Performance, comparison and utilization of reduced sulfur (-2) compounds (S2-, FeS and SCN-) in autotrophic denitrification process by thiosulfate-driven autotrophic denitrifier.

The coexistence of reduced sulfur (-2) compounds (S2-, FeS and SCN-) are found in some industrial wastewaters due to pre-treatment of Fe(II) salts. These compounds as electron donors have attracted increasing interest in autotrophic denitrification process. However, the difference of their functions still remain unknown, which limit efficient utilization in autotrophic denitrification process. The study aimed to investigate and compare utilization behavior of these reduced sulfur (-2) compounds in autotrophic denitrification process activated by thiosulfate-driven autotrophic denitrifiers (TAD). Results showed that the best denitrification performance was observed in SCN-; while the reduction of nitrate was significantly inhibited in S2- system and the efficient accumulation of nitrite was observed in FeS system with cycle experiments continuing. Additionally, intermediates containing sulfur were produced rarely in SCN- system. However, the utilization of SCN- was limited obviously in comparison with S2- in coexistence systems. Moreover, the presence of S2- increased the accumulation peak of nitrite in coexistence systems. The biological results indicated that the TAD utilized rapidly these sulfur (-2) compounds, in which genus of Thiobacillus, Magnetospirillum and Azoarcus might play main roles. Moreover, Cupriavidus might also participate in sulfur oxidation in SCN- system. In conclusion, these might be attributed to the characteristics of sulfur (-2) compounds including the toxicity, solubility and reaction process. These findings provide theoretical basis for regulation and utilization of these reduced sulfur (-2) compounds in autotrophic denitrification process.

Investigation of the nitrogen removal performance and microbial community structure in a full-scale A/O1/H/O2 coking wastewater treatment system.

Biological treatment processes are an effective method for removing the nitrogen-containing contaminants that exist in coking wastewater. However, little is known about microbial composition and keystone taxa involved in biological nitrogen removal processes. In order to improve the removal efficiency of nitrogen-containing contaminants in anaerobic-aerobic-hydrolytic-aerobic (A/O1/H/O2) system, the microbial composition and interactions of keystone taxa should be clarified. The present work clarifies the removal performance of nitrogen-containing contaminants in the A/O1/H/O2 system, identifies the microbial community involved in various bioreactors, and reveals the keystone taxa within the microbial communities. Combined the processes of ammoniation, denitrification, and nitrification, total nitrogen decreased from 248 to 31 mg L-1 and achieved a removal efficiency of 87.5% in the full-scale A/O1/H/O2 system. High-throughput MiSeq sequencing revealed that Proteobacteria was the most abundant phylum in the A/O1/H/O2 system with relative abundances of 24%-50%. Thiobacillus dominated in bioreactors A and O1 with relative abundances of 2.90% and 4.44%, respectively, while Nitrospira was identified as the most dominant genus in bioreactors H and O2, accounting for 13.33% and 18.38%, respectively. The microbial community composition and co-occurrence network analysis showed that the keystone taxa belonged to Thiobacillus, Nitrospira, Bdellovibrio, Planctomyces, Desulfotomaculum, and Sphingobium, which are related to nitrogen degradation.

Microbial community composition and function prediction involved in the hydrolytic bioreactor of coking wastewater treatment process.

The hydrolytic acidification process has a strong ability to conduct denitrogenation and increase the biological oxygen demand/chemical oxygen demand ratio in O/H/O coking wastewater treatment system. More than 80% of the total nitrogen (TN) was removed in the hydrolytic bioreactor, and the hydrolytic acidification process contributed to the provision of carbon sources for the subsequent nitrification process. The structure and diversity of microbial communities were elaborated using high-throughput MiSeq of the 16S rRNA genes. The results revealed that the operational taxonomic units (OTUs) belonged to phyla Bacteroidetes, Betaproteobacteria, and Alphaproteobacteria were the dominant taxa involved in the denitrogenation and degradation of refractory contaminants in the hydrolytic bioreactor, with relative abundances of 22.94 ± 3.72, 29.77 ± 2.47, and 18.23 ± 0.26%, respectively. The results of a redundancy analysis showed that the OTUs belonged to the genera Thiobacillus, Rhodoplanes, and Hylemonella in the hydrolytic bioreactor strongly positively correlated with the chemical oxygen demand, TN, and the removal of phenolics, respectively. The results of a microbial co-occurrence network analysis showed that the OTUs belonged to the phylum Bacteroidetes and the genus Rhodoplanes had a significant impact on the efficiency of removal of contaminants that contained nitrogen in the hydrolytic bioreactor. The potential function profiling results indicate the complementarity of nitrogen metabolism, methane metabolism, and sulfur metabolism sub-pathways that were considered to play a significant role in the process of denitrification. These results provide new insights into the further optimization of the performance of the hydrolytic bioreactor in coking wastewater treatment.

Self-Activated Ni Cathode for Electrocatalytic Nitrate Reduction to Ammonia: From Fundamentals to Scale-Up for Treatment of Industrial Wastewater.

Electrocatalytic reduction has recently received increasing attention as a method of converting waste nitrate into value-added ammonia, but most studies have focused on complex strategies of catalyst preparation and little has been done in the way of large-scale demonstrations. Herein, we report that in situ activation of a pristine Ni electrode, either on a lab scale or a pilot scale, is effective in facilitating nitrate reduction to ammonia, exhibiting extraordinarily high activity, selectivity, and stability. The self-activated Ni cathode has a robust capacity to reduce nitrate over a wide range of concentrations and achieves great conversion yield, NH4+-N selectivity, and Faradaic efficiency, respectively, 95.3, 95.5, and 64.4% at 200 mg L-1 NO3--N and 97.8, 97.1, and 90.4% at 2000 mg L-1 NO3--N, for example. Fundamental research indicates that Ni(OH)2 nanoparticles are formed on the Ni electrode surface upon self-activation, which play crucial roles in governing nitrate reduction reaction (NO3RR) through the atomic H*-mediated pathway and accordingly suppressing hydrogen evolution reaction. More importantly, the self-activated Ni(OH)2@Ni cathode can be easily scaled up to allow large volumes of real industrial wastewater to be processed, successfully transferring nitrate into ammonia with high yields and Faradaic efficiency. This study demonstrates a new, mild, and promising method of cleaning nitrate-laden wastewater that produces ammonia as a valuable byproduct.

Multiphase distribution and migration characteristics of heavy metals in typical sandy intertidal zones: insights from solid-liquid partitioning.

With the increase of development and utilization of coastal tidal flats, the desertification of intertidal zone is becoming more and more serious, which will inevitably lead to changes in the distribution and migration of heavy metals. This study reported the multiphase distribution and solid-liquid partitioning of Cr, Ni, Cu, Zn, Pb and Cd in typical sandy intertidal zones and predicted the migration of heavy metals with stepwise multiple linear regression. The distribution of heavy metals in surface water was comparable with that in pore water, while the content of heavy metals in suspended solids was obviously greater than that in sediments. Compared to non-sandy sediments, the bioavailability state of heavy metals extracted from sandy sediments by diethylene triamine penta-acetic acid was much smaller. The mean partitioning coefficient values (Kd) ranged from 21.56 to 166.18, which were 10-40 times lower than those of organic-rich sediments and 100-750 times lower than those of mineral soils. The dynamics in solid clay, SOC and ORP greatly affected the variations of Kd values. Clay had a significant positive correlation with bioavailability but did not have a significant correlation with logKd, indicating that the adsorption capacity of heavy metals in the intertidal zone is not the only factor controlling heavy metal migration. Stepwise multiple linear regression analysis confirmed that the prediction equations of heavy metals are composed of multiple physicochemical factors. All predicted and tested values were of the same order of magnitude, with R2 values ranging from 0.8223 to 0.9775. Although our data focus on a single species of sandy intertidal zone, characterizing the Kd value and its relationship with site-specific factors provides different tools for assessing the probability of heavy metal contamination and migration in sandy intertidal zones.

The response of polycyclic aromatic hydrocarbon degradation in coking wastewater treatment after bioaugmentation with biosurfactant-producing bacteria Pseudomonas aeruginosa S5.

The polycyclic aromatic hydrocarbons (PAHs) that accumulate during the coking wastewater treatment process are hazardous for the surrounding environment. High molecular weight (HMW) PAHs account for more than 85% of the total PAHs in coking wastewater and sludge, respectively. The degradation of total PAHs increased by 18.97% due to the increased bioavailability of PAHs, after the biosurfactant-producing bacteria Pseudomonas aeruginosa S5 was added. The toxicity of total PAHs to humans was reduced by 26.66% after inoculation with S5. The results suggest biosurfactant-producing bacteria Pseudomonas aeruginosa S5 not only increase the biodegradation of PAHs significantly, but also have a better effect on reducing the human toxicity of PAHs. Kinetic analyses show that PAHs biodegradation fits to first-order kinetics. The degradation rate constant (k) value decreases as the number of PAH rings increases, indicating that HMW PAHs are more difficult to be biodegraded than low molecular weight (LMW) PAHs. The results indicate the bioaugmentation with the biosurfactant-producing strain has significant potential and utility in remediation of PAHs-polluted sites.

Immobilization of Phosphatidylserine by Ethanol and Lysozyme on the Cell Surface for Evaluation of Apoptosis-Like Decay in Activated-Sludge Bacteria.

Accurate determination of microbial viability can be crucial in microbe-dominated biosystems. However, the identification of metabolic decay in bacterial cells can be elaborate and difficult. We sought to identify apoptosis-like bacterial processes by using annexin V-fluorescein isothiocyanate (FITC) (AVF), a probe typically used to stain phosphatidylserine (PS) on exposed cell membranes. The bacterial cell wall provides a barrier that is responsible for low efficiency of direct PS staining of decayed bacterial cells. This can be overcome by pretreatment of the bacteria with 70% ethanol, which fixates the bacteria and preserves the PS status, combined with lysozyme treatment to hydrolyze the cell wall. That treatment improved the efficiency of AVF staining considerably, as shown for pure strains of an Ochrobactrum sp. and a Micrococcus sp. Using this method, decayed bacterial cells (induced by starvation) were more strongly stained, indicating externalization of PS to a greater extent than seen for cells harvested at logarithmic growth. A multispecies microbial sludge was artificially decayed by heat treatment or alternating anoxic-oxic treatment, which also induced increased AVF staining, again presumably via decay-related PS externalization. The method developed proved to be efficient for identification of bacterial decay and has potential for the evaluation of multispecies bacterial samples from sources like soil matrix, bioaerosol, and activated sludge.IMPORTANCE Since the externalization of phosphatidylserine (PS) is considered a crucial characteristic of apoptosis, we sought to identify apoptosis-like decay in bacterial cells by PS staining using AVF. We show that this is possible, provided the bacteria are pretreated with ethanol plus lysozyme to remove a physical staining barrier and preserve the original, decay-related externalization of PS. Our work suggests that PS externalization occurs in starved bacteria and this can be quantified with AVF staining, providing a measure of bacterial decay. Since PS is the common component of the lipid bilayer in bacterial cell membranes, this approach also has potential for evaluation of cell decay of other bacterial species.

Fe2+/HClO Reaction Produces FeIVO2+: An Enhanced Advanced Oxidation Process.

The reaction between Fe2+ and HClO constitutes a promising advanced oxidation process (AOP) for removing pollutants from wastewater, and •OH has been considered the dominant reactive oxidant despite limited evidence for this. Herein, we demonstrate that the Fe2+/HClO reaction enables the production of FeIVO2+ rather than •OH in acid medium, a finding that is strongly supported by multiple lines of evidence. Both X-ray absorption near-edge structure spectroscopic tests and Mössbauer spectroscopic tests confirmed the appearance of FeIVO2+ as the reactive intermediate in the reaction between Fe2+ and HClO. The determination of FeIVO2+ generation was also derived from the methyl phenyl sulfoxide (PMSO)-based probe experiments with respect to the formation of PMSO2 without •OH adducts and the density functional theory studies according to the lower energy barrier for producing FeIVO2+ compared with •OH. A dual-anode electrolytic system was established for the in situ generation of Fe2+ and HClO that allows the production of FeIVO2+. The system exhibits an enhanced capacity for oxidizing a model pollutant (e.g., phosphite) from industrial wastewater, making it an attractive and promising AOP for the abatement of aqueous contaminants.

Discovering the Importance of ClO• in a Coupled Electrochemical System for the Simultaneous Removal of Carbon and Nitrogen from Secondary Coking Wastewater Effluent.

Inorganic constituents in real wastewater, such as halides and carbonates/bicarbonates, may have negative effects on the performance of electrochemical systems because of their capability of quenching HO•. However, we discovered that the presence of Cl- and HCO3- in an electrochemical system is conducive to the formation of ClO•, which plays an important role in promoting the simultaneous elimination of biorefractory organics and nitrogen in secondary coking wastewater effluent. The 6-h operation of the coupled electrochemical system (an undivided electrolytic cell with a PbO2/Ti anode and a Cu/Zn cathode) at a current density of 37.5 mA cm-2 allowed the removal of 87.8% of chemical oxygen demand (COD) and 86.5% of total nitrogen. The electron paramagnetic resonance results suggested the formation of ClO• in the system, and the probe experiments confirmed the predominance of ClO•, whose steady-state concentrations (8.08 × 10-13 M) were 16.4, 26.5, and 1609.5 times those of Cl2•- (4.92 × 10-14 M), HO• (3.05 × 10-14 M), and Cl• (5.02 × 10-16 M), respectively. The rate constant of COD removal and the Faradaic efficiency of anodic oxidation obtained with Cl- and HCO3- was linearly proportional to the natural logarithm of the ClO• concentration, and the specific energy consumption was inversely correlated to it, demonstrating the crucial role of ClO• in pollutant removal.

One-Step Treatment of Phosphite-Laden Wastewater: A Single Electrochemical Reactor Integrating Superoxide Radical-Induced Oxidation and Electrocoagulation.

Elimination of phosphite from water is more difficult than elimination of phosphate owing to its higher solubility and resistance to biotransformation. Herein, we report an efficient, facile, electrochemical method integrating electrooxdiation (EO) and electrocoagulation (EC) to treat phosphite-laden wastewater. The mechanistic studies demonstrate that in-situ-generated Fe2+ at an Fe anode can react with in-situ-generated O2 at a mixed metal oxide (MMO) anode, leading to formation of •O2-, a reactive species predominantly responsible for oxidation of phosphite to phosphate. The phosphate is immediately coagulated by Fe hydroxides that are formed due to the production of OH- at a stainless-steel cathode. The integrated EO/EC system enables a phosphite removal efficiency of 74.25% (MMO anode, 100 mA; Fe anode, 100 mA; reaction time, 60 min), a significantly higher efficiency rate than the rate obtained in the control experiments in the absence of an MMO anode (<23.41%) and the rate obtained with the chemical coagulation process (<5.03%). The quenching experiments with scavengers and electron spin resonance tests verify the pivotal role of •O2- in transformation of phosphite. Tests carried out with nickel-plating wastewater further demonstrate the superiority of this integrated system, as evidenced by efficient removal of phosphite and nickel from the solution.

Simultaneous decarburization, nitrification and denitrification (SDCND) in coking wastewater treatment using an integrated fluidized-bed reactor.

There are two problems in biological treatment of coking wastewater (CWW): incapability of pre-anaerobic treatment to eliminate the toxicity in wastewater, and the lack of carbon source for subsequent denitrification in pre-aerobic treatment. To achieve simultaneous decarburization, nitrification and denitrification (SDCND) in CWW treatment, biological carrier materials was used to build an integrated fluidized-bed reactor (Reactor B, RB). A conventional fluidized-bed reactor (Reactor A, RA) was used as a control reactor under the same condition. The results showed that RB was more advantageous since its removal efficiencies of COD and TN were 90% and 87%, respectively, which were significantly higher than these in RA (82% and 45%), at a hydraulic retention time (HRT) of 60 h. Microelectrode measurement indicated that oxygen transfer was limited inside the carrier where the formation of a dissolved oxygen (DO) concentration gradient was observed. Microbial community analysis showed that the aerobic and anoxic microenvironments in RB promoted the co-existence of a wider variety of bacteria, thus achieving SDCND. These results indicated the integrated fluidized-bed reactor exhibited promising feasibility for simultaneous carbon and nitrogen removal in CWW treatment under the same aeration driven conditions. The SDCND process realized by fluidized-bed reactor provided a reference for the treatment of toxic industrial wastewater with high carbon to nitrogen ratio.

A comprehensive evaluation method for sludge pyrolysis and adsorption process in the treatment of coking wastewater.

This study proposes a new evaluation method based on expert scoring and data normalization to optimize operational conditions of sludge pyrolysis and assess the comprehensive benefits of the adsorption process in coking wastewater treatment. Pyrolysis temperature, holding time and heating rate were considered as the experimental parameters in sludge pyrolysis. They were optimized by the proposed method, considering raw material cost, net energy consumption, carbon emission and adsorption capacity of sludge-derived bio-char (SB). Two operational modes (cyclic centralized and traditional distributed) were compared to identify a better solution for coking wastewater treatment. The results showed that the optimized operational conditions of coking sludge pyrolysis were that temperature of 550 °C, holding time of 60 min and heating rate of 20 °C/min, using the proposed method. Cyclic centralized mode has been demonstrated as the better mode for wastewater treatment by the proposed method, due to the higher comprehensive score of -0.296. It is a promising technology for sustainable wastewater treatment in terms of sludge recycling, energy saving and carbon emission reduction.

Investigation of the fate of heavy metals based on process regulation-chemical reaction-phase distribution in an A-O1-H-O2 biological coking wastewater treatment system.

Regulation mechanism of typical substances including OH-, CN-, SCN-, S2-, NH3 on the distribution of heavy metals was investigated in coking wastewater treatment plant with our self-designed Anaerobic-Oxic-Hydrolytic-Oxic (A-O1-H-O2) system through engineering data exposure and computational density functional theory (DFT) verification. The results showed that coking sludge had superior enrichment ability for heavy metals, especially for the sludge from the A and H tanks. The enrichment ratio of the 8 heavy metals including Cd, Pb, Ni, Zn, Cu, Hg, Cr and As in coking waste sludge was found to be 6232 (comparing to these in the influent wastewater of A-O1-H-O2 system). The distribution of 8 heavy metals was closely related to their chemical (precipitation and/or complexation) and biochemical reaction potential with OH-, CN-, SCN-, S2-, NH3 in the A-O1-H-O2 system. The regulation mechanism of these precipitation and/or complexation agents on heavy metals was confirmed by DFT calculation. The stable energy of complexes formed between typical compounds and common heavy metal ions follow the order: OH: Cu2+>Pb2+>Zn2+>Cd2+>Hg2+>Ni2+; S2-: Pb2+>Cu2+>Zn2+>Cd2+>Hg2+>Ni2+; CN-: Zn2+>Cu2+>Cd2+>Hg2+>Pb2+>Ni2+; SCN-: Zn2+>Cd2+>Pb2+>Hg2+>Cu2+>Ni2+; NH3: Cu2+>Zn2+>Cd2+>Pb2+>Hg2+>Ni2+, providing reference for the judgement of which metal ions were preferentially combined with the typical compounds in coking wastewater. The results of this paper indicated that the enrichment of heavy metal ions in coking wastewater can be achieved by process design combined with the control of operating conditions (dissolved oxygen, hydraulic retention time, sludge retention time and pH), basing on the nature of heavy metal ions. Finally, the separation and differential management of heavy metals can be achieved.

Residual chemical oxygen demand (COD) fractionation in bio-treated coking wastewater integrating solution property characterization.

The refractory nature of residual COD in bio-treated coking wastewater (BTCW) creates barriers for its further treatment and reclamation. It is necessary to fractionate the residual COD in BTCW associated with characterization of solution properties. In this paper, a stepwise process composed of membrane filtration, coagulation, adsorption and ozonation was proposed to fractionate residual COD in the BTCW, in which the COD was stepwise reduced to near zero. In addition, the correlation between COD and water quality indexes as well as solution properties were discussed together with a safety assessment of the water quality. Results showed that the residual COD fractionation percentage contributed by suspended solids, colloids, dissolved organics and reductive inorganic substances in the BTCW was 43.7%, 22.1%, 26.2% and 4.9%, respectively. By stepwise fractionating of these substances, the residual COD was reduced from 168.8 to 5.2 mg L-1, and the UV254 value decreased from 1.90 to 0.15 cm-1. In addition, the particle size of the dominant substances contributing to the residual COD was smaller than 450 nm. Among these substances, the hydrophobic fraction accounted for 78.66% (in the term of TOC). Three-dimensional excitation-emission matrix (3D-EEM) analysis showed that hydrophobic neutral substances (HON) were the main fluorescence constituent in the BTCW, which was highly removable by adsorption. The residual COD after adsorption was mainly composed of reductive inorganic substances. Apart from pursuit of high COD removal rates, more emphasis should be given to the removal of toxic COD. Correlations were observed between the residual COD and water quality indicators as well as solution properties, providing a guideline for optimized removal of residual COD in the BTCW. In summary, these results gave a referential information about the nature of residual COD in the BTCW for the selection of advanced treatment technologies and the management of water quality safety.

In-Situ Synthesis and High-Efficiency Photocatalytic Performance of Cu(I)/Cu(II) Inorganic Coordination Polymer Quantum Sheets.

Two-dimensional (2D) materials ultrathin quantum sheets have the advantage of elevating the catalysis performance and prominent edge effects, but most of them belong to element single valence materials. In this paper, the ultrathin Cu(I)/Cu(II) inorganic coordination polymer quantum sheet (ICPQS) {[CuII(H2O)4][CuI4(CN)6]} n is synthesized by controlling the appropriate molar ratio of raw material, reaction time, and temperature. Transmission electron microscopy (TEM) and atomic force microscope (AFM) analysis show that this ICPQS has a thickness of ∼0.2 nm. Due to the fact that about 58.16% of the Cu(I)/Cu(II) is occupied in molecular structure and most of the metal active sites are fully utilized, this ICPQS can accelerate the photocatalytic degradation of methylene blue (MB) (K = 2.5 mg·L-1·min-1 at pH 3) and organic compounds in coking wastewater and biotreated coking wastewater. Basing on mixed valences, the ICPQS can use visible light to promote energy transfer and increase quantum efficiency, paving the way for developing the next-generation monolayer 2D mixed valence photocatalysts.

Ozonation of aqueous phenol catalyzed by biochar produced from sludge obtained in the treatment of coking wastewater.

Sludge collected from industrial wastewater treatment possesses a threatening effect on environment, and changing it into functional material provides an alternative for its disposal. Biochar synthesized by pyrolysis of sludge obtained from coking wastewater treatment was evaluated for the catalytic ozonation of phenol in aqueous solution. The present work focused on testing the catalytic performance of biochar, deducing the kinetics of phenol removal in various reaction conditions, and finally elucidating the mechanism of biochar-enhanced phenol removal. The results demonstrated that biochars produced at pyrolysis temperatures of 700 and 900 °C revealed highly comparable catalytic activity in phenol ozonation, leading to around 95% phenol removal within 30 min reaction, due to the abundant carbonyl groups on biochar surface. The biochar, however, was suffered from poor stability, which was attributed to biochar loss and changes in surface chemistry. On the basis of examining reaction variables, an empirical kinetic model was developed well matching experimental results. It was found that ozone concentration adsorbed on biochar surface was first increased with a peak (3.8 mg/L for biochar obtained at 700 °C) at reaction time 10 min, after which it decreased along with proceeding reaction. In light of radical scavenging test, superoxide radical (O2-) was identified as main radical species produced from the interaction of ozone with biochar surface, while hydroxyl radical (OH) played negligible role in biochar catalytic ozonation. The promoting mechanism of bicarbonate on phenol ozonation was verified to be the generation of O2- via series reactions of HCO3- with OH and ozone, apart from increase in solution pH. These results provide important implications for future recycling of coking wastewater treatment sludge in environmental remediation.

Spatial distributions, source apportionment and ecological risk of SVOCs in water and sediment from Xijiang River, Pearl River Delta.

Xijiang River is an important drinking water source in Guangxi Province, China. Along the Xijiang River and surrounding tributary, the pollution profile of three important groups of semi-volatile organic compounds, including polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and phthalate esters (PAEs), was analyzed. Relatively low levels of PAHs (64-3.7 × 102 ng L-1) and OCPs (16-70 ng L-1), but high levels of PAEs (7.9 × 102-6.8 × 103 ng L-1) occurred in the water. Comparatively, low levels of OCPs (39-1.8 × 102 ng g-1) and PAEs (21-81 ng g-1), but high levels of PAHs (41-1.1 × 103 ng g-1) were found in sediment. Principal component analyses for source identification indicated petroleum-derived residues or coal and biomass combustion, and vehicular emission was the main sources for PAHs. The OCPs sources of each category were almost independent, whereas the new input of HCHs and p,p'-DDTs probably existed in some areas. PAEs were mainly originated from personal care products of urban sewage, plastic and other industrial sources. Ecological risk through the risk quotient analysis indicated a small or significant potential adverse effect on fish, daphnia and green algae. Nevertheless, the integrated risk of all pollutants should be taken into account in future study.

Pulsed corona discharge for improving treatability of coking wastewater.

Coking wastewater (CW) contains toxic and macromolecular substances that inhibit biological treatment. The refractory compounds remaining in biologically treated coking wastewater (BTCW) provide chemical oxygen demand (COD) and color levels that make it unacceptable for reuse or disposal. Gas-phase pulsed corona discharge (PCD) utilizing mostly hydroxyl radicals and ozone as oxidants was applied to both raw coking wastewater (RCW) and BTCW wastewater as a supplemental treatment. The energy efficiency of COD, phenol, thiocyanate and cyanide degradation by PCD was the subject of the research. The cost-effective removal of intermediate oxidation products with addition of lime was also studied. The energy efficiency of oxidation was inversely proportional to the pulse repetition frequency: lower frequency allows more effective utilization of ozone at longer treatment times. Oxidative treatment of RCW showed the removal of phenol and thiocyanate at 800 pulses per second from 611 to 227mg/L and from 348 to 86mg/L, respectively, at 42kWh/m3 delivered energy, with substantial improvement in the BOD5/COD ratio (from 0.14 to 0.43). The COD and color of BTCW were removed by 30% and 93%, respectively, at 20kWh/m3, showing energy efficiency for the PCD treatment exceeding that of conventional ozonation by a factor of 3-4. Application of lime appeared to be an effective supplement to the PCD treatment of RCW, degrading COD by about 28% at an energy input of 28kWh/m3 and the lime dose of 3.0kg/m3. The improvement of RCW treatability is attributed to the degradation of toxic substances and fragmentation of macromolecular compounds.

Enhanced Photocatalytic Degradation of Environmental Pollutants under Visible Irradiation by a Composite Coating.

Although nanotechnology has offered effective and efficient solutions for environmental remediation, the full utilization of sustainable energy and the avoidance of secondary pollution are still challenges. Herein, we report a two-step modification strategy for TiO2 nanoparticles by first forming a thin, surface-adherent polydopamine (PDA) shell onto the nanoparticles and then assembling core-shell nanoparticles as a photodegradation coating. The composite coating modified from TiO2 could not only realize the highly efficient utilization of photons from the visible region but also avoid the secondary pollution of nanoparticles during application. Additionally, improvements in the adsorption ability after modification greatly facilitated the photocatalytic process of the modified materials. A preliminary in vivo study on Daphnia magna and a wastewater treatment experiment suggest that treatment with the composite coating can effectively eliminate fluorene and significantly reduce its lethality. We believe the two-step modification scheme can open new avenues for the facile modification of nanomaterials for designed purposes, especially in the field of environmental remediation.

Multi-phase distribution and comprehensive ecological risk assessment of heavy metal pollutants in a river affected by acid mine drainage.

To date, there is a lack of a comprehensive research on heavy metals detection and ecological risk assessment in river water, sediments, pore water (PW) and suspended solids (SS). Here, the concentrations of heavy metals, including Cu, Zn, Mn, Cd, Pb and As, and their distribution between the four phases was studied. Samples for analysis were taken from twelve sites of the Hengshi River, Guangdong Province, China, during the rainy and dry seasons. A new comprehensive ecological risk index (CERI) based on considering metal contents, pollution indices, toxicity coefficients and water categories is offered for prediction of potential risk on aquatic organisms. The results of comprehensive analysis showed that the highest concentrations of Cu, Zn and Mn of 6.42, 87.17 and 98.74mg/L, respectively, in PW were comparable with those in water, while concentrations of Cd, Pb and As of 609.5, 2757 and 96.38µg/L, respectively, were 2-5 times higher. The sum of the exchangeable and carbonate fractions of target metals in sediments followed the order of Cd > Mn > Zn > Pb > Cu > As. The distribution of heavy metals in phases followed the order of sediment > SS > water > PW, having the sum content in water and PW lower than 2% of total. The elevated ecological risk for a single metal and the phase were 34,585 for Cd and 1160 for water, respectively, implied Cd as a priority pollutant in the considered area. According to the CERI, the maximum risk value of 769.3 was smaller than 1160 in water, but higher than those in other phases. Out of considering the water categories and contribution coefficients, the CERI was proved to be more reliable for assessing the pollution of rivers with heavy metals. These results imply that the CERI has a potential of adequate assessment of multi-phase composite metals pollution.