Application of a combined three-stage system for reclamation of tunnel construction wastewater.

Kim, Jong-Oh,Cho, Kyung Hwa,Park, Tae-Won,Lim, Seong-Rin,Kang, Seokkoo,Kim, Young Mo Taylor Francis ; Publications Division, Selper Ltd 2015 Environmental Technology Vol.36 No.18

<P>A combined three-stage system, (1) coagulation (2) zeocarbon filtration and (3) membrane filtration, a combination of microfiltration (MF) and reverse osmosis (RO), was investigated for reclamation of tunnel construction wastewater having a salinity of 10.8-12.9 and a concentration of suspended solids (SS) in the range of 264-1084?mg/L. The initial stages - coagulation, zeocarbon filtration and MF - served as a precursor to RO membrane filtration to successfully reduce water contaminants to less than 0.2 nephelometric turbidity units (NTU) of turbidity, thereby minimizing the potential for fouling. The RO system subsequently removed over 99% of remaining pollutants including ionic substances, resulting in less than 0.02 NTU turbidity, less than 0.04?mg/L total nitrogen (TN) and less than 0.01?mg/L total phosphorus (TP). Also, addition of an RO system markedly reduced high salt concentrations (high chloride (Cl(-)) concentrations) in the wastewater, exceeding 99% salt elimination. Thus, reclaimed water from our combined system met and exceeded currently regulatory quality standards for wastewater reuse (turbidity??2.0 NTU; TN??10?mg/L; TP??0.5?mg/L; Cl(-)??250?mg/L).</P>

Oxidation of bisphenol A by UV/S2O8(2-): comparison with UV/H2O2.

Yoon, Sung-Hwan,Jeong, Seongpil,Lee, Seockheon Taylor Francis ; Publications Division, Selper Ltd 2012 Environmental Technology Vol.33 No.1

<P>The UV/S2O8(2-) process was applied to decompose bisphenol A (BPA), which is a representative endocrine-disrupting chemical (EDC), and was comared with the UV/H2O2 process. The BPA degradation efficiency by UV/S2O8(2-) was increased by increasing S2O8(2-) concentration or decreasing BPA concentration. The presence of humic acid caused an inhibitory effect. The BPA oxidation rate by UV/S2O8(2-) was increased in the following order: neutral pH (pH(i) = 7) < acidic pH (pH(i) = 4) < basic pH (pH(i) = 10). The main oxidizing species in the UV/S2O8(2-) system was sulphate radical (SO4(-*)), whereas the main oxidizing species in the UV/H2O2 system was OH radical (OH*). Compared with UV/H2O2, the UV/S2O8(2-) process showed higher performance for not only BPA degradation but also its mineralization, which means that SO4(-*) is a more effective oxidant for BPA than the OH*. The results shown in this study imply that the SO4(-*) -based UV/S2O8(2-) process can be an excellent alternative process for the widely used UV/H2O2 process, with higher remediation performance.</P>

Anaerobic digestion of Chinese cabbage waste silage with swine manure for biogas production: batch and continuous study.

Kafle, Gopi Krishna,Bhattarai, Sujala,Kim, Sang Hun,Chen, Lide Taylor Francis ; Publications Division, Selper Ltd 2014 Environmental Technology Vol.35 No.21

<P>The aim of this study was to investigate the potential for anaerobic co-digestion of Chinese cabbage waste silage (CCWS) with swine manure (SM). Batch and continuous experiments were carried out under mesophilic anaerobic conditions (36-38C). The batch test evaluated the effect of CCWS co-digestion with SM (SM: CCWS=100:0; 25:75; 33:67; 0:100, % volatile solids (VS) basis). The continuous test evaluated the performance of a single stage completely stirred tank reactor with SM alone and with a mixture of SM and CCWS. Batch test results showed no significant difference in biogas yield up to 25-33% of CCWS; however, biogas yield was significantly decreased when CCWS contents in feed increased to 67% and 100%. When testing continuous digestion, the biogas yield at organic loading rate (OLR) of 2.0 g VSL?1 d?1 increased by 17% with a mixture of SM and CCWS (SM:CCWS=75:25) (423 mL g?1 VS) than with SM alone (361 mL g?1 VS). The continuous anaerobic digestion process (biogas production, pH, total volatile fatty acids (TVFA) and TVFA/total alkalinity ratios) was stable when co-digesting SM and CCWS (75:25) at OLR of 2.0 g VSL?1 d?1 and hydraulic retention time of 20 days under mesophilic conditions.</P>

Evaluation of denitrification-nitrification biofilter systems in treating wastewater with low carbon: nitrogen ratios.

Kim, Seungjin,Bae, Wookeun,Kim, Moonil,Kim, Jong-Oh,Chung, Jinwook Taylor Francis ; Publications Division, Selper Ltd 2015 Environmental Technology Vol.36 No.8

<P>A two-stage biological aerated/anoxic filter (BAF) system for denitrification-nitrification was developed to increase nitrogen removal in the treatment of municipal wastewater with low carbon:nitrogen (C/N) ratio [Formula: see text]. This system exhibited a high denitrification efficiency (67%), despite the low C/N ratio, and the ratio of reduced nitrate to consumed organic compounds was greater than the theoretical value due to the minimization of the conversion of organic carbon to biomass growth, the maintenance of low levels of dissolved oxygen in recycled water, and the maximization of use of organic carbon biosorbed inside biomass in the denitrification BAF. The maximum rate of nitrogen removal was achieved at a recycle ratio of 170%, and the headloss in two BAFs was maintained after a 24-h backwash. Biological nitrogen removal in a two-stage BAF system was possible in a short hydraulic retention time (1.2???h) because the maximum reaction rates of nitrifiers and denitrifiers in each column were achieved.</P>

Oxidation of sulphide in abandoned mine tailings by ferrate.

Lee, Yong-Hoon,Yu, Mok-Ryun,Chang, Yoon-Young,Kang, Seon-Hong,Yang, Jae-Kyu Taylor Francis ; Publications Division, Selper Ltd 2015 Environmental Technology Vol.36 No.2

<P>In this study, Fe(VI) was applied to treat three mine tailings containing different amounts of sulphides and heavy metals. Oxidation of sulphides by Fe(VI) was studied at pH 9.2 with variation of solid to solution ratio, Fe(VI) concentration and injection number of Fe(VI) solution. The major dissolved products from the treatment of mine tailings with Fe(VI) solution were sulphate and arsenic. Oxidation efficiency of sulphides was evaluated by reduction efficiency of Fe(VI) as well as by measurement of dissolved sulphate concentration. Even though inorganic composition of three mine tailings was different, reduction fraction of Fe(VI) was quite similar. This result can suggest that Fe(VI) was involved in several other reactions in addition to oxidation of sulphides. Oxidation of sulphides in mine tailing was greatly dependent on the total amount of sulphides as well as kinds of sulphides complexed with metals. Over the five consecutive injections of Fe(VI) solution, dissolved sulphate concentration was greatly decreased by each injection and no more dissolved sulphate was observed at the fifth injection. While dissolved arsenic was decreased lineally up to the fifth injection. Sulphate generation was slightly increased for all mine tailings as Fe(VI) concentration was increased; however, enhancement of oxidation efficiency of sulphides was not directly proportional to the initial Fe(VI) concentration.</P>

Effect of initial salt concentrations on cell performance and distribution of internal resistance in microbial desalination cells.

Yang, Euntae,Choi, Mi-Jin,Kim, Kyoung-Yeol,Chae, Kyu-Jung,Kim, In S Taylor Francis ; Publications Division, Selper Ltd 2015 Environmental Technology Vol.36 No.7

<P>Microbial desalination cells (MDCs) are modified microbial fuel cells (MFCs) that concurrently produce electricity and desalinate seawater, but adding a desalination compartment and an ion-exchange membrane may increase the internal resistance (Ri), which can limit the cell performance. However, the effects of a desalination chamber and initial NaCl concentrations on the internal resistances and the cell performances (i.e. Coulombic efficiency (CE), current and power density) of MDCs have yet to be thoroughly explored; thus, the cell performance and Ri distributions of MDCs having different initial concentrations and an MFC having no desalination chamber were compared. In the MDCs, the current and power density generation increased from 2.82???mA and 158.2???mW/m2 to 3.17???mA and 204.5???mW/m2 when the initial NaCl concentrations were increased from 5 to 30???g/L, as a consequence of the internal resistances decreasing from 2432.0 to 2328.4???곽. And even though the MFC has a lower Ri than the MDCs, lower cell performances (current: 2.59???mA; power density: 141.6???mW/m2 and CE: 62.1%) were observed; there was no effect of improved junction potential in the MFC. Thus, in the MDCs, the higher internal resistances due to the addition of a desalination compartment can be offset by reducing the electrolyte resistance and improving the junction potential at higher NaCl concentrations.</P>