Study On The Characteristics Of Rotating Bio-disc Reactor For SNAD Nitrogen Removal Process

Nitrogen pollution from sources as food processing and agricultural industries is a growing concern to the water environment. Removing nitrogen components effectively from wastewater is an important issue nowadays. However conventional biologial nitrogen removal processes exit some problems such as system complex, large footprint, high operating costs, and ect. Recently, a novel and promising biological nitrogen removal process combining the ANAMMOX, partial nitrification with denitrification reaction in one reactor, entitled nitrogen removal has been developed. This process would lead to an important reduction of operational costs compared to coventional biological nitrogen removal process.In this study, a novel non-woven rotating biological contactor (NRBC) reactor was developed for autotrophic nitrogen removal and heterotrophic COD removal based on partial nitrification, ANAMMOX and denitrification. Firstly, the NRBC was start-up via addition of ANAMMOX sludge seeding sludge to run the ANAMMOX process. Then, the biofilm was inoculated with nitrifying biomass to run the CANON process. Finally, adding COD into the influent, we can obtain the simultaneous partial nitrification, anammox and denitrification (SNAD) process. DO in the reactor was controlled by adjusting the liquid level and changing the rotational speed. One can obtain stable nitrite accumulation in the outer layer of biofilm. Anaerobic environment was provided for the anammox and denitrifying bacteria by DO consumption by nitrosobacteria in the outer layer, to construct a quite stable biofilm system for nitrogen removal. Conclusions are maily following as:1. The rotating biological contactor reactor packed with nonwoven fabrics carrier was used for enrichment of seeding anammox and nitrosobacteria sludge. In the stable SNAD stage, the maximum removal efficiencies of NH₄⁺-N, TN and COD reached 79%, 70% and 94% with the influent NH₄⁺-N and COD average concentrations were controlled at about 200 mg L^-1 and 100 mg L^-1, respectively.2. The morphology of the SNAD biofilm was observed using scanning electron microcope. The photographs showed that the the biomass in the outer layer of biofilm was mostly micrococcus; the biomass in the inner layer of biofilm was typical cauliflower like aggregates with some other shapes.3. Fluorescence in situ hybridization (FISH) analysis using 16S rRNA targeting oligonucleotide probes EUB338, NSO190 and AMX820 showed that the existence of two visible active layers in experimental SNAD biofilm. One is the partial nitrifying layer located in the region of oxygen-rich biofilm interface, dominated by NSO190-positive nitrosobacteria. The other is the ANAMMOX and denitrification active layer located in the region of anoxic biofilm interface, dominated by AMX820-positive anammox microorganisms and some other EUB338-positive only microorganisms. As a result of this study, the nitrosobacteria, anammox bacteria and denitrifying bacteria were present and active in experimental SNAD biofilm, and the cooperation among nitrosobacteria, anammox bacteria and denitrifying bacteria was considered to be responsible for autotrophic nitrogen and heterotrophic COD removal.