Dosing of Ferric Iron for Odour Control in Stormwater Drainage Systems of Hong Kong

Professor LI Xiao-yan (HKU)

Abstract
In recent years, complaints have been often made against the malodorous odour from stormwater drainage systems in Hong Kong, especially in areas near the water-front. Due to the accumulaton of organic-rich deposits in box culverts and nullahs, hydrogen sulphide (H2S) is produced from the sediment. In this study, a cost-effective approach is developed for the control of H2S odour problems by dosing ferric iron (Fe(III)) onto the sediment surface. The method makes use of the high oxidative reactivity of Fe(III) to H2S and the ensured precipitation of S2- with ferrous iron (Fe(II)). The experimental results show that dosing of Fe(III) is effective in suppression of H2S flux from polluted sediment into the overlying water. A dosage of 60-100 g Fe(III)/m2 could keep the sulphide concentration in water below 1 mg/L for over 15 days, in sharp contrast to the gradual increase of sulphide concentration in the control incubator without Fe(III) dosing. In situ ferric iron regeneration from oxidation of ferrous iron was also demonstrated. More laboratory and field tests are being carried out to optimise the iron dosinig scheme for actual application of the ferric-based odour control method.

About the Speaker
Prof. LI obtained his Bachelor and Master degrees in Environmental Engineering from Tsinghua University, China. He received his Ph.D. degree from the University of Arizona. He is a professor in the Department of Civil Engineering at the University of Hong Kong. His research interests include particle transport in water; bioaggregation and granulation; sediment-water-pollutant interactions; and membrane application in water and wastewater treatment. He has developed models for particle flocculation in water, membrane fouling in membrane filtration and membrane bioreactors, and sediment nutrient flux. He has authored or co-authored 100 SCI journal papers with over 2,000 citations.