Contract Wastewater Treatment
December 4, 2001 ISSUE #123
It was at a Tappi Environmental show that Vincent met representatives of Integrated Technical Services of Baton Rouge, Louisiana. This firm specializes in handling waste disposal on a contract basis. Pulp and paper is but one of many industries served by ITS.
Working with Vincent, ITS secured a three year contract to handle wastewater disposal at a Georgia-Pacific mill. The mill, in Crossett, Arkansas, was once the largest mill in the United States. It is rated at 1,600 tons per day, producing softwood Kraft pulp.
The combined wastewater flows of the mill are pumped a few miles off-site to an in-the-ground clarifier. The flow to the clarifier averages fourteen million gallons per day. It includes the undercooked chips, shives, screen rejects, and wash water from all sources.
Underflow from this clarifier is pumped to sidehill screens mounted above Vincent Model VP-16 screw presses. The arrangement has a pair of 3' sidehills over the inlet of each of two presses. These face each other so that any splash flow falls into the press.
The flow to the sidehill screens averages 1% to 2% solids. Even under adverse conditions this is concentrated sufficiently by the screens for the screw presses to operate reliably. Only under very difficult conditions is any polymer used in the treatment.
Press capacity is extremely high. This is due to the effectiveness of the sidehill screens and the high freeness of the Kraft fiber coming from the mill. Throughputs in excess of 70 TPD of air-dry solids per press have been measured. This is an outdoors installation. The only building is a trailer used by an operator. Currently the cake from the presses is landfilled, although there are plans to use the cake as boiler fuel.