Abstract
Phosphorus in wastewater is one the main culprit which accelerates eutrophication in waterbody if it is not being treated properly. Steel slag filter emerged as one alternative treatment for wastewater. However, the variousness of metal oxides including Fe in steel slag will affect the phosphorus removal efficiency. Thus, this study was conducted to investigate the ability of a series of lab-scale high Fe electric arc furnace (EAF- slag) column filters in removing PO43- from synthetic wastewater. The systems were operated under aerated and unaerated within acidic and alkaline conditions. Synthetic wastewater contained 25 mg/L was prepared as the feed and monitored weekly basis for the PO43- removal efficiency and the total metals (Ca, Fe, and Mg) concentrations in the effluents. The results show that both aerated and unaerated high Fe EAF-slag filter systems have high PO43- removal efficiency under acidic condition, which unaerated system performed slightly better. It can be observed that unaerated systems performed better in removing PO43- at acidic and neutral pH values but not at extremely high pH. As for the PO43- removal mechanism was achieved by adsorption and precipitation at acidic pH and the concentration of Ca, Mg and Fe in effluents was related to the PO43- removal efficiency at different pH values.
Highlights
Phosphorus is a culprit nutrient in accelerating of eutrophication in natural surface waters
Phosphorus removal using steel slag system prefers basic condition where adsorption will occur at low pH and Ca PO43 will precipitate at high pH value
For high Fe EAF-slag filters with pH values of 3, 5, 7, and 9, they showed that the unaerated system provide higher PO43removal efficiency compared to the aerated system
Summary
Phosphorus is a culprit nutrient in accelerating of eutrophication in natural surface waters. A by-product from steel manufacturing industry filter is amongst a high potential medium for removing phosphate from wastewater as it contains high concentrations of metal oxides including Ca, Fe, Al and Mg [2]. The removal mechanisms of PO43- is either through adsorption or precipitation depends on the existing of metal oxides concentrations [3]. Phosphorus removal using steel slag system prefers basic condition where adsorption will occur at low pH and Ca PO43 will precipitate at high pH value. Insoluble phosphates in a steel slag filter system are chemically precipitated with ferric iron under aerobic conditions. When high percentage of CaO present in the steel slag in high pH value conditions, precipitation of Ca PO43- is expected to be formed where it dominates the removal mechanism. Fe3+ ions are tend to dissolve in acidic condition which leads to the precipitation of Fe PO43- Ca2+ ions tend to dissolve in basic condition, which related to Ca PO43- formation
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