Characterization of typical taste and odor compounds formed by Microcystis aeruginosa

Production and characteristics of typical taste and odor (T&O) compounds by Microcystis aeruginosa were investigated. A few terpenoid chemicals, including 2-MIB, β-cyclocitral, and β-ionone, and a few sulfur compounds, such as dimethyl sulfide and dimethyl trisulfide, were detected. β-Cyclocitral and β-carotene concentrations were observed to be relevant to the growth phases of Microcystis. During the stable growth phase, 41-865 fg/cell of β-cyclocitral were found in the laboratory culture. β-Cyclocitral concentrations correlated closely with β-carotene concentrations, with the correlation coefficient R2 = 0.96, as it is formed from the cleavage reaction of β-carotene. For dead cell cases, a high concentration of dimethyl trisulfide was detected at 3.48-6.37 fg/cell. Four T&O compounds, including β-cyclocitral, β-ionone, heptanal and dimethyl trisulfide, were tested and found to be able to inhibit and damage Microcystis cells to varying degrees. Among these chemicals, β-cyclocitral has the strongest ability to quickly rupture cells.     

Removal of antibiotic-resistant genes during drinking water treatment: A review

Once contaminate the drinking water source, antibiotic resistance genes (ARGs) will propagate in drinking water systems and pose a serious risk to human health. Therefore, the drinking water treatment processes (DWTPs) are critical to manage the risks posed by ARGs. This study summarizes the prevalence of ARGs in raw water sources and treated drinking water worldwide. In addition, the removal efficiency of ARGs and related mechanisms by different DWTPs are reviewed. Abiotic and biotic factors that affect ARGs elimination are also discussed. The data on presence of ARGs in drinking water help come to the conclusion that ARGs pollution is prevalent and deserves a high priority. Generally, DWTPs indeed achieve ARGs removal, but some biological treatment processes such as biological activated carbon filtration may promote antibiotic resistance due to the enrichment of ARGs in the biofilm. The finding that disinfection and membrane filtration are superior to other DWTPs adds weight to the advice that DWTPs should adopt multiple disinfection barriers, as well as keep sufficient chlorine residuals to inhibit re-growth of ARGs during subsequent distribution. Mechanistically, DWTPs obtain direct and inderect ARGs reduction through DNA damage and interception of host bacterias of ARGs. Thus, escaping of intracellular ARGs to extracellular environment, induced by DWTPs, should be advoided. This review provides the theoretical support for developping efficient reduction technologies of ARGs. Future study should focus on ARGs controlling in terms of transmissibility or persistence through DWTPs due to their biological related nature and ubiquitous presence of biofilm in the treatment unit.     

Degradation of sulfonamides and formation of trihalomethanes by chlorination after pre-oxidation with Fe(Ⅵ)

Sulfonamides are used in human therapy,animal husbandry and agriculture but are not easily biodegradable,and are often detected in surface water.Sulfamethazine(SMZ) and sulfadiazine(SDZ) are two widely used sulfonamide antibiotics that are used heavily in agriculture.In this study,they were degraded in an aqueous system by chlorination after pre-oxidation with ferrate(VI)(FeVIO42-,Fe(VI)),an environmentally friendly oxidation technique that has been shown to be effective in degrading various organics.The kinetics of the degradation were determined as a function of Fe(VI)(0–1.5 mg/L),free chlorine(0–1.8 mg/L) and temperature(15–35°C).According to the experimental results,SMZ chlorination followed second-order kinetics with increasing Fe(VI) dosage,and the effect of the initial free chlorine concentration on the reaction kinetics with pre-oxidation by Fe(VI) fitted a pseudo-first order model.The rate constants of SDZ and SMZ chlorination at different temperatures were related to the Arrhenius equation.Fe(VI) could reduce the levels of THMs formed and the toxicity of the sulfonamide degradation systems with Fe(VI) doses of 0.5–1.5 mg/L,which provides a reference for ensuring water quality in drinking water systems.     

Total and settling velocity-fractionated pollution potential of sewer sediments in Jiaxing,China

Environmental Science and Pollution Research - Sewer sediments and their associated contaminant released along with wet-weather discharges pose potential pollution risks to environment. This paper...     

Comparison of UV/PDS and UV/H2O2 processes for the degradation of atenolol in water

UV/H2O2 and UV/peroxodisulfate (PDS) processes were adopted to degrade a typical β-blocker atenolol (ATL). The degradation efficiencies under various operational parameters (oxidant dosage, pH, HCO3-, humic acid (HA), NO3- , and Cl-) were compared. Principal factor analysis was also performed with a statistical method for the two processes. It was found that increasing the specific dosage of the two peroxides ([peroxide]0/[ATL]0 ) ranging from 1:1 to 8:1 led to a faster degradation rate but also higher peroxide residual. Within the pH range 3-11, the optimum pH was 7 for the UV/PDS process and elevating pH benefitted the UV/H 2O2 process. The presence of HCO3- , HA, and Cl adversely affected ATL oxidation in both processes. The NO3- concentration 1-3 mmol/L accelerated the destruction of ATL by the UV/PDS process, but further increase of NO3- concentration retarded the degradation process, contrary to the case in the UV/H2O2 process. The rank orders of effects caused by the six operational parameters were pH ≈ specific dosage > [HA]0 > [NO3-]0 > [HCO3-]0 > [Cl-]0 for the UV/H2O2 process and specific dosage > pH > [HA]0 > [NO3-]0 > [HCO3-]0 >[Cl-]0 for the UV/PDS process. The UV/PDS process was more sensitive to changes in operational parameters than the UV/H2O2 process but more efficient in ATL removal under the same conditions.     

Degradation of sulfonamides and formation of trihalomethanes by chlorination after pre-oxidation with Fe(VI)

Sulfonamides are used in human therapy, animal husbandry and agriculture but are not easily biodegradable, and are often detected in surface water. Sulfamethazine (SMZ) and sulfadiazine (SDZ) are two widely used sulfonamide antibiotics that are used heavily in agriculture. In this study, they were degraded in an aqueous system by chlorination after pre-oxidation with ferrate(VI) (Fe^VIO₄^2 ?, Fe(VI)), an environmentally friendly oxidation technique that has been shown to be effective in degrading various organics. The kinetics of the degradation were determined as a function of Fe(VI) (0–1.5 mg/L), free chlorine (0–1.8 mg/L) and temperature (15–35°C). According to the experimental results, SMZ chlorination followed second-order kinetics with increasing Fe(VI) dosage, and the effect of the initial free chlorine concentration on the reaction kinetics with pre-oxidation by Fe(VI) fitted a pseudo-first order model. The rate constants of SDZ and SMZ chlorination at different temperatures were related to the Arrhenius equation. Fe(VI) could reduce the levels of THMs formed and the toxicity of the sulfonamide degradation systems with Fe(VI) doses of 0.5–1.5 mg/L, which provides a reference for ensuring water quality in drinking water systems.     

Bacterial community structure and microorganism inactivation following water treatment with ferrate(VI) or chlorine

Drinking water disinfection plays a critical role in protecting humans from waterborne pathogens. Ferrate(VI) (Fe^VIO₄ ^2?) has also been proposed as a disinfectant. This is the first study investigating the bacterial microbiomes of ferrate(VI)-treated water compared to chlorinated water. Tested water was collected after sand filtration and before disinfection from a drinking water treatment plant at Jiaxing, Zhejiang Province, China. A culture-independent method utilizing propidium monoazide was used with quantitative polymerase chain reaction and pyrosequencing of 16S rRNA genes to distinguish between the viable and nonviable bacterial populations. The operational taxonomic units and α-diversity indexes of the live bacterial phylotypes in the samples were determined. Viable bacteria remained in all samples following chlorination or ferrate treatment. However, the genera Vibrio, Salmonella, Shigella, Escherichia, Campylobacter, Yersinia, Plesiomonas, Legionella, and Helicobacter, which contain important human pathogens, were not present among the 25 dominant genera seen in these samples. The profiles of the bacteria remaining after treatment with either chlorine or ferrate differed. The ferrate-treated samples showed a reduced percent relative abundance of operational taxonomic units of the class Alphaproteobacteria within the total remaining viable bacteria. The genera Flavobacterium and Duganella were relatively resistant to treatment by either chlorine or ferrate(VI). At the highest doses of chlorine and ferrate(VI), the genus Sphingobium represented a greater percentage of live bacteria in the chlorinated sample than in the ferrate(VI)-treated sample. The results suggest that ferrate(VI) and chlorine could inactivate slightly different sets of bacteria and could have different mechanisms of bacterial inactivation.