and 10 mM ethanol as electron donor and inoculated with selenate reducers enriched from anaerobic sludge and environmental samples. The bioreactor achieved a selenate reduction rate of 1.75 mM d−1 (250 mg L−1 d−1 selenate or 138 mg L−1 d−1 Se) representing 94% removal during stable performance at a hydraulic retention time of 5 d. The formation of a red precipitate indicated the formation of elemental selenium, and selenite concentration remained predominately at below 0.1 mM during stable operation. Alkalinity was generated during the biological selenate reduction, increasing the wastewater pH from 6.0 to 8.6. Redox potential gradually approached a value ranging from -500 mV to -600 mV vs. Ag/AgCl. The dominant prokaryotic phylum in the bioreactor was Proteobacteria, followed by Firmicutes and Tenericutes. This study affirmed that IFBR is a promising configuration for high-rate removal of selenate from wastewaters. It has the potential to minimise the liabilities associated with environmental impacts of selenium containing mine drainage.

Bioreduction can facilitate oxyanions removal from wastewater. However, simultaneously removing selenate, nitrate and sulfate and recovering high-purity elemental selenium (Se0) from wastewater by a single system is difficult and may lead to carcinogenic selenium monosulfide (SeS) formation. To solve this issue, a two-stage biological fluidized bed (FBR) process with ethanol dosing based on oxidation-reduction potential (ORP) feedback control was developed in this study. FBR1 performance was first evaluated at various ORP setpoints (between −520 and −360 mV vs. Ag/AgCl) and elevated sulfate concentration. Subsequently, ethanol-fed FBR2 was used to reduce sulfate from FBR1 effluent, followed by an aerated sulfide oxidation reactor (SOR). At − 520 mV ≤ ORPs ≤ − 480 mV, FBR1 removed 100 ± 0.1% nitrate and 99.7 ± 0.3% selenate without sulfate reduction. At ORPs ≥ − 440 mV, selenate reduction was incomplete, whereas nitrate removal remained stable. Se0 recovery efficiency from FBR1 effluent was 37.5% with 71% Se purity. FBR2 converted 86% of the remaining sulfate in FBR1 effluent to hydrogen sulfide, but the over-oxidation of dissolved sulfide in SOR decreased the overall sulfate removal efficiency to ~46.3%. Overall, the two-stage FBR process with ORP feedback dosing of ethanol was effective for sequentially removing selenate, nitrate and sulfate and recovering Se0 from wastewater.

Conditioning treatments are extensively employed in wastewater treatment plants (WWTPs) to enhance sludge dewaterability, thereby improving the sludge dehydration during mechanical dewatering. However, it remains unclear whether the sludge conditioning treatments would influence the removal of polycyclic aromatic hydrocarbons (PAHs) during the dewatered sludge composting. In this study, the influences of three sludge conditioning methods, including bioleaching conditioning driven by Acidithiobacillus ferrooxidans, chemical conditioning with Fe[III]/CaO, and chemical conditioning with polyacrylamide (PAM), on the bioavailability of PAHs in dewatered sludge and the PAH removal during the co-compositing of industrial and municipal sewage sludges were investigated. The results showed that bioleaching conditioning was capable to significantly increase the bioavailability of PAHs in dewatered sludge, which was not attained by the other two conditioning methods. During the 39 days composting of dewatered sludge, the total removal efficiency of six detected PAHs (∑PAHs) including acenaphthylene, fluorene, phenanthrene, anthracene, chrysene and benzo(k)fluoranthene was 58.7% in raw sludge, 58.5% in PAM-conditioned sludge, 76.4% in bioleached sludge, and 60.4% in Fe[III]/CaO-conditioned sludge, respectively, and the removal of acenaphthylene, chrysene and benzo(k)fluoranthene was much higher in bioleached sludge than in other sludges. During dewatered sludge composting, PAHs may mainly be degraded by the bacteria belonging to the genera Luteimonas, Glutamicibacter, Alcanivorax, Dechloromonas, Ferribacterium, Truepera and Sphingobacterium. Linear correlation analysis between PAH removal and their bioavailability revealed that the promoted PAH removal during the composting of dewatered bioleached sludge may ascribe to the enhanced bioavailability of individual PAH. Therefore, the combination of bioleaching conditioning and subsequent dewatered sludge composting is effective to remove PAHs in sewage sludge, thus alleviating the loads of PAHs during the land application of sludge compost products.

The layered copper manganese oxide (LCMO) with a bridged monoclinic/tetragonal phase structure was successfully prepared by one-step hydrothermal redox-precipitation method and demonstrated highly efficient and stable catalytic capability to CO and VOCs oxidation. The formation of monoclinic-tetragonal phase interface with abundant defects inhibited the growth of nanoparticles which was benefit to keep smaller crystal size and higher surface area. Characterization results indicated that the interfacial structure of mixed phases can induce the formation of the Cu2+-O2−-Mn4+ entity, which led to abundant of surface oxygen species and oxygen vacancies, as well as improved low-temperature reducibility, which played key roles in catalytic activity. The T50 and T90 in the CO and VOCs oxidation decreased remarkably with the increase of the surface oxygen species and oxygen vacancies content. Furthermore, the LCMO showed an excellent resistance to H2O, SO2, CO2 and other VOCs, which demonstrated the catalyst had great potential for practical application.

Mineralization coupled with neutralization is a dual-function technology for disposing acidic iron-rich waters, which can recover the valuable iron in the form of secondary mineral and concurrently purify the wastewater. In this study, a modified technology for treating high Fe wastewater (sulfur acid spent pickling liquor, 62 g Fe/L) was proposed based on the specific investigation of the mineralization behaviors in Fe concentration range of 20-70 g/L. Results showed that high SO

Co-contamination of arsenic and polycyclic aromatic hydrocarbons (PAHs) in groundwater is frequently reported, and it is thus necessary to develop efficient techniques to tackle this problem. Here, we evaluated the feasibility of utilizing schwertmannite to co-adsorb As(III) and phenanthrene from water solution and regenerating spent schwertmannite via a heterogeneous Fenton-like reaction to degrade adsorbed phenanthrene and meanwhile oxidize adsorbed As(III). The results suggested that schwertmannite with a hedgehog-like morphology was superior to that with a smooth surface for the adsorption removal of As(III) or phenanthrene because of the much higher BET surface area and hydroxyl proportion of the former one, and schwertmannite formed at 72 h incubation effectively co-adsorbed As(III) and phenanthrene from water solution. The adsorption of As(III) and phenanthrene on schwertmannite did not interfere with each other, while the acidic initial solution pH delayed the adsorption of As(III) on schwertmannite but enhanced the adsorption capacity for phenanthrene. The adsorption of As(III) on schwertmannite mainly involved its exchange with SO42− (outer-sphere or inner-sphere) and its complexation with iron hydroxyl surface groups, and phenanthrene adsorption mainly occurred through cation-π bonding and OH-π interaction. During the adsorption-regeneration processes, schwertmannite adsorbed As(III) and phenanthrene firstly, and then it can be successfully regenerated via Fenton-like reaction catalyzed by itself to effectively degrade the adsorbed phenanthrene and meanwhile oxidize the adsorbed As(III) to As(V). Therefore, schwertmanite is an outstanding environmental adsorbent to decontaminate As(III) and phenanthrene co-existing in groundwater.

Electron donors are a major cost-factor in biological removal of oxyanions, such as nitrate and selenate from wastewater. In this study, an online ethanol dosing strategy based on feedback control of oxidation-reduction potential (ORP) was designed to optimize the performance of a lab-scale fluidized bed reactor (FBR) in treating selenate and nitrate (5 mM each) containing wastewater. The FBR performance was evaluated at various ORP setpoints ranging between −520 mV and −240 mV (vs. Ag/AgCl). Results suggested that both nitrate and selenate were completely removed at ORPs between −520 mV and −360 mV, with methylseleninic acid, selenocyanate, selenosulfate and ammonia being produced at low ORPs between −520 mV and −480 mV, likely due to overdosing of ethanol. At ORPs between −300 mV and −240 mV, limited ethanol dosing resulted in an apparent decline in selenate removal whereas nitrate removal remained stable. Resuming the ORP to −520 mV successfully restored complete selenate reduction. An optimal ORP of −400 mV was identified for the FBR, whereby selenate and nitrate were nearly completely removed with a minimal ethanol consumption. Overall, controlling ORP via feedback-dosing of the electron donor was an effective strategy to optimize FBR performance for reducing selenate and nitrate in wastewater.

Acid mine drainage (AMD) is recognized as a challenge encountered by mining industries globally. Cyclic mineralization method, namely Fe2+ oxidation/mineralization–residual Fe3+ reduction–resultant Fe2+ oxidation/mineralization, could precipitate Fe and SO42− present in AMD into iron hydroxysulfate minerals and greatly improve the efficiency of subsequent lime neutralization, but the current Fe0-mediated reduction approach increased the mineralization cycles. This study constructed a bacteria-driven biomineralization system based on the reactions of Acidithiobacillus ferrooxidans-mediated Fe2+ oxidation and Acidiphilium multivorum-controlled Fe3+ reduction, and utilized water-dropping aeration and biofilm technology to satisfy the requirement of practical application. The resultant biofilms showed stable activity for Fe conversion: the efficiency of Fe2+-oxidation, Fe-precipitation, and Fe3+-reduction maintained at 98%, 32%, and 87%, respectively. Dissolved oxygen for Fe-oxidizing bacteria growth was continuously replenished by water-dropping aeration (4.2–7.2 mg/L), and the added organic carbon was mainly metabolized by Fe-reducing bacteria. About 89% Fe and 60% SO42− were precipitated into jarosite mineral after five biomineralization cycles. Fe was removed via forming secondary mineral precipitates, while SO42− was coprecipitated into mineral within the initial three biomineralization cycles, and then mainly precipitated with Ca2+ afterwards. Fe concentration in AMD was proven to directly correlate with subsequent lime neutralization efficiency. Biomineralization for five cycles drastically reduced the amount of required lime and neutralized sludge by 75% and 77%, respectively. The results in this study provided theoretical guidance for practical AMD treatment based on biomineralization technology.

Hydrotalcite precipitation is a promising technology for the on-site treatment of acid mine drainage (AMD). This technology is underpinned by the synthesis of hydrotalcite that can effectively remove various contaminants. However, hydrotalcite precipitation has only limited capacity to facilitate sulfate removal from AMD. Therefore, the feasibility of coupling biological sulfate reduction with the hydrotalcite precipitation to maximize sulfate removal was evaluated in this study. AMD emanating from a gold mine (pH 4.3, sulfate 2000 mg L−1, with various metals including Al, Cd, Co, Cu, Fe, Mn, Ni, Zn) was first treated using the hydrotalcite precipitation. Subsequently, biological treatment of the post-hydrotalcite precipitation effluent was conducted in an ethanol-fed fluidized bed reactor (FBR) at a hydraulic retention time (HRT) of 0.8–1.6 day. The hydrotalcite precipitation readily neutralized the acidity of AMD and removed 10% of sulfate and over 99% of Al, Cd, Co, Cu, Fe, Mn, Ni, Zn. The overall sulfate removal increased to 73% with subsequent FBR treatment. Based on 454 pyrosequencing of 16S rRNA genes, the identified genera of sulfate-reducing bacteria (SRB) included Desulfovibrio, Desulfomicrobium and Desulfococcus. This study showed that sulfate-rich AMD can be effectively treated by integrating hydrotalcite precipitation and a biological sulfate reducing FBR.

In this study, the usefulness of the ZVI/S2O82− system in enhancing the dewaterability of waste activated sludge was studied at different initial sludge pH levels to reveal the associated mechanisms. Results showed that conditioning of sludge by the ZVI/S2O82− system at acidic initial sludge pHs enhanced sludge filterability and the dryness of dewatered sludge cake, while only the sludge filterability was improved at neutral initial sludge pH. In particular, the conditioning treatment using 0.353 g/g DS of ZVI and Na2S2O8 with a mole ratio of 1.25:1, at initial sludge pH 2.52, was the optimum condition to improve sludge dewaterability, which reduced the moisture content of dewatered sludge cake to only 69.8% and meanwhile reduced sludge CST and SRF to only 70.9% and 40.7% of that of raw sludge, respectively. During the conditioning treatment, sludge microbial cell lysis resulting from decreasing the initial sludge pH led to the reduction in the moisture content of dewatered sludge cake, while the oxidation of sludge EPS and the coagulation of the disrupted sludge flocs achieved by the ZVI/S2O82− system improved sludge filterability. A kaolin suspension experiment revealed that with a decrease in system pH, the oxidation effect was gradually inhibited and the coagulation effect offset the disruption effect on sludge flocs to improve the filterability of sludge. Therefore, the conditioning of waste activated sludge using the ZVI/Na2S2O8 system at acidic initial sludge pHs is useful to enhance the sludge filterability and the dryness of dewatered sludge cake, both of which are crucial for improving sludge dewatering performance.

Prior to mechanical dewatering, sludge conditioning is indispensable to reduce the difficulty of sludge treatment and disposal. The effect of bioacidification conditioning driven by Acidithiobacillus ferrooxidans LX5 on the dewatering rate and extent of sewage sludge during compression dewatering process was investigated in this study. The results showed that the bioacidification of sludge driven by A. ferrooxidans LX5 simultaneously improved both the sludge dewatering rate and extent, which was not attained by physical/chemical conditioning approaches, including ultrasonication, microwave, freezing/thawing, or by adding the chemical conditioner cationic polyacrylamide (CPAM). During the bioacidification of sludge, the decrease in sludge pH induced the damage of sludge microbial cell structures, which enhanced the dewatering extent of sludge, and the added Fe2+ and the subsequent bio-oxidized Fe3+ effectively flocculated the damaged sludge flocs to improve the sludge dewatering rate. In the compression dewatering process consisting of filtration and expression stages, high removal of moisture and a short dewatering time were achieved during the filtration stage and the expression kinetics were also improved because of the high elasticity of sludge cake and the rapid creeping of the aggregates within the sludge cake. In addition, the usefulness of bioacidification driven by A. ferrooxidans LX5 in improving the compression dewatering of sewage sludge could not be attained by the chemical treatment of sludge through pH modification and Fe3+ addition. Therefore, the bioacidification of sludge driven by A. ferrooxidans LX5 is an effective conditioning method to simultaneously improve the rate and extent of compression dewatering of sewage sludge.

Herbicide atrazine (ATZ) has caused great environmental concern due to its long-term application in agriculture and persistence nature. This study examined the degradation of ATZ in heterogeneously activated peroxymonosulfate (PMS) oxidation processes, using Co 3 O 4 as the catalyst, finding that high PMS concentrations and near neutral pH (pH 6.0) were beneficial for ATZ degradation. ATZ degradation rate was influenced by functional groups present on the Co 3 O 4 surface at varying pH. Complete removal of 20 μM ATZ was achieved in 15 min, with 2.0 mM PMS and 0.4 g/L Co 3 O 4 at pH 6.0. Minimal cobalt leaching occurred during reaction, shown by a maximum dissolved Co concentration (0.06 mg/L) found at pH 3.0 and decreasing with increasing pH. During the reaction, Co 3 O 4 showed high potential for reusability. Structural properties of the pristine and used Co 3 O 4 catalysts were characterized by scanning electron microscope; X-ray diffraction; and X-ray photoelectron spectroscopy, with no changes observed post-reaction. A total of 7 intermediate products of ATZ were detected by liquid chromatography-tandem mass spectrometry, with quantification of intermediate products allowing the contribution of different pathway for ATZ degradation, to be accessed. Transformation pathways including dealkylation, dechlorination-hydroxylation, and alkylic-oxidation were proposed for catalytic decomposition of ATZ in the Co 3 O 4 /PMS system.

Ultraviolet (UV)/peroxydisulfate (PDS) system has been employed for degrading organic pollutants in water, but the insufficient production of reactive species in the system limits the mineralization of organic pollutants. This study evaluated for the first time the effectiveness of integrating iron hydroxysulfates, including schwertmannite (Sch) and jarosite (Jar), with UV/PDS system for sulfamethoxazole (SMX) degradation in water. The optimal conditions identified for 40 μM SMX degradation were PDS 2 mM, photocatalysts 1 g L-1 and pH 3 in both of Sch/UV/PDS and Jar/UV/PDS systems. A synergetic effect between UV/PDS and Sch/UV processes was found in Sch/UV/PDS system with synergistic factor of 1.15, which drastically enhanced the production of reactive species ( OH and SO4•-) and consequently improved SMX degradation and TOC mineralization. Additionally, schwertmannite exhibited higher photocatalytic activity than jarosite in UV/PDS system for both SMX degradation and TOC mineralization. In Sch/UV/PDS system, ≡Fe(OH)2+ on schwertmannite can be efficiently photolyzed to ≡Fe2+ and OH under UV irradiation with O2– generation, in which the produced reactive species contributed to a relatively small fraction of SMX degradation. More importantly, the regeneration of ≡Fe2+ accelerated PDS activation to SO4•-/ OH, which was responsible for the degradation of most SMX. However, the photoreduction of ≡Fe3+ to ≡Fe2+ on jarosite by UV irradiation was insignificant, thus leading to the poor PDS activation to SO4•-/ OH and a lower SMX degradation rate. The degradation pathways of SMX in Sch/UV/PDS system were further proposed based on the identified degradation intermediates of SMX. Besides, schwertmannite exhibited a good adaptability in wide pH (2–9) range, good stability, and recyclability for catalyzing SMX degradation in UV/PDS system. Therefore, integrating schwertmannite with UV/PDS system is an attractive method for efficiently removing organic pollutants in water.

Acidithiobacillus ferrooxidans ILS-2 was adapted in digested sludge and used to treat sludge for dewaterability improvement. Results showed that increasing ferrous iron loading increased sludge dewaterability, but the inoculation of the bioleaching strain had little effect on sludge dewaterability compared to controls without the strain. The total extracellular polymeric substances (EPS) contents of sludges with and without bioleaching treatment were similar except for bioleaching treatment at 10% ferrous iron loading (on sludge total solids) where total EPS was higher with bioleaching treatment. However, bioleaching treatment for 48 h had a notable effect on removal of heavy metals, such as Mn, Ni and Zn, especially at the high loadings of ferrous iron. In the presence of A. ferrooxidans, the removal of Ni, Mn and Zn reached 93%, 88% and 80%, respectively, at a ferrous iron loading of 21%. The sequencing of 16S rRNA genes indicated that increasing ferrous iron loadings to 15% and 21% increased the relative abundance of Acidithiobacillus, Acidocella (with A. ferrooxidans) and Carboxylicivirga (without A. ferrooxidans) but decreased the abundance of Pseudomonas and Acinetobacter after 48 h treatment. This study enhanced the understanding of the correlations between bioleaching treatment of digested sludge, sludge dewaterability, heavy metal removal and bacterial communities.

Schwertmannite and jarosite, two secondary Fe(III)-hydroxysulfate minerals abundant in acid-mine drainage, can be biosynthesized by an Fe-oxidizing bacterium Acidithiobacillus ferrooxidans, but the differences of their catalytic activities in heterogeneous Fenton-like reactions are still unclear to date. In the present study, the catalytic activities of biosynthesized schwertmannite and jarosite were compared through investigating the heterogeneous Fenton-like degradation of a target organic pollutant phenol. Results showed that these two catalysts efficiently catalyzed heterogeneous Fenton-like degradation of phenol, and the degradation in both systems consisted of an induction period (first-stage) and a followed rapid degradation stage (second-stage). Schwertmannite exhibited a much higher catalytic capacity than jarosite, because of its shorter induction period and higher kinetic rate (k) of the second-stage, but jarosite catalytically degraded phenol in a much wider pH range (pH 3.0–7.5) over schwertmannite (pH 3.0–4.5). Based on the results of radical scavenger effect, H2O2 decomposition, Fe leaching and X-ray photoelectron spectroscopic (XPS) analysis, similar catalytic mechanisms were proposed in schwertmannite/H2O2 and jarosite/H2O2 systems, in which the induction period can be ascribed to the activation of catalysts by H2O2 and the second-stage was mainly attributed to the homogeneous Fenton reaction in bulk solution. During the catalytic degradation of phenol, catechol was firstly accumulated and was then further decomposed into smaller molecular organic acids. The repeated uses of schwertmannite and jarosite for phenol degradation manifested their stability and reusability as Fenton-like catalysts for the degradation of organic pollutants.

Sludge extracellular polymeric substances (EPS) are frequently reported as a main factor determining sludge dewatering, but the role of sludge floc structure in influencing sludge dewatering has not been fully understood. The dewatering of chemically acidified sludge was investigated to reveal the respective role of sludge floc structure and sludge extracellular polymeric substances (EPS) in influencing the removal rate of moisture (i.e., dewatering rate) and the removal amount of moisture (i.e., dewatering extent) of acidified sludge. During the chemical acidification of sludge, serious lysis of microbial cells in sludge was induced to result in a decrease of moisture content in dewatered sludge cake, from 81.8% to only 66.7%, but both the significant increase of sludge outer layer EPS content and the deflocculated sludge flocs led to a serious deterioration of dewatering rate of acidified sludge. Further studies revealed that either decreasing sludge outer layer EPS content or modifying the deflocculated sludge flocs could improve both filtration and expression stages of compression dewatering of acidified sludge to enhance the dewatering rate of acidified sludge. Especially, only 5 mg/g dry solid of anionic synthetic organic polyelectrolyte polyacrylic acid (PAA) could condition acidified sludge to improve its dewatering rate at both filtration and expression dewatering stages through re-flocculating the deflocculated flocs in acidified sludge. Therefore, the deflocculated sludge floc structure is as significant as extracellular polymeric substances in influencing the compression dewatering of acidified sludge, and the treatment of sewage sludge through chemical acidification and followed conditioning using synthetic organic polyelectrolyte PAA can enhance the dewatering extent as well as dewatering rate.

Heterogeneous Fenton-like degradation of phenanthrene in aqueous solution was investigated using schwertmannite biosynthesized by Acidithiobacillus ferrooxidans LX5 as a catalyst. The effects of different reaction parameters including catalyst loading, H2O2 concentration, initial solution pH and inorganic anions on the Fenton-like degradation of phenanthrene were studied. Results showed that the biosynthesized schwertmannite had an effective catalytic ability on phenanthrene degradation. The degradation efficiency of phenanthrene was 99.0% within 3–5 h reaction under conditions of H2O2 200 mg L−1, schwertmannite 1 g L−1, phenanthrene 1 mg L−1 and pH 3.0–4.5. The degradation was mainly via a surface mechanism, in which phenanthrene was readily adsorbed on the surface of schwertmannite and then oxidized by ˙OH produced from H2O2 decomposition. The XPS results of schwertmannite before and after Fenton-like degradation of phenanthrene revealed the change of Fe2+/Fe3+ species on the surface of schwertmannite. Moreover, phthalates, octadecanoic acid and 9,10-phenanthraquinone were identified by GC-MS analyses as the main intermediate compounds during phenanthrene degradation, and all the intermediates were finally mineralized. The repeated use of biosynthesized schwertmannite for phenanthrene degradation illustrated its stability and reusability as a Fenton-like catalyst. Therefore, schwertmannite biosynthesized using A. ferrooxidans is an excellent catalyst for the degradation of phenanthrene in heterogeneous Fenton-like reactions.

Sulfate radical (SO

Schwertmannite, jarosite or goethite are commonly used to remove metals and/or metalloids from contaminated water via adsorption processes, but it is still unclear whether they can be used as adsorbents to remove hydrophobic organic pollutants (HOCs), such as polycyclic aromatic hydrocarbons (PAHs), from groundwater or wastewater. Here, the feasibility of using these iron (oxyhydr) oxide minerals as adsorbents for phenanthrene (a model PAH) adsorption and regenerating the spent adsorbents via heterogeneous Fenton-like reaction was investigated. Results showed that they exhibited rapid adsorption rates and considerable adsorption capacities for phenanthrene. The maximum Langmuir capacities (Qmax) for phenanthrene adsorption at 28 °C were in an ascending order of goethite (567 μg·g-1) schwertmannite (727 μg·g-1) jarosite (2088 μg·g-1). The adsorption process was a spontaneous and exothermic process along with the decrease of randomness at the solid/liquid interfaces, which was influenced by temperature, adsorbent dosage, and the coexistence of inorganic anions. Both schwertmannite and jarosite were superior to goethite in light of their easy separation from the bulk solution after the adsorption processes. A multi-cycle experiment demonstrated that the regeneration efficiency of schwertmannite (97.9-99.7%) was much higher than that of jarosite (80.1-87.2%), and the mineral structure, morphology and functional groups of schwertmannite were not changed during the successive adsorption-regeneration processes. Therefore, among the investigated three iron (oxyhydr) oxide minerals, schwertmannite was an attractive and regenerable adsorbent for the removal of phenanthrene from water owing to its high adsorption capacity, good separation ability, and excellent reusability.

A novel Acidithiobacillus ferrooxidans-mediated approach coupling biological oxidation and chemical reduction for treating acid mine drainage (AMD) was investigated. The results showed that controlled addition of zero valent iron (ZVI) into the coupling system did not exhibit a significant adverse influence on the bacterial activity of Acidithiobacillus ferrooxidans but markedly increased the formation of secondary Fe-minerals. Nutrition did not affect the efficiency of coupling process, except for the bacteria density of A. ferrooxidans. 2 days cyclic treatment performed better than that of 4 and 8 days. After 14 cycles of the coupling process, 89.4% of total iron (2.23 g L−1) was transferred into Fe-minerals finally. In addition, the combined system was highly effective in removing sulfate (63%) from a simulated AMD that contained soluble Cu, Zn, Al, and Mn. Valuable iron-sulfate material e.g. schwertmannite was formed with little co-precipitation of other metals. Therefore, the integration of A. ferrooxidans into the reduction by ZVI may have considerable potential in the enhancement of biomineralization efficiency, which may further decrease soluble TFe and sulfate loads in AMD before lime neutralization.

Animal manures are commonly applied to soil which possibly promote the spread of antibiotic resistance from soil to human beings via food chains. Biogas slurry is an end product of anaerobic digestion of animal manures, which has been widely applied as fertilizers in the agricultural soil. However, effect of long-term biogas slurry application on the soil antibiotic resistance and the associated mechanism still remains unclear. The present study characterized antibiotics, antibiotic resistance genes (ARGs), mobile genetic elements (MGEs) and bacterial community, in different agricultural soils unamended (BS-) and amended (BS+) with biogas slurry (8–18 years) in five field experiments. Our results indicated that long-term application of biogas slurry largely increased the concentrations of tetracyclines in soils, and greatly increased the abundances of ARGs, transposase gene (Tn916/1545) and ARGs-associated bacteria. Long-term application of biogas slurry led to tetracyclines accumulation and ARGs enrichment in agricultural soil, and the selection pressure from tetracyclines and the increase of Tn916/1545 abundace become potential contributors for the increase of soil antibiotic resistance via promoting the enrichment of ARG-associated bacteria. The results of the present study should be taken into consideration to develop policy and practice for mitigating the enrichment and spread of antibiotic resistance during the recycling of biogas slurry into agricultural soil.

Wastewater contaminated with high concentrations of selenium oxyanions requires treatment prior to discharge. Biological fluidized bed reactors (FBRs) can be an option for removing selenium oxyanions from wastewater by converting them into elemental selenium, which can be separated from the treated effluent. In this study, a lab-scale FBR was constructed with granular activated carbon as biofilm carrier and inoculated with a consortium of selenate reducing bacteria enriched from environmental samples. The FBR was loaded with an influent containing ethanol (10 mM) and selenate (10 mM) as the microbial electron donor and acceptor, respectively. The performance of the FBR in reducing selenate was evaluated under various hydraulic retention times (HRTs) (120 h, 72 h, 48 h, 24 h, 12 h, 6 h, 3 h, 1 h and 20 min). After process acclimatization, selenate was completely removed with no notable selenite produced when the HRT was stepwise decreased from 120 h to 6 h. However, decreasing the HRT to 3 h resulted in selenite accumulation (0.17 ± 0.023 mM) in the effluent although selenate removal efficiency remained at 99.8 ± 0.20%. At 1 h HRT, the FBR removed 90.8 ± 1.4% of the selenate at a rate of 9.6 ± 0.15 mM h−1, which is the highest selenate reduction rate reported in the literature so far. However, 1 h HRT resulted in notable selenite accumulation (up to 2.4 ± 0.27 mM). Further decreasing the HRT to 20 min resulted in a notable decline in selenate reduction. Selenate reduction recovered from the “shock loading” after the HRT was increased back to 3 h. However, selenite still accumulated until the FBR was operated in batch mode for 6 days. This study affirmed that FBR is a promising treatment option for selenate-rich wastewater, and the process can be efficiently operated at low HRTs.

Utilization of the filamentous fungus Mucor circinelloides ZG-3 in improving sludge dewaterability during sludge bioleaching was evaluated in the present study. The degradation of sludge dissolved organic matter (DOM) by M. circinelloides ZG-3 shortened the period of complete oxidation of Fe 2+ by Acidithiobacillus ferrooxidans LX5 from 11 days to only 4 days, and the inoculation of M. circinelloides ZG-3 into sludge improved the sludge dewaterability by 8.1 times. The sequential inoculation of M. circinelloides ZG-3 and A. ferrooxidans LX5 on day 0 and the end of day 1, respectively, was associated with a 25.9% lower sludge specific resistance to filtration (SRF) than that achieved using conventional bioleaching with A. ferrooxidans LX5 alone. In sludge bioleaching with the sequential inoculation of filamentous fungus M. circinelloides ZG-3 and A. ferrooxidans LX5, M. circinelloides ZG-3 acted to improve sludge dewaterability and decrease sludge DOM related toxicity to A. ferrooxidans LX5 by degrading toxic sludge DOM, and then A. ferrooxidans LX5 that was not negatively affected by sludge DOM toxicity could better improve sludge dewaterability. The filamentous fungus M. circinelloides ZG-3 was more efficacious than sludge DOM-degrading yeast strains such as Rhodotorula mucilaginosa R30 in enhancing sludge dewaterability during bioleaching.

Sulfate radical (SO4-)-based conditioning methods, such as zero-valent iron (ZVI, i.e., Fe0) or ferrous iron (Fe2+) activated peroxydisulfate (S2O82-), have recently developed to improve sludge dewaterability, but it remains unclear how they impact the intracellular and extracellular antibiotic resistance genes (ARGs) in sewage sludge. In this study, it was found that conditioning treatments that used ZVI/S2O82- or Fe2+/S2O82- system, at an acidic initial sludge pH, removed the intracellular ARGs and intI1 and the extracellular intI1 from sewage sludge, but led to the accumulation of extracellular ARGs of aadA-01, aadA-02, aadA1, aadA2-03, and strB in conditioned sludge. During sludge conditioning with ZVI/S2O82- or Fe2+/S2O82-, bacterial hosts of ARGs and intI1 were seriously lysed to release the intracellular ARGs and intI1 to the extracellular environment, thus removing intracellular ARGs and intI1 in sludge, while the released ARGs and intI1 were primarily degraded by the produced SO4- to attenuate most extracellular ARGs and intI1. However, the relatively lower degradation ability of SO4- for extracellular ARGs of aadA-01, aadA-02, aadA1, aadA2-03, and strB led to their accumulation in conditioned sludge. Therefore, SO4--based conditioning methods can be employed to reduce ARGs in sludge, but the subsequent treatment of sludge dewatering filtrate requires more attention.

Grouted sleeve connectors provide a convenient and economical solution for connecting precast concrete elements in engineering site. However, sleeve connections may include insufficient grouting defects at certain conditions which may significantly decrease the bearing capacity and increase the failure risk of connection joints. In order to better understand the influence of insufficient grouting defects, the mechanical performance of insufficiently grouted sleeve connections with predesigned vertical grouting defects is investigated in this study by considering three loadings: uniaxial tensile loading, cyclic loading at high stress and cyclic loading at large strain. Comparatively, the repaired sleeve connections by refilling grout material to the sleeve enclosing insufficient grout material are considered as well. Total 24 sleeve connection specimens are tested and the correlation of failure mode, force-displacement response and the defect level is analyzed and discussed. It is revealed that the failure mode of defective specimens may shift from the tensile fracture of reinforcing steel bar to the interfacial bond-slip failure of rebar with the decrease of the anchorage length of reinforcing steel bar. Additionally, it is found that the loading condition affects the failure mode too. Moreover, the repaired sleeve connections show similar mechanical performance to the fully grouted sleeve connection except deformation. This indicates that the regrouting operation to repair the grouting defect in the sleeve is effective in engineering applications.

Conditioning can drastically improve the dewaterability of sewage sludge and thus it is widely practiced in most wastewater treatment plants (WWTPs). In WWTPs, various antibiotic resistance genes (ARGs) present in sewage are concentrated in the sewage sludge, but the effect of sludge conditioning on ARGs in sewage sludge remains unclear. Here, we evaluated and compared the effectiveness of four sludge conditioning methods (namely chemical conditioning with polyacrylamide (PAM), chemical conditioning with Fe[III]/CaO, bioleaching conditioning, and chemical acidification conditioning) and an aerobic incubation control in removing 46 target ARGs and intI1 from a municipal sewage sludge. The damage of sludge microbial cells and the change in the sludge bacterial community during the various sludge conditioning treatments were also characterized. The results suggested that the chemical conditioning with PAM and aerobic incubation treatment did not remove ARGs and intI1 from the sewage sludge. The chemical acidification reduced the absolute abundances of most ARGs and intI1, but increased their relative abundances. However, the chemical conditioning with Fe[III]/CaO and bioleaching conditioning reduced both the absolute and relative abundances of most ARGs and removed a majority of extracellular ARGs in the sludge. During sludge conditioning treatments, the sludge microbial cells were severely damaged to decrease the total bacterial biomass in sludge, and accordingly the bacterial hosts carrying ARGs and intI were effectively damaged to reduce the absolute abundances of most ARGs and intI1. In addition, the sludge bacterial community in conditioned sludge determined the relative abundances of residual ARGs. Our findings suggest that sludge conditioning can be an important sludge treatment process in attenuating antibiotic resistance in sewage sludge, and bioleaching and chemical conditioning with Fe[III]/CaO can be employed as effective conditioning ways to reduce ARGs in sewage sludge, potentially limiting their release to the environment.

Prior to mechanical dewatering, sludge conditioning is indispensable to reduce the difficulty of sludge treatment and disposal. The effect of bioacidification conditioning driven by

Conditioning is an indispensable step to improve mechanical dewatering of municipal sewage sludge. However, it is still unclear how sludge conditioning treatments impact the bioavailability of polycyclic aromatic hydrocarbons (PAHs) in sewage sludge that potentially influences the biodegradation of PAHs during the composting of dewatered sludge cake. In the present study, five sludge conditioning treatments, including chemical acidification, bioleaching driven by Acidithiobacillus ferrooxidans, chemical conditioning with Fe[III] and CaO, and chemical conditioning with either aluminum polychloride (PACl) or polyacrylamide (PAM), were investigated to reveal their respective impacts on the bioavailability of pyrene in sewage sludge. The bioavailability of pyrene in conditioned sludge was evaluated by using the n-butanol extraction method. The results showed that the bioavailable fraction of pyrene increased from 59.1% in raw sludge to 68.7% in chemically acidified sludge and 79.3% in bioleached sludge, while the other three conditioning approaches did not significantly change the bioavailability of pyrene. During chemical acidification or bioleaching of sludge, cellular membrane damage of sludge microbial cells induced changes in sludge chemical and physical properties. Ridge regression analysis revealed that during these two conditioning processes the contribution rates of the changes in sludge chemical properties and physical properties on the enhancement of pyrene bioavailability were 33.0% and 67.1%, respectively. Therefore, chemical acidification and bioleaching conditioning treatments can enhance the bioavailability of pyrene in sewage sludge, mainly through changing the relative hydrophobicity and particle size of sludge flocs.

Owing to its controllable tolerance, simple operation and no need for welding at construction site, the composite system involving grouted cement material, steel material and ductile iron material is widely used as grouted splice sleeve (GSS) connector for connecting precast concrete structures. However, the current design recommendations for such a composite connection system do not accurately account for its material nonlinearity behavior. In the present study, a three-dimensional nonlinear finite element model of a GSS connector is developed by considering the nonlinear material behavior of each component to fully investigate its mechanical performance under axial tension. To validate the proposed computational model and demonstrate the nonlinear response of the GSS connector, the pullout experimental test of two engineering specimens is carried out under monotonic tensile load, and a good agreement between the numerical and experimental test results is observed. Then, the sensitivity analysis of some controlling material properties and geometrical parameters is performed using the validated computational model to further understand the performance of such a composite structure in load carrying capacity and ductility of the connections to meet the rapid engineering applications of precast concrete structures.

This study aims to investigate how NO3 − reduction affects the migration of NO3 − in marine sediments and evaluate whether the overlying seawater would be contaminated by NO3 − injection for in situ bioremediation. The migration of NO3 − in sandy silt sediment with high acid volatile sulfide (AVS) content and in clayey silt sediment with relatively low AVS content was investigated through column experiments with 5 weeks of incubation. Results showed that NO3 − reduction through autotrophic denitrification contributed to 93.1 and 48.9 % of total NO3 − reduction in sandy silt and clayey silt sediments, respectively. In sandy silt sediment with high AVS content, NO3 − tended to migrate upwards through gas cavities formed during the movement of N2 gas produced by NO3 − reduction. Meanwhile, greater NO3 − consumption by AVS oxidation can effectively prevent the NO3 − release into seawater. In clayey silt sediment with relatively low AVS content, few gas cavities produced due to insignificant NO3 − reduction and high density of NO3 − solution made the downward NO3 − migration more significant. Without great NO3 − consumption, NO3 − from clayey silt sediment was found to be present in the seawater after 5 weeks of incubation. Autotrophic denitrification has a significant impact on NO3 − reduction in marine sediments. The reduction of NO3 − resulting from autotrophic denitrification can influence its preferential migration path in marine sediment and the possibility of its release into seawater.

The feasibility of removing heavy metals and eliminating pathogens from pig slurry through bioleaching involving the fungus Galactomyces sp. Z3 and two acidophilic thiobacillus (A. ferrooxidans LX5 and A. thiooxidans TS6) was investigated. It was found that the isolated pig slurry dissolved organic matter (DOM) degrader Z3 was identified as Galactomyces sp. Z3, which could grow well at pH 2.5-7 and degrade pig slurry DOM from 1973 to 942 mg/l within 48 h. During the successive multi-batch bioleaching systems, the co-inoculation of pig slurry degrader Galactomyces sp. Z3 and the two Acidithiobacillus species could improve pig slurry bioleaching efficiency compared to the single system without Galactomyces sp. Z3. The removal efficiency of Zn and Cu exceeded 94% and 85%, respectively. In addition, the elimination efficiencies of pathogens, including both total coliform and faecal coliform counts, exceeded 99% after bioleaching treatment. However, the counts of Galactomyces sp. Z3 decreased with the fall of pH and did not restore to the initial level during successive multi-batch bioleaching systems, and it is necessary to re-inoculate Galactomyces sp. Z3 cells into the bioleaching system to maintain its role in degrading pig slurry DOM. Therefore, a bioleaching technique involving both Galactomyces sp. Z3 and Acidithiobacillus species is an efficient method for removing heavy metals and eliminating pathogens from pig slurry.