Advanced Treatment Of Ammonia Nitrogen Wastewater By Electrochemical Reactor Filled With Zeolite Particles

As one of the main pollutants of water eutrophication,ammonia nitrogen was regarded as the main water pollutants binding control indicators in Chinese 12 th Five-Year Plan. So, removal of the ammonia nitrogen from the wastewater has great significance to the protection of water environment quality. The electrochemical reactor filled with zeolite was applied to treat low concentration of ammonia nitrogen wastewater in this papaer, The effects of electrode plate materials, current density,electrolytic voltage,p H,filling particles and aeration on the ammonia removal were investigated. Both the performances of two-dimensional and three- dimensional electrode were compared. Then the ammonia nitrogen removal mechanism of this electrochemical reactor was discussed. Finally, real domestic wastewater was treated. The main conclusions are as follows :(1) The electrochemical reactor filled with zeolite could remove the ammonia nitrogen in the wastewater effectively. Using DSA plate, iron plate and stainless steel plate as anode,activated carbon fiber, titanium wire mesh, iron and stainless steel plate as cathode, clinoptilolite,ferric supported clinoptilolite, mordenite and ferric supported mordenite as filling particles, the optimum experimental conditions are as follows: DSA plate as the anode and ACF as the cathode,current density 6 m A/cm2, electrolysis voltage 20 V, initial p H 5, 240 g/L dosage of ferric supported clinoptilolite, aeration rate 5 L/min, and reaction time 40 min. The results showed that the concentration of ammonia nitrogen in wastewater reduced from 20 mg/L to 3 mg/L.Effluent was clear, and subsequent processing was not needed.(2) SEM images of both DSA plates and ACF plates showed that there was little difference on surface configuration for DSA plates between before and after reaction, and the specific surface area, pore diameter and pore volume size for ACF plates were not changed obviously after reaction. It indicated the electrode plates had good chemical stability. ferric supported clinoptilolite had more apparent layer structure, more rough surface, more fluffy structure compared to natural zeolite, which were advantageous to the ammonia nitrogen removal.(3) The concentration of hydrogen peroxide was up to 380 g/L after 10 min reaction, nitrate concentration in the effluent was 0.4 mg/L after 40 min reaction,. It was concluded that ammonia nitrogen removal is mainly by adsorption and oxidation.(4) Degradation kinetics study of ammonia nitrogen wastewater treatment showed that the degradation process of ammonia nitrogen wastewater fit with the pseudo-second order kinetic equation. The ammonia removal rate k was 0.0059.(5)Under the optimal conditions, the real domestic wastewater was treated by electrochemical reactor filled with ferric supported clinoptilolite particles the results indicated that, ammonia nitrogen removal rate was 82%, the removal rate of COD was 70%, the effluent quality could meet the requirement of grade A of discharge standard of pollutants for municipal wastewater treatment plant(GB18918-2002).