Chemical Disinfection Of Water Research Articles

The removal of pathogenic bacteria and dissolved organic matter from freshwater using microporous membranes: insights into biofilm formation and fouling reversibility

Pathogenic bacteria in drinking-water pose a health risk to consumers, as they compromise the quality of portable water. Chemical disinfection of water containing dissolved organic matter (DOM) causes harmful disinfection by-products. In this work, 4-hydroxybenzoic acid (4-HBA) blended polyethersulfone membranes were fabricated and characterised using microscopic and spectroscopic techniques. The membranes were evaluated for the removal of bacteria and DOM from synthetic and environmental water. Permeate flux increased from 287.30 to 374.60 l m−2 h−1 at 3 bars when 4-HBA increased from 0 to 1.5 wt.%, suggesting that 4-HBA influenced the membrane’s affinity for water. Furthermore, 4-HBA demonstrated antimicrobial properties by inhibiting bacterial growth. The membrane with 1 wt.% 4-HBA recorded 99.4 and 100% bacteria removal in synthetic and environmental water, respectively. Additionally, DOM removal of 55–73% was achieved. A flux recovery ratio (FRR) of 94.6% was obtained when a mixture of bacteria and humic acid was filtered, implying better fouling layer reversibility during cleaning. Furthermore, 100% FRR was achieved when a multimedia granular filtration step was installed prior to membrane filtration. The results illustrated that the membranes had a high permeate flux with low irreversible fouling. This indicated the potential of the membranes in treating complex feed streams using simple cleaning protocols.

Assessing the skin irritation and sensitizing potential of concentrates of water chlorinated in the presence of iodinated X-ray contrast media

Chemical disinfection of water provides significant public health benefits. However, disinfectants like chlorine can react with naturally occurring materials in the water to form disinfection byproducts (DBPs). Natural levels of iodine have been reported to be too low in some source waters to account for the levels of iodinated DBPs detected. Iodinated X-ray contrast media (ICM) have been identified as a potential source of iodine. The toxicological impact of ICM present in source water at the time of disinfection has not been fully investigated. Iopamidol, iohexol, iopromide, and diatrizoate are among the ICM most frequently detected in water. In this study, source water containing one of these four ICM was chlorinated; non-chlorinated ICM-containing water samples served as controls. Reactions were conducted at an ICM concentration of 5 µM and a chlorine dose of 100 µM over 72 hr. Water concentrates (20,000-fold) were prepared by XAD-resin/ethyl acetate extraction and DMSO solvent exchange. We used the MatTek® reconstituted human epithelial skin irritation model to evaluate the water concentrates and also assessed the dermal irritation and sensitization potential of these concentrates using the LLNA:BrdU ELISA in BALB/c mice. None of the water concentrates tested (2500X) resulted in a skin irritant response in the MatTek® skin irritation model. Likewise, none of the concentrates (2500X, 1250X, 625X, 312.5X, 156.25X) produced a skin irritation response in mice: erythema was minimal; the maximum increase in ear thickness was less than 25%. Importantly, none of the concentrates produced a positive threshold response for allergic skin sensitization at any concentration tested in the LLNA:BrdU ELISA. We conclude that concentrates of water disinfected in the presence of four different ICM did not cause significant skin irritation or effects consistent with skin sensitization at the concentrations tested.

Thermal and chemical disinfection of water and biofilms: only a temporary effect in regard to the autochthonous bacteria.

Thermal and chemical disinfection of technical water systems not only aim at minimizing the level of undesired microorganisms, but also at preventing excessive biofouling, clogging and interference with diverse technical processes. Typically, treatment has to be repeated in certain time intervals, as the duration of the effect is limited. The transient effect of disinfection was demonstrated in this study applying different treatments to water and biofilms including heat, chlorination, a combination of hydrogen peroxide and peracetic acid and monochloramine. Despite the diverse treatments, the reduction in live bacteria was followed by regrowth in all cases, underlining the universal validity of this phenomenon. The study shows that autochthonous bacteria can reach the concentrations given prior to treatment. The reason is seen in the nutrient concentration that has not changed and that forms the basis for regrowth. Nutrients are released by disinfection from lysed cells or are still fixed in dead biomass that is subsequently scavenged by necrotrophic growth. Treatment cycles therefore only provide a transient reduction of water microbiology if nutrients are not removed. When aiming at greater sustainability of the effect, biocidal treatment has to be equally concerned about nutrient removal by subsequent cleaning procedures as about killing efficiency.

DISINFEKSI UNTUK PROSES PENGOLAHAN AIR MINUM

Water disinfection means the removal, deactivation or killing of pathogenic microorganisms. Microorganisms are destroyed or deactivated, resulting in termination of growth and reproduction. When microorganisms are not removed from drinking water, drinking water usage will cause people to fall ill. Chemical inactivation of microbiological contamination in natural or untreated water is usually one of the final steps to reduce pathogenic microorganisms in drinking water. Combinations of water purification steps (oxidation, coagulation, settling, disinfection, and filtration) cause (drinking) water to be safe after production. As an extra measure many countries apply a second disinfection step at the end of the water purification process, in order to protect the water from microbiological contamination in the water distribution system. Usually one uses a different kind of disinfectant from the one earlier in the process, during this disinfection process. The secondary disinfection makes sure that bacteria will not multiply in the water during distribution. This paper describes several technique of disinfection process for drinking water treatment. Disinfection can be attained by means of physical or chemical disinfectants. The agents also remove organic contaminants from water, which serve as nutrients or shelters for microorganisms. Disinfectants should not only kill microorganisms. Disinfectants must also have a residual effect, which means that they remain active in the water after disinfection. For chemical disinfection of water the following disinfectants can be used such as Chlorine (Cl2), Hypo chlorite (OCl-), Chloramines, Chlorine dioxide (ClO2), Ozone (O3), Hydrogen peroxide etch. For physical disinfection of water the following disinfectants can be used is Ultraviolet light (UV). Every technique has its specific advantages and and disadvantages its own application area sucs as environmentally friendly, disinfection byproducts, effectivity, investment, operational costs etc. Kata Kunci : Disinfeksi, bakteria, virus, air minum, khlor, hip khlorit, khloramine, khlor dioksida, ozon, UV.

Effect of drinking water disinfection by-products in human peripheral blood lymphocytes and sperm

BackgroundDrinking water disinfection by-products (DBPs) are generated by the chemical disinfection of water and may pose hazards to public health. Two major classes of DBPs are found in finished drinking water: haloacetic acids (HAAs) and trihalomethanes (THMs). HAAs are formed following disinfection with chlorine, which reacts with iodide and bromide in the water. Previously the HAAs were shown to be cytotoxic, genotoxic, mutagenic, teratogenic and carcinogenic. ObjectivesTo determine the effect of HAAs in human somatic and germ cells and whether oxidative stress is involved in genotoxic action. In the present study both somatic and germ cells have been examined as peripheral blood lymphocytes and sperm. MethodsThe effects of three HAA compounds: iodoacetic acid (IAA), bromoacetic acid (BAA) and chloroacetic acid (CAA) were investigated. After determining appropriate concentration responses, oxygen radical involvement with the antioxidants, butylated hydroxanisole (BHA) and the enzyme catalase, were investigated in the single cell gel electrophoresis (Comet) assay under alkaline conditions, >pH 13 and the micronucleus assay. ResultsIn the Comet assay, BHA and catalase were able to reduce DNA damage in each cell type compared to HAA alone. In the micronucleus assay, micronuclei (MNi) were found in peripheral lymphocytes exposed to all three HAAs and catalase and BHA were in general, able to reduce MNi induction, suggesting oxygen radicals play a role in both assays. ConclusionThese observations are of concern to public health since both human somatic and germ cells show similar genotoxic responses.

Genotoxicity testing of three monohaloacetic acids in TK6 cells using the cytokinesis-block micronucleus assay

Chemical disinfection of water generates harmful chemical compounds, known as disinfection by-products (DBPs). One class of DBPs is constituted by haloacetic acids (HAAs), the second major group in prevalence (after trihalomethanes) detected in finished drinking water. In this article, we report the results obtained in the evaluation of the chromosome damage induced by three monohaloacetic acids, namely iodoacetic acid (IAA), bromoacetic acid (BAA) and chloroacetic acid (CAA). To evaluate the induction of chromosome damage, we used the cytokinesis-block micronucleus test that measures the ability of genotoxic agents to induce both clastogenic and/or aneugenic effects. No previous data exist on the effects of these compounds on human chromosomes. We tested five doses of each HAA, in addition to the negative and positive controls. The highest dose tested for each HAA was that immediately lower than the dose producing total cytotoxicity. Our results show that none of the three HAAs tested was able to increase significantly the frequency of micronucleus in binucleated TK6 cells, the rank order in decreasing cytotoxicity was IAA > BAA >> CAA.

Modulation of the Cytotoxicity and Genotoxicity of the Drinking Water Disinfection Byproduct Iodoacetic Acid by Suppressors of Oxidative Stress

Drinking water disinfection byproducts (DBPs) are generated by the chemical disinfection of water and may pose a hazard to the public health. Previously we demonstrated that iodoacetic acid was the most cytotoxic and genotoxic DBP analyzed in a mammalian cell system. Little is known of the mechanisms of its genotoxicity. The involvement of oxidative stress in the toxicity of iodoacetic acid was analyzed with the antioxidants catalase and butylated hydroxyanisole (BHA). lodoacetic acid toxicity was quantitatively measured with and without antioxidants in Salmonella typhimurium strain TA100 and with Chinese hamster ovary (CHO) cells. The endpoints included cytotoxicity in S. typhimurium or in CHO cells, mutagenicity in S. typhimurium, and genotoxicity in CHO cells. Neither catalase nor BHA reduced the level of iodoacetic acid induced cytotoxicity in S. typhimurium. In CHO cells neither antioxidant caused a significant reduction in iodoacetic acid induced cytotoxicity. However, in S. typhimurium, BHA or catalase reduced the mutagenicity of iodoacetic acid by 33.5 and 26.8%, respectively. Likewise, BHA or catalase reduced iodoacetic acid induced genomic DNA damage by 86.5 and 42%, respectively. These results support the hypothesis that oxidative stress is involved in the induction of genotoxicity and mutagenicity by iodoacetic acid.

Component-Based and Whole-Mixture Techniques for Addressing the Toxicity Of Drinking-Water Disinfection By-Product Mixtures

Chemical disinfection of water is of direct public health benefit as it results in decreased water-borne illness. The chemicals used to disinfect water react with naturally occurring organic matter, bromide, and iodide in the source water, resulting in the formation of disinfection by-products (DBPs). Despite the identification of several hundred DBPs, more than 50% of the mass of total organic halide formed during chlorination remains unidentified. The toxic contribution of the DBPs that are formed and present but not yet chemically identified, the unidentified fraction, has been largely unexplored. A better understanding of the potential for adverse human health consequences associated with exposure to the DBPs present in drinking water will be gained by integration of knowledge on the toxicity of individual DBPs; simple, defined DBP mixtures; complex, environmentally realistic DBP mixtures with partial chemical characterization; and the unidentified fraction.

Development of a research strategy for integrated technology-based toxicological and chemical evaluation of complex mixtures of drinking water disinfection byproducts.

Chemical disinfection of water is a major public health triumph of the 20th century. Dramatic decreases in both morbidity and mortality of waterborne diseases are a direct result of water disinfection. With these important public health benefits comes low-level, chronic exposure to a very large number of disinfection byproducts (DBPs), chemicals formed through reaction of the chemical disinfectant with naturally occurring inorganic and organic material in the source water. This article provides an overview of joint research planning by scientists residing within the various organizations of the U.S. Environmental Protection Agency Office of Research and Development. The purpose is to address concerns related to potential health effects from exposure to DBPs that cannot be addressed directly from toxicological studies of individual DBPs or simple DBP mixtures. Two factors motivate the need for such an investigation of complex mixtures of DBPs: a) a significant amount of the material that makes up the total organic halide and total organic carbon portions of the DBPs has not been identified; and b) epidemiologic data, although not conclusive, are suggestive of potential developmental, reproductive, or carcinogenic health effects in humans exposed to DBPs. The plan is being developed and the experiments necessary to determine the feasibility of its implementation are being conducted by scientists from the National Health and Environmental Effects Research Laboratory, the National Risk Management Research Laboratory, the National Exposure Research Laboratory, and the National Center for Environmental Assessment.

By-products formation during drinking water disinfection: a tool to assess disinfection efficiency?

In drinking water treatment, the inactivation of microorganisms increases with increasing disinfectant exposure (product of concentration and contact time, CT). Also, the formation of undesired (toxic) disinfection by-products increases with CT. The present study proposes a new concept that uses this undesired side effect of chemical water disinfection for a fast and reliable test of treatment efficiency. In laboratory systems, bromate formation during ozonation and the formation of trihalomethanes during chlorination were used to calculate the disinfectant exposure, which is a measure for the achieved degree of disinfection.

Farm and management variables linked to fecal shedding of Campylobacter and Salmonella in commercial squab production

A cross-sectional study was performed to determine the relationship of farm variables and management practices to fecal shedding of Campylobacter or Salmonella on commercial squab (young pigeon) farms. A detailed survey provided information on biosecurity, cleaning and disinfection, bird health, vector control, and loft and pen. Twenty pigeons on each of 12 farms were cultured before and after the producers completed a voluntary quality assurance training program (QAP), based on principles of hazard analysis critical control point (HACCP). The prevalence of positive samples for Salmonella and C. jejuni was 1/480 (0.21%) and 19/480 (3.96%), respectively. Campylobacter was present on one farm during both visits; three farms during the first visit, and three farms during the second visit. Analysis by fixed-effects logistic regression showed the probability of having a positive C. jejuni culture was increased by not using dry manure in the nesting material, not cleaning shipping crates, cleaning landing boards, and by increased frequency of chemical disinfection of water. Having a positive parent and higher numbers of squab per pen (density) were also associated with higher odds of being positive for C. jejuni. Factors not associated with a positive C. jejuni culture included, other avian species on the farm, type of shipping crate, covered drinkers, fly problems, bird age, level of nest box within the loft, and QAP training. Prevalence of food safety pathogens was extremely low on the squab facilities tested as compared with reports from commercial broiler or turkey flocks. This observation suggests that one or more farm variables or management practices were effectively reducing infection, or possibly a species-related difference existed in carriage rates and shedding of pathogens. These results emphasize critical control points for food safety pathogens may vary widely, and the formulation of effective QAP programs are dependent on science-based knowledge of diverse animal production systems.

Time dose reciprocity in UV disinfection of water

The microbicidal effect of UV light depends on the dose in both, disinfection processes and natural inactivation by the sunlight in surface water. Deviations of the time dose reciprocity are well known from chemical water disinfection whereas no data are available about this effect in UV inactivation in water. In a previous study we found that the UV inactivation behaviour of yeast strains does not follow the time dose reciprocity, insofar that longer exposure led to higher reduction of cultivable cells. In contrast, an earlier study about E coli B/r claimed a higher inactivation with single exposure compared with fractionated UV irradiation. To investigate this question we selected water-relevant microorganisms and studied their UV inactivation behaviour (253.7nm) by means of a specially designed UV irradiation apparatus (a) under standard irradiation conditions (2W/m2) and (b) with three levels of UV dose rate (2, 0.2 and 0.02W/m2). The test organisms were (i) three E coli strains (ATCC 25922, ATCC 11229 and an isolate from sewage) representing the routinely used faecal indicator, (ii) three bacterial viruses (MS2, ϕX174 and B40-8) proposed as indicators for viral contamination in water and (iii) spores of Bacillus subtilis because of their use as a biodosimeter in prototype testing of commercial UV plants for drinking water disinfection. We found, under standard inactivation conditions, that the E coli strains and phage ϕX174 are most UV susceptible, followed by B40-8 and finally MS2 and bacterial spores. The dose protraction experiments revealed for the E coli strains a higher inactivation with high dose rates compared to low dose rates at the same UV doses (difference of about 1 log10 at 80-100J/m2). The other test organisms did not deviate from the time dose reciprocity in the proven range of dose.

Time dose reciprocity in UV disinfection of water

The microbicidal effect of UV light depends on the dose in both, disinfection processes and natural inactivation by the sunlight in surface water. Deviations of the time dose reciprocity are well known from chemical water disinfection whereas no data are available about this effect in UV inactivation in water. In a previous study we found that the UV inactivation behaviour of yeast strains does not follow the time dose reciprocity, insofar that longer exposure led to higher reduction of cultivable cells. In contrast, an earlier study about E coli B/r claimed a higher inactivation with single exposure compared with fractionated UV irradiation. To investigate this question we selected water-relevant microorganisms and studied their UV inactivation behaviour (253.7nm) by means of a specially designed UV irradiation apparatus (a) under standard irradiation conditions (2W/m2) and (b) with three levels of UV dose rate (2, 0.2 and 0.02W/m2). The test organisms were (i) three E coli strains (ATCC 25922, ATCC 11229 and an isolate from sewage) representing the routinely used faecal indicator, (ii) three bacterial viruses (MS2, φX174 and B40–8) proposed as indicators for viral contamination in water and (iii) spores of Bacillus subtilis because of their use as a biodosimeter in prototype testing of commercial UV plants for drinking water disinfection. We found, under standard inactivation conditions, that the E coli strains and phage φX174 are most UV susceptible, followed by B40–8 and finally MS2 and bacterial spores. The dose protraction experiments revealed for the E coli strains a higher inactivation with high dose rates compared to low dose rates at the same UV doses (difference of about 1 log10 at 80–100J/m2). The other test organisms did not deviate from the time dose reciprocity in the proven range of dose.

The Inactivation of Hepatitis a Virus and other Model Viruses by UV Irradiation

Ultraviolet light is an attractive alternative to chemical disinfection of water, but little is known about its ability to inactivate important waterborne pathogens such as hepatitis A virus. Therefore, the sensitivity of HAV strain HM-175, coxsackievirus type B-5, rotavirus strain SA-11, and bacteriophages MS2 and øX174 to ultraviolet radiation of 254 nm wavelength in phosphate buffered water was determined. Purified stocks of the viruses were combined and exposed to collimated UV radiation in a stirred reactor for a total dose of up to 40 mW sec/cm2. Virus survival kinetics were determined from samples removed at dose intervals. The 4 log,10 (99.99%) inactivation doses for HAV, CB5, SA-11 and øX174 were 16, 29, 42 and 9 mW sec/cm2, respectively. MS2 exhibited the greatest resistance in buffered water with less than a 1 log10 reduction observed after exposure to 25 mW sec/cm2. A 15 mW sec/cm2 exposure induced a 7 log10 reduction of øX174, while inactivation of HAV, CB5 and SAll was intermediate, with at least 3 log10 reductions occurring after a 20 mW sec/cm2 exposure. The results of these experiments indicate that UV radiation can effectively inactivate viruses of public health concern in drinking water.

The Chemical Disinfection of Water

The Chemical Disinfection of Water