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Heavy metal concentrations represent important pollution evaluation indices, and it is necessary to assess the potential environmental and health risks from heavy metals associated with coking wastes from coking plants. In this study, coking sludge (CS), tar residue (TR), coke powder (CP), and sulfur paste (SP) from three coking plants (Plant A, Plant B, and Plant C) in central, western, and southern Shanxi Province and from soils surrounding Plant A were selected as the research objects, and the distributions of Cu, Ni, Pb, Zn, Mn, Cd, and Cr were determined. The results showed that Cd in the four solid wastes far exceeded the soil background value by a factor of 16~195, and the contents of Pb in TR (three plants) and CS (Plant C) exceeded the soil background values 19.70-, 23.57-, 14.46-, and 12.56-fold, respectively. Similarly, the concentrations of Cu, Ni, Pb, Zn, and Cd in soils were higher than the background values by factors of 31.18, 8.35, 34.79, 29.48, and 3.43, respectively. In addition, the Cu, Ni, Pb, and Cr in the four solid wastes and soils mainly existed in the residual state. As depth increased, the overall Ni, Pb, Mn, and Cd concentrations in soils increased. The high ecological risks associated with the four solid wastes were mainly due to the enrichment of Cd. Workers in coking plants face certain Cr health risks. This study provides theoretical support for the coking industry with respect to the treatment, disposal, and management of solid wastes. [ABSTRACT FROM AUTHOR]

Traditional denitrification often produces high operating costs and excessive sludge disposal expenses due to conventional carbon sources. A novel electric–magnetic field (MF) 48 mT with Fe0 and C-Fe0 powder in an upflow microaerobic sludge reactor (UMSR) improved nitrogen removal from wastewater without organic carbon resources and gave richness to the heterotrophic bacterial community. In the current study, the reactor was operated for 78 ± 2 days, divided into five stages (without Fe0, with Fe0, coupling with MF, without coupling with MF, and coupling with MF again), at a hydraulic retention time (HRT) of 2.5 h, with an influent loading of ammonium (NH4+-N) 50 ± 2 mg/L, at 25–27 °C, and less than 1.0 mg/L dissolved oxygen (DO). The results demonstrated nitrogen removal efficiency enhanced after coupling with MF on the levels of NO3−-N by 76% with an effluent concentration of 8.7 mg/L, NH4+-N by 72% with an effluent concentration of 13.6 mg/L, and total nitrogen removal (TN) by 76%, respectively. After coupling the MF with the reactor, the microbial community data analysis showed the dominant abundance of ammonia-oxidizing bacteria, heterotrophic nitrifying bacteria, and denitrifying bacteria on the level of Anaerolineaceae_uncultured 2%, which is capable of denitrification that uses Fe2+ as an electron source, Gemmatimonadaceae_uncultured 4%, Hydrogenophaga 4% which is capable of catalyzing hydrogenotrophic denitrification and correlating to nitrate removal, denitrification and desulfurization bacteria SBR1031_norank 18%, anammox-bacteria Saccharimonadales_norank 2%, and (AOM) Limnobacter 3% in the sludge. [ABSTRACT FROM AUTHOR]

Heavy metal pollution in the soil surrounding solid wastes from coking plants poses potential threats to human health and has attracted widespread attention. This study is the first to assess the spatial variability and risks of heavy metals in the soil surrounding solid waste from coking plants. The results showed that the concentrations of Cu, Ni, Pb, and Cd in the soil were much higher than the background value of the soil. Solid waste had a clear influence on the contents of Ni, Cd, Mn, Pb, and Cr in the soil. The ecological risk assessment of heavy metal pollution demonstrated that the pollution degree of Cu, Pb, and Cd was more serious than others, and the ecological risk of heavy metals was mainly caused by Cd in the soil. The human health risk assessment showed that adults and children near coking plants might face carcinogenic risk from exposure to Cr. This study can provide a theoretical basis for the prevention and management of soil heavy metal pollution surrounding solid waste in coking plants. [ABSTRACT FROM AUTHOR]

In this study, microbial fuel cells (MFCs) were explored to promote the nitrogen removal performance of combined anaerobic ammonium oxidation (anammox) and Fe-C micro-electrolysis (CAE) systems. The average total nitrogen (TN) removal efficiency of the modified MFC system was 85.00%, while that of the anammox system was 62.16%. Additionally, the effective operation time of this system increased from six (CAE system alone) to over 50 days, significantly promoting TN removal. The enhanced performance could be attributed to the electron transferred from the anode to the cathode, which aided in reducing nitrate/nitrite in denitrification. The H+ released through the proton exchange membrane caused a decrease in the pH, facilitating Fe corrosion. The pyrolyzed waste tire used as the cathode could immobilize microorganisms, enhance electron transport, and produce a natural Fe-C micro-electrolysis system. According to the microbial community analysis, Candidatus kuenenia was the major genus involved in the anammox process. Furthermore, the SM1A02 genus exhibited the highest abundance and was enriched the fastest, and could be a novel potential strain that aids the anammox process. [ABSTRACT FROM AUTHOR]

To address the availability of carbon sources for denitrification, the accelerated hydrolysis of the most abundant but low-availability fraction of particulate organic matter (POM) was investigated. Mesh sieves with different pore sizes were used as primary pretreatment at the start-up-stage of the biological process to separate some POM from the liquid system. The changes in soluble carbohydrates and proteins were monitored to investigate the hydrolysis performance of the sieved POM, with waste activated sludge (WAS) as the control test. The results showed that an average of 35% POM could be entrapped before filtrate mat development. In addition, benefiting from the high polysaccharides concentration, as well as the high availability due to the relatively loose physical structure, a 23% hydrolysis efficiency of POM was obtained, in contrast to that of WAS (3.4%), with a hydrolysis constant of 0.39 h−1. The prominent performance was also attributed to the unique microbial communities having been domesticated at a lower temperature, especially the cellulose-degrading bacteria Paraclostridium and psychrophile Psychrobacter, making up 6.94% and 2.56%, respectively. Furthermore, the potential benefits and application of improved POM hydrolysis by start-up stage recovery via mesh sieves combined with anaerobic fermentation were evaluated, including selective POM entrapment, alleviation of blockage and wear, and a reduction in aeration energy. By the proposed strategy, carbon availability for biological nutrient removal (BNR) processes is anticipated to be improved more economically than that can be achieved by primary clarifier elimination. [ABSTRACT FROM AUTHOR]

Phenolic compounds are the dominant pollutants in soils contaminated by the coking industry. Ring opening by the hydroxylase gene (bamA) is the key step in the benzoyl-CoA degradation pathway under anaerobic conditions, and a broad spectrum of microorganisms possesses this functional gene, including denitrifiers. The present study analyzed the community structure of denitrifying bacteria and the diversity of the bamA gene for mixed cultures enriched from soil collected at a coking industrial site and then grown under nitrate-reducing conditions on phenol or p-hydroxybenzoate (4HBA), a key intermediate product of anaerobic phenol degradation. Illumina sequencing of the 16S rRNA gene showed different bacterial compositions between the two cultures. The dominant phyla were Proteobacteria, Armatimonadetes, and Planctomycetes in the phenol culture and Proteobacteria and Bacteroidetes in the 4HBA culture. Phylogenetic analysis further demonstrated that bamA genes were associated with four clusters of bacteria, three of known bacteria and one of uncultured bacteria. The diversity of the bamA gene differed from that reported in anaerobic aromatic degradation cultures, suggesting that these enriched cultures may contain new strains unique to coking-contaminated soils. The present study further validates the potential application of this functional gene as a marker for anaerobic biodegradation processes in enrichment cultures from contaminated soil. [ABSTRACT FROM AUTHOR]

The CdS(HS)/g-C3N4 photocatalysts with an intimate connection was successfully synthesized by a facile deposition method. The CdS hollow microspheres (CdS(HS)) were well anchored on the surface of g-C3N4 to form an intimate connection by the hydrogen bonding between g-C3N4 and CdS(HS). The structures, morphologies, optical and electrical properties and photocatalytic performance of samples were successfully characterized by multiple means. The CdS(HS)/g-C3N4 composites exhibited excellent photocatalytic activity and stability for the photodegradation of RhB, and the degradation rate constant of CdS(HS)/g-C3N4 with optimum CdS(HS) mass ratio of 0.25% was about 2.1 times higher than that of the pure g-C3N4 under the visible light irradiation for 20 min. After four cycles, the CdS(HS)(0.25%)/g-C3N4 composite still maintained the high photocatalytic activity with the RhB degradation efficiency of 95%. Surprisingly, the photocorrosion of CdS(HS) caused by the photogenerated holes was inhibited effectively. The improvement of these properties should be ascribed to the intimate connection between g-C3N4 and CdS(HS) and the hollow structure of CdS(HS). The photocatalytic mechanism was also analyzed systematically. Furthermore, it was of great interest that the CdS(HS)/g-C3N4 composites possessed an excellent sedimentation property and they can be easily separated from the solution, which will be propitious to practical application. [ABSTRACT FROM AUTHOR]

Most studies have employed aeration-biofiltration process for the simultaneous removal of iron, manganese and ammonia in groundwater. However, what's inside the 'black box', i.e., the potential contribution of functional microorganisms behavior and interactions have seldom been investigated. Moreover, little attention has been paid to the correlations between environmental variables and functional microorganisms. In this study, the performance of industrial-scale biofilters for the contaminated groundwater treatment was studied. The effluent were all far below the permitted concentration level in the current drinking water standard. Pyrosequencing illustrated that shifts in microbial community structure were observed in the microbial samples from different depths of filter. Microbial networks showed that the microbial community structure in the middle- and deep-layer samples was similar, in which a wide range of manganese-oxidizing bacteria was identified. By contrast, canonical correlation analysis showed that the bacteria capable of ammonia-oxidizing and nitrification was enriched in the upper-layer, i.e., Propionibacterium, Nitrosomonas, Nitrosomonas and Candidatus Nitrotoga. The stable biofilm on the biofilter media, created by certain microorganisms from the groundwater microflora, played a crucial role in the simultaneous removal of the three pollutants. [ABSTRACT FROM AUTHOR]

For quinoline-denitrifying degradation, very few researches focused on shortcut denitrification process and its bacterial community characteristics. In this study, complete and shortcut denitrification systems were constructed simultaneously for quinoline degradation. By calculation, specific quinoline removal rates were 0.905 and 1.123 g/(gVSS d), respectively, in the complete and shortcut systems, and the latter was 1.24 times of the former. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), high-throughput sequencing, and quantitative PCR (qPCR) techniques based on 16S rRNA were jointly applied to compare microbial community structures of two systems. Many denitrifying bacteria phyla, classes, and genera were detected in the two systems. Phylum Proteobacteria, Class Gammaproteobacteria, and Genus Alicycliphilus denitrificans were the dominant contributors for quinoline-denitrifying degradation. In the shortcut denitrification system, main and specific strains playing crucial roles were more; the species richness and the total abundance of functional genes ( narG, nirS, nirK, and nosZ) were higher compared with the complete denitrification system. It could be supposed that inorganic-nitrogen reductase activity of bacterial community was stronger in the shortcut denitrification system, which was the intrinsic reason to result in higher denitrification rate. [ABSTRACT FROM AUTHOR]

Anaerobic-oxic membrane bioreactor (AOMBR) has been proposed as a highly effective method in municipal and industrial wastewater treatment. In this study, according to the sewage treatment system in a campus, long-term experiments were conducted to assess the impacts of the sludge retention time (SRT) on sludge characteristics and membrane fouling, and the sludge parameters include biomass concentration, particle size distribution, extracellular polymeric substances (EPS), soluble microbial products (SMPs), and specific resistance to filtration (SRF). Our results clearly demonstrated that SRT was one of the most important factors influencing sludge characteristics, and different sludge characteristics resulted in different membrane fouling degrees. A better treatment and filtration performances were observed at the SRT of 30 days compared to two SRTs of 10 and 90 days. Among these parameters, SMP had the most significant correlation with the membrane fouling rate (dTMP/d t), and it had a negative impact on membrane filtration performance. The impact of SRT on membrane fouling process was discussed further by filtration models. At 10 days SRT, the complete-standard blocking model curve had a comparatively higher goodness-of-fit with the fouling process, and at 30 and 90 days SRT, the cake-standard blocking model curve had a relatively higher goodness-of-fit with respective fouling process. [ABSTRACT FROM AUTHOR]

Most studies on the production of volatile fatty acids (VFAs) from waste activated sludge (WAS) digestion have focused on operating conditions, pretreatments and characteristic adjustments. Conditioning by extra carbon sources (ECS), normally added in a solid form, has been reported to be an efficient approach. However, this has caused considerable waste of monomeric sugars in the hydrolysate. In this study, the effects of two added forms (pretreated straw (S) and hydrolyzed liquid (L)) of cornstover (CS) on WAS acidification were investigated. To obtain different cellulosic compositions of CS, low-thermal or autoclaved assisted alkaline (TA or AA) pretreatments were conducted. The results showed that AA-L test achieved the highest VFAs value (653 mg COD/g VSS), followed by AA-S (613 mg COD/g VSS). These values were 12% and 28% higher, respectively, than that obtained in the TA-L and TA-S tests. Meanwhile, higher percentages of acetic acid were observed after AA pretreatment (~62% versus ~53% in TA). The added forms of CS played an important role in structuring the innate microbial community in the WAS, as shown by high-throughput sequencing and canonical correspondence analysis. The findings obtained in this work may provide a scientific basis for the potential implementation of co-digesting WAS with ECS simultaneously obtaining energy and high value-added products. [ABSTRACT FROM AUTHOR]