Research On The Novel Biological Nitrogen Removal Process

In order to develop the anaerobic ammonia oxidation (ANAMMOX) process, which is a novel biological nitrogen removal process, the research was carried out to study the nitrate (or nitrite)-supplier of this biological nitrogen removal system; to evaluate the feasibility of using nitrifying activated sludge as the ANAMMOX bioreactor's inoculum; to investigate how to start up the ANAMMOX bioreactor .The results showed as follows:(1) The performance of granular sludge bed nitrifying bioreactor (GSBNB) was good with strong tolerance to influent ammonia concentration (78.49mmol/L), high volume converting rate (163.18mmol/L-d) and obvious working stability (ammonia removal >94.42%). The GSBNB could be used as the nitrate (or nitrite)-supplier of the new biological nitrogen removal system.(2) During operation of GSBNB, the nitrifying activated sludge was granulated. The nitrifying granular activated sludge began to appear on day 45. Its average diameter was 0.83 mm, settling velocity was 55.53m/h and specific ammonia removal rate was 0.95 mmol (NH/-N)/g (VS)-d. Granules with well settling and high ammonia oxidation activity assured the good performance of GSBNB.(3) A biofilm ANAMMOX reactor was inoculated as nitrifying activated sludge. The reactor was performed at hydraulic retention time (HRT) 1 day for 40 days, meanwhile, the influent ammonia concentration was from 5.07mmol/L to 19.45mmoI/L, ammonia removal rate was kept at 89%; nitrite concentration was from 5.70mmol/L to 20.82 mmol/L, nitrite removal rate was held at 95%.A granular sludge bed ANAMMOX reactor was inoculated with nitrifying granular activated sludge. The reactor was performed at HRT 1 day for more than one month, meanwhile, the influent ammonia concentration was from 4.95mmol/L to 33.09mmol/L, ammonia removal rate was 98.37% and 72.02%, respectively; nitrite concentration was from 5.35mmol/L to 36.11mmol/L, nitrite removal rate was 100% and 82.44%, respectively.The experiment demonstrated that it is feasible to start ANAMMOX reactor with nitrifying activated sludge.(4) The ANAMMOX reactor had good performance and high stability. The highest ammonia volumetric removal efficiency of the biofilm ANAMMOX reactor was 63.23mmol/L-d, volumetric nitrite removal efficiency was 86.32mmol/L-d, and total volumetric nitrogen removal efficiency was 149.55mmol/L-d. During steady-state phase of high volumetric load, average volumetric loading rate ofammonia, nitrite and total nitrogen were 45.96, 43.01, 85.72mmol/L-d, respectively. Average volumetric removal rate of ammonia, nitrite and total nitrogen were 43.08, 41.15, 84.37mmoI/L-d, respectively. Average removal rate of ammonia and nitrite were 96.89% and 99.67%.The highest volumetric ammonia removal efficiency of the granular sludge bed ANAMMOX reactor was 68.86mmol/L-d, nitrite volumetric removal efficiency was 82.36mmol/L-d, and total nitrogen volumetric removal efficiency was 151.22mmol/L-d. During steady-state phase of high volumetric load, average volumetric loading rate of ammonia, nitrite and total nitrogen were 49.25, 51.15, 98.95mmol/L-d, respectively. Average volumetric removal rate of ammonia, nitrite and total nitrogen were 47.82, 51.13, 98.95mmol/L-d , respectively. Average removal rate of ammonia and nitrite were 97.17% and 100%.(5) The effect of retaining sludge in the reactor was good by using padding or culturing ANAMMOX granules. But the former was more effective.