排水中のリンの浮選除去

Abstract

It is difficult to remove effectively phosphorus from wastewaters by coagulation sedimentation method. Especially it is more difficult to remove dilute phosphorus from wastewaters by the above method. Therefore flotation method has been examined to remove those phosphorus, and to meet the water pollution control legislation.In dissolved air flotation under conditions of pH 9-10 and [Ca2+]/[HPO42-] =3 using such a collector as sodium oleate (NaOI), dodecyl amine hydrochloride (DAC) or sodium dodecyl sulphate (SDS), a phosphorus removal showed over 97%(residual phosphorus concentration of about 1mg/l) by using any collector, nearly 100% removal rate being obtainable with SDS in particular.The dissolved air flotation of dilute phosphorus solution containing a HPO42-concentration of 1x10-4 mol/dm3 (P: 3.1 mg/l) was carried out in order to remove phosphorus in sewage or domestic wastewaters. A phosphorus removal rate of 75% was obrained under conditions of 1-10-5 mol/dm3 of SDS, [Ca2+]/[HPO42-] =3 and pH 8, and a residual phosphorus concentration was below 1mg/l. Moreover, thephosphorus removal rate increasing with increase in pH value, at pH 11 a phosphorus removal rate of 95 98%(residual phosphorus concentration of 0.06 0.16mg/l) is obtainable.It is considered that the dissolved air flotation is more advantageous than the crystallization process known as a process for treating wastewaters of such dilute concentration, because of short flotation time and large treatment capacity.