The Technology Research On Selective Removal Of Nitrogen And Sulfide In Anaerobic Denitrification And De-sulfide Treatment Processes

Anaerobic denitrification and de-sulfide treatment processes is commonly adoptedto treat wastewater of high concentration of nitrogen and sulfide by its outstandingadvantages of high load operation, low consumption, low operating costs, low sludgeproduction and renewable sources. This paper aims at enhancing the elemental sulfurand nitrogen conversion rate. The influences of the inoculums, the sulfide load,the different electron acceptors and the influent pH on selective removal of nitrogenand sulfide in anaerobic denitrification and de-sulfide treatment were mainly studiedand the control conditions are obtained. The main conclusions in this paper are asfollows:1. The anaerobic sludge can benefit the selective removal of sulfide and improve theelemental sulfur conversation rate. The elemental sulfur conversation rate is52.57%and the nitrogen conversation rate is88.09%when the sludge dosage is between100to200mL and retention time is less than48h. The ratio between the amount ofbacteria liquid and the sludge dosage of1.0to1.5is favorable for generation ofelemental sulfur and nitrogen and the removal of nitrate at100mL sludge dosage,and the elemental sulfur productivity is54.35%, the nitrogen conversation rate is96.24%.2. The elemental sulfur productivity can reach more than80%when the influentsulfide concentration is bellow400mg/L, and a conversion of98.15%was achievedin a concentration of340mg/L, and5.06mmol nitrate is removed. The nitrogenconversation rate can be100%at280mg/L sulfide. It is beneficial for the selectivitygeneration of nitrogen. 3. The sulfide load tolerance for Thiobacillus denitrificans should be less than280mg/L. The elemental sulfur productivity in nitrate reactor and nitrite reactor is86.33%and87.67%, higher than60.69%in the mixed electron acceptors reactor.The nitrate based reactor can selectively remove nitrate when the influent sulfideconcentration is lower than340mg/L and the nitrate removal rate is91.59%. Thenitrogen yield is9.82and6.88mmol in the nitrate matrix reactor and mixed electronacceptors reactor, both of which are pure bacteria system, higher than6.43mmol inthe nitrite reactor. The influent sulfide concentration should be controlledappropriately below200mg/L.4. The electron acceptor nitrate is more efficient than nitrite in selective sulfideremoval and the sulfide removal rate is97.07%and76.95%, respectively. The nitritematrix reactor has a delay in the elemental sulfur generation. The ratio betweennitrate type and nitrite type equation of1:1can quickly generate elemental sulfur,the elemental sulfur is up to79.52%. The reactors using nitrate used as electronacceptor alone and in the ratio1:1get better results in removing nitrate, the nitrateremoval rate is75.59%and68.72%, the nitrogen yield is4.02and3.83mmol,respectively. Nitrite is easier than nitrate in the conversation to nitrogen and moreefficient in nitrogen yield, so it is effectively by controlling the nitrite as the mainelectron acceptor in the reactor5. The influent pH of7.5~8.0is more conducive to sulfide and ammonia nitrogenremoval, ammonium-nitrogen removal rate is39.49%, the sulfide removal rate is91.68%, the elemental sulfur production rate is up to100%and the nitrogen yield is4.29mmol. The neutral pH is beneficial to the formation of elemental sulfur in thereactor and to the selective removal of nitrogen and sulfide.