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.

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.

Integrated remediation and detoxification of triclocarban-contaminated water using waste-derived biochar-immobilized cells by long-term column experiments.

Triclocarban (TCC), an antibacterial agent commonly used in personal care products, is one of the top ten contaminants of emerging concern in various environmental media, including soil and contaminated water in vadose zone. This study aimed to investigate TCC-contaminated water remediation using biochar-immobilized bacterial cells. Pseudomonas fluorescens strain MC46 (MC46), an efficient TCC-degrading isolate, was chosen, whereas agro-industrial carbonized waste as biochar was directly used as a sustainable cell immobilization carrier. According to the long-term TCC removal performance results (160 d), the biochar-immobilized cells consistently exhibited high TCC removal efficiencies (84-97%), whereas the free MC46 removed TCC for 76-94%. At 100 days, the detachment of the MC46 cells from the immobilized cell column was observed. The micro-Fourier-transform infrared spectroscopy results indicated that extracellular polymeric substance (EPS) was produced, but polysaccharide and protein fractions were washed out of the column. The lipid fraction of EPS adhered to the biochar, promoting TCC sorption for long-term treatment. The shortening of MC46 cells improved the tolerance of TCC toxicity. The TCC-contaminated water was successfully detoxified by the biochar-immobilized MC46 cells. Overall, the waste-derived biochar-immobilized cell system proposed in this study for the removal of emerging contaminants, including TCC, is efficient, economical, and aligned with the sustainable development concept of value-added utilization of waste.

Comparative investigation of known and unknown disinfection by-product precursor removal and microbial community from biological biochar and activated carbon filters.

Biological activated carbon filter (BAC) is one of the most effective technologies for removing disinfection by-product (DBP) precursors from water. Biochar is a lower-cost medium that has the potential to replace granular activated carbon in BAC applications, thus leading to the development of biological biochar filter (BCF). This study compared BCF with BAC for the removal of DBP precursors using column experiments. Both BCF and BAC achieved the removal of DBP precursors, resulting in concentrations of all DBP formation potential below the World Health Organization guideline values for drinking water. Bromodichloromethane and unknown DBP precursor removal by BCF was comparable to that by BAC. However, BAC removed more chloroform and dichloroacetontrile precursors than BCF. For microbial community analysis, cell numbers in a bottom layer (inlet) of BCF and BAC columns were higher than those in the top layer. The abundances of Nordella and a microbial genus from Burkholderiaceae at the bottom layer showed a strong correlation to the number of DBP precursors removed and were comparable in BCF and BAC. This finding likely contributes to the similarities between DBPs species removed and the removal performances of some known and unknown DBP precursors by BCF and BAC. Overall results from this study revealed that biochar can be served as a low-cost and sustainable replacement of activated carbon in water filter for DBP precursor removal.

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.

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.

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.