Activated Carbon Adsorption

Colloidal and soluble organic materials can be removed from solution through adsorption onto granular or powdered activated carbon, such as the particularly troublesome hard surfactants. Refractory substances resistant to biodegradation, such as ABS, are difficult or impossible to remove by conventional biological treatment, and so they are frequently removed by activated carbon adsorption [11]. The activated carbon application is made either in mixed-batch contact tanks with subsequent settling or filtration, or in flow-through GAC columns or contact beds. Obviously, because it is an expensive process, adsorption is being used as a polishing step of pretreated waste effluents. Nevertheless, according to Koziorowski and Kucharski [22] much better results of surfactant removal have been achieved with adsorption than coagulation/ settling. Wang [50-52] used both powdered activated carbon (PAC) and coagulation/settling/ DAF for successful removal of surfactants.

Coagulation/Flocculation/Settling/Flotation

As mentioned previously in Section 7.2.4, the coagulation/flocculation process was found

to be affected by the presence of surfactants

in the raw water or wastewater. Such

interference was

observed for both alum and ferric sulfate coagulant, but the use of

certain organic polymer

Table 10 Effluent Limitations for Subpart P, Liquid

Detergents

Effluent limitations [metric units (kg/1000 kg of anhydrous product)]

Effluent

Maximum for any 1 Average of daily values for 30 consecutive days

characteristic

day

shall not exceed

(a) BPTa

bod5

0.60

0.20

COD

1.80

0.60

TSS

0.015

0.005

Surfactants

0.39

0.13

Oil and grease

0.015

0.005

pH

c

c

(b) BPTb

bod5

0.05

COD

0.15

TSS

0.002

Surfactants

0.04

Oil and grease

0.002

PH

c

(c) BATa

bod5

0.10

0.05

COD

0.44

0.22

TSS

0.01

0.005

Surfactants

0.10

0.05

Oil and grease

0.01

0.005

pH

c

c

(d) BATb

bod5

0.02

COD

0.07

TSS

0.002

Surfactants

0.02

Oil and grease

0.002

pH

c

(e) NSPSa

bod5

0.10

0.05

COD

0.44

0.22

TSS

0.01

0.005

Surfactants

0.10

0.05

Oil and grease

0.01

0.005

pH

c

c

(f) NSPSb

bod5

0.02

COD

0.07

TSS

0.002

Surfactants

0.02

Oil and grease

0.002

PH

c

aFor normal liquid detergent operations.

bFor fast turnaround operation of automated fill lines.

cWithin the range 6.0-9.0.

aFor normal liquid detergent operations.

bFor fast turnaround operation of automated fill lines.

cWithin the range 6.0-9.0.

Figure 20 Process modification for wastewater recycling in detergent manufacture (from Ref. 37).

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