Disinfection processes

One way of implementing the UV disinfection process at existing activated sludge plants involves suspending the UV lights (in the form of low-pressure mercury arc UV lamps with associated reflectors) above the secondary clarifiers. The effluent is exposed to the UV radiation as it rises over the wire in a thin film. 

The interhalogen compounds are the bromine- and iodine-base materials. It is the larger, more positive halogen that is the reactive portion of the interhalogen molecule during the disinfection process. Although only used on a limited basis at present, there are members of this class that show great promise as environmentally safe disinfectants. 

Polcaro AM, Vacca A, Mascia M et al (2007) Characterization of stirred tank electrochemical cell for water disinfection processes. Electrochim Acta 52 2595-2602... 

Inspection of the death curves obtained from viable count data had early ehcited the idea that because there was usually an approximate, and under some circumstances a quite excellent, linear relationship between the logarithm of the number of survivors and time, then the disinfection process was comparable to a unimolecular reaction. This imphed that the rate of killing was a function of the amount of one of the participants in the reaction only, i.e. in the case of the disinfection process the number of viable cells. From this observation there followed the notion that the principles of first-order... 

The more usual pattern found experimentally is that shown by B, which is called a sigmoid curve. Here the graph is indicative of a slow initial rate of kill, followed by a faster, approximately linear rate of kill where there is some adherence to first-order reaction kinetics this is followed again by a slower rate of kill. This behaviour is compatible with the idea of a population of bacteria which contains a portion of susceptible members which die quite rapidly, an aliquot of average resistance, and a residue of more resistant members which die at a slower rate. When high concentrations of disinfectant are used, i.e. when the rate of death is rapid, a curve ofthe type shown by C is obtained here the bacteria are dying more quickly than predicted by first-order kinetics and the rate constant diminishes in value continuously during the disinfection process. 

A, obtained if the disinfection process obeyed the first-order kinetic law. B, sigmoid curve. This shows a slow initial rate of kill, a steady rate and finally a slower rate of kill. This is the form of curve most usually encountered. C, obtained if bacteria are dying more quickly than first-order kinetics would predict. The constant, K, diminishes in value continuously during the process. 

During the disinfection process a change of pH can, at one and the same time, affect 1 the rate of growth of the inoculum ... 

It will be recalled (sechon 1) that research on the time course of the disinfection process was carried out making extensive use of viable counts, and notions concerning the dynamics of the disinfechon process were gathered by these means. 

Tests should also be done in the presenee of organic matter (e.g. albumin) and in hard water. It is important to remember when performing viable counts that care must be taken to ensure that, at the moment of sampling, the disinfection process is immediately arrested by the use of a suitable neutralizer or ensuring inactivation by dilution (Table 11.4). Membrane filtration is an alternative procedure, the principle of whieh is that treated cells are retained on the filter whilst the disinfectant forms the filtrate. After washing in situ, the membrane is transferred to the surface of a solid (agar) reeoveiy medium and the eolonies that develop on the membrane are counted. 

Disinfection, 8 605-672. See also Disinfection processes antimicrobial nanoemulsion technology, 8 630-631 bromine, 8 621-626 bromine chloride, 8 626-628 chlorination, 8 610-615 chlorine dioxide, 8 617-619 dechlorination with sulfur dioxide, 8 615-617... 

Disinfection processes, as advanced wastewater treatment, 25 909-910 Disjoining pressure, 12 6-7 Disk agglomeration, 19 8 Disk atomizer spray dryer, 9 127 Disk bowl centrifuge, theory of performance, 5 518 Disk centrifuges, 18 144... 

In 40 WWTP all over Japan, primary effluents were found to contain mainly NPEOs with longer ethoxy units (ueo = 4-8), while NPECs accounted for <5% (mol mol-1) of total nonylphenolic compounds [18]. The average removal of nonylphenolic compounds was approximately 60% after biological treatment and 70% after full treatment (almost all studied WWTPs have a final disinfection process). 

Fujita et al. [18] studied formation of halogenated (chlorinated and brominated) NPEOs and NPECs during wastewater treatment. Halogenated derivatives were found to be produced during the disinfection processes by chlorination accounting for up to 10% of total nonylphenolic compounds. They were found in 25 of 40 WWTPs with concentrations up to 6.5 xgL 1 in secondary effluent and 52.4 jig L-1 in final effluent. Of all halogenated compounds, BrNPECs (nEo = 1-2) were found to be the most abundant. 

Li Z, Fenet H, Gomez E, Chiron S (2011) Transformation of the antiepileptic dmg oxcarbazepine upon different water disinfection processes. Water Res 45 1587-1596... 

Pereira RO, Postigo C, L6pez de Alda M, Daniel LA, Barceld D (2011) Removal of estrogens through water disinfection processes and formation of by-products. Chemosphere... 

Disinfection by-products (DBPs) form an undesired species in the chlorine disinfection processes of waters (performed with chlorine, chlorine dioxide, and chloramines). The high priority DBPs include brominated, chlorinated, and iodinated species of halomethanes, brominated, and chlorinated forms of haloacetonitriles, haloketones, haloacids, and halonitromethanes, as well as analogues of 3-chloro-(4-dichloromethyl)-5-hydroxy-2(5//)-furanone. All the high priority DBPs included in the Nation-wide DBP occurrence study are listed in Table 18.1 together with other contaminants. 

Water conditions, such as temperature, alkalinity, iron levels, and manganese concentrations are all factors that can potentially affect the generation of mixed oxidants and the overall performance of the disinfection process. Some adjustment of the concentration of the mixed oxidant solution may be necessary to prevent scaling in hard-water areas. 

Chlorine (from the Greek chloros for yellow-green ) is the most abundant halogen (0.19 w% of the earth s crust) and plays a key role in chemical processes. The chlor-alkali industry has been in operation since the 1890s and improvements in the technology are still important and noticeable, for example, the transition from the mercury-based technology to membrane cells [60]. Most chlorine produced today is used for the manufacture of polyvinyl chloride, chloroprene, chlorinated hydrocarbons, propylene oxide, in the pulp and paper industry, in water treatment, and in disinfection processes [61]. A summary of typical redox states of chlorine, standard potentials for acidic aqueous media, and applications is given in Scheme 2. 

This situation provided the opportunity for the decision maker to consider many other factors when the control decision was made. The predominant factors driving the control decision were judgmental and unquantifiable. They included the essentiality of the disinfection process in the control of waterborne disease (which is a large risk), the desire to optimize drinking water quality so as to avoid unnecessary risks, and the consideration of the unique compliance problems of small underfinanced and marginally operated water systems. Ultimately, the decision was driven by the feasibility and costs of treatment process improvements. 

An adequate supply of clean, potable WATER is one of the primary requirements for good health. Traditionally, health hazards associated with water have been the classic waterborne diseases, namely, typhoid, cholera, and hepatitis. The advent, advancement, and practice of the science of bacteriology after the late 18th century led to the recognition of the causes and sources of these diseases, which resulted in the development of disinfection processes and in the recognition of the necessity to prevent public potable water sources from pollution from sewage and postdisinfection contamination. 

BCDMH hydrolyzes to rapidly provide HOBr and then, more slowly, HOC1. As HOBr is consumed during the disinfection process, some bromine is released as bromide ion (Br ), which is oxidized back to HOBr. 

Chlorinated organic compounds present in water, due to their carcinogenic nature, have become a great concern with respect to human health. Such substances are formed when humic acids react with chlorine in disinfection processes. Ozonation alone is generally not suited for the complete oxidation of chlorinated compounds because scavenger compounds such as acetic acid, formic acid, and oxalic acid can form and accumulate as by-products in the... 

Owing to the textile-related topics which are covered in this book, this chapter is devoted to a description of a sensor which has been developed to measure and control high hydrogen peroxide concentrations in bleaching processes, and its extension with a flow-injection system to adopt it for use in disinfecting processes. 

The intent of equipment rinsate blank collection as a field QC sample seems reasonable. In reality, however, equipment blank analyses rarely provide information that can be meaningfully related to the field samples because the only contaminants that are usually present in equipment blanks are common laboratory contaminants or byproducts of water disinfection process. 

The addition of sodium thiosulfate to samples collected for VOC analysis removes residual chlorine that may be present in drinking water as an artifact from water disinfection process. 

If VOCs are not among the contaminants of concern, bottled drinking water or commercially available deionized water often serves as an equitable substitute for analyte-free reagent water. (Certain VOCs are present in drinking water as the artifacts of water disinfection process.) If VOCs are among the project contaminants of concern, commercially available distilled water may be used for a final rinse. When bottled water is not available, and water of unknown quality is used for equipment blank collection, a source blank of such water is analyzed. The only situation when a source blank may be needed is when the sampled medium is water and low contaminant concentrations of organic compounds and metals are a matter of concern. 

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