二氧化氯应用影响因素研究

通过试验研究了不同水质因素对二氧化氯消毒的影响,着重考虑好氧量(CODMn)的作用,研究结果表明,CODMn值的变化对二氧化氯消毒有较大影响,二氧化氯对CODMn的去除率随着CODMn的减少而减小,当CODMn<4 mg/L时,几乎没有去除效果。     

Study on chlorine disinfection of pond effluent

Chlorine disinfection experiments were conducted to investigate the die-off patterns of the fecal coliforms when present in waste stabilization pond effluents containing from 100 to 400 mg l⁻¹ algae. The fecal coliform inactivation was observed to occur at two rates, i.e. an initial rapid kill followed by a slower kill. The magnitude of inactivation was found to be proportional to the initial chlorine dose and contact time and inversely proportional to the algal concentration. A mathematical model was developed to predict the fecal coliform survival ratio during the chlorination of the pond effluent. When compared with the experimental data, the predicted results had a correlation coefficient of 0.981.     

Comparative disinfection of treated sewage with chlorine and ozone: Effect of nitrification

Chlorine and ozone were compared in pilot plants (capacity about 3.2 m³ h⁻¹), which were fed with the same activated sludge treated and filtered water. Together with physico-chemical analysis the water was analysed for different types of microorganisms, including vegetative bacteria (total and thermotolerant coliforms, faecal streptococci and Pseudomonas aeruginosa), bacterial spores (spores of aerobic bacteria at 37°C and sulphite reducing clostridia) and bacterial viruses (somatic coliphages and F-specific bacteriophages).The average chlorine and ozone dose were, respectively, 3.65 and 15.3 mg l⁻¹ of water, while after a contact time for both of about 25 min the average residual concentrations were 1.79 and 0.35 mg l⁻¹ of water. These residuals were measured with the DPD-method. The ammonia-N concentration varied greatly (0.06–72.0 mg l⁻¹) and was used to group the data into four classes: (1) non-nitrified water, defined as water in which nitrate-N was smaller than ammonia-N; (2) moderately nitrified water, in which nitrate-N was larger than ammonia-N and the ammonia-N was higher than 2 mg l⁻¹; (3) well nitrified water, defined as water in which ammonia-N was lower than 2 mg l⁻¹; (4) very well nitrified water, in which ammonia-N was smaller than 0.5 mg l⁻¹.This classification indicated that the concentrations of most other impurities decreased with a better nitrification. Statistical analysis of the data showed also that ozone was a better disinfectant than chlorine in the case where the disinfection is based upon their residual content. The degree of nitrification had a greater effect on chlorine disinfection than on ozone disinfection.During chlorination the total residual chlorine decreased, with better nitrification; the chlorine demand increased; the composition of the residual chlorine changed very much and the inactivation of bacterial viruses improved. The vegetative bacteria showed a varying pattern; most were inactivated in moderately nitrified water, when the dichloramine concentration was highest and false positive FAC concentration was lowest of the four classes. Reduction of bacterial spores was not observed.During ozonization other effects were indicated. Reductions of most organims increased slightly with better nitrification; only reductions of F-specific bacteriophages decreased. There was also a small decrease of bacterial spores. The treated effluent had a high ozone consumption and the inactivation of the organisms was low in relation to ozone dose and residual ozone.The bromide concentration (0.3–2.9 mg l⁻¹) effected the chemistry of chlorine and ozone and had a positive effect on chlorine and ozone disinfection of total coliforms.For most types of micoorganisms the disinfection coefficients of the Selleck model and the germicidal efficiencies could be determined.     

二氧化氯消毒效果影响因素试验研究

通过对比实验,考察了二氧化氯、液氯和氯胺三种常用消毒剂对肠道菌的灭活效果,以及pH、温度、培养基稀释倍数等因素对二氧化氯消毒效果的影响.试验结果表明,二氧化氯消毒剂具有高效性和广谱性;pH值在6.0～9.0内变化,二氧化氯的消毒效果几乎不受影响;温度的升高会加强二氧化氯的灭菌效果;随着培养基稀释倍数的增加,粪肠球菌对二...     

Mechanism of disinfection

Certain biochemical aspects of mechanism of disinfection are discussed in the paper. The total dehydrogenase activity of intact E. coli cells is affected by chlorine dose and this correlates with per cent survivals. The succinic dehydrogenase activity in the crude extract of E. coli is affected by chlorine within the bactericidal concentrations. The dose required for inhibition of above enzyme is less than that for intact cells. To deliniate the mechanism of inhibition of succinic dehydrogenase, the effect of chlorine on thiol groups present in crude extract is studied. After chlorine exposure there is a reduction in thiol groups indicating the thiol groups to be vulnerable to the oxidising influence of chlorine. The inhibition of succinic dehydrogenase induced due to lower doses of chlorine can significantly be reversed with reduced glutathione. The ATP-ase which is localised in cytoplasmic membrane of cell, like succinic dehydrogenase, is not affected to any degree by chlorine in bactericidal concentrations. The catalase activity of E. coli is not affected.     

Inactivation of norovirus by chlorine disinfection of water

In an effort to validate previous research suggesting remarkable resistance of norovirus to free chlorine disinfection, we characterized the disinfection response of purified and dispersed Norwalk virus (NV) by bench-scale free chlorine disinfection using RT-PCR for virus assays. The inactivation of NV by two doses of free chlorine (1 and 5 mg/L) at pH 6 and 5 °C based on two RT-PCR assays was similar to that of coliphage MS2, but much faster than that of poliovirus 1. Despite the underestimation of virus inactivation by RT-PCR assays, the predicted CT values for NV based on RT-PCR assays are lower than the ones for most other important waterborne viruses and the CT guidelines for chlorine disinfection of viruses under the Surface Water Treatment Rule by the United States Environmental Protection Agency. Overall, the results of this study indicate that NV is not highly resistant to free chlorine disinfection as suggested by previous research and it is likely that NV contamination of drinking water can be controlled by adequate free chlorine disinfection practices with provision of proper pre-treatment processes before chlorination.     

Removal of chlorine dioxide disinfection by-products by ferrous salts

Chlorine dioxide when used as an effective disinfectant forms undesirable disinfection by-products, i.e. chlorite and chlorate ions. The aim of this research was to study the removal of these ions by ferrous ions in the presence or absence of oxygen. The efficiency of Fe+2 for ClO2- and ClO3- removal was followed by a determination of their initial and final concentrations, pH and delta Fe+2 consumed/delta ClO2- removed ratios. The optimal weight ratio of delta Fe+2 consumed/delta ClO2- removed for complete ClO2 removal was found to be close to the theoretical calculated value of 3.31. It was proved that ferrous salts can reduce chlorite ions to harmless Cl- ions. This method can be recommended as a part of ClO2 disinfection to ensure safe drinking water, with no harm to water consumers and to the environment.     

再生水中影响加氯消毒的因素探讨与对策分析

针对再生水厂冬春之交突发的清水池耗氯量增加的问题,对影响加氯消毒的因素进行了试验分析,发现耗氯量增高的原因为冬季低水温情况下,清水池中存在不完全硝化反应,生成的亚硝酸盐氮累积到一定程度将大量耗氯。实践证明,冬季过后应及时对清水池进行清洗,一年进行2次,可有效预防和解决耗氯量增高的问题。     

Trihalomethanes formation in point of use surface water disinfection with chlorine or chlorine dioxide tablets

In remote or underdeveloped areas, natural disaster emergencies and armed conflict zones, point‐of‐use surface water disinfection with chlorine tablets provides microbiologically safe water, but disinfection by‐products such as trihalomethanes (THMs) are formed. While the health risks from THMs are much less than the risks from consuming microbiologically unsafe water, it is nonetheless desirable to understand and minimise THM formation. We show that THM concentrations in surface water samples from the Northern British Isles disinfected with chlorine tablets increased with contact time, in some cases to significantly exceed EU, US EPA and WHO drinking water guidance values after more than an hour. More stagnant water from ponds and lochs had higher THM formation than river water. Doubling the chlorine tablet dose slightly enhanced THM formation, and passing water through coffee filter paper reduced it. Chlorine dioxide tablets produced minimal amounts of THMs.     

Enhanced disinfection efficiency of mechanically mixed oxidants with free chlorine

To the best of our knowledge, this study is the first investigation to be performed into the potential benefits of mechanically mixed disinfectants in controlling bacterial inactivation. The purpose of this study was to evaluate the disinfection efficiency of mechanically mixed oxidants with identical oxidant concentrations, which were made by adding small amounts of subsidiary oxidants, namely ozone (O3), chlorine dioxide (ClO2), hydrogen peroxide (H2O2) and chlorite (ClO2(-)), to free available chlorine (Cl2), using Bacillus subtilis spores as the indicator microorganisms. The mechanically mixed oxidants containing Cl2/O3, Cl2/ClO2 and Cl2/ClO2(-) showed enhanced efficiencies (of up to 52%) in comparison with Cl2 alone, whereas no significant difference was observed between the mixed oxidant, Cl2/H2O2, and Cl2 alone. This enhanced disinfection efficiency can be explained by the synergistic effect of the mixed oxidant itself and the effect of intermediates such as ClO2(-)/ClO2, which are generated from the reaction between an excess of Cl2 and a small amount of O3/ClO2(-). Overall, this study suggests that mechanically mixed oxidants incorporating excess chlorine can constitute a new and moderately efficient method of disinfection.     

Comparison of disinfection byproduct formation from chlorine and alternative disinfectants

Seven diverse natural waters were collected and treated in the laboratory under five oxidation scenarios (chlorine, chloramine, both with and without preozonation, and chlorine dioxide). The impact of these disinfectants on the formation of disinfection byproducts was investigated. Results showed that preozonation decreased the formation of trihalomethanes (THMs), haloacetic acids (HAAs) and total organic halogen (TOX) for most waters during postchlorination. A net increase in THMs, HAAs and TOX was observed for a water of low humic content. Either decreases or increases were observed in dihaloacetic acids and unknown TOX (UTOX) as a result of preozonation when used with chloramination. Chloramines and chlorine dioxide produced a higher percentage of UTOX than free chlorine. They also formed more iodoform and total organic iodine (TOI) than free chlorine in the presence of iodide. Free chlorine produced a much higher level of total organic chlorine (TOCl) and bromine (TOBr) than chloramines and chlorine dioxide in the presence of bromide.     

城市污水处理厂液氯消毒加氯量生产试验分析

以某城市污水处理厂工程为例,通过试验,从加氯量、水温、氨氮浓度、消毒时间等方面,分析了影响液氯消毒效果的因素,并对两种检测粪大肠菌群数的方法作了比较,得出了一些有价值的结论。     

The effect of pH on the efficiency of chlorine disinfection and virus enumeration

In the light of increasing world-wide water pollution, the controlled and effective chlorination of water is of paramount importance in the treatment of drinking water supplies. A recent publication indicated that hypochlorite ion (OCl⁻) which is formed at high pH levels appeared to be a more effective virucidal form of free chlorine than hypochlorous acid (HOCl), which occurs at lower pH levels. This was a reversal of the findings of many other research workers. The present paper reports on a further study which confirms that HOCl is a more effective virucide than OCl⁻. It also reports on comparative studies between the PFU and TCID₅₀ methods for virus evaluation at two pH levels in an attempt to find the reasons for the reversal in the results obtained.     

Formation of disinfection by-products after pre-oxidation with chlorine dioxide or ferrate

The effect of pre-oxidation with chlorine dioxide (ClO₂) or ferrate (Fe(VI)) on the formation of disinfection by-products (DBPs) during chlorination or chloramination was tested with natural waters from 12 sources (9 surface waters, 1 groundwater, and 2 wastewater effluents). DBPs investigated included trihalomethanes (THM), chloral hydrate (CH), haloketones (HK), haloacetonitriles (HAN) and trichloronitromethane (TCNM), chlorite and chlorate. Chlorite and chlorate were found in the ClO₂-treated waters. Application of 1 mg/L ClO₂ ahead of chlorination reduced the formation potential for THM by up to 45% and the formation of HK, HAN and TCNM in most of the samples. The CH formation results were mixed. The formation of CH and HK was enhanced with low doses of Fe(VI) (1 mg/L as Fe), but was greatly reduced at higher doses (20 mg/L Fe). Fe(VI) reduced the formation of THM, HAN and TCNM in most of the samples. Reduced potential for the formation of NDMA was observed in most of the samples after both ClO₂ and Fe(VI) pre-oxidation.     

Transformation mechanism of benzophenone-4 in free chlorine promoted chlorination disinfection

The UV-filter BP-4 (2-hydroxy-4-methoxybenzophenone-5-sulfonic acid) has been frequently observed in the environment, showing high potentials to invade drinking water, swimming water, or wastewater reclamation treatment systems. With the help of high performance liquid chromatography-high resolution mass spectrometry and nuclear magnetic resonance spectroscopy, 10 new products from free chlorine-promoted BP-4 disinfection have been disclosed and their possible transformation routes have been investigated. The first route is chlorine substitution of BP-4 and its transformation products, forming mono-, di-, and tri-chlorinated BP-4 analogs. The second is Baeyer–Villiger-Type oxidation, converting diphenyl ketone to phenyl ester derivatives. The third is ester hydrolysis, generating corresponding phenolic and benzoic products. The fourth is decarboxylation, replacing the carboxyl group by chloride in the benzoic-type intermediate. The fifth is desulfonation, degrading the sulfonic group through an alternative chlorine substitution on the benzene ring. Orthogonal experiments have been established to investigate the species transformed from BP-4 at different pH values and free available chlorine (FAC) dosages. The reaction pathways are strongly dependent on pH conditions, while an excessive amount of FAC eliminates BP-4 to the smaller molecules. The initial transformation of BP-4 in chlorination system follows pseudo-first-order kinetics, and its half-lives ranged from 7.48 s to 1.26 × 10² s. More importantly, we have observed that the FAC-treated BP-4 aqueous solution might increase the genotoxic potentials due to the generation of chlorinated disinfection by-products.     

Effect of chlorination condition and permeability of chlorine species on the chlorination of a polyamide membrane

Most studies on membrane chlorination have been investigated in an unpressurized chlorination mode, even if the polyamide membrane was continuously exposed to chlorine under high operating pressure in real water/wastewater treatment plants. In this study, performance changes due to polyamide membrane chlorination were investigated in both pressurized and unpressurized chlorination modes. Chlorination in an unpressurized mode showed a flux increase at high pH and a flux decline at low pH due to the compaction and swelling of the polyamide chains, respectively. On the other hand, chlorination performed in a pressurized mode decreased the water flux in both acidic and alkaline conditions, showing that compaction is overwhelming compared to swelling. The permeability of HOCl, a dominant species at low pH, through the polyamide membrane was pH independent and almost similar to the system recovery, but the permeability of OCl⁻, which is dominant at high pH, was maxima at a neutral pH. The different performance behaviors of membranes chlorinated at various pH conditions in the presence or absence of applied pressure could be explained by the permeability of chlorine species and compaction/swelling of polymer chains after chlorination. The effect of membrane chlorination on the chemical property changes at the two different modes was confirmed using attenuated total reflection Fourier transform infrared analysis, and a conceptual model of performance change was proposed to explain the performance discrepancy between the two chlorination modes.     

二氧化氯消毒副产物亚氯酸盐及氯酸盐的测定

概述了ClO_2消毒技术的特点及消毒副产物对人体健康存在的隐患,介绍了离子色谱仪测饮用水中消毒副产物的检测方法和检测条件,并对某水厂近半年的出厂水中的ClO_2消毒副产物进行检测,结果表明该水厂的出厂水中的消毒副产物符合卫生标准。