Application of Alum Sludge and Aquatic Plant for Advanced Treatment of Municipal Wastewater and Nutrient Recovery

Abstract

 This study investigated advanced treatment of municipal wastewater effluent and nutrient recovery through the application of alum sludge and/or aquatic plant. Three lab-scale filtration columns were prepared; Column 1 and 3 contained alum sludge, and Column 2 gravels as the filtration media. Also, watercress was planted in Column 2 and 3. At the filtration velocity of 0.13 and 0.25 m/d, the three columns performed well with respect to SS removal (the removal efficiency of 88-93%). For Column 1 and 3, T-P was removed almost completely to the level 0.02-0.03 mg/L with the removal efficiency of 97-98%. Alum sludge was estimated to have a maximum adsorption capacity of 0.87 mgPO₄^-3 -P/gDW. The T-N removal efficiency was 55-62% in Run 1 and 20-35% in Run 2, showing impairment of denitrification with the increase of filtration velocity. T-Al concentration in the effluent was similar, approximately 0.04 mg/L, among the three columns, indicating that the dissolution of aluminium from the alum sludge was negligible. 14-19% of N, 8-9% of P and 41-50% of K in the influent were recovered as the harvested aquatic plant, serving to recycle the valuable nutrients.