Optimizing BOD. Removal Under Adverse Operating Condiitons in a Kraft Mill, 1996 Environmental Conference Proceedings

A major forest products company operates a Kraft mill in the Gulf Coast region. Water from the mill operations is treated in a lagoon based wastewater system. The plant is subject to an NPDES permit and state water quality based permit. The water quality permit is restrictive enough as to approach the proposed guidelines for mills under the USEPA “Cluster Rules”. The mill produces high quality bleached board and white top linerboard. The wastewater system consists of a primary clarifier, aeration lagoon and facultative lagoon followed by a tertiary treatment system consisting of several unaerated lagoons connected by effluent ditches prior discharging into the Conecuh River. Wastewater temperatures in the first half of the year measured in the lagoon system, averaged above 40°C. Available literature indicates that biological treatment efficiency declines after operating temperatures exceed 38°C. For this reason, and because of stringent requirements in the water quality permit, the mill evaluated ways to improve the system efficiency, using the addition of thermophilic, cultured microorganisms, directional aeration and effluent recycling to the lagoon. This paper focuses primarily on the application and use of commercial thermophilic microorganisms. To aid in growing microorganisms, three (3) on-site culturing and fermentation systems were developed to apply microorganisms to the lagoon.