Page 230 - Water and wastewater engineering

COAGULATION AND FLOCCULATION 6-7

TABLE 6-1
Frequently used inorganic coagulants
Molecular weight,
Coagulant Chemical formula g/mole Remarks
Aluminum sulfate Al 2 (SO 4 ) 3 · 14H 2 O 594 Hg contamination may
be of concern
Sodium aluminate Na 2 Al 2 O 4 164 Provides alkalinity and
pH control
Aluminum chloride AlCl 3 133.5 Used in blends with
polymers
Polyaluminum chloride Al w (OH) x (Cl) y (SO 4 ) z Variable “PACl” used when
Hg contamination is a
concern
Polyaluminum sulfate Al w (OH) x (Cl) y (SO 4 ) z Variable “PAS” used when Hg
contamination is a
concern
Polyiron chloride Fe w (OH) x (Cl) y (SO 4 ) z Variable
Ferric chloride FeCl 3 162.5
Ferric sulfate Fe 2 (SO 4 ) 3 400

TABLE 6-2
Frequently used cationic organic coagulants

Coagulant Chemical formula

Epichlorohydrin CH 3
dimethylamine
(epi-DMA)
N Cl CH 2 CH 2
CH
CH 3

OH
x
Polydiallyl dimethyl CH CH CH
ammonium
chloride
CH 2 CH 2 CH 2 CH 3
(poly-DADMAC)

N Cl N Cl
CH 3 CH 3 CH 2 CH 3
x
CH CH 2
y