Abstract
Effective utilization of the nutrients contained in anaerobic digestion effluent (ADE) for microalgal cultivation requires removal of pollutants without reducing the nutrient contents. This study was conducted to develop an ADE treatment with appropriate technologies in developing countries. Slow sand filtration (SSF) is a simple, low-cost technique. Activated sludge (AS) process can enlarge particles in ADE with floc formation. Activated carbon filtration is effective for color removal. Therefore, a combination of AS process, SSF, and activated carbon filtration was attempted. The combined process removed 91% of suspended solids. Subsequently, SSF removed 69% of the suspended solids remaining after AS process. Probably, SSF in the combined process maintained a higher removal efficiency because AS promoted flocculation of small particles in ADE, thereby enabling easier trapping of particles on the sand. The average removal efficiency of dissolved organic carbon by activated carbon filtration was 47%. Also, the absorbance of photosynthetically active radiation was lower by 70%. However, inorganic nitrogen and phosphorus concentrations remained after treatment. Taken together, the results indicate that the combination of the three treatments can selectively purify ADE while retaining nutrients for microalgal cultivation.
