Effects of iron dust on the performance of the BNR process

Abstract

Recent studies on wastewater treatment using BNR process have focused on nutrient removal. Although BNR had shown improved nitrogen and phosphorus removal, sludge settleability has not been improved. In this study the effect of iron dust on the performances of BNR process and sludge settleabilty is focused. From the study about upgrading BNR process on sludge settleability using iron dust, two trains of BNR process with iron dust and without iron dust were operated under various operating HRT (4, 6 and 8 hours) and SRT (20 and 40 days). In addition, particle size distribution and dosage of iron dust were investigated. In particle size distribution test, it was found that with size lower than 25㎛ and addition of iron dust of 0.5 g/g MLVSS were optimal to BNR process. It was also found that sludge settleability and nutrient removal were favorable when iron dust was added. It was possible to maintain high biomass concentration by injecting iron dust powder to BNR process. The removal efficiency of T-N and T-P was also improved by iron dust. At low HRT of 6hrs the iron dust was washing-out of from the settlers as well. Oxygen uptake rates were not changed much with iron addition, indicating that the microorganism activity was not deteriorated by the powder. In conclusion, the iron dust appeared quite favorable and efficient in improving the BNR operation as well as sludge settleability.