| In recent years，nitrogen cycle has encountered serious interference due to thedegree of industrialization and urbanization increasing. A lot of nitrogen wastewaterwith or without properly treatment has discharged to river, which caused seriousdamage to environment. Biological denitrification process has many advantagesincluding high removal efficiency, no secondary pollution and low energyconsumption, which becomes one of the most economic nitrogen removal process.People master more and more biological technology with the development of modernbiology. And nitrogen removal process developed toward the direction from the puretechnology reform to biological characteristics reform technology. The purpose of thethese was to achieve the high nitrogen removal high efficiency and low energyconsumption. Many new biological nitrogen removal technologies have come outbased on the type of nitrification-denitrification technology. They made up thedefects of traditional itrification-denitrification technology, improve the nitrogenremoval efficiency and reduce the cost of nitrogen wastewater treatment. Among them,high efficiency and stability of the nitrosation process is the key of realizing shortcutnitrification-denitrification, shortcut nitrification-anaerobic ammonium oxidation,completely autotrophic nitrogen removal over nitrite, oxygen-limited autotrophicnitrification-denitrification. In this study, nitrogen removal performance of short-cutnitrification granular sludge was carried out in a sequencing batch reactor (SBR). Theexperimental process was divided into two stages, which was the study of rapidstart-up short-cut nitrification granular sludge and different temperature controlstrategies on nitrogen removal performance of short-cut nitrification granular sludge.In the period of start-up short-cut nitrification granular sludge, inorganic wastewater was used to wash out heterotrophic bacteria. In addition, the temperature, DOand pH were controlled in the reactor to make proliferation of nitrosation bacteria,which became the advantage strains. Also, strategies of inoculate part of aerobicgranular sludge and horter time precipitation was used to achieve the purpose ofsludge granulation. The start-up period was50d, and the nitrite accumulation finallyreached97%, which implied the system had good shortcut nitrification performance.During the start-up period, the sludge has been turned from dark brown to shallowbrown in color. The SVI decreased from57to33mL/g, while MLSS with3765mg/Lsignificantly decreased to2994mg/L. After the enrichment, sludge size increase to 2.92mm. The sludge type of irregular ellipsoid was major in the reactor, and theyseemed denser. In order to study the progress of sludge granulation better, the changesof polysaccharide and protein in extracellular polymeric substances, hydrophobicityand surface negative charge were detected. The results showed that all of above itemsincreased with the progress of sludge granulation, and achieved the value of4.39,70%,0.274meq/gMLSS, respectively finally.The period of study different temperature control strategies nitrogen removalperformance of short-cut nitrification granular sludge was experienced160days. Theexperiment was divided into three stages, stage A in30℃(1~25d), stage B in25℃(26~57d) and30℃(58-96d),stage C in15℃(97~160d). The results obtained fromthe experiment demonstrated that the shortcut nitrification performance not onlyrelates to temperature, but also affected by structure of short-cut nitrification granularsludge. Stable structure of short-cut nitrification granular sludge contribute the realizeof shortcut nitrification. At30℃, short-cut nitrification granular sludge has stablestructure, which has highly nitrite accumulation. As the temperature decreased to25℃, the electronegativity of sludge increased as well as the hydrophobicitydecreased. The granules disintegrated during this period, at the same time, AOB in thesurface of granules decreased while NOB inside of the sludge retained. Theshort-cut nitrification performance was destroyed, nitrification accumulation ratiowas below35%. At15℃, the shortcut nitrification sludge also disintegrated and had alooser structure. However, the oxygen penetration depth increased at lowertemperature, which made the relative quantity of ammonia oxidizing bacteria (AOB)in reactor increased, the nitrification accumulation was around68%ultimately. |
