Research On Completely Nitritation In Autotrophic Biofilm In MBBR

Accumulation of ammonia in water environment has induced serious deterioration to the quality of water environment. Nitrogen from the wastewaters with low C/N ratio and high strength ammonia, such as digested sludge supernatant and landfill leachate, add up to over 50% total nitrogen form wastewater. Due to the fact that these wastewaters often are riddled by an extremely unfavourable C/N ratio, for the conventional biological nitrification-denitrification, C/N ratios below 4 increase the denitrification volume by a factor of 1.5 to 1.7, with a ratio below 2.5, sufficient denitrification cannot be achieved at all without the use of external carbon sources. Due to the fact that these wastewaters often are riddled by an extremely unfavourable C/N ratio, it is unfit to removal nitrogen from these wastewaters by biological nitrification-denitrification.Based on the latest research findings on biological nitrogen removal on low C/N ratio and high strength ammonia wastewater in both domestic and abroad, start-up and optimization of completely nitrification matched with ANAMMOX(Anaerobic Ammonium Oxidation) was studied in MBBR (Moving Bed Biofilm Reactor) which is widely used in the wastewater treatment. During the long-term operation of the biofilm reactor, the factors which affect on the completely nitrification were studied.The experiment results show that the ammonium in the liquor was nearly completely converted to nitrite with the temperature about 32±1℃at the DO (dissolve oxygen) concentration of 1.5~2.0 mg/L in the reactor, by controlling HRT(Hydraulic Retetion Time) at 1d and pH at 7.7~8.2. In this condition the conversasion rate of ammonia was above 96%, the accumulation rate of nitrite was above 95%. Because of Microbese attached to the fillters in reactor, nitrobacterias couldn't be washed out with Hydraulic. So that the only way to achieve completely nitritation in biofilm reactor was to bate their activetise. In this paper the reactor achieved completely nitritation by control pH, the mechanism of it was that high pH and high concentration of FA bated the activeties of nitrobacterias. the type of nitrification turned from completely nitritation to completely nitrification under the condition of over aeration by extended HRT under low NLR, however it could be resumed by shortened HRT. The bicarbonate (NaHCO3) was the buffer dosage and limiting substrate for the autotrophic bacteria without addition of organic carbon source (COD). The optimum temperature in 32±1℃and pH about 7.5~8.5 adapted to the nitritation, and NLR/DO at 1.0~1.5 were favourable conditions of nitritation matched with ANAMMOX.