Control for chlorine resistant spore forming bacteria by the coupling of pre-oxidation and coagulation sedimentation, and UV-AOPs enhanced inactivation in drinking water treatment.

Spore forming bacteria (SFB) are strongly chlorine resistant. Their presence in drinking water may cause diseases and pose threat to public health. Three SFB strains, i.e. Bacillus alvei, Bacillus cereus, and Lysinibacillus fusiformis, were isolated and identified from the finished water of a drinking water treatment plant where bacteria colonies occasionally reached the limit value. Due to their chlorine resistance, a SFB control strategy coupling pre-oxidation, coagulation sedimentation, and UV-AOPs inactivation in water treatment process was studied in lab scale. Five minutes pre-oxidation treatment by applying Cl2 and ClO2 induced remarkable spore transformation. Longer pre-oxidation exposure time didn't have apparent improvement. Cl2 and ClO2 dosages of 0.9 mg/L and 0.5 mg/L were suggested, respectively. The formed spores can be efficiently removed by the following coagulation sedimentation treatment. At a suggested dosage combination of 20 mg/L PAC and 0.08 mg/L PAM, spore removal efficiency reached about 3.15-lg. Comparing to applying sole UV irradiation, enhanced UV inactivation by adding 0.1 mM H2O2, or Cl2, or peroxymonosulfate (PMS) substantially improved the inactivation of the most chlorine resistant SFB strain, Lysinibacillus fusiformis. UV-AOPs stably achieved 2-lg inactivation rate at UV dosage of 40 mJ/cm2. UV/H2O2, UV/Cl2 and UV/PMS inactivation kinetically enhanced 1.20 times, 1.36 times and 1.91 times over sole UV irradiation. Intracellular DNA and ATP leakages were detected, and remarkable damages of Lysinibacillus fusiformis cells' surface and ultrastructure were observed. These findings evidenced cell wall and cell membrane destructions, guaranteeing substantial SFB cells inactivation. This study was carried out based on three SFB strains isolated from a finished water, and common engineering practical operations. By providing engineeringly relevant references, the outcomes obtained would be helpful for dealing with SFB outbreak risk in drinking water treatment.

Nonradical oxidation from electrochemical activation of peroxydisulfate at Ti/Pt anode: Efficiency, mechanism and influencing factors.

Electrochemical activation of peroxydisulfate (PDS) at Ti/Pt anode was systematically investigated for the first time in this work. The synergistic effect produced from the combination of electrolysis and the addition of PDS demonstrates that PDS can be activated at Ti/Pt anode. The selective oxidation towards carbamazepine (CBZ), sulfamethoxazole (SMX), propranolol (PPL), benzoic acid (BA) rather than atrazine (ATZ) and nitrobenzene (NB) was observed in electrochemical activation of PDS process. Moreover, addition of excess methanol or tert-butanol had negligible impact on CBZ (model compound) degradation, demonstrating that neither sulfate radical (SO4-) nor hydroxyl radical (HO) was produced in electrochemical activation of PDS process. Direct oxidation (PDS oxidation alone and electrolysis) and nonradical oxidation were responsible for the degradation of contaminants. The results of linear sweep voltammetry (LSV) and chronoamperometry suggest that electric discharge may integrate PDS molecule with anode surface into a unique transition state structure, which is responsible for the nonradical oxidation in electrochemical activation of PDS process. Adjustment of the solution pH from 1.0 to 7.0 had negligible effect on CBZ degradation. Increase of either PDS concentration or current density facilitated the degradation of CBZ. The presence of chloride ion (Cl-) significantly enhanced CBZ degradation, while addition of bicarbonate (HCO3-), phosphate (PO43-) and humic acid (HA) all inhibited CBZ degradation with the order of HA >> HCO3- > PO43-. The degradation products of CBZ and chlorinated products were also identified. Electrochemical activation of PDS at Ti/Pt anode may serve as a novel technology for selective oxidation of organic contaminants in water and soil.

[Concentration Variation and Removal of Amino Acids in Typical Drinking Sources in the South of China].

Amino acids are the main components of nitrogenous organic matter in surface water. In order to reveal the concentration variation and removal of amino acids in reservoirs water, the concentration variation of the twenty common amino acids for three main reservoirs' water in a typical southern city of China was monitored between May and October in the year of 2015 by HPLC, and the space distribution and change trend of the twenty amino acids were analyzed. In addition, the removal of the twenty amino acids was also studied by different water treatment processes. The results showed that the amino acids contents and composition were different among the three reservoirs. Aspartic acid, cysteine and leucine were the main amino acids for the three reservoirs. Besides, there was no obvious seasonal variation of amino acids content for reservoir C. However, the concentration of amino acids in autumn was higher than that in summer. Coagulation and sedimentation were main units for the removal of amino acids in conventional and BAC-UF processes while O3 oxidation was the main unit in O3-BAC process. 94.42%, 66.04% and 49.75% of total amino acids contents were removed by the conventional, BAC-UF and O3-BAC processes, respectively.

[Influence of Chemical Pre-oxidation on Chloral Hydrate Formation of Threonine].

The influences of different chemical pre-oxidants, including sodium hypochlorite (NaClO), chlorine dioxide (ClO2), permanganate (KMnO4), hydrogen peroxide (H2O2), ozone (O3) and ozone/hydrogen peroxide (O3/H2O2), on chloral hydrate (CH) formation were studied for threonine that has the highest special chloral hydrate formation potential (SCHFP). Suitable pre-oxidants and corresponding optimal doses were determined to provide guidance for controlling chloral hydrate (CH) formation during drinking water treatment. The results indicated that the pre-oxidants that could decrease CH formation for one day incubation time (CH1d) were H2O2, ClO2, KMnO4 and NaClO, and the corresponding suitable doses were 3, 0.5, 0.6 and 0.5 mg·L-1, and the corresponding CH1d removal rates were 61.54%, 47.63%, 29.77% and 10.94%, respectively. The pre-oxidants that could decrease CH formation potential (CHFP) were KMnO4, NaClO, H2O2 and ClO2, and the corresponding suitable doses were 0.6 mg·L-1, 0.5 mg·L-1, 3 mg·L-1 and 0.5 mg·L-1, and the corresponding CHFP removal rates were 41.01%, 33.38%, 8.36% and 2.40%, respectively. In addition, O3 and O3/H2O2 were not suitable for controlling CH in the conventional treatment process because they could increase CH1d and CHFP.