Research Interests: Hydrology, Environmental Monitoring, Stratification, Multidisciplinary, Animal Husbandry, and 17 moreEndocrine disruptors, Hormones, Si, Soils, Tandem Mass Spectrometry, Water Table, Sol, High Performance Liquid Chromatography, Liquid Chromatography, Manure, Endocrine Disruptors, Sus Scrofa, MSP, Soil Water, SPE, Estradiol, and Soil Pollutants
Biodegradability of dissolved organic nitrogen (DON) has been studied in wastewater, freshwater and marine water but not in drinking water. Presence of biodegradable DON (BDON) in water prior to and after chlorination may promote... more
Biodegradability of dissolved organic nitrogen (DON) has been studied in wastewater, freshwater and marine water but not in drinking water. Presence of biodegradable DON (BDON) in water prior to and after chlorination may promote formation of nitrogenous disinfectant by-products and growth of microorganisms in the distribution system. In this study, an existing bioassay to determine BDON in wastewater was adapted and optimized, and its application was tested on samples from four treatment stages of a water treatment plant including ozonation and biologically active filtration. The optimized bioassay was able to detect BDON in 50 μg L−1 as N of glycine and glutamic solutions. BDON in raw (144–275 μg L−1 as N), softened (59–226 μg L−1 as N), ozonated (190–254 μg L−1 as N), and biologically filtered (17–103 μg L−1 as N) water samples varied over a sampling period of 2 years. The plant on average removed 30% of DON and 68% of BDON. Ozonation played a major role in increasing the amount of BDON (31%) and biologically active filtration removed 71% of BDON in ozonated water.
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A laboratory-scale enricher reactor (ER) - permeable reactive biobarrier (PRBB) system was studied to address performance loss of a PRBB due to substrate interactions among a mixture of benzene, toluene, ethylbenzene, and xylene (BTEX) in... more
A laboratory-scale enricher reactor (ER) - permeable reactive biobarrier (PRBB) system was studied to address performance loss of a PRBB due to substrate interactions among a mixture of benzene, toluene, ethylbenzene, and xylene (BTEX) in groundwater, when the mixture reappeared after a 10-day absence period. Toluene and BTEX as an inducer in ER were compared to investigate toluene as a potential single inducer in ER. PRBBs without ER augmentation experienced performance losses ranging from 11% to 35% for PRBBs initially inoculated with toluene degraders and 22% to 33% for PRBBs initially inoculated with BTEX degraders. Bacterial communities changed substantially in these PRBBs after the absence period, which could contribute to the performance losses. PRBBs augmented with toluene degraders overcame the inhibition interaction between benzene and toluene, and showed a superior removal performance for toluene degradation suggesting that toluene can be used as a single inducer in an ER.
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A comprehensive study on the effects of different carbon sources during the bacterial enrichment on the removal performances of benzene, toluene, ethylbenzene, and xylenes (BTEX) compounds when present as a mixture was conducted. Batch... more
A comprehensive study on the effects of different carbon sources during the bacterial enrichment on the removal performances of benzene, toluene, ethylbenzene, and xylenes (BTEX) compounds when present as a mixture was conducted. Batch BTEX removal kinetic experiments were performed using cultures enriched with individual BTEX compounds or BTEX as a mixture or benzoate alone or benzoate-BTEX mixture. An integrated Monod-type non-linear model was developed and a ratio between maximum growth rate (mu max) and half saturation constant (Ks) was used to fit the non-linear model. A higher mu max/Ks indicates a higher affinity to degrade BTEX compounds. Complete removal of BTEX mixture was observed by all the enriched cultures; however, the removal rates for individual compounds varied. Degradation rate and the type of removal kinetics were found to be dependent on the type of carbon source during the enrichment. Cultures enriched on toluene and those enriched on BTEX mixture were found to have the greatest mu max/Ks and cultures enriched on benzoate had the least mu max/Ks. Removal performances of the cultures enriched on all different carbon sources, including the ones enriched on benzoate or benzoate-BTEX mixture were also improved during a second exposure to BTEX. A molecular analysis showed that after each exposure to the BTEX mixture, the cultures enriched on benzoate and those enriched on benzoate-BTEX mixture had increased similarities to the culture enriched on BTEX mixture.
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A combined enricher reactor (ER)-permeable reactive biobarrier (PRBB) system was developed to treat groundwater with contaminants that appear in batches. An enricher reactor is an offline reactor used to enrich contaminant degraders by... more
A combined enricher reactor (ER)-permeable reactive biobarrier (PRBB) system was developed to treat groundwater with contaminants that appear in batches. An enricher reactor is an offline reactor used to enrich contaminant degraders by supplying necessary growth materials, and the enriched degraders are used to augment PRBB to increase its performance after a period of contaminant absence. Bench-scale experiments on PRBBs with and without bacterial supply from the enricher reactor were conducted to evaluate PRBB removal performances for benzene, which was used as a model contaminant. Benzene absence periods of 10 and 25 days were tested in the presence and absence of ethanol. The PRBBs without the bioaugmentation from the enricher reactor experienced a decrease in performance from approximately 65% to 30% after benzene reappeared. The presence of ethanol accelerated the benzene removal performance recovery of PRBBs. The 25-day benzene absence period caused greater changes in the bacterial community structure, regardless of the ethanol availability.
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The toxic effect of nanoscale zero valent iron (nZVI) particles on bacteria from different growth phases was studied. Four bacterial strains namely Escherichia coli strains JM109 and BW25113, and Pseudomonas putida strains KT2440 and F1... more
The toxic effect of nanoscale zero valent iron (nZVI) particles on bacteria from different growth phases was studied. Four bacterial strains namely Escherichia coli strains JM109 and BW25113, and Pseudomonas putida strains KT2440 and F1 were experimented. The growth curves of these strains were determined. Bacterial cells were harvested based on the predetermined time points, and exposed to nZVI. Cell viability was determined by the plate count method. Bacterial cells in lag and stationary phases showed higher resistance to nZVI for all four bacterial strains, whereas cells in exponential and decline phases were less resistant to nZVI and were rapidly inactivated when exposed to nZVI. Bacterial inactivation increased with the concentration of nZVI. Furthermore, less than 14% bacterial inactivation was observed when bacterial cells were exposed to the filtrate of nZVI suspension suggesting that the physical interaction between nZVI and cell is necessary for bacterial inactivation.
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Multi-criteria analysis and detailed impact analysis were carried out to assess the sustainability of four remedial alternatives for metal-contaminated soil/sediment at former timber treatment sites and harbour sediment with different... more
Multi-criteria analysis and detailed impact analysis were carried out to assess the sustainability of four remedial alternatives for metal-contaminated soil/sediment at former timber treatment sites and harbour sediment with different scales. The sustainability was evaluated in the aspects of human health and safety, environment, stakeholder concern, and land use, under four different scenarios with varying weighting factors. The Monte Carlo simulation was performed to reveal the likelihood of accomplishing sustainable remediation with different treatment options at different sites. The results showed that in-situ remedial technologies were more sustainable than ex-situ ones, where in-situ containment demonstrated both the most sustainable result and the highest probability to achieve sustainability amongst the four remedial alternatives in this study, reflecting the lesser extent of off-site and on-site impacts. Concerns associated with ex-situ options were adverse impacts tied to ...
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Effects of operational changes on membrane fouling were evaluated for a wastewater reclamation facility. The focuses were on addition of a coagulant (ferric chloride) versus no addition and an accidental high chlorine (sodium... more
Effects of operational changes on membrane fouling were evaluated for a wastewater reclamation facility. The focuses were on addition of a coagulant (ferric chloride) versus no addition and an accidental high chlorine (sodium hypochlorite) dose. Two membrane modules with different service ages, 3 years versus 9 months, were compared. Fouling rates ranged between 2 and 3 times higher during no ferric chloride addition. Chemical cleaning frequency was reduced by approximately 5 times during ferric chloride addition for older membranes, while it did not change for newer membranes. High chlorine dose had slightly improved membrane permeability for newer membrane, and reduced the transmembrane pressure (TMP) for both older and newer membranes. Chemical wash with enzymatic detergents substantially improved membrane permeability and reduced TMP for both older and newer membranes. Fouling index values indicated that coagulant addition had greater impact on performance recovery for older mem...
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Photodegradation of haloacetonitriles (HANs), highly carcinogenic nitrogenous disinfection by-products, in water using vacuum ultraviolet (VUV, 185 + 254 nm) in comparison with ultraviolet (UV, only 254 nm) was investigated.... more
Photodegradation of haloacetonitriles (HANs), highly carcinogenic nitrogenous disinfection by-products, in water using vacuum ultraviolet (VUV, 185 + 254 nm) in comparison with ultraviolet (UV, only 254 nm) was investigated. Monochloroacetonitrile (MCAN), dichloroacetonitrile (DCAN), trichloroacetonitrile (TCAN), and dibromoacetonitrile (DBAN) were species of HANs studied. The effect of gas purging and intermediate formation under VUV were examined. The results show that the pseudo first order rate constants for the reduction of HANs under VUV were approximately 2-7 times better than UV. The order of degradation efficiency under VUV and UV was MCAN < DCAN < TCAN < DBAN. The degradation efficiencies of individual HANs under VUV were higher than those of mixed HANs, suggesting competitive effects among HANs. Under nitrogen purging, the removal rate constants of mixed HANs was much higher than that of the aerated condition by 34.4, 34.9, 10.1, and 3.8 times for MCAN, DCAN, TCAN, and DBAN, respectively. The major degradation mechanism for HANs was different depending on HANs species. Degradation intermediates of HANs such as 2-chloropropionitrile, 2,2-dimethylpropanenitrile, and fumaronitrile were produced from the substitution, addition, and polymerization reactions. In addition, chlorinated HANs with lower number of chlorine atom including MCAN and DCAN were found as intermediates of DCAN and TCAN degradation, respectively.
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Research Interests: Water resources, Filtration, Water Resources Management, Multidisciplinary, Developing Country, and 15 moreLand Use, Surface Water, Contamination, Rainfall, Pollutants, Field Study, Streams, Waste Water, Runoff, Industrial wastewater, Best management practice, Urban Runoff, Best Management Practices, Field Studies, and Silt
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A biodegradable dissolved organic carbon (BDOC) method has been developed and used to analyze secondary- and advanced-treated wastewater effluents and to investigate correlations between residual organic content and the solids retention... more
A biodegradable dissolved organic carbon (BDOC) method has been developed and used to analyze secondary- and advanced-treated wastewater effluents and to investigate correlations between residual organic content and the solids retention time (SRT). Conventional biochemical oxygen demand (BOD) bottles and a 28-day incubation period were used. Secondary wastewater effluents from Hawaii were found to contain between 9.0 and 14.0 mg/L of dissolved organic carbon (DOC), of which 23 to 35% was biodegradable in the 28-day BDOC test (from a survey of nine treatment plants). Bench-scale, continuous-flow activated-sludge biological reactors treating synthetic wastewater were operated at SRTs between 2 and 15 days, and effluent BDOCs were determined. A good BDOC prediction equation was developed that incorporates the initial DOC, the DOC remaining after 5 days, and the SRT of the system from which the sample originated. This equation can be used to determine the BDOC value using data that can be obtained during a conventional 5-day BOD test. The determined equation was found to be appropriate for some of the full-scale wastewater effluent survey data.
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ABSTRACT The formation of bromate by ozone-vacuum ultraviolet (VUV) (185 + 254 nm) process in comparison with ozone and ozone-ultraviolet (UV) (254 nm) processes of coagulated and softened water was studied. The effects of pH (7, 9, and... more
ABSTRACT The formation of bromate by ozone-vacuum ultraviolet (VUV) (185 + 254 nm) process in comparison with ozone and ozone-ultraviolet (UV) (254 nm) processes of coagulated and softened water was studied. The effects of pH (7, 9, and 11), ozone dosage (1, 2, and 4 mg O-3/mg C), and VUV power (30, 60, and 120 W) were investigated. Bromate concentrations formed by the ozone-VUV process were up to four and six times less than those by the ozone and ozone-UV processes, respectively. Among the variables studied, ozone dosage had the most effect on bromate formation by the ozone-VUV process. Approximately 64 and 213% increases of bromate concentration were observed when the ozone dosage was increased from 1 to 2 and 4 mg O-3/mg C with VUV power of 120 W at pH 7. The bromate formation also increased as VUV power and pH increased. Hydroxyl radical exposure had a positive relationship with ozone dosage and bromate formation. Results further indicated that it might be difficult to achieve the drinking water standard for bromate and high organic matter removal concurrently. DOI: 10.1061/(ASCE)EE.1943-7870.0000313. (C) 2011 American Society of Civil Engineers.
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This study investigated the effects of the alginate and polyvinyl alcohol (PVA) entrapment on the viability of Escherichia coli cells exposed to single wall carbon nanotubes (SWCNTs) with a diameter of 1-2nm. Viability was examined using... more
This study investigated the effects of the alginate and polyvinyl alcohol (PVA) entrapment on the viability of Escherichia coli cells exposed to single wall carbon nanotubes (SWCNTs) with a diameter of 1-2nm. Viability was examined using a galactosidase enzyme assay, LIVE/DEAD BacLight assay, and total ribonucleic acid quantity. Variables studied included SWCNT concentration (5, 10, 20, 50, 100, 200, 500, and 1000μg/ml), SWCNT length (0.5-2μm for short SWCNTs and 5-30μm for long SWCNTs), and initial bacterial concentration (6.5 log10 CFU and 9 log10 CFU per test). Results showed that both alginate and PVA entrapments mitigate the bactericidal effect of SWCNTs. At the highest SWCNT concentration tested (1000μg/ml), the viability of the cells relative to controls (systems with only E. coli, no SWCNTs), was 0-60% for free cells and 60-90% for alginate and PVA entrapped cells. The bactericidal effect depended on SWCNT type and concentration, and bacterial concentration. In general, long...
The hormone 17β-estradiol (E2) can cause endocrine disruption in sensitive species at part per trillion concentrations. The persistence and transport pathways of manure-borne E2 in agricultural soils were determined by comparing its... more
The hormone 17β-estradiol (E2) can cause endocrine disruption in sensitive species at part per trillion concentrations. The persistence and transport pathways of manure-borne E2 in agricultural soils were determined by comparing its occurrence with the transfer of water and the transport of non-sorbing fluorobenzoic acid (FBA) tracers. This comparison was done using capillary wick lysimeters installed 0.61 m beneath three corn (Zea mays L.) plots that receive swine (Sus scrofa domesticus) manure from various sources. An additional control plot was included that received no manure. Soil water transfer was modeled to compare actual versus predicted percolation. On average, lysimeters collected 61% of the expected percolation and 8% of the FBA. There were frequent E2 detections, where there were an average of 8 detections for the 11 sample events. The average detection was 21 ng L−1 and its range was 1–245 ng L−1. 17β-Estradiol was detected before manure was applied and also in the control plot lysimeters. Furthermore, the average mass recovery of E2 in all the lysimeters was >50%, which was greater than the FBA tracer recovery. Results indicated that tracer was transported with precipitated water infiltrating into the soil surface and percolating down through the soil profile. There was substantial evidence for antecedent E2, which was persistent and mobile. The persistence and mobility of the E2 may result from its associations with colloids, such as dissolved organic matter. Furthermore, this antecedent E2 appeared to overwhelm any observable effect of manure management on E2 fate and transport.
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An Escherichia coli BW25113 wildtype strain and mutant strains lacking genes that protect against oxidative stress were examined at different growth phases for susceptibility to zero-valent iron (nZVI). Viability of cells was determined... more
An Escherichia coli BW25113 wildtype strain and mutant strains lacking genes that protect against oxidative stress were examined at different growth phases for susceptibility to zero-valent iron (nZVI). Viability of cells was determined by the plate count method. All mutant strains were more susceptible than the wild type strain to nZVI; however, susceptibility differed among the mutant strains. Consistent with the role of rpoS as a global stress regulator, an rpoS gene knockout mutant exhibited the greatest susceptibility to nZVI under the majority of conditions tested (except exponential and declining phases at longer exposure time). Mutants lacking genes encoding the inducible and constitutively expressed cytosolic superoxide dismutases, sodA and sodB, respectively, were more susceptible to nZVI than a mutant lacking the gene encoding sodC, a periplasmic superoxide dismutase. This suggests that nZVI induces oxidative stress inside the cells via superoxide generation. Quantitative...
Proventriculus and intestinal samples from 70 North American red-winged blackbirds (Agelaius phoeniceus; order Passeriformes) were examined for the presence of Cryptosporidium by PCR amplification and sequence analysis of the 18S... more
Proventriculus and intestinal samples from 70 North American red-winged blackbirds (Agelaius phoeniceus; order Passeriformes) were examined for the presence of Cryptosporidium by PCR amplification and sequence analysis of the 18S ribosomal RNA (18S rRNA), actin, and 70-kDa heat shock protein (HSP70) genes. Twelve birds (17.1 %) were positive for the Cryptosporidium 18S rRNA gene: six birds were positive at the proventriculus site only and six birds were positive at the proventriculus and intestinal sites. Sequence analysis of the 18S rRNA, actin and HSP70 genes showed the presence of the gastric species Cryptosporidium galli in a single proventriculus sample and a closely related genotype, which we have named Cryptosporidium avian genotype VI, in all other positive samples. These findings contribute to our understanding of Cryptosporidium diversification in passerines, the largest avian order.
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The removal of cyanide (CN(-)) from aqueous solutions using a strongly basic ion-exchange resin, Purolite A-250, was investigated. The effects of contact time, initial CN(-) concentration, pH, temperature, resin dosage, agitation speed,... more
The removal of cyanide (CN(-)) from aqueous solutions using a strongly basic ion-exchange resin, Purolite A-250, was investigated. The effects of contact time, initial CN(-) concentration, pH, temperature, resin dosage, agitation speed, and particle size distribution on the removal of CN(-) were examined. The adsorption equilibrium data fitted the Langmuir isotherm very well. The maximum CN(-) adsorption capacity of Purolite A-250 was found to be 44 mg CN(-) g(-1) resin. More than 90% CN(-) adsorption was achieved for most CN(-) solutions (50, 100, and 200 mg CN(-) L(-1)) with a resin dose of 2 g L(-1). The equilibrium time was ∼20 min, optimum pH was 10.0-10.5, and optimum agitation speed was 150 rpm. An increase in adsorption of CN(-) with increasing resin dosage was observed. Adsorption of CN(-) by the resin was marginally affected (maximum 4% variation) within an environmentally relevant temperature range of 20-50 °C. Fixed-bed column (20.5 mm internal diameters) experiments were performed to investigate the effects of resin bed depth and influent flow rate on breakthrough behaviour. Breakthrough occurred in 5 min for 0.60 cm bed depth while it was 340 min for 5.40 cm bed depth. Adsorption capacity was 25.5 mg CN(-) g(-1) for 5 mL min(-1) flow rate and 3.9 mg CN(-) g(-1) for 20 mL min(-1) flow rate. The research has established that the resin can be effectively used for CN(-) removal from aqueous solutions.
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A bench-scale sand column experiment was conducted to investigate nitrate removal from synthetic agricultural infiltrate by denitrifying bacterial cells entrapped in calcium alginate compared to free cells. The effects of methanol as a... more
A bench-scale sand column experiment was conducted to investigate nitrate removal from synthetic agricultural infiltrate by denitrifying bacterial cells entrapped in calcium alginate compared to free cells. The effects of methanol as a carbon source and cell loading were examined. Low (0 to 50%) nitrate removal was observed in both entrapped and free-cell columns without methanol supplement. In the presence of methanol, nitrate removals of 90 to 99% and 56 to 75% were obtained for entrapped and free-cell columns, respectively. Nitrate removal followed first-order kinetics. The entrapped-cell columns achieved higher nitrate removal than the free-cell columns because of less bacterial losses. Scanning electron microscopic images supported the nitrate removal results that the denitrifying bacteria proliferated in the entrapment matrix, and several nitrogen gas voids were produced from denitrification.
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Wildlife-associated Cryptosporidium are an emerging cause of cryptosporidiosis in humans. The present study was undertaken to determine the extent to which North American tree squirrels and ground squirrels host zoonotic Cryptosporidium... more
Wildlife-associated Cryptosporidium are an emerging cause of cryptosporidiosis in humans. The present study was undertaken to determine the extent to which North American tree squirrels and ground squirrels host zoonotic Cryptosporidium species and genotypes. Fragments of the Cryptosporidium 18S rRNA and actin genes were amplified and sequenced from fecal samples obtained from three tree squirrel and three ground squirrel species. In tree squirrels, Cryptosporidium was identified in 40.5% (17/42) of American red squirrels (Tamiasciurus hudsonicus), 40.4% (55/136) of eastern gray squirrels (Sciurus carolinensis), and 28.6% (2/7) of fox squirrels (Sciurus niger). Human-pathogenic Cryptosporidium ubiquitum and Cryptosporidium skunk genotype were the most prevalent species/genotypes in tree squirrels. Because tree squirrels live in close proximity to humans and are frequently infected with potentially zoonotic Cryptosporidium species/genotypes, they may be a significant reservoir of infection in humans. In ground squirrels, Cryptosporidium was detected in 70.2% (33/47) of 13-lined ground squirrels (Ictidomys tridecemlineatus), 35.1% (27/77) of black-tailed prairie dogs (Cynomys ludovicianus), and the only golden-mantled ground squirrel (Callospermophilus lateralis) that was sampled. Cryptosporidium rubeyi and ground squirrel genotypes I, II, and III were identified in isolates from these ground squirrel species. In contrast to the Cryptosporidium infecting tree squirrels, these species/genotypes appear to be specific for ground squirrels and are not associated with human disease.
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Wildlife-associated Cryptosporidium are an emerging cause of cryptosporidiosis in humans. The present study was undertaken to determine the extent to which North American tree squirrels and ground squirrels host zoonotic Cryptosporidium... more
Wildlife-associated Cryptosporidium are an emerging cause of cryptosporidiosis in humans. The present study was undertaken to determine the extent to which North American tree squirrels and ground squirrels host zoonotic Cryptosporidium species and genotypes. Fragments of the Cryptosporidium 18S rRNA and actin genes were amplified and sequenced from fecal samples obtained from three tree squirrel and three ground squirrel species. In tree squirrels, Cryptosporidium was identified in 40.5% (17/42) of American red squirrels (Tamiasciurus hudsonicus), 40.4% (55/136) of eastern gray squirrels (Sciurus carolinensis), and 28.6% (2/7) of fox squirrels (Sciurus niger). Human-pathogenic Cryptosporidium ubiquitum and Cryptosporidium skunk genotype were the most prevalent species/genotypes in tree squirrels. Because tree squirrels live in close proximity to humans and are frequently infected with potentially zoonotic Cryptosporidium species/genotypes, they may be a significant reservoir of inf...
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Entrapped cell bioaugmentation is an addition of gel or rubber matrices embedded with microorganisms to increase biological activities. The technology is an integration of cell entrapment and cell bioaugmentation techniques. In the last... more
Entrapped cell bioaugmentation is an addition of gel or rubber matrices embedded with microorganisms to increase biological activities. The technology is an integration of cell entrapment and cell bioaugmentation techniques. In the last decade, this technology has been frequently studied for its applications in the environmental field for removing collective and specific contaminants. The technology not only provides sufficient contaminant-degrading
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Cryptosporidium is an apicomplexan parasite that causes the disease cryptosporidiosis in humans, livestock, and other vertebrates. Much of the knowledge on Cryptosporidium diversity is derived from 18S rRNA gene (18S rDNA) phylogenies.... more
Cryptosporidium is an apicomplexan parasite that causes the disease cryptosporidiosis in humans, livestock, and other vertebrates. Much of the knowledge on Cryptosporidium diversity is derived from 18S rRNA gene (18S rDNA) phylogenies. Eukaryote genomes generally have multiple 18S rDNA copies that evolve in concert, which is necessary for the accurate inference of phylogenetic relationships. However, 18S rDNA copies in some genomes evolve by a birth-and-death process that can result in sequence divergence among copies. Most notably, divergent 18S rDNA paralogs in the apicomplexan Plasmodium share only 89-95% sequence similarity, encode structurally distinct rRNA molecules, and are expressed at different life cycle stages. In the present study, Cryptosporidium 18S rDNA was amplified from 28/72 (38.9%) eastern chipmunks (Tamias striatus). Phylogenetic analyses showed the co-occurrence of two 18S rDNA types, Type A and Type B, in 26 chipmunks, and Type B clustered with a sequence previ...
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ABSTRACT Effects of three different operational changes on membrane fouling were evaluated for a wastewater secondary effluent reuse facility: addition and no addition of a coagulant (ferric chloride), an accidental high chlorine (sodium... more
ABSTRACT Effects of three different operational changes on membrane fouling were evaluated for a wastewater secondary effluent reuse facility: addition and no addition of a coagulant (ferric chloride), an accidental high chlorine (sodium hypochlorite) dose, and an extended hydraulic backwash. Two different types of membrane modules were compared: one with 3 years operation and the second with 9 months of operation at the time of data collection. Fouling rates ranged between 2 to 3 times higher during no ferric chloride addition than the ferric chloride addition. Chemical cleaning frequency was reduced by approximately 5 times during the ferric chloride addition for older membranes, while it did not change for newer membranes. High chlorine dose had slightly improved membrane permeability for newer membrane, and reduced the transmembrane pressure (TMP) for both types of membranes. Additionally, extended backwash had shown significant improvement in membrane permeability and reduction in TMP for both types of membranes. Membrane fouling index (MFI) values indicated that coagulant addition had greater impact on performance recovery after hydraulic backwash for older membranes than newer membranes. Moreover, MFI values also indicated that extended hydraulic backwash can lower chemically irreversible fouling.
ABSTRACT A combined enricher reactor (ER) - permeable reactive biobarrier (PRBB) system was developed in this study to treat groundwater with periodically absent contaminants. ER is an offline reactor used to enrich bacteria by supplying... more
ABSTRACT A combined enricher reactor (ER) - permeable reactive biobarrier (PRBB) system was developed in this study to treat groundwater with periodically absent contaminants. ER is an offline reactor used to enrich bacteria by supplying necessary growth materials. Bench scale experiments on PRBBs with and without bacterial supply from the ER were conducted to evaluate PRBB removal performances for benzene absence periods of 10 and 20 days. The removal performance of the system was also investigated for the presence of ethanol during the benzene absence periods. The bioaugmentation from ER maintained the performance of PRBBs while PRBBs without the bioaugmentation experienced performance losses up to 30%. The presence of ethanol during the benzene absence periods also caused performance losses up to 30%. Molecular technique results showed that the longer benzene absence period caused greater changes in the bacterial community structure. The presence of ethanol during both of the benzene absence periods also caused changes in the bacterial community.