Pollutants Removal By Combined Flocculation-adsorption Technology In Black Odor Water:Efficiency And Mechnism

With the acceleration process of modern industrialization,a large amount of black odor waters have been formed in urban cities.This phenomenon would not only made the waters lose their ecological function,but also threatened residents health and the survival of aquatic organisms.At present,there are varoius treatment technologies of black odor waters,but it is difficult to achieve large-scale applications.In order to solve the problem,this paper proposed a technology combined with magnetic flocculation-adsorption that could simultaneously remove multiple pollutants in black odor waters,furthermore,the influential factors of experiments and practical applications in actual black odor waters had been optimized.In addition,the mechanism of this technology applied to black odor waters were also investigated via various systematic charaterizations.The specific research results were as follows:In this study,a magnetic compound flocculant formed with 1000 mesh magnetic powder,PFS and PAM were selected to explored the influencing factors of the flocculant on the removal of turbidity and TP.The best magnetic flocculation conditions were confirmed: the flocculation sedimentation time were completed within 3 min;the optimal dosage of PFS,MPs and PAM were 16 mg/L,100 mg/L and3.6 mg/L,respctively;the order dosing was first PFS+MPs,followed by PAM;the optimum pH value was 6.Under the optimal operating conditions of magnetic compound flocculant,the removal rate of turbidity and TP could reach 98.8 % and77.0 %.Additionally,the removal rate of turbidity and TP could still up to 96.0 % and66.2 % after recycled for 6 times.The removal rate of turbidity,orthophosphoric acid and total phosphorus could reached the requirements of Discharge standard of pollutants for municipal wastewater treatment plat and Class of the surface water environmental quality standard,demostrating its surperior practical application.Secondly,a novel spherical adsorbent PCZ was fabricated by loading protonated chitosan on zeolite.The results of SEM,FTIR,TGA and BET verified that the successful synthesis of PCZ,which possessed mesoporous structure and thermal stability.Afterwards,the various influencing factors about turbidity,ammonia nitrogen and TP removal rate in the adsorption section were further optimized under the optimal magnetic compound flocculation operating conditions.The above results suggested that the optimal dosage of PCZ,pH and adsorption equilibrium time were respectively 1.25 g/L,6 and 7 h;the adsorption of ammonia nitrogen followed the intra-particle diffusion model and Freundlich isotherm model,but the pseudo-first-order kinetic model and Langmuir isotherm model were used to describe the adsorption of TP.Moreover,The determined flocculation-adsorption process was applied to actual black odor waters.The removal rate of turbidity,orthophosphoric acid,total phosphorus and ammonia nitrogen could reached the requirements of Discharge standard of pollutants for municipal wastewater treatment plat and Class of the surface water environmental quality standard,indicating the excellent practical applications of this flocculation-adsorption process.Finally,various characterization methods were used to explore the mechanism of flocculation-adsorption to remove multiple pollutants.The results suggested that the removal of turbidity of the magnetic compound flocculants mainly depended on the charge neutralization.As for the removal of TP,it not only had charge neutralization,but also underwent a series of complex chemical reactions with TP,forming iron phosphate precipitates;the adsorption of ammonia nitrogen by PCZ was attributed to ion exchange,while the removal of TP owed to the electrostatic adsorption.