Pulp and Paper Treatment Plant Upgrade A Case Study on Developing Best Solution

A pulp and paper plant located in South America produces paper made from sugar cane bagasse. Bagasse is the residual fibrous plant material remaining after juice is extracted from the sugar cane plant. The paper production process uses large quantities of water and generates wastewater which includes 1.6 MGD of high strength wastewater with COD of about 8,000 mg/l from the depithing operation which is called desmedulado. The remaining wastewaters are lower strength COD with a flow of 8.4 MGD.The existing aerated stabilization basin (ASB) has accumulated significant quantities of sludge resulting in reduced hydraulic detention time and short circuiting through channels created in the settling lagoon. This facility was beginning to approach effluent non-compliance with both TSS and BOD. Because of a risk of exceeding effluent permit limits for both Country and World Bank discharge limits for BOD and TSS, the plant wanted a design upgrade to the treatment process. It was very uncertain how much time the plant had before a major failure and permit exceedance would be achieved. The focus of the project was to determine if anaerobic treatment with biogas energy recovery was feasible for the high strength desmedulado wastewater. A second focus was to evaluate what was the best solution to converting the ASB to an activated sludge system and what was the best activated sludge alternative.