Mobility and Dispersion Optimization of Nano Zerovalent Iron (nZVI) in Disinfection of Urban Wastewater with Pneumatic Nitrogen Gas Injection

Zero iron nanoparticle is considered as a universal enhancement agent. Its stabilization in aqueous environments with different coatings, reduces the efficiency of nanoparticles to a great extent. This study aimed to optimize the mobility and dispersion of nanoparticles to increase the inactivation efficiency of heterotrophic bacteria in urban sewage effluents. The experiment was carried out on Response Surface Methodology (RSM) and Central Composite Design (CCD) using Design Expert 10 software. Iron nanoparticles were synthesized in two types of carboxymethyl cellulose-coated and simple type. B-nZVI was introduced into the effluent with by pneumatic injection of nitrogen gas. CMC-nZVI was also mixed with a mixer in the effluent. Comparison of the results was done with two HPC and cellular molecular techniques (Genetic sequencing of 16s rRNA bacteria). The highest inactivation efficiency (90%) was observed in minute 23 for pneumonic injection of B-nZVI at a flow rate of 10 L / min. Finally, with the improvement of gas pressure and flow rate, the inactivation efficiency was recorded at 95.6% at 32 minutes. Final model obtained from this process agreed with the quadratic equation. General forecasting of the model was expressed by the correlation coefficient (R2=0.9447) that made good fitness for the response data. The statistical significance was determined using Fisher's statistics (F-value=13.29). For optimal use of nZVI in the inactivation of urban wastewater heterotrophic bacteria, nZVI can be injected into the wastewater by pneumatic injection in two steps with an inert gas such as nitrogen. In the nZVI pneumatic injection, the efficiency of deactivating bacteria in urban wastewater treatment plants was about 17% to 39% better than that of the coated-nZVI such as CMCs.