Removal of ammonium from swine wastewater by zeolite combined with chlorination for regeneration.

This study investigated a process using ammonium ion (NH4(+)) exchange on zeolite in combination with chlorination regeneration for the safe treatment of simulated swine wastewater. Two stages i) 120-min zeolite ion-exchange and ii) 10-min exchanged zeolite regeneration facilitated NH4(+) ion removal from wastewater. Solution pH, contact time, adsorbent dosage, and competitive cations were the significant factors influencing the entire process. The effect of competitive cations on NH4(+) removal effectively followed the order of preference as Na(+)>K(+)>Ca(2+)>Mg(2+) at equivalent concentrations. The chlorination method experimentally removed approximately 99% of the NH4(+) exchanged on the zeolite, without remaining NH4(+) in the regeneration solution. Our analysis revealed that, in this process, the NH4(+) exchanged on the zeolite was first replaced by Na(+) and then oxidized to nitrogen gas. Reuse of the regenerated zeolite (GZ) indicated that the removal efficiency of NH4(+) ions was equal to that of the fresh zeolite modified with NaCl. Results of kinetic analysis revealed that the NH4(+) exchange on the GZ followed the pseudo-second-order model and the intraparticle diffusion model only for the first 60 min. The ion-exchange isotherm results demonstrated that the Langmuir model provided a slightly more consistent fit to the equilibrium data as compared with the Freundlich model. Repetitive experimental results confirmed that the proposed zeolite recycling process was stable and usable in simulated swine wastewater treatment.