Bagasse Pulp Mill Effluent Treatment by Aerobic Biofiltration, 2002 Environmental Conference Proceedings

A. Kantardjieff, C. Carballido, P. Kantardjieff and A. Kantardjieff

Pilot plant trials were run at the Kimberly Clark de Mexico facility in Orizaba in order to validate the applicability of the aerobic biofiltration technology for the treatment of mill effluent.

Under variable organic loadings (5 to 12 kg COD/m3/day) and a COD:BOD ratio of approximately 4:1, the system achieved COD and BOD removal efficiencies greater than 50% and 90%, respectively. The true hydraulic retention time for Biofilter 1 during the tests averaged 3.5 hours (47% of the biofilter media volume is void, while the packing material occupies 53%).

A biological sludge production rate of 0.4 kg of solids produced per kg of BOD removed was established. The system also experienced a five-day mill shutdown, which did not significantly affect the biofilters. It is expected that standard 48-hour shutdowns will not deteriorate the effluent quality significantly. However, electrical shutdowns coupled with mill shutdowns did have greater effects on the system's performance. In addition, elimination of nutrients did not affect the performance of the system. The pool of nutrients and essential elements within the biofilters provided enough support for the biomass to sustain high activity levels. Backwash water settled dramatically well, with a final volume accounting for 10% of the initial volume.