Bamboo Charcoal as a Lactic Acid Bacteria Carrier for Phosphate Removal

Abstract

A decline in the demand for using bamboo products has led to abandoned bamboo forests in Japan. To reduce the area of abandoned bamboo forests, the use of bamboo as a construction material and bamboo charcoal as an absorbent have gained considerable attention in recent years. In the literature, many studies have described the formation of biofilms on biochar, leading bamboo charcoal to be considered as a microbial carrier. The aim of this study was to examine the potential of bamboo charcoal as the microbial carrier of lactic acid bacteria (LAB) for phosphate removal. Bamboo charcoal was immersed in a LAB solution for 24 h for LAB to adhere to the bamboo charcoal. Then, the bamboo charcoal was placed in a bamboo fermented solution. Two types of bamboo charcoal, i.e., without pretreatment and dissolved in tap water, were used in the experiments. The experiments were also conducted with and without aeration to determine the effects of oxygenation. The bamboo charcoal without pretreatment displayed an increase in the phosphate concentration, indicating that phosphate was released from the bamboo charcoal. LAB-attached bamboo charcoal demonstrated a much smaller increase in phosphate concentration, suggesting phosphate was consumed by LAB. Experiments with dissolved bamboo charcoal also indicated a reduction in the phosphate concentration. The removal rate of phosphate decreased with an increase in the solution pH, suggesting that alkaline conditions limited the activity of the bacteria. Furthermore, the redox potential of the solution became negative in the solution without aeration. Overall, the results demonstrated that bamboo charcoal could be a LAB carrier; however, the bamboo charcoal must be dissolved prior to its use for phosphate removal. Furthermore, aeration and an acidic during phosphate removal are needed to obtain a higher removal rate when using LAB.