Effects of treatment processes on AOC removal and changes of bacterial diversity in a water treatment plant

The effectiveness of different treatment processes on assimilable organic carbon (AOC) removal and bacterial diversity variations was evaluated in a water treatment plant. The van der Kooij technique was applied for AOC analysis and responses of bacterial communities were characterized by the metagenomics assay. Results show that the AOC concentrations were about 93, 148, 43, 51, 37, and 38 μg acetate-C/L in effluents of raw water basin, preozonation, rapid sand filtration (RSF), ozonation, biofiltration [biological activated carbon (BAC) filtration], and chlorination (clear water), respectively. Increased AOC concentrations were observed after preozonation, ozonation, and chlorination units due to the production of biodegradable organic matters after the oxidation processes. Results indicate that the oxidation processes were the main causes of AOC formation, which resulted in significant increases in AOC concentrations (18-59% increment). The AOC removal efficiencies were 47, 28, and 60% in the RSF, biofiltration, and the whole system, respectively. RSF and biofiltration were responsible for the AOC treatment and both processes played key roles in AOC removal. Thus, both RSF and biofiltration processes would contribute to AOC treatment after oxidation. Sediments from the raw water basin and filter samples from RSF and BAC units were collected and analyzed for bacterial communities. Results from scanning electron microscope analysis indicate that bacterial colonization was observed in filter materials. This indicates that the surfaces of the filter materials were beneficial to bacterial growth and AOC removal via the adsorption and biodegradation mechanisms. Next generation sequencing analyses demonstrate that water treatment processes resulted in the changes of bacterial diversity and community profiles in filters of RSF and BAC. According to the findings of bacterial composition and interactions, the dominant bacterial phyla were Proteobacteria (41% in RSF and 56% in BAC) followed by Planctomycetes and Acidobacteria in RSF and BAC systems, which might affect the AOC biodegradation efficiency. Results would be useful in developing AOC treatment and management processes in water treatment plants.

Development of a PET/EPRI combined imaging system for assessing tumor hypoxia

Precise quantitative delineation of tumor hypoxia is essential in radiation therapy treatment planning to improve the treatment efficacy by targeting hypoxic sub-volumes. We developed a combined imaging system of positron emission tomography (PET) and electron para-magnetic resonance imaging (EPRI) of molecular oxygen to investigate the accuracy of PET imaging in assessing tumor hypoxia. The PET/EPRI combined imaging system aims to use EPRI to precisely measure the oxygen partial pressure in tissues. This will evaluate the validity of PET hypoxic tumor imaging by (near) simultaneously acquired EPRI as ground truth. The combined imaging system was constructed by integrating a small animal PET scanner (inner ring diameter 62 mm and axial field of view 25.6 mm) and an EPRI subsystem (field strength 25 mT and resonant frequency 700 MHz). The compatibility between the PET and EPRI subsystems were tested with both phantom and animal imaging. Hypoxic imaging on a tumor mouse model using 18F-fluoromisonidazole radio-tracer was conducted with the developed PET/EPRI system. We report the development and initial imaging results obtained from the PET/EPRI combined imaging system.

Application of γ-PGA as the primary carbon source to bioremediate a TCE-polluted aquifer: A pilot-scale study

The effectiveness of using gamma poly-glutamic acid (γ-PGA) as the primary carbon and nitrogen sources to bioremediate trichloroethene (TCE)-contaminated groundwater was studied in this pilot-scale study. γ-PGA (40 L) solution was injected into the aquifer via the injection well (IW) for substrate supplement. Groundwater samples were collected from monitor wells and IW and analyzed for TCE and its byproducts, geochemical indicators, dechlorinating bacteria, and microbial diversity periodically. Injected γ-PGA resulted in an increase in total organic carbon (TOC) (up to 9820 mg/L in IW), and the TOC biodegradation caused the formation of anaerobic conditions. Increased ammonia concentration (because of amine release from γ-PGA) resulted in the neutral condition in groundwater, which benefited the growth of Dehalococcoides. The negative zeta potential and micro-scale diameter of γ-PGA allowed its globule to distribute evenly within soil pores. Up to 93% of TCE removal was observed (TCE dropped from 0.14 to 0.01 mg/L) after 59 days of γ-PGA injection, and TCE dechlorination byproducts were also biodegraded subsequently. Next generation sequence (NGS) analyses were applied to determine the dominant bacterial communities. γ-PGA supplement developed reductive dechlorinating conditions and caused variations in microbial diversity and dominant bacterial species. The dominant four groups of bacterial communities including dechlorinating bacteria, vinyl chloride degrading bacteria, hydrogen producing bacteria, and carbon biodegrading bacteria.

Emulsified polycolloid substrate biobarrier for benzene and petroleum-hydrocarbon plume containment and migration control - A field-scale study

The objective of this field-scale study was to assess the effectiveness of applying an emulsified polycolloid substrate (EPS; containing cane molasses, soybean oil, and surfactants) biobarrier in the control and remediation of a petroleum-hydrocarbon plume in natural waters. An abandoned petrochemical manufacturing facility site was contaminated by benzene and other petroleum products due to a leakage from a storage tank. Because benzene is a petroleum hydrocarbon with a high migration ability, it was used as the target compound in the field-scale study. Batch partition and sorption experiment results indicated that the EPS to water partition coefficient for benzene was 232 mg/mg at 25 °C. This suggests that benzene had a higher sorption affinity to EPS, which decreased the benzene concentrations in groundwater. The EPS solution was pressure-injected into three remediation wells (RWs; 150 L EPS in 800 L groundwater). Groundwater samples were collected from an upgradient background well, two downgradient monitor wells (MWs), and the three RWs for analyses. EPS injection increased total organic carbon (TOC) concentrations (up to 786 mg/L) in groundwater, which also resulted in the formation of anaerobic conditions. An abrupt drop in benzene concentration (from 6.9 to below 0.04 mg/L) was observed after EPS supplementation in the RWs due to both sorption and biodegradation mechanisms. Results show that the EPS supplement increased total viable bacteria and enhanced bioremediation efficiency, which accounted for the observed decrease in benzene concentration. The first-order decay rate in RW1 increased from 0.003 to 0.023 d^-1 after EPS application. Injection of EPS resulted in significant growth of indigenous bacteria, and 23 petroleum-hydrocarbon-degrading bacterial species were detected, which enhanced the in situ benzene biodegradation efficiency. Results demonstrate that the EPS biobarrier can effectively contain a petroleum-hydrocarbon plume and prevent its migration to downgradient areas, which reduces the immediate risk presented to downgradient receptors.

Application of an emulsified polycolloid substrate biobarrier to remediate petroleum-hydrocarbon contaminated groundwater

Emulsified polycolloid substrate (EPS) was developed and applied in situ to form a biobarrier for the containment and enhanced bioremediation of a petroleum-hydrocarbon plume. EPS had a negative zeta potential (-35.7 mv), which promoted its even distribution after injection. Batch and column experiments were performed to evaluate the effectiveness of EPS on toluene containment and biodegradation. The EPS-to-water partition coefficient for toluene (target compound) was 943. Thus, toluene had a significant sorption affinity to EPS, which caused reduced toluene concentration in water phase in the EPS/water system. Groundwater containing toluene (18 mg/L) was pumped into the three-column system at a flow rate of 0.28 mL/min, while EPS was injected into the second column to form a biobarrier. A significant reduction of toluene concentration to 0.1 mg/L was observed immediately after EPS injection. This indicates that EPS could effectively contain toluene plume and prevent its further migration to farther downgradient zone. Approximately 99% of toluene was removed after 296 PVs of operation via sorption, natural attenuation, and EPS-enhanced biodegradation. Increase in total organic carbon and bacteria were also observed after EPS supplement. Supplement of EPS resulted in a growth of petroleum-hydrocarbon degrading bacteria, which enhanced the toluene biodegradation.

Development of a two-stage biotransformation system for mercury-contaminated soil remediation

Utilization of bacterial volatilization can be problematic to remediate mercury (Hg)-contaminated soils because most of the Hg in soils is bound to soil particles. The objective of this study was to develop a two-stage system (chemical extraction followed by microbial reduction) for Hg-contaminated soil remediation. The tasks were to (1) select the extraction reagents for Hg extraction, (2) assess the effects of extraction reagents on the growth of Hg-reducing bacterial strains, and (3) evaluate the effectiveness of Ca²⁺ and Mg²⁺ addition on merA gene (Hg reductase) induction. Bacterial inhibition was observed with the addition of 0.1 M ethylenediaminetetraacetic acid or citric acid. Up to 65% of Hg was biotransformed (Hg concentration = 69 mg/kg) from the soils after a 24 h extraction using 0.5 M ammonium thiosulfate. Ca²⁺ and Mg²⁺ were selected because they have the same electric charge as Hg and the studied groundwater contained high concentrations of Ca²⁺ and Mg²⁺. Results showed that the addition of 200 mg/L Ca²⁺ or 650 mg/L Mg²⁺ could reach effective merA induction. In the two-stage experiment, 120 mg/kg Hg-contaminated soils were extracted with 2 rounds of extraction processes for 10 h using 0.5 M ammonium thiosulfate. Approximately 77% of Hg was extracted from the soils after the first-step extraction process. Up to 81% of Hg²⁺ was transformed from the washing solution via the biotransformation processes with Enterobacter cloacae addition and Ca²⁺ and Mg²⁺ supplementation. The two-stage remedial system has the potential to be developed into a practical technology to remediate Hg-contaminated sites.

Source identification and ecological impact evaluation of PAHs in urban river sediments: A case study in Taiwan

The Love River and Ho-Jin River, two major urban rivers in Kaohsiung City, Taiwan, are moderately to heavily polluted because different types of improperly treated wastewaters are discharged into the rivers. In this study, sediment and river water samples were collected from two rivers to investigate the river water quality and accumulation of polycyclic aromatic hydrocarbons (PAHs) in sediments. The spatial distribution, composition, and source appointment of PAHs of the sediments were examined. The impacts of PAHs on ecological system were assessed using toxic equivalence quotient (TEQ) of potentially carcinogenic PAHs (TEQ^carc) and sediment quality guidelines. The average PAHs concentrations ranged from 2161 ng/g in Love River sediment to 160 ng/g in Ho-Jin River sediment. This could be due to the fact that Love River Basin had much higher population density and pyrolytic activities. High-ring PAHs (4-6 rings) contributed to 59-90% of the total PAHs concentrations. Benzo(a)pyrene (BaP) had the highest toxic equivalence quotient (up to 188 ng TEQ/g). Moreover, the downstream sediments contained higher TEQ of total TPHs than midstream and upstream sediment samples. The PAHs were adsorbed onto the fine particles with high organic content. Results from diagnostic ratio analyses indicate that the PAHs in two urban river sediments might originate from oil/coal combustion, traffic-related emissions, and waste combustion (pyrogenic activities). Future pollution prevention and management should target the various industries, incinerators, and transportation emission in this region to reduce the PAHs pollution.

Aerobic Biodegradation of OCDD by P. Mendocina NSYSU: Effectiveness and Gene Inducement Studies

  The goals of this study were to assess the effectiveness of (1) enhancing octachlorinated dibenzo-p-dioxin (OCDD) biodegradation under aerobic conditions by Pseudomonas mendocina NSYSU (P. Mendocina NSYSU) with the addition of lecithin, and (2) inducing OCDD ring-cleavage genes by pentachlorophenol (PCP) and OCDD addition. P. Mendocina NSYSU could biodegrade OCDD via aerobic cometabolism and lecithin was used as a primary substrate. Approximately 74 and 67% of OCDD biodegradation was observed after 60 days of incubation with lecithin and glucose supplement, respectively. Lecithin was also used as the solubilization additive resulting in OCDD solubilization and enhanced bioavailability of OCDD to P. Mendocina NSYSU. Two intradiol and extradiol ring-cleavage dioxygenase genes (Pmen_0474 and Pmen_2526) were identified from gene analyses. Gene concentration was significantly enhanced after the inducement by PCP and OCDD. Higher gene inducement efficiency was obtained using PCP as the inducer, and Pmen_2526 played a more important role in OCDD biodegradation.

Note: Rapid measurement of fluorescence lifetimes using SiPM detection and waveform sampling

In fluorescence spectroscopy and imaging, fluorescence lifetime measurement-assessing the average time fluorophores spend in their excited state before returning to their ground state-offers a number of advantages over quantifying fluorescence intensities that include resistance to photo-bleaching and independence from fluorophore concentration, excitation intensity, and measurement methodology. Despite growing interest, fluorescence lifetime techniques frequently mandate relatively complex instrumentation, slow data acquisition rates, and significant data analyses. In this work, we demonstrate the feasibility of measuring fluorescence lifetimes using off-the-shelf analog silicon photomultipliers and switched-capacitor array waveform sampling techniques, with precision matching that of much larger and more elaborate commercial instruments.

Developing an Integrated Modeling Tool for River Water Quality Index Assessment

  The goal of this study was to establish a modeling tool for river water quality with a direct linkage to the water quality index (WQI5) calculation and the river water quality model, the Water Quality Analysis Simulation Program (WASP), for pollutant transport modeling. The integrated WASP and WQI5 tool was field-tested to assess pollutant loadings and their impacts on river environment. Suspended solid (SS) and electric conductivity (EC) correlation equations and the WQI5 calculation tool were included in the water quality model and direct WQI5 calculation. The SS concentration, which was influenced by river flows, had crucial effects on river water quality and WQI5 values. EC value was controlled by dissolution of soil minerals, which was affected by the watershed drainage area and surface runoff. The integrated system could establish a direct correlation for river water quality, river flow, and WQI5.

Acidification and sulfide formation control during reductive dechlorination of 1,2-dichloroethane in groundwater: Effectiveness and mechanistic study

To enhance the reductive dechlorination of 1,2-dichloroethane (DCA) in groundwater, substrate injection may be required. However, substrate biodegradation causes groundwater acidification and sulfide production, which inhibits the bacteria responsible for DCA dechlorination and results in an odor problem. In the microcosm study, the effectiveness of the addition of ferrous sulfate (FS), desulfurization slag (DS), and nanoscale zero-valent iron (nZVI) on acidification and sulfide control was studied during reductive dechlorination of DCA, and the emulsified substrate (ES) was used as the substrate. Up to 94% of the sulfide was removed with FS and DS addition (0.25 wt%) (initial DCA concentration = 13.5 mg/L). FS and DS amendments resulted in the formation of a metal sulfide, which reduced the hydrogen sulfide concentration as well as the subsequent odor problem. Approximately 96% of the DCA was degraded under reductive dechlorination with nZVI or DS addition using ES as the substrate. In microcosms with nZVI or DS addition, the sulfide concentration was reduced to less than 15 μg/L. Acidification can be controlled via hydroxide ions production after nZVI oxidation and reaction of free CaO (released from DS) with water, which enhanced DCA dechlorination. The quantitative polymerase chain reaction results confirmed that the microcosms with nZVI added had the highest Dehalococcoides population (up to 2.5 × 10(8) gene copies/g soil) due to effective acidification control. The α-elimination mechanism was the main abiotic process, and reductive dechlorination dominated by Dehalococcides was the biotic mechanism that resulted in DCA removal. More than 22 bacterial species were detected, and dechlorinating bacteria existed in soils under alkaline and acidic conditions.

Bioremediation of 1,2-dichloroethane contaminated groundwater: Microcosm and microbial diversity studies

In this study, the effectiveness of bioremediating 1,2-dichloroethane (DCA)-contaminated groundwater under different oxidation-reduction processes was evaluated. Microcosms were constructed using indigenous bacteria and activated sludge as the inocula and cane molasses and a slow polycolloid-releasing substrate (SPRS) as the primary substrates. Complete DCA removal was obtained within 30 days under aerobic and reductive dechlorinating conditions. In anaerobic microcosms with sludge and substrate addition, chloroethane, vinyl chloride, and ethene were produced. The microbial communities and DCA-degrading bacteria in microcosms were characterized by 16S rRNA-based denatured-gradient-gel electrophoresis profiling and nucleotide sequence analyses. Real-time polymerase chain reaction was applied to evaluate the variations in Dehalococcoides spp. and Desulfitobacterium spp. Increase in Desulfitobacterium spp. indicates that the growth of Desulfitobacterium might be induced by DCA. Results indicate that DCA could be used as the primary substrate under aerobic conditions. The increased ethene concentrations imply that dihaloelimination was the dominate mechanism for DCA biodegradation.

Application of a long-lasting colloidal substrate with pH and hydrogen sulfide control capabilities to remediate TCE-contaminated groundwater

A long-lasting emulsified colloidal substrate (LECS) was developed for continuous carbon and nanoscale zero-valent iron (nZVI) release to remediate trichloroethylene (TCE)-contaminated groundwater under reductive dechlorinating conditions. The developed LECS contained nZVI, vegetable oil, surfactants (Simple Green™ and lecithin), molasses, lactate, and minerals. An emulsification study was performed to evaluate the globule droplet size and stability of LECS. The results show that a stable oil-in-water emulsion with uniformly small droplets (0.7 μm) was produced, which could continuously release the primary substrates. The emulsified solution could serve as the dispensing agent, and nZVI particles (with diameter 100-200 nm) were distributed in the emulsion evenly without aggregation. Microcosm results showed that the LECS caused a rapid increase in the total organic carbon concentration (up to 488 mg/L), and reductive dechlorination of TCE was significantly enhanced. Up to 99% of TCE (with initial concentration of 7.4 mg/L) was removed after 130 days of operation. Acidification was prevented by the production of hydroxide ion by the oxidation of nZVI. The formation of iron sulfide reduced the odor from produced hydrogen sulfide. Microbial analyses reveal that dechlorinating bacteria existed in soils, which might contribute to TCE dechlorination.

Enhanced anaerobic biodegradation of OCDD-contaminated soils by Pseudomonas mendocina NSYSU: microcosm, pilot-scale, and gene studies

In this study, microcosm and pilot-scale experiments were performed to investigate the capability and effectiveness of Pseudomonas mendocina NSYSU (P. mendocina NSYSU) on the bioremediation of octachlorodibenzo-p-dioxin (OCDD)-contaminated soils. The objectives were to evaluate the (1) characteristics of P. mendocina NSYSU, (2) feasibility of enhancing OCDD biodegradation with the addition of P. mendocina NSYSU and lecithin, and (3) variation in microbial diversity and genes responsible for the dechlorination of OCDD. P. mendocina NSYSU was inhibited when salinity was higher than 7%, and it could biodegrade OCDD under reductive dechlorinating conditions. Lecithin could serve as the solubilization agent causing the enhanced solubilization and dechlorination of OCDD. Up to 71 and 62% of OCDD could be degraded after 65 days of incubation under anaerobic conditions with and without the addition of lecithin, respectively. Decreased OCDD concentrations caused significant increase in microbial diversity. Results from the pilot-scale study show that up to 75% of OCDD could be degraded after a 2.5-month operational period with lecithin addition. Results from the gene analyses show that two genes encoding the extradiol/intradiol ring-cleavage dioxygenase and five genes encoding the hydrolase in P. mendocina NSYSU were identified and played important roles in OCDD degradation.

Development of KMnO(4)-releasing composites for in situ chemical oxidation of TCE-contaminated groundwater

The objective of this study was to develop a controlled-oxidant-release technology combining in situ chemical oxidation (ISCO) and permeable reactive barrier (PRB) concepts to remediate trichloroethene (TCE)-contaminated groundwater. In this study, a potassium permanganate (KMnO4)-releasing composite (PRC) was designed for KMnO4 release. The components of this PRC included polycaprolactone (PCL), KMnO4, and starch with a weight ratio of 1.14:2:0.96. Approximately 64% (w/w) of the KMnO4 was released from the PRC after 76 days of operation in a batch system. The results indicate that the released KMnO4 could oxidize TCE effectively. The results from a column study show that the KMnO4 released from 200 g of PRC could effectively remediate 101 pore volumes (PV) of TCE-contaminated groundwater (initial TCE concentration = 0.5 mg/L) and achieve up to 95% TCE removal. The effectiveness of the PRC system was verified by the following characteristics of the effluents collected after the PRC columns (barrier): (1) decreased TCE concentrations, (2) increased ORP and pH values, and (3) increased MnO2 and KMnO4 concentrations. The results of environmental scanning electron microscope (ESEM) analysis show that the PCL and starch completely filled up the pore spaces of the PRC, creating a composite with low porosity. Secondary micro-scale capillary permeability causes the KMnO4 release, mainly through a reaction-diffusion mechanism. The PRC developed could be used as an ISCO-based passive barrier system for plume control, and it has the potential to become a cost-effective alternative for the remediation of chlorinated solvent-contaminated groundwater.

Application of polycolloid-releasing substrate to remediate trichloroethylene-contaminated groundwater: a pilot-scale study

The objectives of this pilot-scale study were to (1) evaluate the effectiveness of bioremediation of trichloroethylene (TCE)-contaminated groundwater with the supplement of slow polycolloid-releasing substrate (SPRS) (contained vegetable oil, cane molasses, surfactants) under reductive dechlorinating conditions, (2) apply gene analyses to confirm the existence of TCE-dechlorinating genes, and (3) apply the real-time polymerase chain reaction (PCR) to evaluate the variations in TCE-dechlorinating bacteria (Dehalococcoides spp.). Approximately 350L of SPRS solution was supplied into an injection well (IW) and groundwater samples were collected and analyzed from IW and monitor wells periodically. Results show that the SPRS caused a rapid increase of the total organic carbon concentration (up to 5794mg/L), and reductive dechlorination of TCE was significantly enhanced. TCE dechlorination byproducts were observed and up to 99% of TCE removal (initial TCE concentration=1872μg/L) was observed after 50 days of operation. The population of Dehalococcoides spp. increased from 4.6×10(1) to 3.41×10(7)cells/L after 20 days of operation. DNA sequencing results show that there were 31 bacterial species verified, which might be related to TCE biodegradation. Results demonstrate that the microbial analysis and real-time PCR are useful tools to evaluate the effectiveness of TCE reductive dechlorination.

Biodegradation of Polychlorinated Dibenzo--Dioxins by Strain NSYSU

The dioxin-degrading bacterium strain NSYSU (NSYSU strain) has been isolated from dioxin-contaminated soil by selective enrichment techniques. In the present study, the NSYSU strain was investigated for its capability to biodegrade polychlorinated dibenzo--dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) under aerobic and anaerobic conditions. High-resolution gas chromatography-mass spectrometry and a chemically activated luciferase gene expression bioassay were performed to determine the presence of dioxin compounds. The results indicate that the NSYSU strain could degrade PCDDs and PCDFs under anaerobic conditions in liquid cultures. The main intermediates of the dechlorination process were identified. The results of the bioreactor test indicate that the NSYSU strain could also degrade PCDDs and PCDFs effectively in soil slurries under aerobic conditions. Results from the bioreactor experiment show that approximately 98 and 97% of octachlorodibenzofuran and OCDD were degraded, respectively. The dioxin concentrations in soil slurry decreased from 5823 to 1198 pg toxic equivalency g, resulting in total dioxin removal of 79%. These first findings suggest that the NSYSU strain has the potential to be an effective tool for the bioremediation of soils contaminated with highly recalcitrant organic compounds.

Control of trichloroethylene plume migration using a biobarrier system: a field-scale study

The objective of this field-scale study was to evaluate the effectiveness of controlling trichloroethylene (TCE) plume migration using the polycolloid substrate (PS) biobarrier. The developed PS (containing soybean oil, lactate and surfactants) could release substrate to enhance the TCE dechlorination. In this study, a biobarrier comprising PS injection wells was installed. Injection wells were installed at 5-m intervals, and approximately 15 L of PS was injected into each well. Results show that TCE concentrations in the injection wells dropped from an average of 87 μg/L to below 1 μg/L after 35 days of PS injection. The total organic carbon concentrations in the injection wells increased from an average of 2.1-543 mg/L after 30 days of PS injection. The dissolved oxygen (DO) concentrations and oxidation-reduction potential (ORP) values dropped from an average of 1.6 mg/L to below 0.1 mg/L and from 124 mv to -14 mv after 20 days of injection, respectively. The DO and ORP remained in anaerobic conditions during the remaining 100 days of the operational period. TCE degradation by-products were observed in groundwater samples during the operational period. This reveals that the addition of PS could effectively enhance the reductive dechlorinating of TCE.

Development of a slow polycolloid-releasing substrate (SPRS) biobarrier to remediate TCE-contaminated aquifers

In this study, an in situ slow polycolloid-releasing substrate (SPRS) biobarrier system was developed to continuously provide biodegradable substrates for the enhancement of trichloroethylene (TCE) reductive dechlorination. The produced SPRS contained vegetable oil (used as a slow-released substrate), cane molasses [used as an early-stage (fast-degradable) substrate], and surfactants [Simple Green (SG) and soya lecithin (SL)]. An emulsification study was performed to evaluate the globule droplet size and stability of SPRS. The distribution and migration of the SPRS were evaluated in a column experiment, and an anaerobic microcosm study was performed to assess the capability of SPRS to serve as a slow and long-term carbon-releasing substrate for TCE dechlorination. The results show that a stable oil-in-water (W/O, 50/50) emulsion (SPRS) with uniformly small droplets (D₁₀, 0.93 μm) has been produced, continuously supplying primary substrates. The emulsion containing the surfactant mixture (with 72 mg/L SL and 71 mg/L SG) had a small absolute value of the zeta potential, which reduced the inter-particle repulsion, leading the emulsion droplets to adhere to one another after collision. The addition of SPRS creates anaerobic conditions and leads to a more complete and thorough removal of TCE through biodegradation and sorption mechanisms.

An Application of Micro-channel Plate Photomultiplier Tube to Positron Emission Tomography

We are developing a Time-of-Flight Positron Emission Tomography detector using flat panel micro-channel plate photomultiplier tubes (MCP PMT). The high-speed waveform sampling data acquisition is adopted to exploit the fast time response of MCP PMT efficiently by using transmission-line readout scheme. To demonstrate the feasibility of the proposed detector, prototype detector modules were built using Photonis XP85022 MCP PMT, transmission-line board (TL), and high-speed waveform sampling electronics equipped with DRS4 chips. The MCP/TL module was coupled to single LYSO crystal, and experimental tests have been conducted in a coincidence setup to measure the responses to 511 keV annihilation photon. The details of the prototype module, experimental setup, and the preliminary results are presented and discussed.

Use of specific gene analysis to assess the effectiveness of surfactant-enhanced trichloroethylene cometabolism

The objective of this study was to evaluate the effectiveness of in situ bioremediation of trichloroethylene (TCE)-contaminated groundwater using specific gene analyses under the following conditions: (1) pretreatment with biodegradable surfactants [Simple Green™ (SG) and soya lecithin (SL)] to enhance TCE desorption and dissolution, and (2) supplementation with SG, SL, and cane molasses as primary substrates to enhance the aerobic cometabolism of TCE. Polymerase chain reaction (PCR), denaturing gradient gel electrophoresis (DGGE), and nucleotide sequence analysis were applied to monitor the variations in specific activity-dependent enzymes and dominant microorganisms. Results show that TCE-degrading enzymes, including toluene monooxygenase, toluene dioxygenase, and phenol monooxygenase, were identified from sediment samples collected from a TCE-spill site. Results from the microcosm study show that addition of SG, SL, or cane molasses can enhance the aerobic cometabolism of TCE. The TCE degradation rates were highest in microcosms with added SL, the second highest in microcosms containing SG, and lowest in microcosms containing cane molasses. This indicates that SG and SL can serve as TCE dissolution agents and act as primary substrates for indigenous microorganisms. Four dominant microorganisms (Rhodobacter sp., Methyloversatilis sp., Beta proteobacterium sp., and Hydrogenophaga pseudoflava) observed in microcosms might be able to produce TCE-degrading enzymes for TCE cometabolic processes.

In situ oxidation of petroleum-hydrocarbon contaminated groundwater using passive ISCO system

Groundwater contamination by gasoline spill is a worldwide environmental problem. Gasoline contains methyl tertiary-butyl ether (MTBE) (a fuel oxygenates) and benzene, which are the chemicals of concerns among the gasoline components. In this study, an in situ chemical oxidation (ISCO) barrier system was developed to evaluate the feasibility of applying this passive system on the control of MTBE and benzene plume in aquifer. The developed ISCO barrier contained oxidant-releasing materials, which could release oxidants (e.g., persulfate) when contact with water for the contaminants' oxidation in groundwater. In this study, laboratory-scale fill-and-draw experiments were conducted to determine the component ratios of the oxidant-releasing materials and evaluate the persulfate release rates. Results indicate that the average persulfate-releasing rate of 7.26 mg S(2)O(8)(2-)/d/g was obtained when the mass ratio of sodium persulfate/cement/sand/water was 1/1.4/0.24/0.7. The column study was conducted to evaluate the efficiency of in situ application of the developed ISCO barrier system on MTBE and benzene oxidation. Results from the column study indicate that approximately 86-92% of MTBE and 95-99% of benzene could be removed during the early persulfate-releasing stage (before 48 pore volumes of groundwater pumping). The removal efficiencies for MTBE and benzene dropped to approximately 40-56% and 85-93%, respectively, during the latter part of the releasing period due to the decreased persulfate-releasing rate. Results reveal that acetone, byproduct of MTBE, was observed and then further oxidized completely. Results suggest that the addition of ferrous ion would activate the persulfate oxidation. However, excess ferrous ion would compete with organic contaminants for persulfate, and thus, cause the decrease in contaminant oxidation rates. The proposed treatment scheme would be expected to provide a more cost-effective alternative to remediate MTBE, benzene, and other petroleum-hydrocarbon contaminated aquifers. Results from this study will be useful in designing a scale-up system for field application.

Remediation of TCE-contaminated groundwater using acid/BOF slag enhanced chemical oxidation

The objective of this study was to evaluate the potential of applying acid/H(2)O(2)/basic oxygen furnace slag (BOF slag) and acid/S(2)O(8)(2-)/BOF slag systems to enhance the chemical oxidation of trichloroethylene (TCE)-contaminated groundwater. Results from the bench-scale study indicate that TCE oxidation via the Fenton-like oxidation process can be enhanced with the addition of BOF slag at low pH (pH=2-5.2) and neutral (pH=7.1) conditions. Because the BOF slag has iron abundant properties (14% of FeO and 6% of Fe(2)O(3)), it can be sustainably reused for the supplement of iron minerals during the Fenton-like or persulfate oxidation processes. Results indicate that higher TCE removal efficiency (84%) was obtained with the addition of inorganic acid for the activation of Fenton-like reaction compared with the experiments with organic acids addition (with efficiency of 10-15% lower) (BOF slag=10gL(-1); initial pH=5.2). This could be due to the fact that organic acids would compete with TCE for available oxidants. Results also indicate that the pH value had a linear correlation with the observed first-order decay constant of TCE, and thus, lower pH caused a higher TCE oxidation rate.

Development of the sediment and water quality management strategies for the Salt-water River, Taiwan

The Salt-water River watershed is one of the major river watersheds in the Kaohsiung City, Taiwan. Water quality and sediment investigation results show that the river water contained high concentrations of organics and ammonia-nitrogen, and sediments contained high concentrations of heavy metals and organic contaminants. The main pollution sources were municipal and industrial wastewaters. Results from the enrichment factor (EF) and geo-accumulation index (Igeo) analyses imply that the sediments can be characterized as heavily polluted in regard to Cd, Cr, Pb, Zn, and Cu. The water quality analysis simulation program (WASP) model was applied for water quality evaluation and carrying capacity calculation. Modeling results show that the daily pollutant inputs were much higher than the calculated carrying capacity (1050 kg day(-1) for biochemical oxygen demand and 420 kg day(-1) for ammonia-nitrogen). The proposed watershed management strategies included river water dilution, intercepting sewer system construction and sediment dredging.

Application of persulfate-releasing barrier to remediate MTBE and benzene contaminated groundwater

The objective of this study was to assess the potential of using an in situ oxidation barrier system to remediate gasoline-contaminated groundwater. The passive remedial system included a persulfate-releasing barrier containing persulfate-releasing materials to release persulfate for contaminant oxidation. Bench experiments were performed to determine the components and persulfate-releasing rate of the persulfate-releasing materials. Column experiments were conducted to evaluate the effectiveness of the designed persulfate-releasing materials on the control of petroleum-hydrocarbon plume. In this study, methyl tert-butyl ether (MTBE) and benzene were used as the target compounds. The optimal persulfate releasing rate was obtained when the mass ratio of persulfate/cement/sand/water was 1/1/0.16/0.5, and the rate varied from 31 to 8 mg persulfate per day per g of material. Significant amounts of MTBE and benzene were removed through the oxidation process due to the release of persulfate, and the produced tert-butyl formate (TBF) and tert-butyl alcohol (TBA), byproducts of MTBE, were further oxidized in the system. Results suggest that the oxidation rate would be affected by the oxidant reduction potential and concentrations of ferrous iron and persulfate.

Developing nonpoint-source suspended solids control strategies using multimedia watershed management modeling

Kaoping River Basin is the largest and most intensively used river basin in Taiwan. In this study, 14 types of land-use patterns in the basin are classified with the aid of the Erdas Imagine process (Erdas, Inc., Atlanta, Georgia) and ArcView geographic information system (GIS) (ESRI, Redlands, California). Results from GIS identification and field verification indicate that orchard gardens, rice paddies, and sugarcane fields dominate the farmland areas in the basin. Investigation results indicate that nonpoint-source (NPS) pollution has significant contributions to the suspended solids load to the Kaoping River during the wet season. The average suspended solids concentrations increased from below 64 mg/ L in dry seasons to more than 1700 mg/L in wet seasons. The Integrated Watershed Management Model (Systech Engineering, Inc., San Ramon, California) was applied to simulate the water quality and evaluate the NPS suspended solids load to the river. Modeling results show that forestation and land-use management are feasible best management practices for NPS suspended solids reduction.

Biodegradation of propionitrile by Klebsiella oxytoca immobilized in alginate and cellulose triacetate gel

A microbial process for the degradation of propionitrile by Klebsiella oxytoca was studied. The microorganism, K. oxytoca, was isolated from the discharged wastewater of metal plating factory in southern Taiwan and adapted for propionitrile biodegradation. The free and immobilized cells of K. oxytoca were then examined for their capabilities on degrading propionitrile under various conditions. Alginate (AL) and cellulose triacetate (CT) techniques were applied for the preparation of immobilized cells. The efficiency and produced metabolic intermediates and end-products of propionitrile degradation were monitored in bath and continuous bioreactor experiments. Results reveal that up to 100 and 150 mM of propionitrile could be removed completely by the free and immobilized cell systems, respectively. Furthermore, both immobilized cell systems show higher removal efficiencies in wider ranges of temperature (20-40 degrees C) and pH (6-8) compared with the free cell system. Results also indicate that immobilized cell system could support a higher cell density to enhance the removal efficiency of propionitrile. Immobilized cells were reused in five consecutive degradation experiments, and up to 99% of propionitrile degradation was observed in each batch test. This suggests that the activity of immobilized cells can be maintained and reused throughout different propionitrile degradation processes. A two-step pathway was observed for the biodegradation of propionitrile. Propionamide was first produced followed by propionic acid and ammonia. Results suggest that nitrile hydratase and amidase were involved in the degradation pathways of K. oxytoca. In the continuous bioreactor, both immobilized cells were capable of removing 150 mM of propionitriles completely within 16h, and the maximum propionitriles removal rates using AL and CT immobilized beads were 5.04 and 4.98 mM h(-1), respectively. Comparing the removal rates obtained from batch experiments with immobilized cells (AL and CT were 1.57 and 2.18 mM h(-1) at 150 mM of propionitrile, respectively), the continuous-flow bioreactor show higher potential for practical application.

Constructed wetland for water quality improvement: a case study from Taiwan

In Taiwan, more than 20% of the major rivers are mildly to heavily polluted by domestic, industrial, and agricultural wastewaters due to the low percentage of sewers connected to wastewater treatment plants. Thus, constructed or engineered wetlands have been adopted as the major alternatives to clean up polluted rivers. Constructed wetlands are also applied as the tertiary wastewater treatment systems for the wastewater polishment to meet water reuse standards with lower operational costs. The studied Kaoping River Rail Bridge Constructed Wetland (KRRBCW) is the largest constructed wetland in Taiwan. It is a multi-function wetland and is used for polluted creek water purification and secondary wastewater polishment before it is discharged into the Kaoping River. Although constructed wetlands are feasible for contaminated water treatment, wetland sediments are usually the sinks for organics and metals. In this study, water and sediment samples were collected from the major wetland basins in KRRBCW. The investigation results show that more than 97% of total coliforms (TC), 55% of biochemical oxygen demand (BOD), and 30% of nutrients [e.g. total nitrogen (TN), total phosphorus (TP)] were removed via the constructed wetland system. However, results from the sediment analyses show that wetland sediments contained high concentrations of metals (e.g. Cu, Fe, Zn, Cr, and Mn), organic contents (sediment oxygen demand = 1.7 to 7.6 g O(2)/m(2) d), and nutrients (up to 18.7 g/kg of TN and 1.22 g/kg of TN). Thus, sediments should be excavated periodically to prevent the release the pollutants into the wetland system and causing the deterioration of wetland water quality. Results of polymerase chain reaction (PCR), denaturing gradient gel electrophoresis (DGGE), and nucleotide sequence analysis reveal that a variation in microbial diversity in the wetland systems was observed. Results from the DGGE analysis indicate that all sediment samples contained significant amounts of microbial ribospecies, which might contribute to the carbon degradation and nitrogen removal. Gradual disappearance of E. coli was also observed along the flow courses through natural attenuation mechanisms.

Preliminary identification of watershed management strategies for the Houjing river in Taiwan

The Houjing River watershed is one of the three major river watersheds in the Kaohsiung City, Taiwan. Based on the recent water quality analysis, the Houjing River is heavily polluted. Both point and non-point source (NPS) pollutants are the major causes of the poor water quality in the Houjing River. Investigation results demonstrate that the main point pollution sources included municipal, agricultural, and industrial wastewaters. In this study, land use identification in the Houjing River watershed was performed by integrating the skills of geographic information system (GIS) and global positioning system (GPS). Results show that the major land-use patterns in the upper catchment of the Houjing River watershed were farmlands, and land-use patterns in the mid to lower catchment were residential and industrial areas. An integrated watershed management model (IWMM) and Enhanced Stream Water Quality Model (QUAL2K) were applied for the hydrology and water quality modeling, watershed management, and carrying capacity calculation. Modeling results show that the calculated NH₃-N carrying capacity of the Houjing River was only 31 kg/day. Thus, more than 10,518 kg/day of NH₃-N needs to be reduced to meet the proposed water quality standard (0.3 mg/L). To improve the river water quality, the following remedial strategies have been developed to minimize the impacts of NPS and point source pollution on the river water quality: (1) application of BMPs [e.g. source (fertilizer) reduction, construction of grassy buffer zone, and land use management] for NPS pollution control; (2) application of river management scenarios (e.g. construction of the intercepting and sewer systems) for point source pollution control; (3) institutional control (enforcement of the industrial wastewater discharge standards), and (4) application of on-site wastewater treatment systems for the polishment of treated wastewater for water reuse.

Using a constructed wetland for non-point source pollution control and river water quality purification: a case study in Taiwan

The Kaoping River Rail Bridge Constructed Wetland, which was commissioned in 2004, is one of the largest constructed wetlands in Taiwan. This multi-function wetland has been designed for the purposes of non-point source (NPS) pollutant removal, wastewater treatment, wildlife habitat, recreation, and education. The major influents of this wetland came from the local drainage trench containing domestic, agricultural, and industrial wastewaters, and effluents from the wastewater treatment plant of a paper mill. Based on the quarterly investigation results from 2007 to 2009, more than 96% of total coliforms (TC), 48% of biochemical oxygen demand (BOD), and 40% of nutrients (e.g. total nitrogen, total phosphorus) were removed via the constructed wetland system. Thus, the wetland system has a significant effect on water quality improvement and is capable of removing most of the pollutants from the local drainage system before they are discharged into the downgradient water body. Other accomplishments of this constructed wetland system include the following: providing more green areas along the riversides, offering more water assessable eco-ponds and eco-gardens for the public, and rehabilitating the natural ecosystem. The Kaoping River Rail Bridge Constructed Wetland has become one of the most successful multi-function constructed wetlands in Taiwan. The experience obtained from this study will be helpful in designing similar natural treatment systems for river water quality improvement and wastewater treatment.

Treatment of tetrachloroethylene-contaminated groundwater by surfactant-enhanced persulfate/BOF slag oxidation--a laboratory feasibility study

The main objective of this study was to evaluate the feasibility of remediating tetrachloroethylene (PCE)-contaminated groundwater (with initial PCE concentration of approximately 20 mg L(-1)) via persulfate oxidation activated by basic oxygen furnace slag (S(2)O(8)(2-)/BOF slag) with the addition of biodegradable surfactant (Tween 80). Results indicate that only 15% of PCE can be removed in experiment with the addition of S(2)O(8)(2-) only (S(2)O(8)(2-)/PCE=30/1). PCE removal can be increased to 31% while both S(2)O(8)(2-) and BOF slag (10 g L(-1)) were added. This indicates that BOF slag was able to activate the persulfate oxidation mechanism, and cause the decrease in PCE concentration via oxidation process. Results also reveal that PCE degradation rates increased to 92% with the presence of Tween 80 (S(2)O(8)(2-)/Tween 80/PCE=30/2/1). In the presence of 10 g L(-1) BOF slag, the reaction rate constant (k(obs)) values were found to be 3.1 x 10(-3), 8.7 x 10(-3), 1.6 x 10(-2), and 5.8 x 10(-2)h(-1), as the S(2)O(8)(2-)/Tween 80/PCE molar ratios were 30/0/1, 30/0.5/1, 30/1/1, and 30/2/1, respectively. The reaction rate constant increased as the Tween 80 concentration increased. The significantly increased k(obs) could be caused by the enhanced solubilization of PCE by Tween 80. The increase in initial surfactant concentration would cause the increase in the solubilization of PCE, and thus, enhance the oxidation rate. This was confirmed by the total amount of chloride ions produced after the reaction. Results from this study indicate that BOF slag-activated persulfate oxidation enhanced by surfactant addition is a potential method to efficiently and effectively remediate chlorinated solvents contaminated groundwater.

Application of integrated GIS and multimedia modeling on NPS pollution evaluation

In Taiwan, nonpoint source (NPS) pollution is one of the major causes of the impairment of surface waters. I-Liao Creek, located in southern Taiwan, flows approximately 90 km and drains toward the Kaoping River. Field investigation results indicate that NPS pollution from agricultural activities is one of the main water pollution sources in the I-Liao Creek Basin. Assessing the potential of NPS pollution to assist in the planning of best management practice (BMP) is significant for improving pollution prevention and control in the I-Liao Creek Basin. In this study, land use identification in the I-Liao Creek Basin was performed by properly integrating the skills of geographic information system (GIS) and global positioning system (GPS). In this analysis, 35 types of land use patterns in the watershed area of the basin are classified with the aid of Erdas Imagine process system and ArcView GIS system. Results indicate that betel palm farms, orchard farms, and tea gardens dominate the farmland areas in the basin, and are scattered around on both sides of the river corridor. An integrated watershed management model (IWMM) was applied for simulating the water quality and evaluating NPS pollutant loads to the I-Liao Creek. The model was calibrated and verified with collected water quality and soil data, and was used to investigate potential NPS pollution management plans. Simulated results indicate that NPS pollution has significant contributions to the nutrient loads to the I-Liao Creek during the wet season. Results also reveal that NPS pollution plays an important role in the deterioration of downstream water quality and caused significant increase in nutrient loads into the basin's water bodies. Simulated results show that source control, land use management, and grassy buffer strip are applicable and feasible BMPs for NPS nutrient loads reduction. GIS system is an important method for land use identification and waste load estimation in the basin. Linking the information of land utilization with the NPS pollution simulation model may further provide essential information of potential NPS pollution for all subregions in the river basin. Results and experience obtained from this study will be helpful in designing the watershed management and NPS pollution control strategies for other similar river basins.

Treatment of petroleum-hydrocarbon contaminated soils using hydrogen peroxide oxidation catalyzed by waste basic oxygen furnace slag

The contamination of subsurface soils with petroleum hydrocarbons is a widespread environmental problem. The objective of this study was to evaluate the potential of applying waste basic oxygen furnace slag (BOF slag) as the catalyst to enhance the Fenton-like oxidation to remediate fuel oil or diesel contaminated soils. The studied controlling factors that affect the removal efficiency of petroleum hydrocarbons included concentrations of H(2)O(2), BOF slag dosages, types of petroleum hydrocarbons (e.g., fuel oil and diesel), and types of iron mineral. Experimental results indicate that oxidation of petroleum hydrocarbon via the Fenton-like process can be enhanced with the addition of BOF slag. Results from the X-ray powder diffraction analysis reveal that the major iron type of BOF slag/sandy loam system was iron mineral (e.g., alpha-Fe(2)O(3) and alpha-FeOOH). Approximately 76% and 96% of fuel oil and diesel removal were observed (initial total petroleum hydrocarbon (TPH) concentration=10,000 mg kg(-1)), respectively, with the addition of 15% of H(2)O(2) and 100 g kg(-1) of BOF slag after 40 h of reaction. Because BOF slag contains extractable irons such as amorphous iron and soluble iron, it can act as an iron sink to supply iron continuously for Fenton-like oxidation. Results demonstrate that Fenton-like oxidation catalyzed by BOF slag is a potential method to be able to remediate petroleum-hydrocarbon contaminated soils efficiently and effectively.

Methyl tert-butyl ether (MTBE) degradation by ferrous ion-activated persulfate oxidation: feasibility and kinetics studies

The objective of this study was to evaluate the feasibility of using ferrous ion-activated persulfate oxidation to remediate groundwater contaminated with methyl tert-butyl ether (MTBE). In this study, batch experiments were conducted to evaluate the effects of various factors on the efficiency of MTBE degradation including persulfate concentrations, ferrous ion concentrations, and persulfate coupled with hydrogen peroxide. Results show that ferrous ion-activated persulfate oxidation was capable of degrading MTBE efficiently. Persulfate and ferrous ion concentrations correlated with MTBE degradation rates. However, excess addition of ferrous ion resulted in decreased MTBE degrading rates most likely because of competition for sulfate free radicals between ferrous ion and MTBE. Two main byproducts of MTBE degradation, tert-butyl formate and tert-butyl alcohol, were detected in the experiments; both were, however, subsequently degraded. Results of sulfate analysis show that proper addition of ferrous ion could prevent unnecessary persulfate decomposition.

Evaluation of biological stability and corrosion potential in drinking water distribution systems: a case study

The appearance of assimilable organic carbon (AOC), microbial regrowth, disinfection by-products (DBPs), and pipe corrosion in drinking water distribution systems are among those major safe drinking water issues in many countries. The water distribution system of Cheng-Ching Lake Water Treatment Plant (CCLWTP) was selected in this study to evaluate the: (1) fate and transport of AOC, DBPs [e.g., trihalomethanes (THMs), haloacetic acids (HAAs)], and other organic carbon indicators in the selected distribution system, (2) correlations between AOC (or DBPs) and major water quality parameters [e.g. dissolved oxygen (DO), free residual chlorine, and bacteria, and (3) causes and significance of corrosion problems of the water pipes in this system. In this study, seasonal water samples were collected from 13 representative locations in the distribution system for analyses of AOC, DBPs, and other water quality indicators. Results indicate that residual free chlorine concentrations in the distribution system met the drinking water standards (0.2 to 1 mg l(-1)) established by Taiwan Environmental Protection Administration (TEPA). Results show that AOC measurements correlated positively with total organic carbon (TOC) and UV-254 (an organic indicator) values in this system. Moreover, AOC concentrations at some locations were higher than the 50 microg acetate-C l(-1) standard established by Taiwan Water Company. This indicates that the microbial regrowth might be a potential water quality problem in this system. Higher DO measurements (>5.7 mg l(-1)) might cause the aerobic biodegradation of THMs and HAAs in the system, and thus, low THMs (<0.035 mg l(-1)) and HAAs (<0.019 mg l(-1)) concentrations were observed at all sampling locations. Results from the observed negative Langelier Saturation Index (LSI) values, higher Ryznar Stability Index (RSI) values, and high Fe3+ concentrations at some pipe-end locations indicate that highly oxidative and corrosive conditions occurred. This reveals that pipe replacement should be considered at these locations. These findings would be helpful in managing the water distribution system for maintaining a safe drinking water quality.

Application of surfactant enhanced permanganate oxidation and bidegradation of trichloroethylene in groundwater

The industrial solvent trichloroethylene (TCE) is among the most ubiquitous chlorinated solvents found in groundwater contamination. The main objectives of this study were to evaluate the feasibility of using non-ionic surfactant Simple Green (SG) to enhance the oxidative dechlorination of TCE by potassium permanganate (KMnO4) employing a continuous stir batch reactor system (CSBR) and column experiments. The effect of using surfactant SG to enhance the biodegradation of TCE via aerobic cometabolism was also examined. Results from CSBR experiments revealed that combination of KMnO4 with surfactant SG significantly enhanced contaminant removal, particularly when the surfactant SG concentrated at its CMC. TCE degradation rates ranged from 74.1% to 85.7% without addition of surfactant SG while TCE degradation rates increased to ranging from 83.8% to 96.3% with presence of 0.1wt% SG. Furthermore, results from column experiments showed that TCE was degraded from 38.1microM to 6.2microM in equivalent to 83.7% of TCE oxidation during first 560min reaction. This study has also demonstrated that the addition of surfactant SG is a feasible method to enhance bioremediation efficiency for TCE contaminated groundwater. The complete TCE degradation was detected after 75 days of incubation with both 0.01 and 0.1wt% of surfactant SG addition. Results revealed that surfactant enhanced chemical oxidation and bioremediation technology is one of feasible approaches to clean up TCE contaminated groundwater.

Application of biofiltration system on AOC removal: column and field studies

The Cheng-Ching Lake Water Treatment Plant (CCLWTP) is the main supplier of domestic water for the Greater Kaohsiung area, the second largest metropolis in Taiwan. Biological activated carbon (BAC) filtration is one of the major treatment processes in CCLWTP. The objectives of this study were to evaluate the effectiveness of BAC filtration on water treatment in the studied advanced water treatment plant and its capability on pollutants [e.g., AOC (assimilable organic carbon), bromide, bromate, iron] removal. In this study, water samples from each treatment process of CCLWTP were collected and analyzed periodically to assess the variations in concentrations of AOC and other water quality indicators after each treatment unit. Moreover, the efficiency of biofiltration process using granular activated carbon (GAC) and anthracite as the fillers was also evaluated through a column experiment. Results show that the removal efficiencies for AOC, bromide, bromate, and iron are 86% 100%, 17%, and 30% after the BAC filter bed, respectively. This indicates that BAC filtration plays an important role in pollutant removal. Results also show that AOC concentrations in raw water and effluent of the CCLWTP are approximately 143 and 16 microg acetate-Cl(-1), respectively. This reveals that the treatment processes applied in CCLWTP is able to remove AOC effectively. Results of column study show that the AOC removal efficiencies in the GAC and anthracite columns are 60% and 17%, respectively. Microbial colonization on GAC and anthracite were detected via the observation of scanning electron microscopic images. The observed microorganisms included bacteria (rods, cocci, and filamentous bacteria), fungi, and protozoa. Results from this study provide us insight into the mechanisms of AOC removal by advanced water treatment processes. These findings would be helpful in designing a modified water treatment system for AOC removal and water quality improvement.

Application of Klebsiella oxytoca immobilized cells on the treatment of cyanide wastewater

Klebsiella oxytoca, isolated from cyanide-containing industrial wastewater, has been shown to be able to biodegrade cyanide to non-toxic end products. The technology of immobilized cells can be applied in biological treatment to enhance the efficiency and effectiveness of biodegradation. In this study, potassium cyanide was used as the target compound and both alginate and cellulose triacetate techniques were applied for the preparation of immobilized cells. Results from this study show that KCN can be utilized as the sole nitrogen source by K. oxytoca. The free suspension systems reveal that the cell viability was highly affected by initial KCN concentration and pH. Results show that immobilized cell systems could tolerate a higher level of KCN concentration and wider ranges of pH. In the batch experiments, the maximum KCN removal efficiencies using alginate and cellulose triacetate immobilized beads were 0.108 and 0.101mM h(-1) at pH 7, respectively. Results also indicate that immobilized system can support a higher biomass concentration. Complete KCN degradation was observed after the operation of four consecutive degradation experiments with the same batch of immobilized cells. This suggests that the activity of immobilized cells can be maintained and KCN can be used as the nitrogen source throughout KCN degradation experiments. The maximum KCN removal rates using alginate and cellulose triacetate immobilized beads in continuous-column system were 0.224 and 0.192mMh(-1) with initial KCN concentration of 3mM, respectively. Results indicate that the immobilized cells of K. oxytoca would be applicable to the treatment of cyanide-containing wastewaters.

Application of in situ biosparging to remediate a petroleum-hydrocarbon spill site: field and microbial evaluation

In this study, a full-scale biosparging investigation was conducted at a petroleum-hydrocarbon spill site. Field results reveal that natural attenuation was the main cause of the decrease in major contaminants [benzene, toluene, ethylbenzene, and xylenes (BTEX)] concentrations in groundwater before the operation of biosparging system. Evidence of the occurrence of natural attenuation within the BTEX plume includes: (1) decrease of DO, nitrate, sulfate, and redox potential, (2) production of dissolved ferrous iron, sulfide, methane, and CO(2), (3) decreased BTEX concentrations along the transport path, (4) increased microbial populations, and (5) limited spreading of the BTEX plume. Field results also reveal that the operation of biosparging caused the shifting of anaerobic conditions inside the plume to aerobic conditions. This variation can be confirmed by the following field observations inside the plume due to the biosparging process: (1) increase in DO, redox potential, nitrate, and sulfate, (2) decrease dissolved ferrous iron, sulfide, and methane, (3) increased total cultivable heterotrophs, and (4) decreased total cultivable anaerobes as well as methanogens. Results of polymerase chain reaction, denaturing gradient gel electrophoresis, and nucleotide sequence analysis reveal that three BTEX biodegraders (Candidauts magnetobacterium, Flavobacteriales bacterium, and Bacteroidetes bacterium) might exist at this site. Results show that more than 70% of BTEX has been removed through the biosparging system within a 10-month remedial period at an averaged groundwater temperature of 18 degrees C. This indicates that biosparging is a promising technology to remediate BTEX contaminated groundwater.

Enhancement of electrokinetic remediation of hyper-Cr(VI) contaminated clay by zero-valent iron

This paper investigated the effectiveness of incorporating zero-valent iron (ZVI) into electrokinetic (EK) to remediate hyper-Cr(VI) contaminated clay (2497 mg/kg). A ZVI wall was installed in the center of the soil specimen and was filled with 1:1 (w/w) ratio of granular ZVI and sand. Results show that transport of H(+) is greatly retarded by the strong opposite migration of anionic chromate ions, whereupon a revered electroosmosis flow (EO) was resulted and alkaline zone across the specimen was developed promoting the release of Cr(VI) from the clay. Chromium removal was characterized by high Cr(VI) concentration occurred in the anolyte and the presence of Cr(III) precipitates in the catholyte. The Cr(VI) reduction efficiencies for the process without ZVI wall were 68.1 and 79.2% for 1 and 2V/cm, respectively. As ZVI wall was installed, the corresponding reduction efficiencies increased to 85.8 and 92.5%. The costs for energy and ZVI utilized in this process are US$ 41.0 and 57.5 per cubic meter for the system with electric gradient of 1 and 2V/cm, respectively. The role of ZVI wall effectively reducing Cr(VI) contamination and the operation simultaneous collection of Cr(VI) from the electrode reservoirs are two major advantages of this process.

Application of immobilized cells to the treatment of cyanide wastewater

Cyanide is highly toxic to living organisms, particularly in inactivating the respiration system by tightly binding to terminal oxidase. To protect the environment and water bodies, wastewater containing cyanide must be treated before discharging into the environment. Biological treatment is a cost-effective and environmentally acceptable method for cyanide removal compared with the other techniques currently in use. Klebsiella oxytoca (K. oxytoca), isolated from cyanide-containing industrial wastewater, has been shown to be able to biodegrade cyanide to non-toxic end products. The technology of immobilized cells can be applied in biological treatment to enhance the efficiency and effectiveness of biodegradation. In this study, potassium cyanide (KCN) was used as the target compound and both alginate (AL) and cellulose triacetate (CTA) techniques were applied for the preparation of immobilized cells. Results from this study show that KCN can be utilized as the sole nitrogen source by K. oxytoca. The free suspension systems reveal that the cell viability was highly affected by initial KCN concentration, pH, and temperature. Results show that immobilized cell systems could tolerate a higher level of KCN concentration and wider ranges of pH and temperature, especially in the system with CTA gel beads. Results show that a longer incubation period was required for KCN degradation using immobilized cells compared to the free suspended systems. This might be due to internal mass transfer limitations. Results also indicate that immobilized systems can support a higher biomass concentration. Complete KCN degradation was observed after the operation of four consecutive degradation experiments with the same batch of immobilized cells. This suggests that the activity of the immobilized cells can be maintained and KCN can be used as the nitrogen source throughout KCN degradation experiments. Results reveal that the application of immobilized cells of K. oxytoca is advantageous to the maintenance of KCN degradation efficiency. Thus, it is conceivable that the immobilized cells of K. oxytoca would be applicable to the treatment of cyanide-containing wastewaters.

Application of a constructed wetland for industrial wastewater treatment: a pilot-scale study

The main objective of this study was to examine the efficacy and capacity of using constructed wetlands on industrial pollutant removal. Four parallel pilot-scale modified free water surface (FWS) constructed wetland systems [dimension for each system: 4-m (L)x1-m (W)x1-m (D)] were installed inside an industrial park for conducting the proposed treatability study. The averaged influent contains approximately 170 mg l(-1) chemical oxygen demand (COD), 80 mg l(-1) biochemical oxygen demand (BOD), 90 mg l(-1) suspend solid (SS), and 32 mg l(-1) NH(3)-N. In the plant-selection study, four different wetland plant species including floating plants [Pistia stratiotes L. (P. stratiotes) and Ipomoea aquatica (I. aquatica)] and emergent plants [Phragmites communis L. (P. communis) and Typha orientalis Presl. (T. orientalis)] were evaluated. Results show that only the emergent plant (P. communis) could survive and reproduce with a continuous feed of 0.4m(3)d(-1) of the raw wastewater. Thus, P. communis was used in the subsequent treatment study. Two different control parameters including hydraulic retention time (HRT) (3, 5, and 7d) and media [vesicles ceramic bioballs and small gravels, 1cm in diameter] were examined in the treatment study. Results indicate that the system with a 5-d HRT (feed rate of 0.4m(3)d(-1)) and vesicles ceramic bioballs as the media had the acceptable and optimal pollutant removal efficiency. If operated under conditions of the above parameters, the pilot-plant wetland system can achieve removal of 61% COD, 89% BOD, 81% SS, 35% TP, and 56% NH(3)-N. The treated wastewater meets the current industrial wastewater discharge standards in Taiwan.

Enzymatic degradation of nitriles by Klebsiella oxytoca

Klebsiella oxytoca, isolated from cyanide-containing wastewater, was able to utilize many nitriles as sole source of nitrogen. The major objective of this study was to explore the ability of K. oxytoca to utilize some nitriles and then further evaluate the pathways of transformation of cyanide compounds by K. oxytoca. Results from this study indicate that succinonitrile and valeronitrile were the most optimal sources of nitrogen for the growth of K. oxytoca. The biodegradation of acetonitrile proceeded with the formation of acetamide followed by acetic acid. The production of ammonia was also detected in this biodegradation experiment. Similar results were observed in the propionitrile biodegradation experiments. Collectively, this study suggests that the breakdown of acetonitrile or propionitrile by this bacterium was via a two-step enzymatic hydrolysis with amides as the intermediates and organic acids plus with ammonia as the end products.

Application of monitored natural attenuation to remediate a petroleum-hydrocarbon spill site

Contamination of groundwater by petroleum-hydrocarbons is a serious environmental problem. The Monitored Natural Attenuation (MNA) approach is a passive remediation to degrade and dissipate groundwater contaminants in situ. In this study, a full-scale natural bioremediation investigation was conducted at a gasoline spill site. Results show that concentrations of major contaminants (benzene, toluene, ethylbenzene, and xylenes) dropped to below detection limit before they reached the downgradient monitor well located 280 m from the spill location. The results also reveal that natural biodegradation was the major cause of the observed contaminant reduction. The calculated natural first-order attenuation rates for BTEX and 1,2,4-trimethylbenzene (1,2,4-TMB) ranged from 0.051 (benzene) to 0.189 1/day (1,2,4-TMB). Evidence for the occurrence of natural attenuation includes the following: (1) depletion of dissolved oxygen, nitrate, and sulfate; (2) production of dissolved ferrous iron, sulfide, and CO2; (3) decreased BTEX concentrations and BTEX as carbon to TOC ratio along the transport path; (4) increased alkalinity and microbial populations; (5) limited spreading of the BTEX plume; and (6) preferential removal of certain BTEX components along the transport path. Additionally, the biodegradation capacity (44.73 mg/L) for BTEX and 1,2,4-TMB was much higher than other detected contaminants within the plume. Hence, natural attenuation can effectively contain the plume, and biodegradation processes played an important role in contaminant removal.

Natural attenuation of MTBE at two petroleum-hydrocarbon spill sites

Methyl tert-butyl ether (MTBE) has been used as a gasoline additive to improve the combustion efficiency and to replace lead since 1978. Because it is widely used and it has been disposed inappropriately, MTBE has become a prevalent groundwater contaminant worldwide. In this study, two petroleum-hydrocarbon contaminated sites (Sites A and B) were selected to evaluate the occurrence and effectiveness of natural attenuation of MTBE at these two sites. Field investigation results indicate that the natural attenuation mechanisms of MTBE at both sites were occurring with the first-order attenuation rates of 0.0021 and 0.0048 1day(-1) at Sites A and B, respectively. Results also reveal that the intrinsic biodegradation pattern was the most important mechanism among the natural attenuation processes at both sites. Results from BIOSCREEN simulation suggest that biodegradation was responsible for 78 and 59% of MTBE mass reduction at Sites A and B, respectively. Investigation results show that MTBE plume at Site B could be effectively controlled via natural attenuation processes. However, MTBE plume at Site A has migrated to a farther downgradient area and passed the boundary line of the site. Thus, more active groundwater remedial technologies should be applied at Site A to protect the downgradient environment. Results from this study suggest that natural attenuation might be feasible to be used as a remedial option for the remediation of MTBE-contaminated site on the premise that (1) detailed site characterization has been conducted and (2) the occurrence and effectiveness of natural attenuation processes have been confirmed.

Factors affecting the biodegradation of PCP by Pseudomonas mendocina NSYSU

A pentachlorophenol (PCP) degrading bacterium was isolated from PCP-contaminated soils and identified as Pseudomonas mendocina NSYSU (P. mendocina NSYSU). The main objectives of this study were to (1) clarify the factors affecting the ability and efficiency of PCP biodegradation by P. mendocina NSYSU, and (2) optimize the use of this bacterium in bioremediation of PCP. Microcosm experiments were conducted to fulfill the objectives. In batch cultures, P. mendocina NSYSU used PCP as its sole source of carbon and energy and was capable of completely degrading this compound. This was confirmed by the stoichiometric release of chloride ion. Moreover, P. mendocina NSYSU was able to mineralize a high concentration of PCP (150 mg/L). Results from the oxygen concentration experiment reveal that the growth of P. mendocina NSYSU was inhibited under low oxygen and anaerobic conditions. Results indicate that the optimal growth conditions for P. mendocina NSYSU include the following: slightly acidic (6<pH<7), aerobic, and relatively moderate ambient temperature (20 degrees C<temperature<30 degrees C) conditions. Addition of extra carbon sources (sodium acetate and glucose) could not enhance the PCP biodegradation. No PCP byproducts were detected after eight days of incubation in this study. This suggests that P. mendocina NSYSU is able to effectively biodegrade PCP and its biodegradation byproducts without the accumulation of inhibitory toxic compounds. Results from this study could be used to assist the optimization of its use in bioremediation of PCP.

Utilization of the metal-cyano complex tetracyanonickelate (II) by Azotobacter vinelandii

AIMS

The ability of Azotobacter vinelandii, a N(2)-fixing bacterium, to biodegrade tetracyanonickelate (TCN) was evaluated.

METHODS AND RESULTS

The amounts of TCN were measured spectrophotometrically. Ammonia was determined colorimetrically by the indophenol method. The produced methane from TCN conversion by A. vinelandii was detected by gas chromatography. Results showed that A. vinelandii was able to biodegrade 1 mmol l(-1) of TCN. Ammonia and methane were detected during the process of TCN degradation. Effects of exogenous nitrogen sources on TCN degradation were addressed in this study. Results revealed that the addition of ammonia (1, 5 and 10 mmol l(-1)) into the reaction mixtures caused decrease of TCN degradation rate during a 24-h incubation period. This inhibition was also observed when nitrite (5 and 10 mmol l(-1)) was added, whereas TCN degradation still proceeded after the addition of nitrate at the same concentrations. Furthermore, the rate of TCN utilization was strikingly enhanced when 0.8% of glucose was added.

CONCLUSIONS

Azotobacter vinelandii can degrade 1 mmol l(-1) of TCN into ammonia and methane. However, the inhibitory effects of exogenous ammonia and nitrite on TCN degradation by this bacterium were found in this study.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report defining the capability of A. vinelandii to degrade TCN. This bacterium might have potential value in applied strategies for removing metal-cyano wastes. Furthermore, these findings would be helpful in designing a practical system inoculated with A. vinelandii for the treatment of TCN.

Evaluation of natural and enhanced PCP biodegradation at a former pesticide manufacturing plant

Pentachlorophenol (PCP) has been used in the past as a pesticide, herbicide, antifungal agent, bactericide, and wood preservative. Thus, PCP is among the most ubiquitous chlorinated compounds found in groundwater contamination. A former pesticide manufacturing plant located in southern Taiwan has been identified as a PCP spill site. In this study, groundwater samples collected from the PCP site were analyzed to assess the occurrence of natural PCP biodegradation. Microcosm experiments were conducted to (1) evaluate the feasibility of biodegrading PCP by indigenous microbial consortia under aerobic and cometabolic conditions, and (2) determine the potential of enhancing PCP biodegradation using cane molasses and biological sludge cake as the substitute primary substrates under cometabolic conditions. The inocula used in this microcosm study were aquifer sediments collected from the PCP site and activated sludges collected from the municipal and industrial wastewater treatment plants. Results from this field investigation indicate that the natural biodegradation of PCP is occurring and causing the decrease in PCP concentration. Microcosm results show that the indigenous microorganisms can biodegrade PCP under both aerobic and aerobic cometabolism conditions. A PCP-degrading bacterium was isolated from the collected aquifer sediments and identified as Pseudomonas mendocina NSYSU via some biochemical tests and further conformation of DNA sequencing. In batch cultures, P. mendocina NSYSU used PCP as its sole source of carbon and energy. The isolated bacterium, P. mendocina NSYSU, was capable of completely degrading PCP as indicated by the increase in biomass formation with the decrease in PCP concentrations occurred in the carbon-free medium simultaneously. Results indicate that the in situ or on-site aerobic bioremediation using indigenous microorganisms or inoculated bacteria would be a feasible technology to clean up the studied PCP-contaminated site. Results from this study will be useful in designing a scale-up in situ or on-site PCP bioremediation system (e.g., on-site bioreactor) for field application.