Charcoal stabilizes pH and improves nutrients removal of bacteria-microalgae interaction: A potential for improving water quality in aquaculture

Abstract

Aquaculture is prone to pH fluctuations depending on dominating microbial pathway in the management. The present study takes advantage of the influence of pH in changing the properties of charcoal to condition the pH and improve nutrient removal. Two Synthetic aquaculture wastewaters of 100 mg/L TAN were designed to test the pathway's nutrient removal and pH stability. Glucose at 15 C/N was added to one wastewater, favoring heterotrophic pathway. The other was free of organic carbon, favoring autotrophic pathway. Powdered charcoal was added to each pathway at 0.5, 1.0, 2.0, and 4.0% (charcoal weight/volume of media) compared to the 0 % group without charcoal. The result revealed that as charcoal percentages increase, the pH shifts towards stabilization and improves nutrient removal (<i>p</i> ≤ 0.05). At 4.0% charcoal, the pH was stabilized at 6.0 – 7.5 in heterotrophic and 7.5 – 7.9 in autotrophic pathways, which are within the optimum range for the survival of aquatic organisms, corresponding to the removal efficiency of TAN (99.96 and 50 %), and phosphate (55 and 17 %) within 6 days. Hence, for every 100 mg/L of TAN in wastewater, 4.0% of the wastewater volume as charcoal could stabilize pH and improve microbial nutrient removal.