Experimental Study On Using Flocculating Chemical Precipitation Method To Treat Ammonia Nitrogen Wastewater With Vanadium And Chromium

Wastewater with sedimentated vanadium emissioned from steel plants not only contain V5+ and Cr6+,also have high concentration ammonia nitrogen,the high state of vanadium and chromium irons can bioconcentrate in the environment,and ammonia nitrogen can lead to eutrophication.Currently for high ammonia nitrogen wastewater with Chromium and vanadium irons have no viably integrated treatment technology,So this thesis use Jianlong steel wastewater?after vanadium precipitation?as study object,successively by flocculation precipitation,chemical precipitation?MAP method?and adsorption method to deal with low vanadium,high ammonia nitrogen and chromium compound wastewater.Details are as follows:?1?The experiments of vanadium and chromium ions wastewater treatment.Use deoxidation precipitation method to treat the composite wastewater,through single factor experimental design,the theies discussed the types of reductant,the pH value during the precipitation reduction and acidification phase,reaction time and reducing agent inventory the influence on the removal rate of vanadium,chromium ion and total chromium.After the comparison and analysis get the optimal combination of parameters:using Na2S2O5 as the reducing agent,in reducing acidification phase,the pH was adjusted to 2.85,reducing agent Na2S2O5 investment quantity is theory of dosage of 5 times,reaction time was 20min,precipitation process to adjust pH 8.50.The concentration of vanadium in waste water treatment for 1.714mg L^-1,the total chromium content 1.312mg·L^-1,hexavalent chromium concentration for 0.269mg·L^-1 to national emission standards.?2?The experiments of ammonia nitrogen wastewater treatment.Use MAP method to treat wastewater that have removed off chrome and vanadium ions.First of all,Through single factor experiment design discussed the influence of precipitation agent combinations,pH value,reaction time,n?Mg2+?:n?NH4+?:n?PO43-?on the ammonia nitrogen removal rate,and get the optimum range.Secondly,using Minitab software Box Behnken design multi factor modeling response surface method inspection main influencing factors of pH value,Mg:N and P:N the interact influence on ammonia nitrogen removal rate,established a quadratic polynomial equation that ammonia nitrogen removal rate as response value between multi factors and test its significane,and determinethe optimal MAP crystallization conditions of ammonia nitrogen recovery.The results showed that:Use MgCl2·6H2O and Na2HPO4·12H2O as precipitation agents,set pH to 9.5 in the precipitation process,and make sure n?Mg2+?:n?NH4+?=1.22,n?PO43-?:n?NH4+?=1.10,the best reaction time is 20min.Under these conditions,the concentration of ammonia nitrogen was 149.04mg·L^-1.And ammonia nitrogen transformed into a high degree of crystallinity of magnesium ammonium phosphate?MAP?,the recovery was 88.13%,have considerable economic benefits.The supernatant under the MAP maximum yields condition was imported into zeolite adsorption device,half-hour later the concentration of ammonia nitrogen was 13.5 mg·L^-1,can achieve the emission standard well.