Nitrogen Removal by HN-AD Bacteria Immobilized on Modified Absorbent Stone

W. Zhang, Z. Zhang and S. Wang

Abstract
How to simplify the nitrogen removal process, reduce the cost and improve the efficiency has become an urgent problem to be solved. In this research, the isolated HNAD (heterotrophic nitrification and aerobic denitrification) bacteria were used to remove the nitrogen in wastewater. Modified absorbent stone was used as high-efficiency and low-cost immobilized material. The modification effect was determined by the changes in mechanical strength, Zeta potential, pore structure, micrographs and biomass. The practicability of the modified carrier was further proved by experiments of environmental effect and reuse. The modified carrier had excellent performance. By comparing the degradation effects of immobilized microorganism and free microorganism, it was proved that the immobilized microorganisms have broad application prospects and strong adaptability to environmental factors. Under the optimum conditions (temperature of 30 oC, pH of 7, dissolved oxygen of 3.5 mg L–1), the removal efficiency of ammonia nitrogen reached 100 % in 40 hours, the removal efficiency of total nitrogen reached 60.11 % in 50 hours, and the removal rate of total nitrogen was 2.404 mg-NL–1 h–1 by immobilized microorganisms with the treatment of simulated nitrogen-containing wastewater. This research provides new material for the immobilization of HN-AD bacteria and a new way for nitrogen removal.

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Keywords
immobilized microbial degradation, HN-AD bacteria, modified absorbent stone