"Treatment and disposal of waste sludge significantly impacts operating costs and environmental sustainability of the activated sludge process, one of the most widely used effluent treatment systems in Brazilian kraft pulp mills. Therefore, use of the chemical supplements folic acid and 3,3’,4’,5-tetrachlorosalicylanilide (TCS) for reducing sludge production was investigated using laboratory bench-scale sequencing batch reactors. Folic acid (0.5 mg/L) reduced sludge yield by 24%, while TCS (1.0 mg/L) reduced yield by 19%, without negatively affecting COD removal efficiency, under varying organic loading rates. Sludge settleability was unaffected or improved at the optimum supplement doses. However, both supplements increased sludge specific oxygen uptake rates and hindered removal or increased effluent toxicity during biological treatment. Therefore, the decision to use either supplement in an existing activated sludge plant must consider available aeration capacity and effluent dilution in receiving waters.

Keywords: eucalypt, folic acid, TCS, toxicity, treatment efficiency.


Authors*: Teynha V. Stoppa
Ann H. Mounteer1
Pedro H. G. Alves
Frederico H. C. Gomes

O PAPEL vol. 75, num. 12, pp. 76 - 81 DEC 2014