Nutrient removal in a three-step sequencing batch reactor with different carbon sources

A three-step sequencing batch reactor was used for nutrient (COD, NH4-PO4-P) removal from synthetic wastewater by using different carbon sources. The operation consisted of anaerobic, anoxic and oxic (An/Ax/Ox) phases with durations of 2/1/4.5 h. Different carbohydrates, glucose, lactose, sucrose, maltose and a mixture of glucose/maltose (50/50), were used as the sole carbon source in the first phase of experiments. Sludge age was kept constant at 10 days. Glucose was found to be the most suitable carbohydrate source with percent COD, NH4-N and PO4-P removals of 96%, 99% and 94%, respectively. Nutrient removals obtained with sucrose as the sole carbon source were close to those obtained with glucose. A mixture of glucose and organic acids (50/50) such as acetic, citric, propionic and butyric acid were used as carbon source in the second phase of the experiments. Maximum percent COD, NH4-N and PO4-P removals were 93%, 97% and 96%, respectively when a mixture of glucose and acetic acid (50/50) was used. Glucose-citric acid (50/50) combination also resulted in comparable nutrient removals.