Page 121 - Industrial Wastewater Treatment, Recycling and Reuse

Advanced Physico-chemical Methods of Treatment for Industrial Wastewaters 95

Process improvement using coagulant formulation
pH range

3-11 PAC:PolyDADMAC
(200:100)
pH range
3-9 PAC:PolyDAD MAC
(200:60)
pH range
5-7
PAC:PolyDADMAC
(200:20)
Figure 2.5 Process improvement using binary coagulant formulations.

100

80 PAC: Alum: PolyDADMAC
% Color removal 60 100:500:60

100:500:60
40

20

0
3
5
7
pH 9
11
12
Figure 2.6 Process improvement using three-component coagulant formulations.

ineffective, while for alum, the required dosage was >500 ppm. The behav-
ior here highlights three key issues:
1. For dye removal, the use of inorganic coagulants is quite effective, and
close to 100% removal is possible.
2. Inorganic polymer PAC performs much better as compared to conven-
tional inorganic coagulants such as ferrous sulfate or alum.
3. Even with PAC, the minimum required dose varies with nature of dye.
The use of the coagulant PAC alone has many limitations, such as applica-
bility in a very limited range of pH with best results at pH 5. The issues
pertaining to such limitations can be best resolved using suitable coagulant