Triclocarban-contaminated wastewater treatment by innovative hybrid moving entrapped bead activated sludge reactor (HyMER): Continuous performance and computational dynamic simulation analysis.

Triclocarban (TCC) has been used in consumer products and is a widespread contaminant in municipal wastewater treatment systems that ultimately accumulates in natural receiving water and soil. This work aims to apply an innovative hybrid moving entrapped bead activated sludge reactor (named "HyMER") that integrates entrapped TCC-degrading microbes and freely suspended activated sludge to treat TCC-contaminated wastewater. A previously isolated TCC-degrading bacterium (Pseudomonas fluorescens strain MC46, called MC46) and barium alginate entrapment were applied. The synthetic TCC-contaminated wastewater treatment (with TCC concentration of 10 mg/L) was performed using 20-cycle fed-batch reactor operation with feeding times of 12 and 24 h and cycle times of 13 and 25 h. The results indicated that the HyMER effectively reduced chemical oxygen demand by up to 80 and 95 % and TCC by up to 53 and 83 %, respectively, with feeding times of 12 and 24 h. Three TCC degradation intermediate products were found-3,4-dichloroaniline, 4-chloroaniline, and aniline. Scanning electron microscopic analysis revealed shorter cells and bacterial appendage development as cell adaptations against TCC and its intermediates. The live/dead assay indicated high survival of entrapped MC46 in toxic conditions, with up to 84 % viable cells. Based on computational fluid dynamic analysis, no entrapped cell agglomeration showed in the reactor, indicating the potential application of HyMER for real wastewater treatment. These results exhibit the feasibility of HyMER and its applicability for future toxic wastewater treatment.

Characterization of dissolved organic carbon and disinfection by-products in biochar filter leachate using orbitrap mass spectrometry.

Biochar is a low-cost adsorbent with considerable potential for utilization as a water filtration medium; however, organic matter leaching from biochar can lead to the formation of disinfection by-products (DBPs). This study investigated the leaching of dissolved organic carbon (DOC) from eucalyptus-derived biochar and the formation of DBPs generated by chlorination and chloramination. Column experiments with empty bed contact times (EBCTs) of 10 and 30 min were conducted for 200 bed volumes (BVs). The highest DOC concentration (3.5 µg-C/g-biochar) was detected with an EBCT of 30 min. Chloroform (49 µg/L) and dichloroacetonitrile (7 µg/L) because of chlorination were found during the first five BVs, but were reduced thereafter. During the first 10 BVs, unknown chlorinated DBPs generated (CHOCl) by chlorination and chloramination (193 and 152 formulae, respectively) were tentatively identified via an unknown screening analysis. The release of DBP precursors from biochar tentatively identified in this study will impact water filtration applications.

Interactions between natural organic matter fractions and nanoscale zero-valent iron.

The presence of natural organic matter (NOM) in groundwater could play an important role in the removal of contaminants by nanoscale zero-valent iron (NZVI). NOM has a heterogeneous structure and can be divided into 6 fractions based on polarity and charges: hydrophobic acid (HPOA), hydrophobic base (HPOB), hydrophobic neutral (HPON), hydrophilic acid (HPIA), hydrophilic base (HPIB), and hydrophilic neutral (HPIN). The objective of this study was to evaluate the interactions between NOM fractions and NZVI using two approaches: 1) the interaction between NOM fraction isolates and NZVI and 2) bulk NOM fractionation before and after reaction with NZVI. Two sources of NOM-groundwater (GWNOM), Khon Kaen, Thailand and Suwannee River NOM (SRNOM), USA-were examined. The isolated NOM had more interactions with NZVI at pH 5 compared to pH 7 and 9 for both GWNOM and SRNOM. HPOA of GWNOM had the highest adsorption capacity (qe) of 6.95 mg/g (pH 5), and that was also the case for HPIA of SRNOM (18.66 mg/g, pH 5). HPIN of both GWNOM and SRNOM yielded the lowest qe among the six fractions. The adsorption capacities of NOM fractions were well correlated with specific ultraviolet absorbance. Fluorescence excitation-emission spectra revealed that protein-like components preferentially reacted with NZVI. The results of bulk NOM fractionation after reacting with NZVI indicated that NOM not only adsorbed on NZVI but also reacted with NZVI and transformed to become more hydrophilic and neutral. This study's findings suggest that different NOM fractions had varying interactions with NZVI. The acid fractions tended to interact more than the other fractions. This work provides a deeper understanding of the reactivity between NOM and NZVI.

Manganese-contaminated groundwater treatment by novel bacterial isolates: kinetic study and mechanism analysis using synchrotron-based techniques.

The occurrence of manganese in groundwater causes coloured water and pipe rusting in water treatment systems. Consumption of manganese-contaminated water promotes neurotoxicity in humans and animals. Manganese-oxidizing bacteria were isolated from contaminated areas in Thailand for removing manganese from water. The selected bacterium was investigated for its removal kinetics and mechanism using synchrotron-based techniques. Among 21 isolates, Streptomyces violarus strain SBP1 (SBP1) was the best manganese-oxidizing bacterium. At a manganese concentration of 1 mg L-1, SBP1 achieved up to 46% removal. The isolate also successfully removed other metal and metalloid, such as iron (81%) and arsenic (38%). The manganese concentration played a role in manganese removal and bacterial growth. The observed self-substrate inhibition best fit with the Aiba model. Kinetic parameters estimated from the model, including a specific growth rate, half-velocity constant, and inhibitory constant, were 0.095 h-1, 0.453 mg L-1, and 37.975 mg L-1, respectively. The synchrotron-based techniques indicated that SBP1 removed manganese via combination of bio-oxidation (80%) and adsorption (20%). The study is the first report on biological manganese removal mechanism using synchrotron-based techniques. SBP1 effectively removed manganese under board range of manganese concentrations. This result showed the potential use of the isolate for treating manganese-contaminated water.

Vacuum ultraviolet irradiation for mitigating dissolved organic nitrogen and formation of haloacetonitriles.

The main objective of this work was to investigate the feasibility of using vacuum ultraviolet (VUV, 185 + 254 nm) and ultraviolet (UV, 254 nm) for the reduction of dissolved organic nitrogen (DON) and haloacetonitrile formation potential (HANFP) of surface water and treated effluent wastewater samples. The results showed that the reduction of dissolved organic carbon (DOC), DON, hydrophobicity (HPO), absorbance at 254 nm (UV254), and fluorescence excitation-emission matrix (FEEM) of both water samples by VUV was higher compared to using UV. The addition of H2O2 remarkably improved the performances of VUV and UV. VUV/H2O2 exhibited the highest removal efficiency for DOC and DON. Even though HANFP increased at the early stage, its concentration decreased (19-72%) at the end of treatment (60 min). Decreases in DON (30-41%) and DOC (51-57%) led to HANFP reduction (53-72%). Moreover, FEEM revealed that substantial reduction in soluble microbial product-like compounds (nitrogen-rich organic) had a strong correlation with HANFP reduction, implying that this group of compounds act as a main precursor of HANs. The VUV/H2O2 system significantly reduced HANFP more than UV/H2O2 and therefore is suitable for controlling HAN precursors and HAN formation in drinking water and reclaimed wastewater.

Simultaneous manganese adsorption and biotransformation by Streptomyces violarus strain SBP1 cell-immobilized biochar.

Consumption of water containing high proportions of manganese could cause Parkinson's like symptoms and damage the central nervous systems. This study aims to investigate the potential of manganese removal through the development of microbial cell-immobilized biochar. The wood vinegar industry generates a large volume of carbonized wood waste (natural biochar) from the pyrolytic process. This is the first investigation utilizing this low value waste combined with biological treatment for water purification. Raw and hydrogen peroxide-modified biochars were used to immobilize an effective manganese-oxidizing bacterium, Streptomyces violarus strain SBP1 (SBP1). The results demonstrated that the modified biochar had a higher proportion of oxygen-containing functional groups leading to better manganese removal. Manganese adsorption by the modified biochar fitted pseudo-second-order and Langmuir models with the maximum adsorption capacity of 1.15 mg g-1. The modified biochar with SBP1 provided the highest removal efficiency at 78%. The advanced synchrotron analyses demonstrated that manganese removal by the biochar with SBP1 is due to the synergistic combination of manganese adsorption by biochars and biological oxidation by SBP1.

Reduction of silver nanoparticle toxicity affecting ammonia oxidation using cell entrapment technique.

Occurrence of silver nanoparticles (AgNPs) in wastewater treatment systems could impact the ammonia oxidation (AO). This study investigated the reduction of AgNPs and dissociated silver ion (Ag+) toxicity on nitrifying sludge using cell entrapment technique. Three entrapment materials, including barium alginate (BA), polyvinyl alcohol (PVA), and a mixture of polyvinyl alcohol and barium alginate (PVA-BA), were applied. The BA beads provided the highest reduction of silver toxicity (up to 90%) and durability. Live/dead assays showed fatality of entrapped cells after exposure to AgNPs and Ag+. The maximum AO rate of the BA-entrapped cells was 5.6 mg-N/g-MLSS/h. The AO kinetics under the presence of silver followed an uncompetitive inhibition kinetic model. The experiments with AgNPs and Ag+ gave the apparent maximum AO rates of 4.2 and 4.8 mg-N/g-MLSS/h, respectively. The apparent half-saturation constants of the BA-entrapped cells under the presence of silver were 10.5 to 13.4 mg/L. Scanning electron microscopic observation coupled with energy-dispersive X-ray spectroscopy indicated no silver inside the beads. This elucidates that the silver toxicity can be reduced by preventing silver penetration through the porous material, leading to less microbial cell damage. This study revealed the potential of the entrapment technology for mitigating the effect of silver species on nitrification.

Performance and kinetics of triclocarban removal by entrapped Pseudomonas fluorescens strain MC46.

This study investigated removal of triclocarban (TCC) from contaminated wastewater by Pseudomonas fluorescens strain MC46 entrapped in barium alginate. Appropriate entrapped cell preparation conditions (cell-to-entrapment material ratio and cell loading) for removing TCC were examined. The highest TCC removal by the entrapped and free cell systems at the initial TCC concentration of 10 mg/L was 72 and 45%, respectively. TCC was degraded to less toxic compounds. Self-substrate inhibition was found at TCC concentration of 30 mg/L. The kinetics of TCC removal by entrapped and free cells fitted well with Edwards model. Scanning and transmission electron microscopic observations revealed that entrapment matrices reduced TCC-microbe contact, which lessened TCC inhibition. A live/dead cell assay also confirmed reduced microbial cell damage in the entrapped cell system compared to the free cell system. This study reveals the potential of entrapment technology to improve antibiotic removal from the environment.

A sustainable solution for removal of glutaraldehyde in saline water with visible light photocatalysis.

Glutaraldehyde (GA) is the most common biocide used in unconventional oil and gas production. Photocatalytic degradation of GA in brine simulating oil and gas produced water using Ag/AgCl/BiOCl composite as a photocatalyst with visible light was investigated. Removal of GA at 0.1 mM in 200 g/L NaCl solution at pH 7 was 90% after 75 min irradiation using 5 g/L of the photocatalyst. The GA removal followed pseudo-first order reaction with a rate constant of 0.0303 min-1. At pH 5 or at 300 g/L NaCl, the photocatalytic removal of GA was almost completely inhibited. Similar inhibitions were observed when adding dissolved organic carbon (from humic acid) at 10 and 200 mg/L, or Br- at 120 mg/L to the system. The removal rate of GA markedly increased with increasing pH (5-9), photocatalyst loading (2-8 g/L) and under 350 nm UV (compared to visible light). On the contrary, the removal rate of GA markedly decreased with increasing NaCl and initial GA concentrations (0-300 g/L for NaCl and 0.1-0.4 mM for GA). A quenching experiment was also conducted; electron holes (h+) and superoxide () were found as the main reactive species responsible for the removal of GA while OH had a very limited effect.

Photolysis of glutaraldehyde in brine: A showcase study for removal of a common biocide in oil and gas produced water.

Glutaraldehyde (GA) has been used extensively as a biocide in hydraulic fracturing fluid leading to its presence in oil and gas produced water. In this study, photolysis was used to degrade GA from brine solutions simulating produced water. Photolysis of GA was performed under ultraviolet (UV) irradiation. GA can be photolyzed by UV at all studied conditions with the efficiency ranging from 52 to 85% within one hour irradiation. Photolysis of GA followed pseudo-first order kinetics. A photolysis rate constant of GA at 0.1 mM in 200 g/L of salt at pH 7 was 0.0269 min-1 with a quantum yield of 0.0549 under 224 W illumination. The degradation rate of GA increased with increasing incident light intensity and decreasing pH. Increasing initial GA concentration resulted in decreasing degradation rate of GA. The degradation of GA was affected by salt concentration. At lower salt concentrations, notable retardation of GA photodegradation rate was observed while at higher salt concentrations GA photodegradation was improved compared to those without salt. OH was more dominant in sample without salt than sample with salt suggesting different photolytic mechanisms, indirect and direct photolysis, respectively. Oligomers were identified as the main photoproducts of GA photolysis.

Photodegradation of haloacetonitriles in water by vacuum ultraviolet irradiation: Mechanisms and intermediate formation.

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.

Mineralization and biodegradability enhancement of natural organic matter by ozone-VUV in comparison with ozone, VUV, ozone-UV, and UV: effects of pH and ozone dose.

The increase in mineralization and biodegradability of natural organic matter (NOM) by ozone-vacuum ultraviolet (VUV) in comparison with ozone, VUV, ozone-ultraviolet (UV), and UV were investigated. The effects of operating parameters including pH and ozone dose were evaluated. Results showed that the mineralization rate of dissolved organic carbon (DOC) provided by the processes tested was in the following order: ozone-VUV > VUV > ozone-UV > ozone > UV. Among three pH studied (7, 9, and 11), pH 7 provided the highest DOC mineralization rate and biodegradability increase. A synergistic effect was observed when combining ozone with UV or VUV at pH 7 and 9 but not at pH 11. The oxidized NOM samples were separated into six fractions based on polarity (hydrophobic/hydrophilic) and charge (acid/neutral/base) to reveal NOM characteristic changes. Ozone-VUV was effective in mineralizing hydrophobic neutral and acid fractions. The hydrophilic neutral fraction was a major NOM fraction after oxidation (39-87%) and was contributed to by the biodegradable DOC produced during oxidation. High performance size exclusion chromatography results revealed that the combination of UV or VUV with ozone was more effective in the decomposition of high molecular weight compounds than ozone alone.

Rapid fractionation of natural organic matter in water using a novel solid-phase extraction technique.

This paper introduces a novel natural organic matter (NOM) fractionation technique using solid-phase extraction cartridges. The new technique requires only 6 hours of fractionation time, which is much faster than traditional fractionation techniques (24 hours). It uses three Bond Elute ENV cartridges (Varian, Inc., Lake Forest, California), one Strata X-C cartridge (Phenomenex, Torrance, California), and one Strata X-AW cartridge (Phenomenex) in series and was tested by using to fractionate NOM from Suwannee River, Georgia (SRNOM) and Red River, Minnesota (RRNOM). Hydrophobic acid was a major fraction and accounted for 66 to 70% and 36% of SRNOM and RRNOM, respectively. The NOM fractions obtained from the developed method were characterized using Fourier transformed infrared spectroscopy and 13C nuclear magnetic resonance. The acid fractions of SRNOM mainly consisted of carboxylic acids. An application of this new technique was demonstrated by using it to investigate the effectiveness of water treatment processes in removing different NOM fractions.

Use of biomass sorbents for oil removal from gas station runoff.

The use of biomass sorbents, which are less expensive and more biodegradable than synthetic sorbents, for oil removal from gas station runoff was investigated. A bench-scale flume experiment was conducted to evaluate the oil removal and retention capabilities of the biomass sorbents which included kapok fiber, cattail fiber, Salvinia sp., wood chip, rice husk, coconut husk, and bagasse. Polyester fiber, a commercial synthetic sorbent, was also experimented for comparison purpose. Oil sorption and desorption tests were performed at a water flow rate of 20 lmin-1. In the oil sorption tests, a 50 mgl(-1) of used engine oil-water mixture was synthesized to simulate the gas station runoff. The mass of oil sorbed for all sorbents, except coconut husk and bagasse, was greater than 70%. Cattail fiber and polyester fiber were the sorbents that provided the least average effluent oil concentrations. Oil selectivity (hydrophobic properties) and physical characteristics of the sorbents are the two main factors that influence the oil sorption capability. The used sorbents from the sorption tests were employed in the desorption tests. Results indicated that oil leached out of all the sorbents tested. Polyester fiber released the highest amount of oil, approximately 4% (mass basis) of the oil sorbed.