Paper Mill Treatment Plant Cost-Effectively to Meet 40-Fold Reduction in Wasteload, 1999 Environmental Conference Proceedings

Robert W. Martin & Mike Welliver

Grays Harbor Paper, L.P.

Robert J. York

CH2M HILL

The Grays Harbors Paper L.P. mill in Hoquiam, Washington is a non-integrated fine paper mill located at the site of a former dissolving sulfite mill. The now oversized wastewater treatment system was originally designed to handle roughly 5 times the present hydraulic load and approximately 40 times the present organic load. Cost-effective strategies were implemented that saved energy, improved treatment efficiency, and reduced odor. A deteriorating static tube aeration system was replaced by a new coarse-bubble floating lateral diffused aeration system that employs 12 independent zones of aeration. A programmable logic controller (PLC) opens and closes valves sequentially to each zone. A single 200-kilowatt (kw) blower, which replaced six 670-kw blowers, keeps over 95,000 cubic meters of aeration volume well mixed. This system, which maintains dissolved oxygen levels over 3 mg/L, was installed without removing the aeration basin from service and using many components of the present system. The secondary clarifier underflow is returned to the primary clarifier, cutting hydraulic retention time in the primary clarifier in half and alleviating odors.