Advanced Nitrogen Removal Of Denitrification Filter With Agri-cultural Residue As Sustained-release Carbon

The C/N ratio of urban sewage of China is commonly low, which is controlled and and restricted by inefficiency of carbon source. Traditional additional carbon source of small molecfule has potential to the environment, causing deputy deputy pollution. Biodegradable polymer as novel additional carbon source is high in cost, which limits its application. Therefore, agricultural residue,which is easy to get and low in cost, has become a hot topic as additional carbon source.Two types of common low-cost agricultural residue in China, corncobs and straws, have been chosen for discovery of economic efficient additional carbon source, using as sustained-release carbon source for advanced nitrogen removal of municipal wastewater.Carbon source, nitrogen source and phosphorus source of original, alkali-pretreatment and heat- pretreatment corncobs and straws in water can effect water quality, and their release regulations were analyzed.After immersed in water for a long period, the concentration of each substance in the water is lower than 1 mg/(g·d). Heat-pretreatment and alkali-pretreatment were considered to be able to improve the release of soluble carbon source.Both the materials’ had soarse surface, which could promotes microbial attachment. Considering the denitrification potential, static denitrification efficacy and physical state, corncobs, alkali-pretreatment corncobs and heatpretreatment corncobs were selected as the sole carbon source as well as the only biocarrier.Ceramsite, which cannot serve as slow-release carbon source,was chosen as blank reference. The optimum HRT of corncob reactor is 50 min, and the optimal p H is 7. After operated for a long time,by the end of the reaction, the corncob reactor, heat-pretreated corncob reactor and the alkali-pretreated reactor’ remain TN removal ratesof 25%, 20%, 53% separately. Denitrification efficiency of heat-pretreated corncob reactor was better than ceramiste reactor, and denitrification efficiency of original corncob reactor was even better, while heat-pretreated corncob reactor had the best efficiency. Alkali-pretreated corncobs maintained high denitrification efficiency, indicating that alkali-pretreated corncobs can serve as slow-release carbon source for a long period. Scan of the surface of the sustained carbon before and after operation using environmental scanning electron microscopy, showed that cellulose of corncob was severely damaged by microorganisms.The microbial communities and function relationship in different water treatment systems were analyzed hrough Illumina high throughput sequencing technology. The ceramic reactor is highest in fungus diversity, while corncob reactor is highest in bacteria diversity. The ceramic reactor has high abundance of the denitrifying bacteria, but there was barely any denitrification happened for the lack of carbon source. The other three reactors have high abundance of cellulose degrading bacteria and common denitrifying bacteria, which matches with the high process of alkaline-pretreatment corncob. Most fungi in the four sets of reactors are saprophytic bacteria Cellulose degrading bacteria, which are usually common,are low in abundance in all of the four samples.