Effect Of Fe On Carbon Enrichment And Anaerobic Fermentation Of High Load Activated Sludge

Due to the disadvantages of the traditional secondary treatment of urban sewage,such as high capital cost,high energy consumption and poor carbon rich effect,this study adopts the chemical and biological flocculation enhanced primary treatment of urban domestic sewage.Test in the experiment,on the basis of Fe salt on high load are analyzed the influence of the activated sludge system,then the process is studied through field test device in the actual effect of sewage treatment,and research the different valence state of iron influence on excess sludge anaerobic fermentation,using fluorescence spectrum and Fourier infrared spectrum analysis method to characterize the sludge anaerobic fermentation process.The main research contents and results are as follows:1.Batch experiments were conducted to study the effect of enhanced bioflocculation of municipal wastewater with different concentrations of polymeric ferric chloride(measured with Fe³⁺),so as to determine the optimal use concentration of Fe salt.Zeta potential,qualitative and semi-quantitative analysis of organic components,three-dimensional fluorescence spectra and dimensional exclusion and resistance chromatography were used to further verify the effect of iron salt enhanced bioflocculation on organics removal.Through the analysis of COD and TP,it is concluded that the optimal use concentration is 30 mg/L,and zeta potential needs to be maintained within the appropriate range to achieve efficient removal efficiency of organics;The organic matter in effluent is mainly composed of hydrophilic components,accounting for about 60%.The components are mainly humic acids,and the dissolved organic matter is mainly of small molecular weight.2.The optimal concentration of Fe salt obtained in the batch experiment was applied to the pilot plant,and the operating effect and organic matter enrichment before and after the pilot plant was dosed were compared.The results showed that after adding 30 mg/L of PCL into the pilot plant,the COD removal rate increased by20%;TP removal rate increased by 35%.The effluent reaches the specified limit of level A discharge standard;The removal rate of TN did not change significantly after dosing.Most of the organic matter in the system can be quickly absorbed with the residual sludge discharge system,and the system has a better effect on organic matter enrichment.The practical operation effect of Fe salt enhanced biological flocculation treatment of urban sewage is relatively ideal,which can effectively remove COD,nitrogen and phosphorus,providing a precondition for the successful operation of the next process.3.The effect of Fe salt on the biological flocculation performance of the reaction system before and after the addition of Fe salt was studied on the basis of the field pilot test device.It was found that the removal efficiency of SCOD was reduced by 15%after 30 mg/L Fe salt was added to the stably operated high active sludge system.Meanwhile,the addition of Fe salt reduced the total amount of EPS,in which the content of polysaccharides and humus varied little,while the protein concentration decreased significantly.The results showed that the addition of Fe salt with a certain concentration had an inhibitory effect on the secretion of the sludge extracellular polymer,which affected the total amount of EPS mainly by inhibiting its secretion of protein,thereby reducing the ability of sludge particles to form large aggregates,and to some extent weakening the system's biological flocculation ability.The bioflocculation performance of the pilot test system can be characterized by the fluorescence intensity of protein-like substances in the sludge of the pilot test system.When the fluorescence peak of protein-like substances is significantly reduced,the bioflocculation performance will be correspondingly reduced.4.Batch experiments were conducted to study the effects of different valence states of Fe on the effluent quality of anaerobic fermentation systems,and further analysis of three-dimensional fluorescence spectra by parallel factor analysis.The results showed that the addition of proper Fe²⁺was beneficial to the release of phosphorus from sludge and significantly promoted the transformation of COD.In the anaerobic fermentation process of sludge,three kinds of fluorescent materials including protein,coenzyme NADH and coenzyme F420 are produced.After the addition of appropriate amount of Fe²⁺,the fluorescence intensity of coenzyme F420was significantly enhanced compared with that of the blank group,and the proteinoid and coenzyme NADH were also enhanced,indicating that appropriate amount of Fe²⁺could promote sludge fermentation.The FT-IR was used to analyze and characterize the experimental samples,in order to study the promoting mechanism of the experimental process.Fe²⁺enhances the functional groups such as carboxyl group,alcohol group and phenol in the sludge,which may be due to the fact that proper amount of Fe²⁺is conducive to promoting the release of dissolved cells of microbial cells,producing more important anaerobic fermentation products such as acetic acid and hydrogen.