Performance and mechanism of artificial zeolite on nitrogen removal from low C/N sewage

Artificial zeolite was used as an adsorbent to treat sewage with low C/N from an expressway service area. The effect of zeolite dosage on nitrogen removal from sewage was investigated. The factors affecting the adsorption effect of NH3-N by artificial zeolite were discussed by orthogonal experiments. The mechanism of NH3-N removal by artificial zeolite was discussed by means of adsorption kinetics and thermodynamics, specific surface area analysis (BET) and scanning electron microscopy (SEM). The results showed that artificial zeolite could significantly remove NH3-N and TN in sewage in a short time, and could effectively increase the C/N of sewage. After 24 h reaction, 40 g/L artificial zeolite could reduce NH3-N and TN in sewage to (13.45±0.39) mg/L and (19.23±0.21) mg/L, with the removal rates of (91.14±0.32)% and (87.12±0.10)%, respectively. Meanwhile, the C/N increased from 1.30±0.01 to 5.47±0.07. The orthogonal experiments showed that the effect of various factors on nitrogen removal of artificial zeolite was as follows: zeolite dosage>aeration volume>initial concentration of NH3-N. The adsorption process of NH3-N by artificial zeolite conformed to the quasi-secondary reaction kinetic model (R2=0.990), and the adsorption was a heat-absorbing process. The efficient removal of NH3-N by artificial zeolite was mainly due to its large specific surface area (493.23 m2/g) and its mesoporous pores with a wide distribution range. After adsorption, the particles on zeolite surface became smooth, compact and reduced in number.