SenGupta and student receive patent for sludge-recovery technique

Arup K. SenGupta, professor and chair of the department of civil and environmental engineering, and Prakhar Prakash, a Ph.D. candidate in environmental engineering, have been awarded U.S. patent 6,495,047 for a “Process for selective coagulant recovery from water treatment plant sludge.”

The new process, which is the subject of Prakash’s doctoral work, uses a membrane separation technique called Donnan Dialysis to recover alum and ferric salts from the sludges of water treatment plants. Alum and ferric salts are the most widely used coagulants to clarify river or lake water in over one thousand water treatment plants in the U.S.

In the new process, which is driven by an electrochemical potential gradient, a cation exchange membrane, Nafion 117, is utilized to purify and concentrate the coagulant from a large volume of sludge. The recovered coagulant is essentially free from impurities and can be reused in water treatment plants.

The process was tried on sludges collected from the Allentown Water Treatment plant and from the Baxter Plant near Philadelphia. More than 75% of the coagulant could be easily recovered in less than a day. The process reduces the amount of sludge generated in water treatment plants by 40-60 percent, decreasing the volume of disposal to landfills.

The study was funded through an “Industrial Ecology Fellowship” grant made to SenGupta by Lucent Technologies and the National Science Foundation.