Chemical oxidation demand

Ot = the chemical oxidation demand (COD) of trade effluent after one hour settlement at pH 7 (mg/1). 

In the author s experience, no truly satisfactory method yet exists for the determination of chemical oxidation demand in highly saline samples such as seawater. With reservations, several of the above methods are, however, applicable to estuarine waters of low salinity. 

Wanpeng et al. have also applied a Fenton reagent oxidation for the treatment of a dye H-acid containing wastewater.These investigators found that the process not only removed chemical oxidant demand effectively, but also improved the biodegradability by combining with the coagulation process. 

The radicals are then involved in oxidations such as formation of ketones (qv) from alcohols. Similar reactions are finding value in treatment of waste streams to reduce total oxidizable carbon and thus its chemical oxygen demand. These reactions normally are conducted in aqueous acid medium at pH 1—4 to minimize the catalytic decomposition of the hydrogen peroxide. More information on metal and metal oxide-catalyzed oxidation reactions (Milas oxidations) is available (4-7) (see also Photochemical technology, photocatalysis). 

COD (Chemical Oxygen Demand) Legislation and controls Oxidation by dichromate... 

COD Chemical oxygen demand - the amount of oxygen in mg/1 required to oxidize both organic and oxidizable inorganic compounds. 

Chemical oxygen demand (COD) A measure of the amount of oxygen, expressed in milligrams per liter, required to oxidize organie matter present in a substanee using a ehemieal oxidation method. 

The byproduct is a stoichiometric amount of 60 wt % H2S04, which is used in the chemical industry. The wastewater (0.3 m3/100 kg active matter), which contains paraffin, oxidation products of the paraffin, alkanesulfonate, and sulfur dioxide, has a chemical oxygen demand (COD) of 1800 mg/L and is readily biodegradable (>95% after 7 days). The sulfur dioxide emission after repeated washing of the off-gas amounts to 0.5 g/100 kg active matter [6]. 

The chemical composition of the soil and groundwater, specifically the amount of natural organic matter (NOM) and other reduced species, such as iron (II) or manganese (II) often analyzed as the chemical oxygen demand (COD) of the soil, or the soil oxidant demand. 

Chemical oxidation—Fuel oxygenates can be destroyed using hydroxyl radical oxidation the oxidant dosage and contact time are based more on overall oxidant demand of extracted groundwater than on types of oxygenate contaminants. 

The chemical method for the determination of the chemical oxygen demand of non-saline waters involves oxidation of the organic matter with an excess of standard acidic potassium dichromate in the presence of silver sulfate catalyst followed by estimation of unused dichromate by titration with ferrous ammonium sulfate. Unfortunately, in this method, the high concentrations of sodium chloride present in sea water react with potassium dichromate producing chlorine ... 

Because of the invalidity of the classical procedure, several workers have attempted to devise a method that is free from interference by chloride. Chloride interference can be eliminated by preventing the concurrent oxidation of organic material and chloride. This can be effected in two ways - either by leaving the chloride in the test mixture but preventing its oxidation, or by removing the chloride prior to the chemical oxygen demand test. 

Some routes of chemical transformations of nitrile oxides connected with the problem of their stability were briefly discussed in Section 1.2. Here only two types of such reactions, proceeding in the absence of other reagents, viz., dimerization to furoxans and isomerization to isocyanates, will be considered. All other reactions of nitrile oxides demand a second reagent (in some cases the component is present in the same molecule, and the reaction takes place intramolecularly) namely, deoxygenation, addition of nucleophiles, and 1,3-dipolar cycloaddition reactions. Also, some other reactions are presented, which differ from those mentioned above. 

Rautenbach and MeUis [75] describe a process in which a UF-membrane fermentor and a subsequent NF-treatment of the UF-permeate are integrated. The retentate of the NF-step is recycled to the feed of the UF-membrane reactor (Fig. 13.8). This process has been commercialised by Wehrle-Werk AG as the Biomembrat -plus system [76] and is well suited for the treatment of effluents with recalcitrant components. The process also allows for an additional treatment process, like adsorption or chemical oxidation of the NF-retentate, before returning the NF-retentate to the feed of the UF-membrane fermentor. Usually, the efficiency of these treatment processes is increased as the NF-retentate contains higher concentrations of these components. Pilot tests with landfiU leachates [75] and wastewater from cotton textile and tannery industry have been reported [77]. An overview of chemical oxygen demand (COD) reduction and COD concentrations in the permeate are shown in... 

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