Frontiers of Environmental Science & Engineering

ISSN 2095-2201

ISSN 2095-221X(Online)

CN 10-1013/X

2015 Impact Factor: 1.799

Cover Story   2019, Volume 13 Issue 1
Exposure to ambient PM2.5 and its constituents has led to millions of premature death globally. The exposure mainly occurs indoors where people spend over 80% of their time. To better understand health effects of PM2.5 and control indoor PM2.5 exposure, the first step is to accurately characterize indoor PM2.5< [Detail] ...
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Effect of chemical dose on phosphorus removal and membrane fouling control in a UCT-MBR
Guangrong Sun, Chuanyi Zhang, Wei Li, Limei Yuan, Shilong He, Liping Wang
Front. Environ. Sci. Eng.. 2019, 13 (1): 1-.

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Phosphorus removal was enhanced effectively by dosing aluminum sulfate and effluent phosphorus concentration was lower than 0.5 mg/L.

Sludge activity was not inhibited but improved slightly with addition of aluminum sulfate.

EPS concentrations both in mixed liquid and on membrane surface were decreased, contributing to the effective mitigation of membrane fouling.

To enhance phosphorus removal and make the effluent meet the strict discharge level of total phosphorus (TP, 0.5 mg/L), flocculant dosing is frequently applied. In this study, the performance of aluminum sulfate dosing in a University of Cape Town Membrane Bioreactor (UCT-MBR) was investigated, in terms of the nutrients removal performance, sludge characteristics and membrane fouling. The results indicated that the addition of aluminum sulfate into the aerobic reactor continuously had significantly enhanced phosphorus removal. Moreover, COD, NH4+-N and TN removal were not affected and effluent all met the first level A criteria of GB18918-2002. In addition, the addition of aluminum sulfate had improved the sludge activity slightly and reduced trans-membrane pressure (TMP) increase rate from 1.13 KPa/d to 0.57 KPa/d effectively. The membrane fouling was alleviated attributed to the increased average particle sizes and the decreased accumulation of the small sludge particles on membrane surface. Furthermore, the decline of extracellular polymeric substance (EPS) concentration in mixed sludge liquid decreased its accumulation on membrane surface, resulting in the mitigation of membrane fouling directly.

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Source attribution for mercury deposition with an updated atmospheric mercury emission inventory in the Pearl River Delta Region, China
Jiajun Liu, Long Wang, Yun Zhu, Che-Jen Lin, Carey Jang, Shuxiao Wang, Jia Xing, Bin Yu, Hui Xu, Yuzhou Pan
Front. Environ. Sci. Eng.. 2019, 13 (1): 2-.

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Estimated anthropogenic Hg emission was 11.9 tons in Pearl River Delta for 2014.

Quantifying contributions of emission sources helps to provide control strategies.

More attentions should be paid to Hg deposition around the large point sources.

Power plant, industrial source and waste incinerator were priorities for control.

A coordinated regional Hg emission control was important for controlling pollution.

We used CMAQ-Hg to simulate mercury pollution and identify main sources in the Pearl River Delta (PRD) with updated local emission inventory and latest regional and global emissions. The total anthropogenic mercury emissions in the PRD for 2014 were 11,939.6 kg. Power plants and industrial boilers were dominant sectors, responsible for 29.4 and 22.7%. We first compared model predictions and observations and the results showed a good performance. Then five scenarios with power plants (PP), municipal solid waste incineration (MSWI), industrial point sources (IP), natural sources (NAT), and boundary conditions (BCs) zeroed out separately were simulated and compared with the base case. BCs was responsible for over 30% of annual average mercury concentration and total deposition while NAT contributed around 15%. Among the anthropogenic sources, IP (22.9%) was dominant with a contribution over 20.0% and PP (18.9%) and MSWI (11.2%) ranked second and third. Results also showed that power plants were the most important emission sources in the central PRD, where the ultra-low emission for thermal power units need to be strengthened. In the northern and western PRD, cement and metal productions were priorities for mercury control. The fast growth of municipal solid waste incineration were also a key factor in the core areas. In addition, a coordinated regional mercury emission control was important for effectively controlling pollution. In the future, mercury emissions will decrease as control measures are strengthened, more attention should be paid to mercury deposition around the large point sources as high levels of pollution are observed.

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Upgrading VFAs bioproduction from waste activated sludge via co-fermentation with soy sauce residue
Yanqing Duan, Aijuan Zhou, Kaili Wen, Zhihong Liu, Wenzong Liu, Aijie Wang, Xiuping Yue
Front. Environ. Sci. Eng.. 2019, 13 (1): 3-.

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SSR addition upgraded VFAs production from WAS.

Structure modification by pretreatments led to performance distinctions.

Distinctions in microbial community was observed by pretreatments selection.

Up to 0.49‒0.65 billion €/year of market value potential was preliminary estimated.

Conditioning of extra carbon sources has been widely reported to facilitate fermentation of waste activated sludge (WAS). Soy sauce residue (SSR) was a relatively untapped carbon source for sludge conditioning. This batch study aimed to evaluate the possible implementation of SSR for volatile fatty acids (VFAs) production from WAS. To upgrade the bioavailability of feedstock, three typical pretreatment methods were conducted, i.e., ammonium hydroxide (AH), sulfuric acids (SA) and thermal assisted alkaline (TA). AH pretreated test (AH-PT) outperformed due to a relatively strong structure decomposition of cellulosic materials as revealed by infrared spectroscopic analysis and crystal index. As a result, performed a high hydrolysis rate of 4449 mg COD/d, 1.12-1.23-fold higher than that in TA and SA pretreated tests (TA-PT and SA-PT), and 7.8-fold higher than that in the Control test. Meanwhile, a volatile fatty acids (VFAs) contribution of 401.2 mg COD/g SSR∙L and a maximum acidification rate of 3.59 d-1 was recorded, with a high sum proportion of mall molecular acetic and propionic 82.2%, 11% ‒70% increase over the other three tests. Besides, speciation process characterized with functional genus differentiation was identified by microbial diversity and distribution investigation and canonical correspondence analysis (CCA). Finally, a potential market value of 0.49‒0.65 Billion €/year was preliminary estimated, showing promise of resource recovery from both WAS and SSR instead of extensive disposal.

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Designing an in situ remediation strategy for polluted surface water bodies through the specific regulation of microbial community
Boran Wu, Xiaoli Chai, Youcai Zhao, Xiaohu Dai
Front. Environ. Sci. Eng.. 2019, 13 (1): 4-.

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Remediation of polluted water body via microbial community regulation is proposed.

EAS-induced microbial growth can enhance self-purification of polluted water body.

Principle of EAS is elaborated by the conceptual model description.

This paper proposes an in situ restoration strategy, ecosystem activation system (EAS), for self-purification abilities of polluted water ecosystems through the specific regulation of microbial community. EAS utilizes polyhydroxyalkanoates (PHA) to modify indigenous microbial communities of polluted water bodies. Microorganisms preferentially utilizing PHA as the carbon source for their enhanced growth are defined as specific, and those with no special selectivity to PHA and raw-water dissolved organic matter are defined as non-specific and can be phased out during EAS operation. As a result, the microbial community can be regulated to the specific structure, which is beneficial for the water quality improvement. The developed model described the above principle with accounting for the growth kinetics of specific microorganisms, competitive inhabitation of specific microorganisms on non-specific microorganisms, and coupled EAS-induced self-purification of polluted water bodies. The conceptual model is believed to be a primary step toward quantitative design, operation, and optimization of EAS.

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Relations between indoor and outdoor PM2.5 and constituent concentrations
Cong Liu, Yinping Zhang
Front. Environ. Sci. Eng.. 2019, 13 (1): 5-.

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Factors impacting indoor-outdoor relations are introduced.

Sulfate seems a fine tracer for other non-volatile species.

Particulate nitrate and ammonium desorb during outdoor-to-indoor transport.

OC load increases during the transport due to sorption of indoor SVOCs.

Outdoor PM2.5 influences both the concentration and composition of indoor PM2.5. People spend over 80% of their time indoors. Therefore, to assess possible health effects of PM2.5 it is important to accurately characterize indoor PM2.5 concentrations and composition. Controlling indoor PM2.5 concentration is presently more feasible and economic than decreasing outdoor PM2.5 concentration. This study reviews modeling and measurements that address relationships between indoor and outdoor PM2.5 and the corresponding constituent concentrations. The key factors in the models are indoor-outdoor air exchange rate, particle penetration, and deposition. We compiled studies that report I/O ratios of PM2.5 and typical constituents (sulfate (SO42-), nitrate (NO3-), ammonium (NH4+), elemental carbon (EC), and organic carbon (OC), iron (Fe), copper (Cu), and manganese (Mn)). From these studies we conclude that: 1) sulfate might be a reasonable tracer of non-volatile species (EC, Fe, Cu, and Mn) and PM2.5 itself; 2) particulate nitrate and ammonium generally desorb to gaseous HNO3 and NH3 when they enter indoors, unless, as seldom happens, they have strong indoor sources; 3) indoor-originating semi-volatile organic compounds sorb on indoor PM2.5, thereby increasing the PM2.5 OC load. We suggest further studies on indoor-outdoor relationships of PM2.5 and constituents so as to help develop standards for healthy buildings.

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Effect of nitrobenzene on the performance and bacterial community in an expanded granular sludge bed reactor treating high-sulfate organic wastewater
Jun Li, Wentao Li, Gan Luo, Yan Li, Aimin Li
Front. Environ. Sci. Eng.. 2019, 13 (1): 6-.

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Less than 50 mg/L nitrobenzene brought little effect on anaerobic sulfate reduction.

Kinetics of sulfate reduction under different nitrobenzene contents was studied.

Increased nitrobenzene contents greatly changed the bacterial community structure.

Genus Desulfovibrio played the key role in anaerobic sulfate reduction process.

Nitrobenzene (NB) is frequently found in wastewaters containing sulfate and may affect biological sulfate reduction process, but information is limited on the responses of sulfate reduction efficiency and microbial community to the increased NB contents. In this study, a laboratory-scale expanded granular sludge bed reactor was operated continuously to treat high-sulfate organic wastewater with increased NB contents. Results successfully demonstrated that the presence of more than 50 mg/L NB depressed sulfate reduction and such inhibition was partly reversible. Bath experiments showed that the maximum specific desulfuration activity (SDA) decreased from 135.80 mg SO42?/gVSS/d to 30.78 mg SO42?/gVSS/d when the NB contents increased from none to 400 mg/L. High-throughput sequencing showed that NB also greatly affected bacterial community structure. Bacteroidetes dominated in the bioreactor. The abundance of Proteobacteria increased with NB addition while Firmicutes presented an opposite trend. Proteobacteria gradually replaced Firmicutes for the dominance in response to the increase of influent NB concentrations. The genus Desulfovibrio was the dominant sulfate-reducing bacteria (SRB) with absence or presence of NB, but was inhibited under high content of NB. The results provided better understanding for the biological sulfate reduction under NB stress.

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Characterization of CANON reactor performance and microbial community shifts with elevated COD/N ratios under a continuous aeration mode
Yao Zhang, Yayi Wang, Yuan Yan, Haicheng Han, Min Wu
Front. Environ. Sci. Eng.. 2019, 13 (1): 7-.

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COD/N at low ratios (0–0.82) improved N removals of CANON.

CANON performance decreased after COD/N up to 0.82.

The relative abundance of AOB decreased continuously with increasing COD/N.

AOB outcompeted at a high COD load led to CANON failure.

The relative abundance of AnAOB decreased and increased with increasing COD/N.

The effects of increasing COD/N on nitrogen removal performance and microbial structure were investigated in a SBR adopting a completely autotrophic nitrogen removal over nitrite process with a continuous aeration mode (DO at approximately 0.15–0.2 mg/L). As the COD/N increased from 0.1 to≤0.59, the nitrogen removal efficiency (NRE) increased from 88.7% to 95.5%; while at COD/N ratios of 0.59–0.82, the NRE remained at 90.7%–95.5%. As the COD/N increased from 0.82 to 1.07, the NRE decreased continuously until reaching 60.1%. Nitrosomonas sp. (AOB) and Candidatus Jettenia (anammox bacteria) were the main functional genera in the SBR. As the COD/N increased from 0.10 to 1.07, the relative abundance of Nitrosomonas decreased from 13.4% to 2.0%, while that of Candidatus Jettenia decreased from 35% to 9.9% with COD/N<0.82 then increased to 45.4% at a COD/N of 1.07. Aerobic heterotrophic bacteria outcompeted AOB at high COD loadings (650 mg/L) because of oxygen competition, which ultimately led to deteriorated nitrogen removal performance.

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Influence of reclaimed water discharge on the dissemination and relationships of sulfonamide, sulfonamide resistance genes along the Chaobai River, Beijing
Ning Zhang, Xiang Liu, Rui Liu, Tao Zhang, Miao Li, Zhuoran Zhang, Zitao Qu, Ziting Yuan, Hechun Yu
Front. Environ. Sci. Eng.. 2019, 13 (1): 8-.

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Reclaimed water threatens the ecological safety of the Chaobai River.

SMX, TMP, and SDZ were the first three abundant antibiotics in the research area.

SRGs and intI1 were widespread with high abundance after reclaimed water recharge.

The SRGs values followed the sequence: Summer>autumn>spring>winter.

Strong correlations were detected between SRGs and environmental factors.

Reclaimed water represents an important source of antibiotics and antibiotic resistance genes, threatening the ecological safety of receiving environments, while alleviating water resource shortages. This study investigated the dissemination of sulfonamide (SAs), sulfonamide resistance genes (SRGs), and class one integrons (intI1) in the surface water of the recharging area of the Chaobai River. The three antibiotics sulfamethoxazole, trimethoprim, and sulfadiazine had the highest abundance. The highest absolute abundances were 2.91×106, 6.94×106, and 2.18×104 copies/mL for sul1, sul2, and intI1 at the recharge point, respectively. SRGs and intI1 were widespread and had high abundance not only at the recharging point, but also in remote areas up to 8 km away. Seasonal variations of SRGs abundance followed the order of summer>autumn>spring>winter. Significant correlations were found between SRGs and intI1 (R2 = 0.887 and 0.786, p<0.01), indicating the potential risk of SRGs dissemination. Strong correlations between the abundance of SRGs and environmental factors were also found, suggesting that appropriate environmental conditions favor the spread of SRGs. The obtained results indicate that recharging with reclaimed water causes dissemination and enrichment of SAs and SRGs in the receiving river. Further research is required for the risk assessment and scientific management of reclaimed water.

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Development of combined coagulation-hydrolysis acidification-dynamic membrane bioreactor system for treatment of oilfield polymer-flooding wastewater
Xue Shen, Lei Lu, Baoyu Gao, Xing Xu, Qinyan Yue
Front. Environ. Sci. Eng.. 2019, 13 (1): 9-.

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• We created a combined system for treating oilfield polymer-flooding wastewater.

• The system was composed of coagulation, hydrolysis acidification and DMBR.

• Coagulant integrated with demulsifier dominated the removal of crude oil.

• The DMBR proceed efficiently without serious membrane fouling.

A combined system composed of coagulation, hydrolysis acidification and dynamic membrane bioreactor (DMBR) was developed for treating the wastewater produced from polymer flooding. Performance and mechanism of the combined system as well as its respective units were also evaluated. The combined system has shown high-capacity to remove all contaminants in the influent. In this work, the coagulant, polyacrylamide-dimethyldiallyammonium chloride-butylacrylate terpolymer (P(DMDAAC-AM-BA)), integrated with demulsifier (SD-46) could remove 91.8% of crude oil and 70.8% of COD. Hydrolysis acidification unit improved the biodegradability of the influent and the experimental results showed that the highest acidification efficiency in hydrolysis acidification reactor was 20.36% under hydraulic retention time of 7 h. The DMBR proceeded efficiently without serious blockage process of membrane fouling, and the concentration of ammonia nitrogen (NH3-N), oil, chemical oxygen demand and biological oxygen demand in effluent were determined to be 3.4±2.1, 0.3±0.6, 89.7±21.3 and 13±4.7 mg/L.

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Unlocked disinfection by-product formation potential upon exposure of swimming pool water to additional stimulants
Alvyn P. Berg, Ting-An Fang, Hao L. Tang
Front. Environ. Sci. Eng.. 2019, 13 (1): 10-.

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• Swimming pool water was studied for DBPs upon exposure to additional stimulants.

• DBP formation could be induced by residual chlorine and extended incubation.

• Urine led to a massive formation of chloroform with additional stimulants.

• Reactions between chlorine and anthropogenic organics were slow and long-lasting.

• Urine control and air ventilation should be on the priority list for pool management.

Anthropogenic organics are known to be responsible for the formation of harmful disinfection by-products (DBPs) in swimming pool water (SPW). The research explored an important scenario of SPW with no additional anthropogenic organic input. With stimulations by residual chlorine or additional chlorine and extended incubation, the formation of DBPs, especially chloroform, was significantly induced. Similar observations were found by investigating synthetic SPW made with sweat and urine. The presence of urine led to a massive formation of chloroform, as noted by an approximate 19-fold increase after 165-day incubation with a shock chlorine dose. The research suggests that consistent residual chlorine and long water retention as two typical features of SPW could unlock the DBP formation potential of anthropogenic organics. Thus, limiting the introduction of anthropogenic organics may not have an immediate effect on reducing DBP levels, because their reactions with chlorine can be slow and long-lasting. Pool management should prioritize on control of urine and improving air ventilation. This work is useful to deepen understandings about DBP formation in SPW and provide implications for pool management and prospective legislation.

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Augmented hydrogen production by gasification of ball milled polyethylene with Ca(OH)2 and Ni(OH)2
Giovanni Cagnetta, Kunlun Zhang, Qiwu Zhang, Jun Huang, Gang Yu
Front. Environ. Sci. Eng.. 2019, 13 (1): 11-.

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PE ball milling pretreatment induces higher H2 production and purity by gasification.

Ca(OH)2 reacts at solid state with PE boosting H2 and capturing CO2.

Ca(OH)2 significantly reduces methanation side-reaction.

Polymer thermal recycling for hydrogen production is a promising process to recover such precious element from plastic waste. In the present work a simple but efficacious high energy milling pre-treatment is proposed to boost H2 generation during polyethylene gasification. The polymer is co-milled with calcium and nickel hydroxides and then it is subjected to thermal treatment. Results demonstrate the key role played by the calcium hydroxide that significantly ameliorates hydrogen production. It reacts in solid state with the polyethylene to form directly carbonate and hydrogen. In this way, the CO2 is immediately captured in solid form, thus shifting the equilibrium toward H2 generation and obtaining high production rate (>25 L/mol CH2). In addition, high amounts of the hydroxide prevent excessive methane formation, so the gas product is almost pure hydrogen (~95%).

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Label-free colorimetric nanosensor with improved sensitivity for Pb2+ in water by using a truncated 8–17 DNAzyme
Abdul Ghaffar Memon, Xiaohong Zhou, Yunpeng Xing, Ruoyu Wang, Lanhua Liu, Mohsin Khan, Miao He
Front. Environ. Sci. Eng.. 2019, 13 (1): 12-.

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• Unmodified-AuNP based, colorimetric nanosensor was constructed for Pb2+ detection.

• 5-nucleotide truncation in DNAzyme made complete substrate detachment upon Pb2+.

• Ultrasensitive and selective detection of Lead (II) was achieved with 0.2×10-9 mol/L LOD.

Water pollution accidents, such as the Flint water crisis in the United States, caused by lead contamination have raised concern on the safety of drinking water distribution systems. Thus, the routine monitoring of lead in water is highly required and demands efficient, sensitive, cost-effective, and reliable lead detection methods. This study reports a label-free colorimetric nanosensor that uses unmodified gold nanoparticles (AuNPs) as indicators to enable rapid and ultra-sensitive detection of lead in environmental water. The 8–17 DNAzyme was truncated in this study to facilitate the detachment of single-stranded DNA fragments after substrate cleavage in the presence of Pb2+. The detached fragments were adsorbed over AuNPs and protected against salt concentration-induced aggregation. Accordingly, high Pb2+ would result in rapid color change from blue to pink. The established sensing principle achieved a sensitive limit of detection of 0.2×10-9 mol/L Pb2+, with a linear working range of two orders of magnitude from 0.5×10-9 mol/L to 5×10-9 mol/L. The selectivity of the nanosensor was demonstrated by evaluating the interfering metal ions. The developed nanosensor can serve as a substitute for the rapid analysis and monitoring of trace lead levels under the drinking water distribution system and even other environmental water samples.

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Transferral of HMs pollution from road-deposited sediments to stormwater runoff during transport processes
Qian Wang, Qionghua Zhang, Mawuli Dzakpasu, Nini Chang, Xiaochang Wang
Front. Environ. Sci. Eng.. 2019, 13 (1): 13-.

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Ratio of turbidity and TSS (Tur/TSS) was used to characterize PSD of stormwater particles.

Pb and Zn preferred to accumulate in finer RDS, while Cu, Cr and Ni in coarser RDS.

HMs pollution in stormwater particles increased linearly with Tur/TSS.

Dissolvability of HMs and PSD variations contribute to the differences between RDS and stormwater.

Stormwater runoff, derived from the wash-off of road-deposited sediments (RDS), contains elevated heavy metal (HM) concentrations and, thus, imposes an increasing threat to urban aquatic ecosystems. In-depth understanding of the variations of HMs pollution from RDS to stormwater during transport processes facilitates the development of effective RDS and stormwater control strategies. Toward this end, the distribution of HMs (Cu, Pb, Zn, Cr, and Ni) in RDS and stormwater were investigated simultaneously. The results show a preferential accumulation of Pb and Zn in the finer (<38.5 μm) RDS, and Cu, Cr and Ni in the coarser (38.5–150 μm) RDS. For stormwater, n.d.~48.6% of HMs fractionated into the dissolved phase, and stormwater particles constitute the primary carriers of HMs. Furthermore, the accumulation of HMs in stormwater particles increased linearly with finer particle size distributions (PSD). Geoaccumulation index (Igeo) highlighted the predominant pollution of both RDS and stormwater particles by Cu, Pb and Zn. Nonetheless, Cu, Pb, and Ni mostly contributed the potential ecological risk of RDS, whereas Cu, Pb, and Zn mainly contributed that of stormwater particles. Moreover, contamination by Cu, Pb and Zn was significantly higher in stormwater particles than that in RDS. These differences are attributable to the solubility and size-dependent accumulation of HMs in RDS, as well as the PSD variations during transport processes. The study outcomes highlight the importance of very fine (nano- and submicron- scale) RDS in stormwater pollution and the necessity of control.

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Removal of tetrachlorobisphenol A and the effects on bacterial communities in a hybrid sequencing biofilm batch reactor-constructed wetland system
Xiaohui Wang, Shuai Du, Tao Ya, Zhiqiang Shen, Jing Dong, Xiaobiao Zhu
Front. Environ. Sci. Eng.. 2019, 13 (1): 14-.

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SBBR-CW system was proposed to effectively treat wastewater containing TCBPA.

CW unit contributed more than SBBR to the removal of TCBPA.

TCBPA changed the composition and structure of bacterial community in the system.

GAOs massively grew in SBBR, but did not deteriorate TP removal efficiency.

Tetrachlorobisphenol A (TCBPA) released into the sewage may cause environmental pollution and health risk to human beings. The objective of this study was to investigate the removal of TCBPA and bacterial community structures in a laboratory-scale hybrid sequencing biofilm batch reactor (SBBR)-constructed wetland (CW) system. The results showed that the removal efficiency of chemical oxidation demand (COD), ammonia, total nitrogen and total phosphorus in the SBBR-CW system was 96.7%, 97.3%, 94.4%, and 88.6%, respectively. At the stable operation stage, the system obtained a 71.7%±1.8% of TCBPA removal efficiency with the influent concentration at 200 mg/L. Illumina MiSeq sequencing of 16S rRNA gene revealed that the presence of TCBPA not only reduced the bacterial diversity in the SBBR-CW system, but also altered the composition and structure of bacterial community. After the addition of TCBPA, Proteobacteria increased from 31.3% to 38.7%, while Acidobacteria and Parcubacteria decreased greatly in the SBBR. In contrast, Acidobacteria replaced Proteobacteria as the dominant phylum in the upper soils of CW. The results indicated that TCBPA stimulated the growth of GAOs in the SBBR without deteriorating the phosphorus removal due to the presence of sufficient carbon sources. The ammonia oxidizing bacteria, Nitrosomonas, and denitrification bacteria, Hyphomicrobium and Pseudomonas, were inhibited by TCBPA, resulting in a decreasing the removal efficiency of TN and ammonia.

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Effect of biological activated carbon filter depth and backwashing process on transformation of biofilm community
Wanqi Qi, Weiying Li, Junpeng Zhang, Xuan Wu, Jie Zhang, Wei Zhang
Front. Environ. Sci. Eng.. 2019, 13 (1): 15-.

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We studied BAC biofilm during the process of initial operation and backwash.

Microbial diversity decreased gradually with the increase of BAC filter depth.

Proteobacteria dominated at the phylum level among the BAC biofilm samples.

α-proteobacteria increased about 10% in all carbon filter depth after backwash.

The biological activated carbon (BAC) is a popular advanced water treatment to the provision of safe water supply. A bench-scale device was designed to gain a better insight into microbial diversity and community structure of BAC biofilm by using high-throughput sequencing method. Both samples of BAC biofilm (the first, third and fifth month) and water (inlet water and outlet water of carbon filter, outlet water of backwashing) were analyzed to evaluate the impact of carbon filter depth, running time and backwash process. The results showed that the microbial diversity of biofilm decreased generally with the increase of carbon filter depth and biofilm reached a steady-state at the top layer of BAC after three months’ running. Proteobacteria (71.02%–95.61%) was found to be dominant bacteria both in biofilms and water samples. As one of opportunistic pathogen, the Pseudomonas aeruginosa in the outlet water of device (1.20%) was about eight times higher than that in the inlet water of device (0.16%) at the genus level after five-month operation. To maintain the safety of drinking water, the backwash used in this test could significantly remove Sphingobacteria (from 8.69% to 5.09%, p<0.05) of carbon biofilm. After backwashing, the operational taxonomic units (OTUs) number and the Shannon index decreased significantly (p<0.05) at the bottom of carbon column and we found the Proteobacteria increased by about 10% in all biofilm samples from different filter depth. This study reveals the transformation of BAC biofilm with the impact of running time and backwashing.

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15 articles