Study on reactivation cycle of biological activated carbon (BAC) in water treatment

• Proposed the improved testing methods of Iodine number and MB value for the spent AC.
• Recovery of adsorption capacity of AC is inversely proportional to the service time.
• Higher running load is not conducive to the recovery of adsorption capacity for AC.
• 2 h of reactivation at 850 °C is more desirable for the spent AC.
• The best reactivation cycle for BAC is within 1.5 years and less than 2 years.

This paper focused on the study of the reactivation cycle of biological activated carbon, which depended on the service time of BAC, running load, and reactivation time, reactivation yield, and reactivation cost etc. Six advanced water treatment plants (WTP1, WTP2, WTP3, WTP4, WTP5 and WTP6) of Jiangsu Provence in southern China, using BAC processes, were selected for the study. BAC samples of different service life were tested, and periodic sampling and testing were conducted for WTP1. The effects of service time, BAC loading, and reactivation time on the recovery rate of adsorption capacity of reactivated AC were investigated, which indicated that 2 h of reactivation at 850 °C is the better choice for the recovery of the adsorption capacity. Considering the reactivation yield, the reactivation cycle should be less than 3 years. Based on the above, using 0.4 or 0.5 times of virgin AC price as the reactivation cost, the best reactivation cycle for BAC is within 1.5 years and cannot be more than 2 years.