PROCESS FOR WATER PURIFICATION

摘要

1. Process of purification of polluted water of a type in which the water to be treated is made to percolate from above to below through a submerged and fixed bed of granular filtering material with the insufflation at an intermediate level of the bed of an oxygenated gaseous flow rising, the process being characterized in that the flows of water to be treated and the oxygenated gas are regulated so as to satisfy the following relations : Q1 /S =< (alpha epsilon-K1 ) Q2 /S =< K2 . R/DO v (alpha epsilon-K1 ) and, simultaneously : Q2 . DO/S.h =< K3 or Q2 /S =< K3 . h/DO in which : - Q1 is the oxygenated gas flow, in m**3 /h - Q2 the flow of water to be treated, lower than 10 m**3 /h/m**2 of bed section - epsilon the porosity of the bed of granular material, preferably comprised between 0,45 and 0,55 - alpha the maximum fraction of pores volume which can be occupied by the gas without affecting the efficacity of the treatment ; alpha fluctuating between 0,2 and 0,6 - S the cross section of the bed, in m**2 - h the height of the bed, in meter - v the vertical component of the mean velocity of the rising gas bubbles, comprised between 200 and 400 m/h - K1 a constant, comprised between 0,2 and 0,08 m**3 /m**3 , corresponding to the fraction of the volume of the bed occupied by immobilised gas pockets - K2 the oxygen concentration of the gas, preferably comprised between 0,20 and 1,40 kg/m**3 - K3 the value of the oxygen demand (DO) which can satisfy 1 m**3 of granular material in an hour under the operating conditions (in kg/m**3 /h), K3 being lover than 0,8 kg of O2 /h/m**3 of granular material - DO the demand in oxygen to be satisfied, in kg per m**3 of water to be treated and corresponding to the relation : total DO = (0,7 to 1,2) DBO5 + (4 to 5) N (from NH4 ) - R the global yield of transfer (or fraction : weight of effectively dissolved oxygen/weight of oxygen injected in the bed), R being a function of the saturation (CS ) and real (C) concentrations in oxygen in the bed, according to the relation : R = K (CS -C) where the constant K is between 2,7 . 10**-3 and 25 . 10**-3 in (mg/l)**-1 m**-1.