Removing nitrogen cpds. from water - by nitrification and withdrawing carbon di:oxide before denitrification in amt. corresp. to carbon di:oxide formed

摘要

In removal of NH4 and other organic N cpds. from water by a nitrification stage, in which the N is oxidised to nitrate, and a denitrification stage in which the nitrate formed is reduced to N2 with addn. of an electron donor as reducing agent, there is extracted from the water before the denitrification stage, an amt. of CO2 corresp. to the amt. of CO2 formed in the denitrification stage. Extn. of the CO2 is by blowing with air and the effluent air is used partly as O2 feed in the nitrification stage and is recycled into the extn. stage. Part of the water from the outlet from the denitrification stage may be recycled to the inlet of the nitrification stage, when the CO2 is withdrawn from the recycled water. USE/ADVANTAGE - Change of the water compsn. by accumulation of salts is avoided, less alkali is needed for neutralisation, the process is cheaper, and the carbonate hardness of the water can be regulated. The process can be applied to processing drinking water, cleaning ground water, and cleaning process water for re-use.