Cellulose oxygen demand

The thin film composite membrane exhibited superior overall rejection performance in these tests, with ammonia and nitrate rejection showing an outstanding improvement. It has also been reported that silica rejection by the thin film composite membranes is superior to that of cellulose acetate. While the above data indicates a marginal improvement in the rejection of chemical oxygen demand (COD), which is an indication of organic content, other tests conducted by membrane manufacturers show that the polyurea and polyamide membrane barrier layers exhibit an organic rejection that is clearly superior to that of cellulose acetate. Reverse osmosis element manufacturers should be contacted for rejection data on specific organic compounds. ... 

The difficulties with the COD method as a measure of oxygen demand is that acidified dichromate is such a strong oxidizer that it oxidizes substances that are very slow to consume oxygen in natural waters and that therefore pose no real threat to their oxygen content. In other words, dichromate oxidizes substances that would not be oxidized by O2 in the determination of the BOD. Because of this excess oxidation, namely of stable organic matter such as cellulose to CO2, and ofCU to CI2, the COD value for a water sample as a rule is slightly higher than its BOD. 

The production of cellulose represents 70% of the total pollution of wastewaters from chemical industry on the basis of BOD5 (biological oxygen demand). Polluted wastewaters from the production of sulphite cellulose cause a brown colour in surface waters, as well as their frothiness due to the surface activity, and they have an unpleasant odour. 

Wastewaters from paper factories containing dyes particularly aniline and sulfur ones are generated from the paper treatment process consisting in the addition of fillers and dyes to the bleached cellulose material. As a result of multi-stage purification of wastewaters from the cellulose plants, there is obtained a low value of BOD (biochemical oxygen demand) - 4 mg/L but COD (chemical oxygen demand) is maintained on the level 75 mg/L. These waste-waters contain a small amormt of suspended matter - 5 mg/L, but they are characterized by intensive colour - 40 mg Pt/L [21]. 

As indicated, any given aliphatic chemical is likely to be made by a number of processes from several raw materials. Important examples are acetic anhydride and acetic acid (2) production of the former was about 900,000,000 pounds in 1950 and that of the latter was about half as great. The large demand for these related products is primarily the result of the requirements of cellulose acetate rayon for acetic anhydride. The economic complexities in the production of the aliphatic oxygenated chemicals are probably best illustrated by these two products. 

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