Application of ABR/zeolite for TKN removal from compost leachate

Abstract

Compost leachate is a strong wastewater with high organics, TKN, and ammonia nitrogen and anaerobic processes like the ones carried out in an ABR are of interest. ABR is highly efficient in removing COD but the TKN removal performance in this reactor has been reported to be low, and only some part of organic nitrogen is converted to ammonia in it. Ammonia has inhibitory effects on the acetogenic bacteria and the biogas production efficiency. In this work, a pilot scale of ABR with 8 compartments was used, and its last four compartments were filled with zeolite. Based on the EDS analysis, the zeolite used was clinoptilolite with an ammonium adsorption capacity equal to 1.02 meq/g. The bioreactor was operated at HRTs of 3, 4, and 5 days, the filling ratios of 10%, 20%, and 30%, and the initial COD concentrations of 10 000, 20 000, and 30 000 mg/L. The results showed that the maximum removal efficiency of TKN and organic nitrogen was, respectively, equal to 48% and 100%. Increasing the filling ratio in the reactor increased the removal efficiency of TKN and organic nitrogen but increasing OLR reduced the removal efficiency of the reactor. The initial TKN/ammonia ratio was 0.45, which was increased by elevating the filling ratio in the reactor, and in 30%, it reached 0.91. The results obtained also showed that zeolite had a great effect on the ABR performance; therefore, it could be used to treat a highly strong wastewater to suppress the anaerobic biological growth inhibitors like ammonia.