Biological Nitrogen Removal Using Bacteria Immobilized by Pva-Drying Method

Abstract

This research deals with development of an innovative system for complete nitrogen removal from municipal wastewater. This stage of the process development was dedicated to the selection of the appropriate method of autotrophic bacteria immobilization. PVA-drying method with either gel-beads or gel threads was selected as most suitable among the tested methods. This method of bacteria entrapment is non-toxic to the biomass and provides gel with good physical properties. This gel is relatively inexpensive and available due to wide use of PVA in chemical industries. The developed immobilized bacteria system can provide effective nitrification within HRT of one hour, which can be stable for at least twelve months. An optimal concentration of the biomass seeded in gel was determined experimentally. This concentration was 3gVSS/L gel and 4.5gVSS/L gel respectively for Lentisol TM and PVA-glycerol prepolymers tested in this work. Gel-thread reactor was developed to provide possibility for better heterotrophic bacteria washout as well ass better substrate mass transfer. The results demonstrated that nitrification of the synthetic ammonia wastewater by the thread immobilized biomass biomass is approximately three times more effective than that of gel beads. Furthermore, the data showed that seeded biomass concentration might be reduced when applying gel threads. The selected method for bacteria immobilization was applied for verification of feasibility of the nitrification interruption for the agricultural needs. The results showed that nitrification rate successfully recovered after three months of ammonia starvation. Reactor that received small ammonia portions on a weekly basis demonstrated excellent immediate recovery. The system that did not receive any ammonium provided half of the original activity instantaneously with feed renewal. Only two weeks were needed in order to reach full original nitrification activity.