Chlorine dioxide advantages

Towers. Towers are required to provide retention times from 30 minutes, as in the chlorination and hypochlorite stages, to as much as five hours in some chlorine dioxide stages. Upflow and downflow towers are common. Upflow towers are often used for medium consistency stages. These are particularly advantageous when a hydrostatic head must be maintained on a gaseous solution, as in chlorine dioxide stages. 

The uses for chlorine dioxide take advantage of the high oxidising power and broad-spectrum disinfection capabiUty. 

Chlorine dioxide yields of 95% or greater have been demonstrated. The use of chlorine as an oxidant has distinct advantages because it is usually present in municipal water treatment plants for water disinfection. 

Chlorine dioxide has been evaluated as a replacement for chlorine [1630]. Gaseous chlorine as a biocide for industrial applications is declining because of safety and environmental and community impact considerations. Various alternatives have been explored, for example, bromo-chorodimethyl hydan-toin (BCDMH), nonoxidizing biocides, ozone, and chlorine dioxide. Chlorine dioxide offers some unique advantages because of its selectivity, effectiveness over a wide pH range, and speed of kill. Safety and cost considerations have restricted its use as a viable replacement. 

The chlorine dioxide emission totals following this scrubbing procedure are very low, and result from the use of low concentrations of hydrogen peroxide. The advantages are that the peak loads of chlorine can be controlled more easily and the amounts of hydrogen peroxide needed (and therefore its cost) are relatively small. 

Where chlorine dioxide is used, it is normally advantageous to feed it directly to the recirculating water pump suction to ensure that the maximum concentration is available to scour the cooling tower distribution decks and other areas that may be subject to heavy fouling by algal slimes. 

Alternatives most frequently considered for taste and odor removal include breakpoint chlorination, aeration, ozonation, and oxidation with chlorine dioxide or potassium permanganate. None of these technologies have been found to approach the activated carbon adsorption process iri terms of effective treatment for this particular water quality problem. Another alternative is sorption onto other solids such as bleaching clays, synthetic resins or manganese dioxide. A brief summary of the advantages, disadvantages and cost factors associated with adsorption and alternative treatments for removal of tastes and odors... 

The third reagent used for the preparation of wood holocelluloses, per-oxyacetic add, is of more recent date. It has been claimed to have certain advantages over sodium chlorite. Leopold found that the peroxyacetic acid method, when used in conjunction with sodium borohydride, gives a superior holocellulose. It is interesting to note that both peroxyacetic acid and chlorine dioxide are, apparently, able to effect an oxidative ringopening of phenolic compounds. ... 

Stabilised chlorine dioxide has some advantages over chlorine including ... 

The synthesis of chlorine dioxide has eui extensive literature, especially in the patent area. This is doubtless because it is widely used as a bleach, particularly for wood pulp and flour. The primary source of chlorine dioxide is sodium chlorate. Sodium chlorite also serves as a source, but since this compound itself is always made from chlorine dioxide, its advantages derive from its ease of application or from the purity of the chlorine dioxide produced. 

In comparison with ozone and chlorine dioxide, the main advantage of chlorine species as disinfectants is their reservoir effect in a system over increased time. The main disadvantage is the formation of halogenated by-products. Because of this, and to avoid microorganism adaptation effects, continuous use of disinfection cells without periodic interruption is not recommended. 

Constant-current potentiometry seems to have the advantage of error-free operation, as compared to the conventional amperometric endpoint detection in the case of chlorine determinations in water. Barbolani et al. [7] employed 1 jxA DC between two identical platinum electrodes and measured the potential difference between them to detect the endpoint of the titrations. Chlorine was titrated with phenylarsine oxide at pH 7 chlorine and chlorine dioxide were titrated analogously in the presence of iodide ions, and all three components were titrated at pH 2 in the presence of iodide. The method was used for water samples (taken from a water purification plant) containing both chlorine and chlorine dioxide. 

Give one major advantage and one major disadvantage of using chlorine dioxide for water disinfection. 

The following sections discuss the primary biocide used today, chlorine, and alternative physical and chemical techniques to address membrane biofouling control. The most common alternative techniques examined here include chloramine, chlorine dioxide, ozone, UV, and non-oxidizing biocides such as DBNPA and isothiazolone. Table 8.12 summarizes advantages and limitations of these techniques (adapted from Kim, 2009). It is important to note that some of these biocides/disinfectants can contact the membranes, and others must be removed or destroyed before the water is introduced to the membrane system itself. 

The advantages of chlorine dioxide are that it does not yield THMs and HAAs and that it is a more effective disinfectant than chlorine. Its limitations include ... 

Oxidation of manganese is one of the main uses of chlorine dioxide. Another advantage of chlorine dioxide is its effectiveness in inactivating Cryptosporidium. Although it is sometimes used as a residual disinfectant in the distribution system, it is more common to use chlorine dioxide only as a primary disinfectant and then use chlorine or chloramines to provide a distribution system residual. 

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