Interaction between organic species in the formation of haloacetic acids following disinfection

Formation of trihalomethanes of dissolved organic matter fractions in reservoir and canal waters

The formation of trihalomethanes (THMs) of hydrophobic organic fraction (HPO), transphilic organic fraction (TPI), and hydrophilic organic fraction (HPI) of reservoir and canal waters from the U-Tapao River Basin, Songkhla, Thailand was investigated. Water samples were collected three times from two reservoirs, upstream, midstream, and downstream of the U-Tapao canal. The HPO was the major dissolved organic matter (DOM) fraction in reservoir and canal waters. On average, the HPO accounted for 53 and 45% of the DOM in reservoir and canal waters, respectively. The TPI of 19 and 23% in reservoir and canal waters were determined, respectively. The HPI of 29% of the reservoir water and HPI of 32% of the canal water were detected. For the reservoir water, the highest trihalomethane formation potential (THMFP)/dissolved organic carbon (DOC) was determined for the HPI, followed by the TPI and HPO, respectively. The average values of the THMFP/DOC of the HPI, TPI, and HPO of the reservoir water were 78, 52, and 49 µg THMs/mg C, respectively. The highest THMFP/DOC of the canal water was detected for the HPI, followed by HPO and TPI, respectively. Average values of the THMFP/DOC of HPI of water at upstream and midstream locations of 58 µg THMs/mg C and downstream location of 113 µg THMs/mg C were determined. Average values of THMFP/DOC of HPO of water at upstream and midstream and downstream locations were 48 and 93 µg THMs/mg C, respectively. For the lowest THMFP/DOC fraction, the average values of THMFP/DOC of TPI of water at upstream and midstream and downstream locations were 35 and 73 µg THMs/mg C, respectively.

Selective adsorption mechanisms of antilipidemic and non-steroidal anti-inflammatory drug residues on functionalized silica-based porous materials in a mixed solute

The selective adsorption mechanisms of naproxen (NAP), acetaminophen (ACT), and clofibric acid (CFA) on silica-based porous materials were examined by single and mixed-batch adsorption. Effects of the types and densities of surface functional groups on adsorption capacities were determined, including the role of hydrophobic and hydrophilic dissolved organic matters (DOMs). Hexagonal mesoporous silica (HMS), superparamagnetic HMS (HMS-SP) and SBA-15 were functionalized and applied as adsorbents. Compared with powdered activated carbon (PAC), amine-functionalized HMS had a better adsorption capacity for CFA, but PAC possessed a higher adsorption capacity for the other pharmaceuticals than HMS and its two derivatives. In contrast to PAC, the adsorption capacity of the mesoporous silicas varied with the solution pH, being highest at pH 5. Electrostatic interactions and hydrogen bonding were found to be the main mechanisms. Increase in grafted amine group density on silica surfaces can enhance the CFA adsorption capacity. Further, hydrophilic DOM can decrease CFA adsorption capacities on amino-grafted adsorbents by adsorption site competition, while hydrophobic DOM can interfere with CFA adsorption by the interaction between hydrophobic DOM and CFA. Finally, in a competitive adsorption study, the adsorption capacity of hydrophilic adsorbents for acidic pharmaceuticals varied with their pKa values.

Reduction of DOM fractions and their trihalomethane formation potential in surface river water by in-line coagulation with ceramic membrane filtration

This research was aimed at investigating the reduction of DOM fractions and their trihalomethane formation potential (THMFP) by in-line coagulation with 0.1 μm ceramic membrane filtration. The combination of ceramic membrane filtration with a coagulation process is an alternative technology which can be applied to enhance conventional coagulation processes in the field of water treatment and drinking water production. The Ping River water (high turbidity water) was selected as the raw surface water because it is currently the main raw water source for water supply production in the urban and rural areas of Chiang Mai Province. From the investigation, the results showed that the highest percent reductions of DOC, UV-254, and THMFP (47.6%, 71.0%, and 67.4%, respectively) were achieved from in-line coagulation with ceramic membrane filtration at polyaluminum chloride dosage 40 mg/L. Resin adsorption techniques were employed to characterize the DOM in raw surface water and filtered water. The results showed that the use of a ceramic membrane with in-line coagulation was able to most efficiently reduce the hydrophobic fraction (HPOA) (68.5%), which was then followed by the hydrophilic fraction (HPIA) (49.3%). The greater mass DOC reduction of these two fractions provided the highest THMFP reductions (55.1% and 37.2%, respectively). Furthermore, the in-line coagulation with ceramic membrane filtration was able to reduce the hydrophobic (HPOB) fraction which is characterized by high reactivity toward THM formation. The percent reduction of mass DOC and THMFP of HPOB by in-line coagulation with ceramic membrane filtration was 45.9% and 48.0%, respectively.

The role of nitrobenzene on the yield of trihalomethane formation potential in aqueous solutions with Microcystis aeruginosa

Algae are one of the most important disinfection by-product (DBP) precursors in aquatic environments. The contents of DBP precursors in algae are influenced by not only environmental factors but also some xenobiotics. Trihalomethane formation potential (THMFP) in both the separate and interactive pollution of Microcystis aeruginosa and Nitrobenzene (NB) was investigated in batch experiment to discover the effects of xenobiotics on the yield of DBP precursors in the algal solution. The results show that in the separate NB solution, NB did not react with Cl(2) to form trihalomethane (THM), whereas in the algae solution, THMFP had a significant positive linear correlation with M. aeruginosa density in both solution and extracellular organic matter (EOM). The correlation coefficients were 0.9845 (p = 3.567 × 10(-4)) and 0.9854 (p = 1.406 × 10(-4)), respectively. According to regression results, about 77.9% of the total THMFP came from the algal cells, while the rest came from EOM. When the interactive pollution of M. aeruginosa and NB occurred, the growth of algae was inhibited by NB. The density of M. aeruginosa in a high concentration NB solution (280 μg/L) was only 71.1% of that in the solution without NB after 5 days of incubation. However, THMFP in the mixture (algae and NB) and the EOM did not change significantly, and the productivity of THMFP by the algae (THMFP/10(8)cells) increased with the increase in NB concentration. There was a significant linear correlation between THMFP/10(8)cell and NB concentration (r = 0.9117, p < 0.01), which shows the contribution of the algae to THM formation was enhanced by NB. This result might be caused by the increased protein productivity and the biodegradation of NB by M. aeruginosa.

Isolation and characterization of a novel haloacid permease from Burkholderia cepacia MBA4

Burkholderia cepacia MBA4 is a bacterium that can utilize 2-haloacids as carbon and energy sources for growth. It has been proposed that dehalogenase-associated permease mediates the uptake of haloacid. In this paper, we report the first cloning and characterization of such a haloacid permease. The structural gene, designated deh4p, was found 353 bases downstream of the dehalogenase gene deh4a. Quantitative analysis of the expression of deh4p showed that it was induced by monochloroacetate (MCA), to a level similar to the MCA-induced level of deh4a. The nucleotide sequence of deh4p was determined, and an open reading frame of 1,656 bp encoding a putative peptide of 552 amino acids was identified. Deh4p has a putative molecular weight of 59,414 and an isoelectric point of 9.88. Deh4p has the signatures of sugar transport proteins and integral membrane proteins of the major facilitator superfamily. Uptake of [(14)C]MCA into the cell was Deh4p dependent. Deh4p has apparent K(m)s of 5.5 and 8.9 muM and V(max)s of 9.1 and 23.1 nmol mg(-1) min(-1) for acetate and MCA, respectively. A mutant with a transposon-inactivated haloacid operon failed to grow on MCA even when deh4a was provided in trans.