Assessment of a UASB reactor with high ammonia concentrations : Effect of 2 zeolite addition on process performance 3 4

15 The UASB process for wastewater treatment has been extensively studied, but the use of zeolite to improve 16 UASB reactor performance has rarely been explored. In this study, a UASB reactor modified with natural 17 zeolite operating at high nitrogen concentrations (0.5 g/L, 0.7 g/L and 1 g/L) was evaluated. Two laboratory 18 bioreactors, one with zeolite and one without, were operated at ambient temperatures ranging between 18oC 19 and 21°C. The experimental phase had a start-up period of 21 days. In the reactor with zeolite, the pH was 20 found to be between 7.9 and 9.1, with a COD removal efficiency of about 60% after 80 days of operation at 21 ammonia concentrations of between 0.229 and 0.429 g/L in the effluent. In the reactor without zeolite, the pH 22 was between 8.3 and 9.3, and the COD removal efficiency was about 40% at ammonia concentrations 23 2 between 0.244 and 0.535 g/L in the effluent. The addition of zeolite also decreased the volatile suspended 24 solids (VSS) concentration in the effluent, generating a biomass with larger granules and higher settling rates 25 as compared to a UASB reactor without zeolite. Taking the lower ammonia concentration, the higher COD 26 removal and the improved granulation into account, it can be concluded that natural zeolite positively 27 influenced the behavior and performance of the UASB reactor operating with high nitrogen concentrations. 28 29