Research of batch and fixed-bed column adsorption for phosphorus removal from wastewater using sewage sludge biochar

Wastewater treatment and the efficient use of sewage sludge biochar are critical in addressing the needs of ever-increasing population in the world. Recently, phosphorus (P) removal from wastewater has become highly relevant and important, primarily to reduce eutrophication in surface waters. Using sewage sludge biochar as an adsorbent for phosphate removal from wastewater offers an opportunity to reuse sewage sludge (SS) and return phosphorus to the biogeochemical cycle. In this study, the efficiency of two phosphate removal methods - batch adsorption and fixed-bed column process – was investigated using pyrolyzed sewage sludge biochar (PSSB) produced at different temperatures (300 °C, 400 °C, 500 °C, 600 °C). In the batch adsorption experiment, direct mixing of 600 °C pyrolyzed sewage sludge biochar with wastewater resulted in a relatively low phosphate removal efficiency (only about 18 %) at an initial phosphate concentration of 100 mg/l. In contrast, the fixed-bed column process, using PSSB as a filter for phosphate adsorption, showed significantly better results. The highest phosphate removal efficiency (up to 90%) was achieved after 30 min of filtration, using an initial phosphate concentration of 30 mg/l initial and biochar pyrolyzed at 600 °C.