Study on Compound Biofilm Formation on the surface of Iron Oxide Coated Sands and Its Removal Efficiency to Ammonia-Nitrogen

By using a homemade Iron Oxide Coated Sands filtration medium (for short: IOCS), start-up behaviors of compound biofilm formation on the surface of IOCS were investigated with the help of a series of experiments, and its removal efficiencies to Ammonia-Nitrogen contained in micropollution raw water were analyzed as well. The differences of removal efficiency between raw quartz sands (for short: RQS) coated biofilm and bio-IOCS were discussed. Surface morphologic properties of two kinds of bio-sands were analyzed too. The results are shown as follows: The biomass of BioRQS, and Bio-IOCS are 15.46 nmolP/(g sand) and 13.79 nmolP/(g sand) at the initial stage of biofilm formation, 18.75 nmolP/(g sand) and 20.09 nmolP/(g sand) at the stable stage. When the concentration of Ammonia-Nitrogen is in the range of 1.0 mg/L to 2.0mg/L, removal rate of BioRQS and Bio-IOCS is 92%, 95% separately at the initial stage, and it is 60%, 80% respectively at the stable stage. If concentration of Ammonia-Nitrogen varies from 0.5 mg/L to 4.0mg/L, removal rate of BioRQS increases from 60% to 80%, and Bio-IOCS from 70% to 95%. The surface morphologic properties of the two filters are quite different before and after filtration and its biofilm formation. The surface pore sizes become smaller, surface appearances are rougher and its porosity is high. Surface morphologic characteristics of BioIOCS are changed more markedly than those of IOCS and bioRQS. Keywords-Iron Oxide Coated Sand; Bio-Raw Quartz Sands; Bio-Iron Oxide Coated Sands; Compound Formation; AmmoniaNitrogen;Removal Efficiency; Morphologic Properties