Oxygen-demanding materials

Water pollutant type Point sources Non-point sources  

The amount of oxygen required for oxidizing a substance to carbon dioxide and water may be sto-ichiometrically calculated if the chemical composition of the substance is known. In contrast, the 

Example 8.2 A general reaction that occurs in the COD test is represented as follows  

Effects of Pollutants on the Chemistry of the Atmosphere, Hydrosphere, and Lithosphere 

One must inhibit nitrification in order to distinguish between carbonaceous and nitrogenous BOD. 

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Sewer Disposal. Photoprocessing and printing wastes tend to be aqueous solutions that ate combined with other plant effluents and sent to the local sewer plant for treatment. The parameters of concern include silver, pH, and biological oxygen demand (BOD). BOD is a measure of how well a waste material degrades in the environment. Lower values ate preferred. Silver-bearing waste streams ate typically treated on-site, and the treated effluent is released to the drain. The printer usually receives a small cash credit for silver recovered. 

Discussion. One very important application of potassium dichromate is in a back-titration for the environmental determination16 of the amount of oxygen required to oxidise all the organic material in a sample of impure water, such as sewage effluent. This is known as the chemical oxygen demand (C.O.D.) and is expressed in terms of milligrams of oxygen required per litre of water, mg L l. The analysis of the impure water sample is carried out in parallel with a blank determination on pure, double-distilled water. 

The traditional areas of wet chemistry came under very close scrutiny and it was felt that whilst the overall size of Part D could be justifiably reduced, the chapter on titrimetry required modification to include a section on titrations in non-aqueous solvents as these are of particular application to organic materials. It was also felt that environmentally important titrations such as those for dissolved oxygen and chemical oxygen demand should be introduced for the first time. By way of contrast to this we considered that gravimetry has greatly diminished in application and justified a substantial reduction in volume. This in no way undermines its importance in terms of teaching laboratory skills, but the original multitude of precipitations has been substantially pruned and experimental details abbreviated. 

The chemical compositions of materials are usually expressed in terms of simple oxides calculated from elemental analysis determined by x-ray fluorescence. For spent foundry sand, the chemical parameters include bulk oxides mass composition, loss on ignition, and total oxygen demand. Table 4.6 lists the general chemical properties of spend foundry sand. It is shown that spent foundry sand consists primarily of silica dioxide. 

Amuda, O.S. and Ibrahim, A.O., Industrial wastewater treatment for chemical oxygen demand (COD) sing natural material as adsorbent, African Journal of Biotechnology, 5 (16), 148-1487, 2006. 

A strain of yeast and a strain of bacterium were co-immobilized to fabricate a biochemical oxygen demand (BOD) sensor based on sol-gel derived composite materials97. This novel type of biosensor was developed for water monitoring and was used to determine the BOD values of OECD synthetic wastewater, domestic wastewater, and lake waters. The microorganisms Trichosporon cutaneum and Bacillus subtilis were coimmobilized in the sol-gel composite material, which was composed of silica and the grafting copolymer of poly (vinyl alcohol) and 4-vinylpyridine (PVA-g-P(4-VP)). 

Consequently the consumption of dichromate is many times higher than that due to organic material in the sample. To complicate matters, any amines in the sample consume and release chlorine in a cyclic process, leading to high chemical oxygen demands. 

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. 

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