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1.
In this study, chlorine dioxide (ClO(2)) was used as an alternative disinfection agent with humic acid as the organic precursor in a natural aquatic environment. The major topics in this investigation consisted of the disinfection efficiency of ClO(2), the formation of disinfection by-products (DBPs), and the operating conditions. The results indicated that the pH value (pH 5-9) did not affect the efficiency of disinfection while the concentration of organic precursors did. The primary DBPs formed were trihalomethanes (THMs) and haloacetic acids (HAAs). The distribution of the individual species was a function of the bromide content. The higher the ClO(2) dosage, the lower the amount of DBPs produced. The amount of DBPs increased with reaction time, with chlorite ions as the primary inorganic by-product. 相似文献
2.
Antoniadis A Poulios I Nikolakaki E Mantzavinos D 《Journal of hazardous materials》2007,146(3):492-495
The application of high intensity, low frequency ultrasound for the disinfection of simulated and septic tank wastewaters is evaluated in this work. Laboratory scale experiments were conducted at 24 and 80kHz ultrasound frequency with horn-type sonicators capable of operating in continuous and pulsed irradiation modes at nominal ultrasound intensities up to 450W. For the experiments with simulated wastewaters, Escherichia coli were used as biological indicator of disinfection efficiency, while for the experiments with septic tank wastewaters, the total microbiological load was used. Complete elimination of E. coli could be achieved within 20-30min of irradiation at 24kHz and 450W with the efficiency decreasing with decreasing intensity and frequency. Moreover, continuous irradiation was more effective than intermittent treatment based on a common energy input. Irradiation of the septic tank effluent prior to biological treatment at 24kHz and 450W for 30min resulted in a three-log total microbiological load reduction, and this was nearly equal to the reduction that could be achieved during biological treatment. Bacterial cell elimination upon irradiation was irreversible as no reappearance of the microorganisms occurred after 24h. 相似文献
3.
Tapas K. Das 《Clean Technologies and Environmental Policy》2002,4(1):32-43
With increasing emphasis on promoting a sustainable ecological future and concern over introducing a toxic chemical in the
water, the design of the disinfection process is increasingly leaning toward technologies that destroy the pathogens while
balancing the effects of this disinfected wastewater on the population of aquatic biota or a drinking water supply. Since
ultraviolet (UV) irradiation is not a chemical additive, it does not leave or produce any by-product toxic compounds in the
wastewater, like traditional chlorination and de-chlorination processes do. Therefore, the use of UV does not affect a drinking
water supply or the aquatic biota in receiving waters.
Life cycle assessment or analysis (LCA) is used to quantify the environmental benefits of using UV disinfection technology
(as well as better protecting public health), instead of chlorination and de-chlorination methods. LCA tools are being used
to evaluate the short and long term environmental effects of both processes, and to select the best sustainable process. The
approach here combines environmental LCA with these disinfection processes incorporating economic criteria and all aspects
of the environment: chemical use, electricity use, and releases to water, air, and land. The environmental, health, and economic
benefits and other effects show the greater sustainability of UV technology (a "clean" ecological disinfection process) in
comparison to that of traditional disinfection with chlorine.
Electronic Publication 相似文献
4.
Relationship of chlorine decay and THMs formation to NOM size 总被引:5,自引:0,他引:5
Because of increasing concern about balancing health risks for pathogen control and disinfection by-product (DBP) formation in water supplies, utilities are forced to closely examine and optimize their disinfection practices. A better understanding of the relationship between the molecular weights of the natural organic matter (NOM), chlorine decay kinetics and THMs formation can help the utilities to minimize the DBP concentrations, providing healthier and microbially safer water. The authors present data on chlorine decay kinetics and total trihalomethanes (TTHM) formation kinetics and modeling with different molecular weights NOM fractions of Mississippi River water. TTHM modeling results indicated that the TTHM formation in fractionated NOM was a function of chlorine consumption. TTHM yield coefficients ranged from 31 to 42 microg-TTHM/mg-Cl2. As the molecular weight of the fractions decreased, TTHM yield coefficients increased. 相似文献
5.
River water sample was collected from Guangzhou section of the Pearl River to investigate soluble organic fractions and formation of trihalomethane (THMs) after chlorine and chlorine dioxide treatments. The water sample was passed through Amicon YC-05, YM-1, YM-3, YM-10, YM-30, YM-100 and ZM-500 series membranes after a pre-treatment. The molecular weight distribution and the specific ultra-violet absorbance (SUVA(254)) of each fraction obtained from membrane were analyzed, and these fractions were further disinfected with chlorine and chlorine dioxide. The results showed that reverse osmosis (RO) fraction contained mainly dissolved organic matter (DOM) from the water sample, suggesting that the water has been highly contaminated by anthropogenic activities. Meanwhile, the THMs concentration and SUVA(254) increased gradually as the molecular weight of the obtained fractions reduced, indicating that the low molecular weight DOM was the major THMs precursor in the disinfection process with chlorine and chlorine dioxide. The results suggest that THMs in source water of Pearl River could be effectively reduced when pollution of human activity is greatly controlled. Between the two disinfection processes tested, chlorine dioxide produced less THMs than chlorine in this study. 相似文献
6.
The effects of combined ultraviolet (UV) and chlorine disinfection on corrosion and water quality were assessed in a model reclaimed water distribution system (RWDS) using annular reactors (ARs). UV irradiation not only enhanced the inactivation of heterotrophic bacteria, but also reduced the required initial chlorine dose. Moreover, UV pretreatment induced less changes of corrosion products composition and decreased iron release and turbidity of effluents resulted from Larson–Skold Index (Li) of reclaimed water changing, enhancing the stability of water quality through RWDS. The corrosion bacteria within the biofilm on the corrosion scales could grow selectively with different disinfection processes. In the AR with combined UV and chlorine treatment, the iron-oxidizing bacterium (IOB) Acidovorax defluvii and the iron-reducing bacteria (IRB) uncultured Rhodoferax sp. and uncultured Geobacter sp. appeared on the biofilm. In contrast, in the AR treated with chlorine alone, the IOB Sediminibacterium salmoneum and the IRB uncultured Geobacter sp. were predominant in the biofilm. In the latter, S. salmoneum respiration predominantly contributed to the oxidization of Fe(II), whereas in the former, either Fe(II) or acetate acted as a donor for A. defluvii respiration, causing an increased depletion of oxygen by the oxidation of Fe(II). Therefore, under the former conditions, the composition of corrosion bacteria could result in lower corrosion rate, decreasing the effect of Li changes on iron release. All results indicated that UV irradiation enhanced water quality stability in the RWDS. 相似文献
7.
This paper reports the positive effects of chlorine ion on the forsterite formation rate. The influence of mechanical activation of talc and magnesium carbonate mixture on the formation of forsterite structure was studied in the presence of chlorine ion. Mechanical activation increased the contact surface area of the reacting phases as a consequence of intensively reduced particle size, which is very important in the case of diffusion-controlled reactions. Besides, the presence of chlorine ion affected the forsterite formation rate following annealing. The single-phase nanostructure forsterite powder with a crystallite size of about 20 nm was obtained by 5 h of mechanical activation and subsequent annealing at 1000 °C for 2 min in the presence of the chlorine ion. 相似文献
8.
Oxidation of various reactive dyes with in situ electro-generated active chlorine for textile dyeing industry wastewater treatment 总被引:1,自引:0,他引:1
The present investigation revealed that all the reactive dyes were degraded in chlorine mediated electrochemical oxidation. Titanium based dimensionally stable anode (DSA) was used for in situ generation of chlorine in the dye solution. All classes of reactive dyes (100 mg/L) showed a complete color removal at a supporting electrolyte concentration of 1.5 g/L NaCl and 36.1 mA/cm(2) current density. The chemical oxygen demand (COD) and total organic carbon (TOC) removals were from 39.5 to 82.8% and from 11.3 to 44.7%, respectively, for different reactive dyes. It can be concluded in general that the triazine containing higher molecular weight diazo compounds takes more time for complete de-colorization than the mono azo or anthraquinone containing dye compounds. The degradation rate of mixed dye compounds was affected by reaction temperature, current density, NaCl concentration and initial dye concentration. However, the initial pH of the dye solution ranging from 4.3 to 9.4 did not show significant effect on de-colorization. A complete color removal with 73.5% COD and 32.8% TOC removals were obtained for mixed reactive dyes (200 mg/L) at the end of 120 min of electrolysis under the optimum operating conditions of 4 g/L NaCl concentration and 72.2 mA/cm(2) current density. 相似文献
9.
2-Chlorophenol (2-CP) degrading aerobic granules were cultivated in a sequencing batch reactor (SBR) in presence of glucose. The organic loading rate (OLR) was increased from 6.9 to 9.7 kg COD m(-3)d(-1) (1150-1617 mg L(-1)COD per cycle) during the experiment. The alkalinity (1000 mg L(-1) as CaCO(3)) was maintained throughout the experiment. The specific cell growth rate was found to be 0.013 d(-1). A COD removal efficiency of 94% was achieved after steady state at 8h HRT (hydraulic retention time). FTIR, UV, GC, GC/MS studies confirmed that the biodegradation of 2-CP occurs via chlorocatechol (modified ortho-cleavage) pathway. Biodegradation kinetics followed the Haldane model with kinetic parameters: V(max)=840 mg2-CPgMLVSS(-1)d(-1), K(s)=24.61 mg L(-1), K(i)=315.02 mg L(-1). Abiotic losses of 2-CP due to volatilization and photo degradation by sunlight were less than 3% and the results of genotoxicity showed that the degradation products are eco-friendly. 相似文献
10.
Dissolved natural organic matter (DOM) in a filtered river water was isolated and fractionated into six different fractions. Trihalomethanes (THMs) and haloacetic acids (HAAs) formed from these isolated DOM fractions during chlorination and chloramination were determined. Results show that the hydrophobic acid, hydrophilic acid, hydrophilic base and hydrophobic neutral are major precursors of THMs and HAAs. There exist good correlations between the values of specific ultraviolet absorbance at 254nm of the individual DOM fractions and their disinfection by-products formation potential, indicating that aromatic moieties are responsible for disinfection by-products formation for both hydrophobic and hydrophilic DOM fractions. Chloramination of the DOM fractions yields much less THMs and HAAs than chlorination. For the dominant DOM fraction (i.e. hydrophobic acid) in the water, the yields of THMs and HAAs increase more significantly in chlorination than those in chloramination with the increase of disinfectant dosage, contact time and dissolved organic carbon content. 相似文献
11.
This study investigated the possibility of a statistical model application for the prediction of N-nitrosodimethylamine (NDMA) formation. The NDMA formation was studied as a function of monochloramine concentration (0.001-5mM) at fixed dimethylamine (DMA) concentrations of 0.01mM or 0.05mM. Excellent linear correlations were observed between the molar ratio of monochloramine to DMA and the NDMA formation on a log scale at pH 7 and 8. When a developed prediction equation was applied to a previously reported study, a good result was obtained. The statistical model appears to predict adequately NDMA concentrations if other NDMA precursors are excluded. Using the predictive tool, a simple and approximate calculation of NDMA formation can be obtained in drinking water systems. 相似文献
12.
The information available on the lethal toxicity of chlorine to animals and man has been reviewed in a previous paper. In the present paper this information is used to derive a revised estimate for the lethal toxicity to man. A distinction is made between less vulnerable and more vulnerable populations and between different levels of physical activity, with a standard level defined which is applicable to most daytime activity. Mortality is expressed in terms of a lethal toxic load which is a function of concentration and time. The concentrations lethal at the 50% level for a 10 min exposure with standard level of activity are estimated as 433, 173 and 364 ppm for the regular, vulnerable and average population, respectively, and those for a 30 min exposure as 250, 100 and 210, respectively. The probit equation derived for the regular population at the standard level of activity is Y = ?8.29 + 0.92 ln L* with L* = Σ C2T where C is concentration (ppm), L* toxic load (ppm2 min), T time (min) and Y the probit. A methodology for the application of the toxicity relationships in hazard assessment is given.
The symbols used are as in Reference [1] plus | |
k | constant |
Pa | probability of acute death |
ψ1 | inhalation rate factor |
ψ2 | medical treatment factor |