The Research Of Ammonia Removal Using Biochar Three-Dimensional-Electrode PRB(Permeable Reactive Barriers)

According to the limitations on absorption efficiency and reuse of PRB(Permeable Reactive Barriers) in removal of ammonia in groundwater, as well as the advantages in water pollution treatment efficiency of three-dimensional electrode reactor, we combined these two concepts and then come up with the research of biochar three-dimensionalelectrode PRB equipment, while we studied the ammonia removal characteristics from waterbody, and analyses the influencing factor experiments of test.The main conclusions:1) Three-dimensional electrode reactor owned high efficiency of ammonia removal within short period of time, and achieve 45.72% in 3h, which is far higher than the 3.76% removing efficiency of the biochar's adsorption in the stimulated PRB. Kinetic fitting test revealed that the ammonia removing process into the reactor could fit the first-order kinetic model, which indicate that it is the primitive electrochemical reaction with the pollution translate into stable product.2) Alkalinity OH- is main condition of ammonia oxidation and have a significant promoting role in ammonia removing. The ammonia removal process is under the control of it's concentration and in proportion to reactant concentration; NH3-N finally transform into stable NO3--N, and also into gaseous phase in a large part through enhanced electrochemical oxidation.3) In the three-dimensional reaction system, the main ammonia removing pathway is through hydroxyl radicals(·OH) oxidation, which were generated with electrochemical reaction in the three-dimensional electrode reactor, then ammonia oxidized into N2 and NO3--N, the production meets n(NO3--N):n(N2) =1:1.4) Hydraulic standing time has an obvious impact on ammonia removal in the threedimensional-electrode PRB, there are no difference between T=3h and T=4h, while have definite advantage compared with that of T=2h. Ammonia and nitrate nitrogen concentration in effluent reached stable in T=6h.5)In the long-periods running tests, the effluent ammonia shows the trend of fluctuation in a narrow range and decline slightly during the 0-15 periods, after then it reached a stable range of 6.35 mg/L--6.84mg/L and doesn't change over the inflow concentration, which revealed the removal efficiency come to a steady state. Over the running, the pore structure becomes more regular and developed, carbon surface polarity increasing along with the active site?ammonia adsorption with mass transfer and its migration and transformation degree improved significantly.6) The study of compound pollution with ammonia and Cr(VI)coupling removing features revealed that the removal efficiency of Cr(VI) is much stronger than that of ammonia, at the beginning of it's running they both showed the mutual promotion and high removal function, while with the cumulative of acidity during the operation in that equipment, the ammonia removal efficiency mitigated relatively, and thus limiting the Cr(VI) removal effect and its removal ability. Overall, the compound pollution can promote the removal efficiency of ammonia.