Challenge

Facing new OCPSF (organic chemicals, plastics, and synthetic fibers) requirements for effluent discharge, the Nalco Chemical Co. plant at Garyville, LA, had to make changes in its wastewater treatment operation.

Three isolated waste streams are generated in the manufacturing of specialty chemicals Nalco supplies to the water treatment chemical markets, and contain various monomers. While they represent only 10 percent of the hydraulic flow, TOC (total organic carbon) levels can range from 1,000 parts per million to 10,000 ppm. The streams are also odorous.

Solution

Siemens Water Technologies supplied a two-stage aerobic PACT® system. The system is operated in series, and design flow is 450,000 gallons per day (hydraulic capacity 1.4 million gpd).

In the aeration tanks, powdered activated carbon and activated sludge deliver physical adsorption and biological treatment simultaneously. The combination produces a high quality effluent, even at high organic loadings. After a dose of polymer, the treated water settles in a clarifier, and then is discharged to the Mississippi River. Waste sludge is aerobically digested, dewatered, and disposed of as a non-hazardous material in a landfill.

Results

The PACT system has performed well, even in times of stress, since its startup in November, 1990. Benefits include:

• 96-plus percent reductions in COD and TOC, meeting the requirements for the OCPSF industry
• The PACT system minimizes stripping of volatiles and odors off the surface of the aeration tank
• Effective oxygen transfer
• Sludge settleability