Chih-Hung Wu

Bioaugmented remediation of high concentration BTEX-contaminated groundwater by permeable reactive barrier with immobilized bead.

Ineffective biostimulation requires immediate development of new technologies for remediation of high concentration BTEX-contaminated (benzene, toluene, ethylbenzene and xylene) groundwater. In this study, bioaugmentation with Mycobacterium sp. CHXY119 and Pseudomonas sp. YATO411 immobilized bead was used to remediate BTEX-contaminated groundwater with about 100 mg l(-1) in total concentration. The batch test results showed that the CHXY119 and YATO411 immobilized bead completely biodegraded each BTEX compound, and the maximum biodegradation rates were 0.790 mg l(-1) h(-1) for benzene, 1.113 mg l(-1) h(-1) for toluene, 0.992 mg l(-1) h(-1) for ethylbenzene and 0.231 mg l(-1) h(-1) for p-xylene. The actual mineralization rates were 10.8% for benzene, 10.5% for toluene, 5.8% for ethylbenzene and 11.4% for p-xylene, which indicated that the bioremediation of BTEX by the immobilized bead requires a rather small oxygen supply. Degradation rates achieved by the bioaugmented permeable reactive barrier (Bio-PRB) system of the immobilized bead were 97.8% for benzene, 94.2% for toluene, 84.7% for ethylbenzene and 87.4% for p-xylene; and the toxicity of the groundwater fell by 91.2% after bioremediation by the bioaugmented PRB, which confirmed its great potential for remediating groundwater with high concentrations of contaminants.

Novel oxygen-releasing immobilized cell beads for bioremediation of BTEX-contaminated water

Novel oxygen-releasing bead (ORB) and oxygen-releasing immobilized cell bead (ORICB) were prepared. Their oxygen releasing characteristics and effect on degradation of benzene, toluene, ethylbenzene, and xylene (BTEX)-contaminated groundwater were evaluated in a column. ORB prepared by CaO(2)-encapsulated freezing had much better oxygen-releasing capacity (0.526 mg O(2) per ORB) than that by the mixing-freezing method. The encapsulated-ORB did not influence groundwater pH. Two BTEX degraders were utilized to prepare the ORICB. The ORICBs-column rapidly (hydraulic retention time: 0.872 day) degraded BTEX after a 2-5 day acclimation period. The BTEX removal increased as flow distances increased. At BTEX concentration of 120 mg L(-1), 67% of benzene and 81-90% of TEX were removed. The SEM shows that micropores existed in the ORBs and BTEX degraders were immobilized. The denaturing gradient gel electrophoresis profiles indicate that BTEX degraders were distributed throughout the column. The BTEX concentration of 120 mg L(-1) markedly altered the structure of the indigenous microbial community.

Electricity production and benzene removal from groundwater using low-cost mini tubular microbial fuel cells in a monitoring well

A low-cost mini tubular microbial fuel cell (MFC) was developed for treating groundwater that contained benzene in monitoring wells. Experimental results indicate that increasing the length and density, and reducing the size of the char particles in the anode effectively reduced the internal resistance. Additionally, a thinner polyvinyl alcohol (PVA) hydrogel separator and PVA with a higher molecular weight improved electricity generation. The optimal parameters for the MFC were an anode density of 1.22xa0gxa0cm-3, a coke of 150xa0μm, an anode length of 6xa0cm, a PVA of 105,600xa0gxa0mol-1, and a separator thickness of 1xa0cm. Results of continuous-flow experiments reveal that the increasing the sets of MFCs and connecting them in parallel markedly improved the degradation of benzene. More than 95% of benzene was removed and electricity of 38xa0mWxa0m-2 was generated. The MFC ran continuously up to 120 days without maintenance.

Alleviation of metal and BTEX inhibition on BTEX degradation using PVA-immobilized degrader: kinetic model of BTEX degradation

Alleviation of metal inhibition on BTEX degradation using PVA-immobilized degrader (Mycobacterium sp. CHXY119) was investigated. When BTEX of 29xa0mg L−1 [B:T:E:Xxa0=xa01:1:1:1 (mg)] was used, more than 99xa0% of BTEX was simultaneously degraded by the free cells within 170xa0h. In contrast, BTEX of 114–172xa0mg L−1 seriously inhibited degradation. High concentrations of metals (Mn2+: 15, Ni2+: 10, and Zn2+: 10xa0mg L−1) also strongly inhibited BTEX degradation by the free cells at BTEX of 29xa0mg L−1. Immobilization of degraders alleviated the inhibition of BTEX and heavy metals at high concentrations. A modified non-competitive inhibition model well described the BTEX degradation by the free and immobilized cells in the absence and presence of metal ions (R2xa0=xa00.92–0.99). The above results provide valuable information on treatment of metal-BTEX co-contaminated wastewater by the immobilized degrader.

Biodegradation of semiconductor volatile organic compounds by four novel bacterial strains: a kinetic analysis.

This study isolated pure microorganisms for further bioreactor applications. Four novel strains of Pseudomonas citronellolis YAIP521, Paracoccus versutus HSAC51, Burkholderia sp. HUEL671, and Pseudomonas aeruginosa JUPG561 were isolated and tested for biodegradation of isopropyl alcohol (IPA), acetone, ethyl lactate (EL), and propylene glycol mono methyl ether acetate (PGMEA), respectively. The maximum biodegradation rates for IPA, acetone, EL, and PGMEA were 5.27, 3.87, 26.86, and 48.93xa0mg L−1 h−1, respectively. The Haldane kinetic parameters determined for these strains when degrading targeted volatile organic compounds were maximum specific growth rate, half-saturation constant, and inhibition constant. The isolated strains have potential application in various bioreactors. The kinetic parameters obtained in this study provide a basis for further bioreactor experiments.

Innovative encapsulated oxygen-releasing beads for bioremediation of BTEX at high concentration in groundwater

Both a low concentration of dissolved oxygen and the toxicity of a high concentration of BTEX inhibit the bioremediation of BTEX in groundwater. A novel method of preparing encapsulated oxygen-releasing beads (encap-ORBs) for the biodegradation of BTEX in groundwater was developed. Experimental results show that the integrality and oxygen-releasing capacity of encap-ORBs exceeded those of ORBs. The use of polyvinyl alcohol (PVA) with high M.W. to prepare encap-ORBs improved their integrality. The encap-ORBs effectively released oxygen for 128 days. High concentration of BTEX (480xa0mgxa0L-1) inhibited the biodegradation by the free cells. Immobilization of degraders in the encap-ORB alleviated the inhibition. Scanning electron microscope analysis reveals that the BTEX degraders grew on the surface of encap-ORB after bioremediation. The above results indicate that the encap-ORBs were effective in the bioremediation of BTEX at high concentration in groundwater.