Operational Experience with Anaerobic/Aerobic Treatment System for Paper Mill Wastewater

Abstract

The paper mill located in Indiana began operation in 1975. The initial effluent treatment system was aeration stablization and settling basins. The waste system discharged to the Wabash River. Primary solids from the clarifier are recycled to the mill. Secondary solids from the settling basins were applied to farm land. Original B.O.D. load entering the first aeration basin was 4,000 Kg per day @ 3786 cubic meters water per day. Present raw waste discharge is about 11,000 Kg per day @ 3786 cubic meters. The production rate has increased from 318 to 545 metric tons per day. The designed waste treatment system was 240 horsepower of surface aeration. In an attempt to keep up with the increasing B.O.D. load, surface aeration horsepower was increased to 450. This combination resulted in greater production of secondary solids (biomass). An anaerobic pilot plant study was conducted in 1978. Based on the study's results, the Indiana Water Pollution Control Division approved conversion of the Newport effluent treatment system to an anaerobic/aerobic system. In November 1978 we converted one aeration basin to an anaerobic cell. (The first paper mill in North America to have such a system). The other aeration basin received a total of 300 horsepower available aeration. From November 1978 to April 1979 we learned the operational controls and modified the anaerobic cell. In May 1979 the anaerobic pond efficiency was 80% B.O.D. reduction. Total effluent system efficiency has averaged 98% for the past 3 years. Aerobic biomass generation has been reduced 80 to 90% as measured by settleable solids. Recent studies and project modifications will reduce the aerobic biomass even further. In changing to anaerobic-aerobic treatment a seventy percent production increase has been possible without expansion of the wastewater treatment facilities.