Study On The Application Of Straw Biochar In Wastewater Denitrification

The eutrophication caused by nitrogen and phosphorus in the surface water and the excessive nitrate in groundwater are two major problems in the environment.In this paper,the effect of secondary effluent and groundwater denitrification was studied by using straw biochar as adsorbent and carbon source.The research contents include the adsorption effect of straw biochar as adsorbent on ammonia nitrogen and nitrate nitrogen in wastewater,biochar is used as denitrification carbon source to remove nitrate in secondary effluent and effect of common ions in groundwater on the removal of nitrogen from groundwater by biochar.Through a series of studies,the following conclusions are drawn:(1)Through the comparative study of the comparative study of the removal of ammonia nitrogen and nitrate nitrogen from waste water by using granular biochar and powder biochar as adsorbents showed that the adsorption effect of granular s biochar on ammonia nitrogen was better than that of powder biochar,but the adsorption of NO3--N was not obvious,and a certain amount of NO3--N was produced.After modification with FeCl3 and CaCl2,the powder biochar can effectively adsorb nitrate nitrogen,and the former is better than the latter.(2)the adsorption isotherms of unmodified powder and granular biochar on ammonia adsorption accord with the Freundich adsorption model,but for the kinetic equation,the powdered biochar conforms to the pseudo two order kinetic equation,and the granular biochar conforms to the pseudo first order kinetic equation.The adsorption isotherm of the modified powder biochar on the nitrate nitrogen was in accordance with the Langmuir adsorption model,and the kinetic equation was in accordance with the quasi-second order kinetic equation.(3)The modified powder biochar had a good adsorption effect on nitrate nitrogen(17.5mg/L),ammonia nitrogen(5.0mg/L)and total phosphorus(2.9mg/L)in secondary efflue nt.Among them,the removal rates of FeCl3 modified powder biochar were 54.40%,31.75% and 80.25% respectively,and the removal rates of CaCl2 modified powder biochar were 41.18%,26.46% and 30.18% respectively.(4)Three kinds of denitrifying bacteria WS,PYS and YS were isolated from the sewage treatment station of China University of Mining and Technology,and all belonged to Pseudomonas,but the best denitrification effect was PYS.With PYS as the denitrifying bacteria,biological carbon particles as the carbon source denitrification and filler used in the shaking table experiment and the continuous experiment of the removal of nitrate from the secondary efflue nt,the results showed that were very good denitrification effect,and without the nitrate accumulat io n.(5)The effects of common ions on groundwater nitrate removal in groundwater were studied by using granular biochar as a filler for removal of nitrate in groundwater.The results showed that ion type and concentration could cause the difference of nitrate removal.Among them,SO42-has obvious inhibitory effect,and caused a lot of nitrite accumulation;Ca2+,Na+ and HCO3-are promoting effect,but the lower the concentration effect more obvious;Cl-was inhibited at high concentration(600 mg/L)and promoted at low concentration,and the lower the concentratio n,the better the effect.