Effect of calcium addition to aerobic granular sludge systems under high (conventional SBR) and low (simultaneous fill/draw SBR) selection pressure

This paper investigated the effect of calcium addition on the formation and properties of aerobic granules under high (conventional SBR) and low (simultaneous fill/draw SBR) selection pressure. Additionally, the simultaneous removal of carbon, nitrogen, and phosphorus, and the operational stability were assessed. The conventional SBRs showed earlier granule development (20 days) than the simultaneous fill/draw SBRs. The effect of calcium on granulation was more accentuated in conventional SBRs, forming larger granules in a shorter interval of time due to the higher EPS production. Additionally, higher amounts of calcium were found in the EPS matrix, mainly during the formation of granules. The operation regime and the addition of calcium did not affect the removal of carbon, nitrogen, and phosphorus. However, they both influenced the granulation time, settleability charac-teristics, size, and granule composition.

Automated summary

The addition of calcium had a significant effect on granulation, particularly in conventional SBRs where larger granules formed in a shorter period of time due to higher EPS production. While the removal of carbon, nitrogen, and phosphorus was not affected, the addition of calcium influenced granulation time, settleability characteristics, size, and granule composition.