Performance and Case Studies

Battelle Northwest and the Eimco Division of the Envirotech Corporation each conducted major investigations in the use of powdered carbon for the treatment of municipal wastewaters. One study was conducted by Battelle Northwest and the other was conducted by the Eimco Division of the Envirotech Corporation. 

In the Battelle Northwest study (15,17), raw sewage was contacted with PAC to effectively remove the dissolved organic matter. An inorganic coagulant (alum) was then used to aid in subsequent clarification. Polyelectrolytes were added, followed by 

Based on the favorable results of the Battelle Northwest laboratory study, a 100,000 gpd pilot plant was constructed in Albany, NY, USA. The pilot plant comprised two major systems a liquid treatment system and a carbon regeneration facihty. During the 1972 operations, the average effluent turbidity, suspended sohds, COD, and BOD concentrations were 0.67 JTU, 3.1 mg/L, 39 mg/L, and 17 mg/L, respectively. This represented average removals of 98.1% suspended solids, 82.6% COD, and 81.3% BOD. These results were achieved at total plant detention times averaged slightly less than 90 min. Recovery of 91% of powdered carbon was achieved. 

In the Eimco study (18,19), a 100 gpm pilot plant in Salt Lake City, UT, USA, was constructed for the evaluation of PAC treatment of raw sewage. The pilot plant was operated for 16 mo to evaluate lime, alum, and ferric iron coagulation as well as single-and two-stage countercurrent carbon treatment processes. The chemically treated effluent then flowed to the carbon contactors, which could be operated either as a single-stage (parallel) treatment process or a two-stage countercurrent (series) treatment process. PAC was fed and maintained as concentrated slurry. 

Another study examined the PAC-activated sludge process (14). The addition of powdered carbon directly into mixed liquor in an activated sludge plant aeration basin is referred to as the PACT process. The benefits attributed to this system are numerous, such as improved BOD and COD removal by adsorption, adsorption of color and toxic agents, reduction of aerator and effluent foam, and so on. The goal of the PACT process is to improve organic removal or to improve sludge settling characteristics. 

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