[Simultaneous Conversion Conditions of Ammonia and Sulfate in ANAMMOX Systems]

A continuous flow stirred tank reactor (CFSTR) was used to inoculate mixed sludge (with an ANAMMOX sludge to sewage concentrate sludge ratio of 1:1) to study the simultaneous conversion of NH₄⁺ and SO₄^2-. The ORP value in the system was stabilized at (-200±50)mV by continuously adding sludge. The simultaneous conversion lasted for 42 days. The average conversion of NH₄⁺-N was 14.81 mg·L^-1 while that of sulfate-sulfur was 8.77 mg·L^-1. In the batch experiment, the anaerobic conditions were influenced by whether the solution was filled with glass bottles. Both NH₄⁺ and SO₄^2- in the non-filled group were reduced, but their transformation was not simultaneous. In the fully filled group, NH₄⁺ was not transformed, the concentration of SO₄^2- decreased significantly, and S^2- was detected in the later stages of the experiment. It is indicated that the general conditions for the phenomenon of simultaneous conversion are:①sufficient NH₄⁺ and SO₄^2-, ② inoculating mixed sludge with appropriate concentration, ③ leaking oxygen, ④ the detection value of ORP within the range of -150 to -300 mV. At the same time, the experimental conditions used in this paper and in other related literature cannot prove that the simultaneous conversion of NH₄⁺ and SO₄^2- is the result of mutual transformation; on the contrary, observations are more conducive to the independent transformation of NH₄⁺ and SO₄^2-.