Improved process for waste water treatment by removal of sodium sulfate

摘要

Waste H2O streams contg. more than 20% Na2SO4 (I) are treated as follows: (a) a solvent (II) miscible in aq. soln. at 20-110 deg.C is added to ppte. crystalline (I); (b) the stream is biologically pre-treated with activated sludge (III); (c) denitrification is effected with (III); and (d) nitrification is effected with (III). Step (a) (II) is pref. MeOH, EtOH, i-PrOH, Me2CO, and monoethanolamine, and amt. added is pref. 20-70 wt.% of total H2O and (II). Crystalline is pref. at 40-80 deg.C. The aq. streams pref. contain polyethyleneimine or cyclohexanone or by-prods. from their prodn., or mixts.. Initial removal of the high Na2SO4 levels allows the subsequent biological pre-treatment and denitrification and nitrification to be effected by a conventional 2 sludge waste H2O treatment process. The method is esp. useful for the treatment of waste H2O streams generated from prodn. of polyethyleneimine and cyclohexanone, when TOC content in the H2O is significantly reduced prior to its introdn. to the main waste H2O stream, overall nitrification time is reduced, and lower NH3 and TOC content are provided in the final effluent. Waste H2O flow is increased, thus increasing the amt. of H2O that can be processed in a given time or allowing smaller tanks to be used.