Removal Of Humic Acid By PAC In Enhanced Coagulation Process

Natural organic substance of humic acid is a kind of contamination which is concerned. Humic acid (HA) not only affects the color,odour of the water,but is also the main precursor of THMs. The normal method for getting rid of HA are Chemical oxidation, biological oxidation, and activated carbon adsorption, but these methods are not effective enough to remove soluble hurnic acid which is difficult to biologic removal. Therefore, enhanced coagulation is one of a focused research task for treating that kind of organic now.For that, firstly, Polyaluminum Chloride (PAC) is used as coagulant, the effect of different conditions for coagulating humic acid is studied. The experimental results show that, under the coagulation procedure mix 30s (250rpm) stir 15min (40rpm) settling 30min and removal conditions pH=6.5, dosage of PAC 12mg/L, the removal rate of humic acid dissolved in water is amounted to 89.34%, and the removal rate of turbidity is 91.34%;According to above concentration condition, charge neutralization and electric double-layer compression become the main mechanisms of coagulation.Secondly, in order to improve the removal efficiency of humic acid during enhanced coagulation process and reduce disposal costs, on the basis of the conventional PAC coagulation, the PAC compounded with clay mineral which is used as a coagulant aids is studied. The experimental results show that, the flocculant compounded with clay can make a better coagulation effect, 12mg/L PAC compounded with 120mu 12mg/L kaolin, the removal rate of turbidity is 98.9%, of humic acid is 97.9% and concentration of residual aluminum is 0.16mg/L. The aluminum species distributions change while total aluminum and dissolved aluminum contents descend.Finally, a variety of attapulgite modifications are researched to prepare a new type of modified attapulgite for removal of humic acid. The results show that the attapulgite, for purification and heat-aicd modification, is used as a flocculant in the 5mg/L dosage condition, the removal rate of humic acid is up to 92.03%.