Removal of Chronic Toxicity and Organic Matter from a Paper Mill Effluent in an MBBR Process, 2003 Environmental Conference Proceedings

A full scale moving bed biofilm reactor (MBBR) was installed to reduce the chronic toxicity of a fine paper mill effluent. The effluent treatment consists of primary clarification, two MBBR tanks in series and two dissolved air flotation (DAF) units in parallel. The total reactor volume is 6,000 m3, and the average hydraulic retention time (HRT) is 5 hours.

In the first 6 months of operation the chronic toxicity of the treated water varied between 30 and 100 %, where a level of 100% exhibits no measurable chronic toxicity. This performance in toxicity removal is well below the limit of 3.1 % that is currently set by the state of Maine. The MBBR process has also exhibited a high and stable removal of chemical oxygen demand (COD) and biochemical oxygen demand (BOD), with the average removal efficiencies being 66 and 87 % respectively.

The MBBR process performance has been found to be insensitive to variations in flow, organic loading and temperature and has also recovered rapidly after shutdowns.