M.S Thesis

Treatment of raw reject water by aerobic and anaerobic ammonium oxidizer immobilized in PVA/alginate


Daehee Choi


Department of Environmental Engineering

Graduate School

Yeungnam University

(Supervised by professor Jinyoung Jung)


ABSTRACT


The reject water which contains high concentration of ammonium nitrogen can affect high nitrogen loading to main stream in the range of 20 - 40 % although the quantity is only 2-3 % of main stream. In general, nitrogen in the reject water is hard to remove by conventional nitrogen removal process because of insufficient alkalinity and high aeration energy for nitrification and requirement of external carbon source for denitrification. Recently, integrated partial nitritation (PN) and anaerobic ammonium(Anammox) processes are widely studied due to the saving of aeration energy and no requirement of external carbon source than those of conventional nitrogen removal processes. The purpose of this study is to evaluate the nitrogen conversion and removal efficiency in the partial nitritation and anammox reactors by using raw reject water taken from G wastewater treatment plant in Gyeongsan city, respectively. Both reactors are continuous stirred tank system packed with PVA/alginate gel. Whole cell entrapment technique with PVA/alginate is used to immobilize ammonia oxidizing bacteria for PN reactor and anaerobic ammonium oxidizer for anammox reactor. As result of PN reactor operation, partial nitritation, 1 of effluent NO2-/NH4+ ratio, was represented within 18 days of continuous operation showing 0.4 kgN/m3·d of nitrite production rate (NPR). The oxygen uptake rate of the immobilized gels at different HRT conditions were used to find the optimum activity of AOB in the PN reactor, then 6 hours of HRT was determined. In addition, stable partial nitritation over 100 days can be maintained at 5-6 hours of HRT corresponding to 2.0 kgN/m3·d of NPR. In the anammox reactor, the specific anammox activity after immobilization was measured and showed 44% of activity than that of the seeding sludge, however, the activity of anammmox gel was rapidly recovered within 6 days of continuous operation in the anammox reactor. Maximum nitrogen removal rate(NRR) at 1.6 kgN/m3·d of NLR, 1.43 kgN/m3·d, was showed when the synthetic wastewater is used as an influent. In addition, 1.0 kgN/m3·d of maximum NRR was represented at 1.2 kgN/m3·d of NLR when raw reject water is used as an influent.