Research On Sulfite-Dependent Anaerobic Ammonium Oxidation In EGSB Reactor

Anaerobic Ammonium Oxidation?Anammox?is a biological process that uses nitrite as an electron acceptor to oxidize ammonia to nitrogen.It has the characteristics of no additional carbon source,no need for aeration,and high denitrification load.It is a new energy-saving nitrogen removal tool with broad application prospects.The discovery of this technique is of landmark significance in denitrification.The transformation of Anammox process matrix and intermediate products mainly depends on various catalytic enzymes in the Anaerobic Ammonia Oxidation Bacteria?AnAOB?and class C heme proteins that transport electrons.In particular,8-/5-heme cytochrome C has the ability to reduce nitrites or sulfites and the Gibbs free energy of ammonia oxidation and sulfite reduction in actual thermodynamic calculations is-54.18 KJ/mol,which shows that SO₃^2-has the potential as an electron acceptor.However,no research has been reported so far.Therefore,this paper firstly explored the situation of using SO₃^2-and NH₄⁺as the substrate to cultivate anaerobic ammonia-oxidizing microorganisms.In the EGSB reactor,microorganisms were enriched by long-term experiments,and the effects of temperature and pH on sulfite anaerobic ammonia oxidation were studied through batch experiments.High-throughput sequencing technology was used to detect changes in microbial community structure in the EGSB reactor and analyze possible functional microbes.The main conclusions are as follows:?1?Using traditional nitrite-type anammox sludge as inoculum and sulfite as electron acceptor to acclimate microorganisms,the reactors were operated for a total of350 days.The results showed that SO₃^2-and NH₄⁺can be removed simultaneously in the reactor.The ammonia nitrogen removal rate can be maintained at 0.25-0.3gN/?L·d?when the reactor is operating stably,and the sulfite removal rate is up to 1.3g SO₃/?L·d?,the consumption of the mass ratio of N and S is approximately 1:4?molar ratio approximately3:2?.The color of the sludge also changed from the original reddish-brown to the earthen yellow,and a large yellow unknown substance appeared,maybe there were sulfides.?2?In the batch experiment,the NH₄⁺removal rate was the highest at pH 7.5 at temperature of 35°C:7.0 mg/?gVSS·h?,while the SO₃^2-removal rate was highest at pH6.5:4.3 mgSO₃/?gVSS·h?;When pH is 7.5,the highest removal rate of NH₄⁺at 40°C is 3.5 mgN/?gVSS·h?,while the removal rate of SO₃^2-at 30°C is the highest:3.6mgSO₃/?gVSS·h?;This shows the complexity of the sulfite-type anammox oxidation process and there may be multiple reactions involved in the removal of SO₃^2-and NH₄⁺in the reactor.?3?The dominant bacterium of AnAOB in the EGSB reactor was transformed from Ca.Kuenenia to Ca.Jettenia,and the trend of Thiobacillus which is the dominant bacterium in sulfur autotrophic denitrification,was increased,but the entire experimental process did not detect the previously reported the dominant anaerobic ammonium sulfate anaerobic bacteria-Bacillus benzoevorans,showed a certain difference between the sulfite-type anaerobic ammonia-oxidizing dominant flora and the nitrite-type and sulfate-type anaerobic ammonia oxidation.