Biological Treatment of Formaldehyde by Activated Sludge

The effect of formaldehyde (HCHO) on activated sludge was investigated. More than 3.3mg/l of HCHO showed lag type toxicity for O_2 uptake of nonacclimated sludge. Acclimation studies for highly concentrated HCHO showed that activated sludge could remove 90% of 5,500mg/l HCHO at 40 hours. Changes in pH, COD, and sludge weight during HCHO removal were investigated. In glucose-containing medium, sludge weight increased. Oxidation of glucose and increase of sludge weight occurred when HCHO was removed more than 80% and pH raised to 5.5. Optimal pH for HCHO removal by acclimated sludge was 6. Those results suggest that activated sludge oxidizes HCHO but are not utilized as a carbon source; addition of a carbon source such as glucose is necessary for treatment of highly concentrated HCHO.