Treatment Of Ammonia-nitrogen Contaminated Wastewater By Sulfur Autotrophic Denitrification

Since tradition denitrification was substituted by sulfur autuotrophic denitrification at the 20^th century 70s,sulfur autuotrophic denitrification was studied widely and in-depth.Sulfur autuotrophic denitrification was an autuotrophic denitrification technique which use sulfur as an electron donor and nitrate as electron acceptor under anxoia condition.The possibility of nitrogen removal for synthetic wastewater was studied in a sulfur-shell packed-bed reactor.The concentration and pH of influent and hydraulic retention time on sulfur autotrophic denitrification properties were studied.The kinetic analysis of sulfur autotrophic denitrification was conducted on the basis of experiment results.Conclusions were as follows.(1) It was feasible for nitrogen contaminated wastewater treatment use a sulfur-shell packed-bed.H⁺ can be well neutralization by shell and the shell can provide the carbon which denitrification required.The pH of effluent can meet the requirements.(2) The effluent nitrate increased slightly with the influent nitrite increased when the hrdraulic retention time was 24 h at the stage of nitrate denitrification.The removal rates of nitrite remain more than 95%throughout the stage.The shock load of a sulfur-shell packed bed was srong.(3) The effluent nitrite increased and the effluent pH decreased rapidly when the hydraulic retention time below 4 h when the influent concentration of nitrite was 50 mg·L^-1.The effluent nitrate increased and the effluent pH decreased rapidly when the hydraulic retention time below 1 h when the influent concentration of nitrate was 50 mg·L^-1.the effluent pH decreased due to the H⁺ which produced by denitrification had been discharged when it has not be neutralized by the CaCO₃.(4) The enfluent concentration of nitrite of nitrite-denitrification was more than the enfluent concentration of nitrate of nitrate-denitrification when the influent concentration of nitrite was equal as the influent concentration of nitrate at the same hydraulic retention time.And the effluent pH of nitrite-denitrification was more than that of nitrate-denitrification.(5) For nitrate-denitrification,the removal rate of nitrate come to a head when the influent pH=8.0.For nitrite-denitrification,the removal rate of nitrite come to a head when the influent pH=7.0.The sulfate production only related with the nitrate reduction.It has nothing tio do with pH. (6) The experiments were carried out at room temperature.A high denitrification efficiency still was achieved at the temperature as low as 11℃in winter.It shows that the temperature was not the main affected factors of denitrification.(7) The denitrification rate of sulfur-shell packed bed reactor filter followed a half-order kinetics mode.