WASTE MANAGEMENT IN LEATHER INDUSTRY

25 382. The nitrogen released through protein breakdown and the deliming processis in the form of ammonia. The latter can be converted by bacteria over severalstages into water and nitrogen gas which is ultimately released into theatmosphere. Both of these breakdown products are non- toxic, yet large volumesof oxygen are needed in the process. If oxygen demand is greater than the levelsupplied naturally by the water course, toxic anaerobic is conditions can rapidlydevelop.The nitrogenous compounds can be broken down by combining intensiveaerobic and anoxic biological treatment. The oxygen demand is very high, thusleading to correspondingly high operation and energy costs. The compoundscontaining nitrogen can be determined by the Kjeldahl method of analysis.5.1.3.2 Ammonium Content As Nitrogen (N)Often confused with TKN, this value is sometimes require in discharge limitsand. As ammonium compounds are part of TKN, the problems associated withrapid plant growth and oxygen demand are the same. These compounds aremostly the outcome of the deliming process, with comparatively small volumesbeing produced from liming and unhairing. The analysis is similar to TKN, butomits the initial digestion stage. This excludes the nitrogen component resultingfrom protein wastes.5.1.4 Sulfides(Environmental, Health, and Safety Guidelines for Tanning and LeatherFinishing, (2007)) Sulfides are used in the dehairing process. Hydrogen sulfide(H2S) may be released when sulfide- containing liquors are acidified and duringnormal operational activities (e.g. opening of drums during the deliming process,cleaning operations/ sludge removal in gullies and pits, and bulk deliveries of