Research On Optimization Of The Anammox Process And The Cultivation Strategy Of Denitrifying Granules

The anaerobic ammonium oxidation(anammox) process is a promising alternative in biological nitrogen removal field with advantages of high-efficiency, cost-efficiency and environment friendly. Addtion of trace metal ions and optimization of feeding regime are benefit to cultivating anammox bacteria as well as the process capacity. Coupling anammox with denitrification may successfully improve the total nitrogen removal rate(NRE). This paper aimed to investigate the influence of metal ions addition on the ananmmox process, and to explore the potential of anammox anaerobic baffled reactor(ABR) by optimizing the feeding regime. Furthermore, to find ways cultivating denitrifying effectively in preparation for the establishment of coupled anammox-denitrifying system. The main results achived in this study are as follows:(1) The results of one factor batch assays and response surface analysis found the optimal metal dosage and the composition was Fe3+ 6.61 mg L-1, Cu2+1.18 mg L-1 and Ni2+1.11 mg L-1. The Fe3+-Cu2+-Ni2+ continuous test was carried out at the labolaroty at ambient tempreture, and the results addressed that the nitrogen removal capacity of the reactor enhanced by Fe3+-Cu2+-Ni2+ addition was 50% higher than the control reactor. Moreove, Fe3+ was chosen to conduct the one factor continuous test at a dosage of 3.68 mg Fe3+ L-1, and the nitrogen removal rate increased 20%.(2) In this study, the common feeding regime was transferred to flow switched feeding regime, and partial substrate inhibition problems in the traditional anaerobic baffled reactors(ABR) were effectively overcome. The NRE and the nitrogen removal rate increased from 75.4% and 3.00 kg N m-3 d-1 to 83.1% and 3.49 kg N m-3 d-1. Moreover, the biomass characteristics in each compartment were greatly enhanced including particle size, settling velocity, extracellular polymeric substance(EPS) and specific anammox activity. The data during the reactor operation was analized by modified Stover-Kincannon model and the result found that the maximum theoretical substrate removal rate of the flow switched ABR was 10-folds that of the common ABR(46.38 and 4.28 kg N m-3 d-1).(3) In this study, different Mg2+ supplementation strategies were used to find the proper way to cultivate denitrifying granules(R0 was operated without Mg2+, R1 was continusously supplied with 50 mg L-1 Mg2+, R2 was intermittently supplied with 50 mg L-1 Mg2+), and granulation appeared in R1 first. When the granules were mature, the granules in R1 and R2 were with larger particles, faster settling velocities, more EPS contents and greater specific denitrifying activity than the one from R0. The data of the kinetic batch assays were analized by Haldane model and the maximum theoretical nitrogen removal rate for R0, R1 and R2 were73.9, 100.0 and 112.0 mg N h-1 g-1VSS, respectively.