Technical help: How effective is the flocculant?
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This post was last edited by hesonchang214 on 2011-10-24 at 23:00. What are the effects of using aggregated aluminum trichloride and anionic polyacrylamide? Can they reduce the COD level in wastewater?
The main function of the chemical is to promote the flocculation and precipitation of suspended solids; it can also reduce some amount of COD, though not by much.
This post was last edited by hesonchang214 on 2011-10-24 at 23:01. Whether it is a coagulant or a flocculant, they generally reduce COD; however, the water after the addition of these chemicals sees its COD decrease further after filtration!
This post was last edited by hesonchang214 on 2011-10-24 23:01. Coagulants are organic polymers, and an improper amount of them can actually increase COD!
PAC is a coagulant, while PAM is a flocculant aid. It mainly removes suspended solids from water; however, PAC absorbs some of the COD while forming flocs, which thus reduces the COD level. If there is a high amount of suspended solids in the water, the removal rate of COD is relatively higher as well. However, the removal rate of soluble COD is not high. PAM is a polymer coagulant; it is itself also a flocculant, so its dosage should not be too high, as excessive amounts can increase COD.
Polyaluminum chloride is primarily used as a coagulant, while polyacrylamide can serve as a flocculant aid; using both together yields better results. Generally, an addition amount of polyacrylamide of around 2% to 5% of that of polyaluminum chloride gives the best flocculation and sedimentation effects.
Depending on your dosage control and the type of COD, the COD removal rate is generally very low.