Use Of Alternative Disinfectants Research Articles

Emerging Trends in Disinfection: Lessons From AWWA's Disinfection Survey.

Key TakeawaysEvery 10 years, AWWA releases a survey of disinfection practices in the water sector; taken together, these surveys frame the evolution of potable water disinfection.The most recent survey was conducted in 2017; the report, published in 2018, summarized trends, advantages, and challenges in using the numerous available disinfection technologies.As common as chlorine is for disinfection, its use also comes with challenges. Thus, the 2017 survey examined utilities’ use of alternative disinfectants.

To regulate or not to regulate? What to do with more toxic disinfection by-products?

Since the first regulation of disinfection by-products (DBPs) in the 1970s, >700 DBPs have been identified, and many of these are much more toxic than those regulated. Moreover, drinking water today is not the same as it was in the past, with increasing use of alternative disinfectants like chloramine, ozone, chlorine dioxide, and UV (which can form other types of DBPs), as well as new impacts on our source waters from climate change, population increases, wastewater intrusion, and energy exploration. The question today is whether we are regulating the right DBPs to protect human health, and if not, what should be done. New approaches may involve (1) the use of in vitro data and a Precautionary Principle approach, (2) using surrogate metrics of finished waters, such as total organic bromine/iodine, total nitrosamines, or total organic nitrogen rather than creating longer lists of regulated DBPs, and (3) using toxicity assays for whole drinking water extracts to pinpoint potential problems, then using chemical analyses to identify the toxic agents, and finally, (4) invoking different treatment strategies to reduce the toxicity. While the early regulations likely significantly improved the safety of drinking water, DBP exposure is a constant in modern life, and there is more that we can do.

A Review on Formation and Decay Kinetics of Trihalomethanes in Water of Different Qualities

Despite the many disadvantages associated with the use of chlorine for disinfecting drinking water, chlorination is still the main method used for this purpose worldwide. Low chlorine concentrations in water distribution systems increase health risks whereas high chlorine concentrations are associated with the formation of disinfection by‐products such as trihalomethanes which are suspected carcinogens. Due to their negative health impacts, trihalomethanes occurrence in finished drinking water has received great attention from researchers and scientists worldwide. This manuscript critically reviews and discusses up to date knowledge on the occurrence of trihalomethanes in chlorinated drinking water and their associated health risks and identifies research gaps. The models for trihalomethane formation and decay have been compiled with special emphasis on the impact of the bromide ion on the total trihalomethane levels and speciation. Furthermore, the fate and transport of trihalomethanes in drinking water supplies and in groundwater have been investigated. Finally, management options for the reduction of trihalomethanes in chlorinated drinking water such as the removal of precursors from raw water, the use of alternative disinfectants and the removal of trihalomethanes from finished drinking water have been critically investigated and discussed.

Assessment of a chlorine dioxide proprietary product for water and wastewater disinfection

Chlorine on its own is adequate for many, if not most, potable water pre-oxidation and disinfection systems at plants where the application is straightforward. Similarly, most wastewater plants can be disinfected by chlorine in one of its commercially available forms. However, when more intense pre-oxidation is required or significant iron or manganese is present in a potable supply, the use of alternative disinfectants is often preferable. Similarly, when secondary problems are present in wastewater effluent, such as high ammonia, a stronger oxidant may be preferable. Hitherto, the use of stronger oxidants has been limited to large works due to the complexity of the operational processes required. Recently, the use of ozone has spread to smaller works as new developments in equipment have become available. However, chlorine dioxide has not been used in small works until now. This paper provides details regarding a product which is simply dissolved in water in tablet or granular form and generates chlorine dioxide on solution in water. The solution is stable over weeks or even months and can be used for disinfection and or pre-oxidation purposes. The chemical was assessed in a series of tests. The performance of the chlorine dioxide product was compared against sodium hypochlorite, for different water types. The reduction in microbial counts was monitored in a secondary effluent sample and a high-ammonia secondary effluent sample. The oxidation ability in a high iron and manganese water was also assessed. A cost assessment was carried out and compared to the use of sodium hypochlorite. Other factors such as safety ease of use, and storage requirements are discussed. Keywords: chlorine, chlorine dioxide, oxidant, iron, manganese

Disinfection byproducts in Canadian provinces: Associated cancer risks and medical expenses

Chlorination for drinking water forms various disinfection byproducts (DBPs). Some DBPs are probably linked to human cancer (e.g., bladder, colorectal cancers) and other chronic and sub-chronic effects. This emphasizes the need to understand and characterize DBPs in drinking water and possible risks to human health. In this study, occurrences of DBPs throughout Canada were investigated. Trihalomethanes (THMs) were observed to be highest in Manitoba followed by Nova Scotia and Saskatchewan, while haloacetic acids were highest in Nova Scotia followed by Newfoundland and Labrador. Based on the characterization of DBPs, risk of cancer from exposure to THMs was predicted using ingestion, inhalation and dermal contact pathways of exposure. In Canada, approximately 700 cancer cases may be caused by exposure to THMs in drinking water. Medical expenses associated with these cancer incidents are estimated at some $140 million/year. Expense may be highest in Ontario (∼$47 million/year) followed by Quebec (∼$25 million/year) due to a greater population base. This paper suggests improvements in water treatment, source protection and disinfection processes, and caution in the use of alternative disinfectants to reduce DBPs. Finally, elements are provided to mitigate risks and reduce cost estimates in future studies.

Haloacetonitriles vs. Regulated Haloacetic Acids: Are Nitrogen-Containing DBPs More Toxic?

Haloacetonitriles (HANs) are toxic nitrogenous drinking water disinfection byproducts (N-DBPs) and are observed with chlorine, chloramine, or chlorine dioxide disinfection. Using microplate-based Chinese hamster ovary (CHO) cell assays for chronic cytotoxicity and acute genotoxicity, we analyzed 7 HANs: iodoacetonitrile (IAN), bromoacetonitrile (BAN), dibromoacetonitrile (DBAN), bromochloroacetonitrile (BCAN), chloroacetonitrile (CAN), dichloroacetonitrile (DCAN), and trichloroacetonitrile (TCAN). The cytotoxic potency (%C1/2 values) ranged from 2.8 microM (DBAN) to 0.16 mM (TCAN), with a descending rank order of DBAN > IAN approximately BAN > BCAN > DCAN > CAN > TCAN. HANs induced acute genomic DNA damage; the single cell gel electrophoresis (SCGE) genotoxicity potency ranged from 37 microM (IAN) to 2.7 mM (DCAN). The rank order of declining genotoxicity was IAN > BAN approximately DBAN > BCAN > CAN > TCAN > DCAN. The accompanying structure-activity analysis of these HANs was in general agreement with the genotoxicity rank order. These data were incorporated into our growing quantitative comparative DBP cytotoxicity and genotoxicity databases. As a chemical class, the HANs are more toxic than regulated carbon-based DBPs, such as the haloacetic acids. The toxicity of N-DBPs may become a health concern because of the increased use of alternative disinfectants, such as chloramines, which may enhance the formation of N-DBPs, including HANs.

Occurrence of a New Generation of Disinfection Byproducts

A survey of disinfection byproduct (DBP) occurrence in the United States was conducted at 12 drinking water treatment plants. In addition to currently regulated DBPs, more than 50 DBPs that rated a high priority for potential toxicity were studied. These priority DBPs included iodinated trihalomethanes (THMs), other halomethanes, a nonregulated haloacid, haloacetonitriles, haloketones, halonitromethanes, haloaldehydes, halogenated furanones, haloamides, and nonhalogenated carbonyls. The purpose of this study was to obtain quantitative occurrence information for new DBPs (beyond those currently regulated and/or studied) for prioritizing future health effects studies. An effort was made to select plants treating water that was high in total organic carbon and/or bromide to enable the detection of priority DBPs that contained bromine and/or iodine. THMs and haloacetic acids (HAAs) represented the two major classes of halogenated DBPs formed on a weight basis. Haloacetaldehydes represented the third major class formed in many of the waters. In addition to obtaining quantitative occurrence data, important new information was discovered or confirmed at full-scale plants on the formation and control of DBPs with alternative disinfectants to chlorine. Although the use of alternative disinfectants (ozone, chlorine dioxide, and chloramines) minimized the formation of the four regulated THMs, trihalogenated HAAs, and total organic halogen (TOX), several priority DBPs were formed at higher levels with the alternative disinfectants as compared with chlorine. For example, the highest levels of iodinated THMs-which are not part of the four regulated THMs-were found at a plant that used chloramination with no prechlorination. The highest concentration of dichloroacetaldehyde was at a plant that used chloramines and ozone; however, this disinfection scheme reduced the formation of trichloroacetaldehyde. Preozonation was found to increase the formation of trihalonitromethanes. In addition to the chlorinated furanones that have been measured previously, brominated furanones-which have seldom been analyzed-were detected, especially in high-bromide waters. The presence of bromide resulted in a shift to the formation of other bromine-containing DBPs not normally measured (e.g., brominated ketones, acetaldehydes, nitromethanes, acetamides). Collectively, -30 and 39% of the TOX and total organic bromine, respectively, were accounted for (on a median basis) bythe sum of the measured halogenated DBPs. In addition, 28 new, previously unidentified DBPs were detected. These included brominated and iodinated haloacids, a brominated ketone, and chlorinated and iodinated aldehydes.

Comparative Study of Chemical Disinfection in Drinking Water Supply

applied to waters with moderate to high bromide levels. Kinetic disinfection models are the basis for assessing the performance and design of contactor systems. Over the years, a number of kinetic models have been proposed in order to help formulate criteria for an optimal disinfection design. Model adequacy depends on the robustness of the underlying inactivation rate law if the model accounts for the disappearance of the chemical disinfectant during the contact time. The CT concept is a simple approach used to develop disinfection requirements under the water treatment rule. The validity of using the CT concept to represent the inactivation kinetics of total coliforms including that by various disinfectants including free chlorine has been questioned recently. There is a need for development of a more comprehensive model to determine future requirements for drinking water disinfection. In 1989, research was initiated on the use of alternative disinfectants in Korea; at present, free chorine is

Water mutagenicity and toxicology in Rio Tercero (Cordoba, Argentina)

A study on the water quality from the Rio Tercero River was performed for 14 months. The aim of the work was not only to assess the control of bacteriological, phycological and chemical aspects, but also to measure genotoxicity of drinking water and its relation with the water treatment technique employed. Bacteriological parameters are negative in general, apparently indicating low levels of contaminants. Algae were present in the untreated water, especially several diatoms (Bacillariophyceae) and potentially hepatotoxin-producing cyanobacteria (blue-green algae). The chemical analysis detected arsenic (up to 0.114 mg/l) and vanadium (up to 0.109 mg/l). Water was genotoxic and clastogenic over several biological systems. The use of alternative disinfectants, such as chlorine-dioxide or ozone, and granular activated carbon are recommended.

Use of alternative disinfectants, individually and in combination, in aquacultural wastewater treatment

The inactivation effect of chlorine, iodine, ozone and UV irradiation was compared between phosphate buffered saline and waste water collected from a fish farm, with the fish-pathogenic bacterium Aeromonas salmonicida subsp. salmonicida as the model organism. In addition, the effect of combining chlorine, iodine or ozone with UV was evaluated. A tenfold increase in initial chlorine concentration, from 0.2 to 2.0 mg l−1. had to be applied to maintain the same level of inactivation in waste water as in PBS. Iodine was less efficient than chlorine in PBS. by demanding a concentration of 1.0 mg l−1 to obtain the same rate of inactivation as with 0.2 mg l−1 chlorine. However, no difference between the two halogens was evident in the low-quality water. An initial ozone concentration of 0.1 mg l−1 in PBS caused a rapid drop in bacterial viability for the first 20 s after which the curve levelled off. By continuous ozonation of waste water, a residual oxidant concentration of about 0.3 mg l−1 had to be established before a rapid inactivation was observed. The UV inactivation profiles in PBS and waste water were almost identical, with a 99.9% reduction in viability after 48 and 50 s. respectively. When UV irradiation was combined with chlorine, a less than additive effect, as compared with the sum of individual death rates by the two treatments, was observed. The corresponding UV/iodine combination at least gave an additive effect in both water qualities. No increment in inactivation rate in PBS was observed when ozone was used in combination with UV, as compared with ozone alone.