Performance of a biofilm airlift suspension reactor for synthetic wastewater treatment

Performance stability of a biofilm airlift suspension reactor (BASR) was studied using ethanol as a substrate. The main objective of this research was to investigate the applicability of the reactor as a wastewater treatment process by examining the effects of soluble chemical oxygen demand (SCOD) loading rate and hydraulic retention time (HRT) on the performance of the reactor. SCOD removal of 90% or higher was achieved at an HRT of 45 min with loading rates from 10 to 18 kg SCOD/m(3) day. Similar results were obtained at HRTs of 60 and 90 min and a SCOD loading rate of 10 kg SCOD/m(3) day. Nitrification occurred in the system when the ratio of SCOD to ammonia nitrogen was changed from 10: 1 to 6:1. The morphology of the biofilm in the BASR was denser and thicker when nitrifiers grew in the biofilm. Filamentous overgrowth was observed from time to time and proper chlorine dose successfully suppressed its growth. The oxygen uptake rate was an effective tool for monitoring the effect of chlorination.