Environmental Technology

Bai, Yaohui; Liang, Jinsong; Liu, Ruiping; Hu, Chengzhi; Qu, Jiuhui

doi: 10.1080/09593330.2014.911361pmid: 25145207

Microbial communities play a critical role in the degradation of effluent contaminants in constructed wetlands. Many questions remain, however, regarding the role of microbial communities in rhizospheric soil. In this study, we used metagenomic analysis to assess microbial community composition and function in a constructed wetland receiving surface water. The diversity of the microbial community of rhizosphere soil was found to be significantly greater than that of the wetland influent water. This enhancement is likely due to the availability of diverse habitats and nutrients provided by the wetland plants. From function annotation of metagenomic data, a number of biodegradation pathways associated with 14 xenobiotic compounds were identified in soil. Nitrogen fixation, nitrification and denitrification genes were semi-quantitatively analysed. By screening of manganese transformation genes, we found that the biological oxidation of Mn2+ (mainly catalysed by multicopper oxidase) in the influent water yielded insoluble Mn4+, which subsequently precipitated and were incorporated into the wetland soil. These data show that the use of metagenomic analysis can provide important new insights for the study of wetland ecosystems and, in particular, how biologically mediated transformation or degradation can be used to reduce contamination of point and non-point source wastewater.

Xu, G.R.; Tang, J.H.; Li, G.B.; Spinosa, L.

doi: 10.1080/09593330.2014.911754pmid: 25145208

The primary goal of this study was to compare the pollutant removal efficiency of the reactivated activated-ferric-sludge (AFS) with that of the activated sludge (AS). Most tested organic pollutants were preferably removed by reactivated AFS. The optimal reactivated conditions for AFS were a reactivation time of 3 h, pH of 5–9, AFS dose of 5 g/L and dissolved oxygen of 2–6 mg/L. The results revealed a positive correlation between microbial activity and the removal efficiency of organic pollutants, with a higher microbial activity being associated with a better removal efficiency of organic pollutants. Additionally, variations in extracellular polymeric substances were found to be crucial to the microbial activity and adsorption capacity of reactivated AFS. After reactivation, reactivated AFS was superior to AS for the removal of most pollutants. Finally, the mechanism of AFS reactivation was investigated. Overall, the results of the present study demonstrate that reactivated AFS has the potential for widespread application in the removal of organic pollutants during the wastewater treatment process.

Song, Yongwei; Zheng, Guanyu; Huo, Minbo; Zhao, Bowen; Zhou, Lixiang

doi: 10.1080/09593330.2014.911755pmid: 25145209

It is well documented that bioleaching with the co-inoculation of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans can drastically enhance sludge dewaterability under ambient temperature condition, but little information on low temperature effect on bioleached sludge dewaterability is available. In this study, the optimum sludge retention time of bioleaching treatment and the mechanisms responsible for the dewaterability enhancement of bioleached sludge were studied in two bioleaching systems conducted at a low temperature of 10°C and a normal temperature of 28°C, respectively. Results showed that Acidithiobacillus bacteria involved in the bioleaching were still active at 10°C, and sludge capillary suction time (CST) decreased in the first 3 days of bioleaching. Nevertheless, the degree of sludge dewaterability enhancement by bioleaching was much lower at 10°C than that at 28°C. The only slight decreases in the sludge pH value and relative high contents of extracellular polymeric substances (EPS) and bound water at a low temperature were responsible for the relatively lower dewaterability enhancement of bioleached sludge compared to that at the normal temperature. Moreover, statistical results showed that sludge CST had significant positive correlations with the sludge pH value, and EPS and bound water contents in the optimum bioleaching process (from day 0 to day 3). Therefore, reducing medium pH, and/or removing EPS from bioleaching bacteria and bound water of bioleached sludge through forced physical–chemical approaches prior to mechanical dewatering might be a good method to greatly improve sludge dewatering at a low temperature.

Kim, D.-G.; Jeong, K.; Ko, S.-O.

doi: 10.1080/09593330.2014.911777pmid: 25145210

Highway runoff is known to be an important non-point source (NPS), increasing the load of pollutants in receiving water. For reducing NPS pollutants in runoff, removal of road deposited sediment (RDS) by sweeping is considered effective. However, the contribution of sweeping to the improvement of runoff quality has not been clearly and quantitatively demonstrated so far. In this study, a field test was carried out on a section of operating highway in Korea to investigate the effectiveness of sweeping on improving the quality of highway runoff. Results showed that the average reduction in the load of RDS by sweeping was 61.10% with a standard deviation of 1.74%. RDS removal efficiency decreased when the sweeping speed increased from 4–8 to 20 km h−1, the load decreased from 12.5 to 1.25 g m−2 and particle size decreased from sand to silt/clay size ranges. Runoff was induced by applying a 15 mm h−1 artificial rainfall to both swept and non-swept sections. Analysis of runoff quality showed that the event mean concentrations of total suspended solid, biological oxygen demand, chemical oxygen demand, nutrients and most of the heavy metals were reduced by 31–87% after sweeping. In addition, field tests for RDS build-up indicated a sweeping frequency of once every four or five days to prevent re-suspension of RDS. The results of this study suggest that sweeping can be the best management practice for effectively reducing RDS on highways and improving the quality of highway runoff.

Li, Yin-Ming; Zhang, Fu-Shen

doi: 10.1080/09593330.2014.912253pmid: 25145211

This study was carried out to develop a cost-effective and practicable sorbent for application in abrupt perfluorooctane sulphonate (PFOS) pollution accidents. The main merit of this work was that a waste material, namely construction and demolition (C&D) waste, was employed as a raw base material for the sorbent synthesis. The waste material underwent alkaline fusion-hydrothermal synthesis and a cationic surfactant cetyltrimethyl ammonium bromide (CTAB) modification process to form a CTAB-modified sorbent (CMCDSS). Experimental results showed that PFOS concentrations and solution pH had significant effect on the PFOS sorption on construction and demolition waste synthesized sorbent (CDSS) and CMCDSS (using 0.2CMCDSS as representative). PFOS could be effectively and rapidly adsorbed on CMCDSS, and sorption equilibrium was achieved within 2.5 h. The sorption amounts of PFOS on CMCDSSs enhanced along with the increase in CTAB loading amounts. Moreover, the CMCDSS can be applied effectively under acidic condition at pH 2–6 and various removal mechanisms were clarified at different sorption conditions. Accordingly, this work developed a novel and applicable material for dealing with abrupt environmental PFOS contamination accidents.

Sensai, P.; Thangamani, A.; Visvanathan, C.

doi: 10.1080/09593330.2014.913688pmid: 25145212

Anaerobic co-digestion of high solids containing distillers grains and swine manure (total solids, 27±2% and 18±2%, respectively) was evaluated in this study to assess the effect of C/N ratio and organic loading rate (OLR). Feed mixture was balanced to achieve a C/N ratio of 30/1 by mixing distillers grains and swine manure. Pilot-scale co-digestion of distillers grains and swine manure was carried out under thermophilic conditions in the continuous mode for seven different OLRs from R1 to R7 (3.5, 5, 6, 8, 10, 12 and 14 kg VS/m3 day) under high solid anaerobic digestion. The methane yield and volatile solid (VS) removal were consistent; ranging from 0.33 to 0.34 m3CH4/kg VS day and 50–53%, respectively, until OLR 8 kg VS/m3 day. After which methane yield and VS removal significantly decreased to 0.26 m3 CH4/kg VS day and 42%, respectively, when OLR was increased to 14 kg VS/m3 day. However, during operation, at OLR of 10 kg VS/m3 day, the methane yield and VS removal increased after the 19th day to 0.33 m3CH4/kg VS day and 46%, respectively, indicating that a longer acclimatization period is required by methanogens at a higher loading rate.

Li, Fen; Yan, Bo; Zhang, Yanping; Zhang, Linhuan; Lei, Tao

doi: 10.1080/21622515.2014.913689pmid: 25145213

Sludge-activated carbons (SACs) prepared with excess of activated sludge are used to solve the problems of sludge disposal and odour pollution in a sewage treatment plant. For the preparation, ZnCl 2, KOH and H 2SO 4 are used as activators, respectively. The structure of the SACs are characterized by scanning electron microscope, X-ray photoelectron spectrometer, specific surface area and pore structure technologies, and the adsorption performance of H 2S is investigated. Results indicate that the desulphurization activity of SACs, whose activators are ZnCl 2 and KOH (SACZ and SACK), is better than that of carbon with H 2SO 4 as the activator (SACH). The breakthrough time of SACZ and SACK is up to 86 min, the sulphur capacity is 7.7 mg/cm3, and the maximal iodine value is 409.95 mg/g. While the breakthrough time of SACH is only 26 min with the sulphur capacity of 2.3 mg/cm3. A large percentage of pore volume with a diameter of 2–5 nm in the total pore volume is conductive to the desulphurization reaction. The large amount of surface acid functional groups is also helpful to the adsorption of H 2S. The desulphurization activity of SACZ and SACK is superior over that of commercial-activated carbon.

Raboni, Massimo; Torretta, Vincenzo; Viotti, Paolo; Urbini, Giordano

doi: 10.1080/09593330.2014.913690pmid: 25145214

This article presents the results of an experimental study on the correlation among the specific denitrification rate (SDNR), the dissolved oxygen concentration (DO), the F:M ratio (F:M) and the mixed-liquor (ML) recycle in the pre-denitrification reactors fed by domestic sewage. The experimental curves reveal a 28.8–32.0% reduction in the SDNR at 20°C () with DO equal to 0.1 mgO 2 L−1 and F:M in the range 0.2–0.4 kgBOD5 kgMLVSS−1 d−1. The SDNR reduction increases to 50.0–55.9% with DO=0.3 mgO2 L−1. A mathematical correlation of these results and an equation for calculating as function of the F:M as well as the average DO and BOD5 in the total flow rate fed in the denitrification stage are proposed. The conducted experience gives useful suggestions for practical usage, in particular regarding the denitrification reactor design, and represents a good starting point for future applications with the aim to optimize the biological process in domestic sewage treatment plants.

Shim, Jaehong; Babu, A. Giridhar; Velmurugan, Palanivel; Shea, Patrick J.; Oh, Byung-Taek

doi: 10.1080/09593330.2014.913691pmid: 25145215

A bacterial strain (JH 70-4) exhibiting plant growth promoting characteristics (indoleacetic acid production and 1-aminocyclopropane-1-carboxylate deaminase activity), as well as heavy metal(loid) (HM) tolerance and Pb precipitation, was isolated from HM-contaminated soil at an abandoned mine site. The bacterium was identified as Pseudomonas fluorescens based on 16S rDNA sequencing. The JH 70-4 strain induced precipitation of Pb as PbS nanoparticles, confirmed by X-ray diffraction. Solution pH, incubation time, and Pb concentration influenced removal and PbS formation. Inoculating contaminated soil with JH 70-4 decreased Pb availability; exchangeable Pb decreased while organic- and sulphide-bound Pb increased. The toxicity characteristic leaching procedure showed a 65% decrease in Pb in leachate 60 d after inoculating soil with JH 70-4. Shoot and root lengths of Sudan grass grown in the inoculated soil were greater than in the uninoculated soil. Findings suggest that microbial Pb fixation is a viable strategy for remediating soil and promoting plant growth for phytostabilization of contaminated sites.

Oveissi, Farshad; Fatehi, Pedram

doi: 10.1080/09593330.2014.913692pmid: 25145216

Wood chips are pretreated with steam prior to refining in the thermomechanical pulping process. The steam treatment dissolves part of lignin of wood chips in the spent liquor (SL) of this process, and subsequently the SL is sent to the wastewater system of the process. However, the lignin of SL can be used in the production of value-added chemicals, but it should first be separated from the SL in order to have a feasible downstream process. In this study, activated carbon (AC) was considered as an adsorbent to isolate lignin from SL. The results showed that the maximum adsorption of lignin on AC was166 mg/g under the optimal conditions of pH 5.2, 30 °C and 3 h treatment. Furthermore, the separation of lignin from SL was improved from 45% to 60% by having a two-stage adsorption process at pH 5.2, which also reduced the turbidity and chemical oxygen demand of SL by 39% and 32%, respectively.