Activated carbon-enhanced filtration

Primary treatment (solid settling and removal) is required, secondary treatment (use of bacteria and aeration to enhance organic degradation) is becoming more routine, and tertiary treatment (filtration through activated carbon, applications of ozone, and chlorination) has been, or is being, implemented by all refineries. 

Figure 17 PACT wastewater treatment system general process diagram. Powdered activated carbon is added to the aeration tank influent in an activated sludge system. Polyelectrolyte is added to enhance flocculation of carbon flnes and microorganisms. Filtration may or may not be required. (From Ref. 27.)...

The potential development of electrokinetic geotextUes offers an opportunity to increase the redevelopment of derelict land as a means of reducing the pressure for construction within the natural environment. This electrically conductive material enhances the filtration and drainage functionalities by electro-osmosis and ion migration. Various types of conductive component can be incorporated in the geotextile structure to achieve this effect, but the possible use of activated carbon fibre or similar additives with pollution sorptive surface properties can aid land recovery of poUuted areas. 

In actual practice, powdered activated carbon is added to the wine or the must in amounts equal to about 0.05 to 1 g. of activated to each liter of wine, but to avoid loss of quality, the smallest effective dose should be used. The dose can be determined by laboratory tests on the wine. A suspension of carbon in a small amount of wine is first prepared and then added to the rest of the wine (must) contained in a vat. The adsorptive purification can be enhanced by stirring the contents of the vat or by bubbfing air fed at the bottom of the vat. This process takes several hours, after which the spent-up activated carbon can be separated by sedimentation followed by filtration in a filter press or in a centrifuge. 

The PAC activated slndge system is a modified activated sludge process. PAC is added to the aeration tank where it is mixed with the biological solids. The mixed liquor solids are settled and separated from the treated effluent in a gravity clarifier. Polyelectrolyte will normally be added prior to the clarification step to enhance solids-liquid separation. If phosphorus removal is necessary, alum is often added at this point. Even with polyelectrolyte addition, tertiary filtration is normally required to reduce the level of effluent suspended solids. The clarifier nnderflow solids are continuously returned to the aeration tank. A portion of the carbon-biomass mixture is wasted periodically to maintain the desired solids inventory in the system. 

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