Optimizing Aeration in Pulp Mill Secondary Treatment Systems

Abstract

With better spill control and lower carbon loads to the treatment system, there is excess aeration occurring at the lagoon. This leads to unnecessary power costs, especially during peak demand summer periods. A study was conducted to determine lagoon performance so as to prioritize which aerators could be shut off and under what conditions. The two major elements of the study were (a) detailed lithium tracer work to identify the relatively stagnant zones in the pond, and (b) a radiotracer study to measure BOD loss in different parts of the system. Based on these results, it was concluded that about 15% of aeration capacity could be curtailed during routine operations. BOD and COD profiles taken before and after this 15% reduction showed no deterioration in effluent quality.