| In recent decades nitrogen pollution has been becoming serious. Anaerobic ammonium oxidation (Anammox) completes autotrophic denitrification with nitrite as electron acceptor and ammonium as electron donor. Anammox process has the advantages of high nitrogen removal efficiency, low energy consumption and environment-friendly. However, the growth rate of Anammox bacteria is too slow with the doubling time of10-12d, which is the major obstacle for the engineering application of Anammox process.Tourmaline is a kind of complex borosilicate comprised of Al, Na, Fe, Ca, Mg and other metal elements with the features of spontaneous and permanent poles, pyroelectricity and piezoelectricity. Previous researches indicated that tourmaline had a promoting effect on microbial growth and metabolism. However, to the best of our knowledge, there are no studies on the effect of tourmaline on the activity of Anammox bacteria so far.This study investigated the influence of tourmaline on the reaction characteristics of Anammox bacteria. The effects on Anammox activity, pH and Oxidation Reduction Potential (ORP), the granulation of Anammox sludge, microbial separation and evolution were analyzed in detail. The main research conclusions have been summarized as follows:(1) Anammox bacteria purified by percoll density-gradient centrifugation to avoid influence of other bacteria on the experimental results was conducted to investigate the effect of tourmaline on Anammox activity by batch tests. Tourmaline increased the activity of Anammox bacteria significantly. When the amount of200g tourmaline g-1VSS L"1was applied with the culture time of24h, the activity of Anammox bacteria was176.6%of that without addition of tourmaline. After48h batch tests, the maximum increase of carbohydrate, protein and total Extracellular Polymeric Substances (EPS) production were17.3%,356.2%and179.7%, respectively. Tourmaline could regulate the pH and ORP values effectively to make them more suitable for Anammox bacteria, thus enhanced the environmental adaptability.(2) Two parallel lab-scale Continuously Stirred Tank Reactors (CSTR) with tourmaline addition (R2) and without tourmaline as control (R1) respectively were conducted to investigate the effect of tourmaline on the enrichment of Anammox bacteria and the start-up of reactors inoculated with activated sludge. Time of sludge adaptation period of R2was shorter than that of R1by42days with a stronger capacity for nitrogen removal and resisting nitrogen shock load. Tourmaline could control pH and ORP values to provide a stable environment for enrichment of Anammox bacteria. Tourmaline promoted the growth and metabolism of Anammox bacteria and enhanced the activity of Anammox reaction, but was not benefit for the granulation of Anammox sludge.(3) Two parallel lab-scale CSTR bioreactors, one with tourmaline addition (R2) and the other without tourmaline (R1) as control, were conducted to investigate the effect of tourmaline on the operation of Anammox bioreactor system for nitrogen removal. During the operation, the maximum Nitrogen Removal Rate (NRR) of the reactor (R2) with tourmaline addition (NRR=515.5mg-N L-1d-1) was11.4%higher than that of the control reactor (R1)(NRR=462.8mg-N L-1d-1), meanwhile, R2showed a stronger ability for resisting nitrogen shock load. |
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