Effect Of Fiber Carbon On The Preparation Of Anaerobic Granular Sludge And Rapid Start-up Of UASB Reactor

The development of anaerobic biotechnology has a history of hundreds of years.At present,anaerobic activated sludge process is widely used in the treatment of high concentration organic wastewater,but it is prone to some disadvantages,such as poor sludge sedimentation performance,unstable nature,and serious loss.Granular sludge has better sedimentation performance due to the agglomeration of microorganisms into particles,and the distribution of microorganisms is relatively concentrated,which improves the resistance to environmental changes and perfectly eliminates these shortcomings.Therefore,it has attracted more and more attention in the industry.UASB reactor has the advantages of convenient management and simple operation,can withstand high OLR,and the operating system is relatively stable.It is widely used in anaerobic wastewater treatment.In addition,the UASB reactor has high hydraulic shear force,it is also suitable as the main container for cultivating granular sludge.In this paper,the rapid start-up of the UASB reactor was studied by adding loaded sludge materials.Compared with the reactor without sludge carrier materials,the influence of biological fiber carbon materials on sludge particle formation and the change of sludge anaerobic performance were explored,and the micro biodiversity and population richness in the process of anaerobic particle formation were analyzed.Firstly,after obtaining biological fiber carbon materials,in order to improve the efficiency of the anaerobic granular sludge culture test,the single factor test of fiber carbon dosage and the response surface analysis based on the optimization of three metal ion concentrations of Ca²⁺,Mg²⁺and Fe²⁺are designed.It is found that the best test conditions are:fiber carbon dosage of0.5 g/g VS,Ca Cl₂concentration of 288.41 mg/L,Mg SO₄·7H₂O concentration of 643.70 mg/L and Fe SO₄·7H₂O concentration of 502.50mg/L.Secondly,the rapid start-up of the UASB reactor based on the above optimization conditions was studied.Two reactors of the same model were set up in the experiment.The start-up process lasted for 57 days.The sludge particle culture was strengthened through three stages of increasing COD load in turn and the composite mode of gradually shortening hydraulic retention time.In the experimental group with fiber carbon loading material,the organic component of sludge in the reactor was higher,the sedimentation performance of sludge was better,and the particle size of mature granular sludge was larger.The granular sludge grown with fiber carbon as the skeleton structure was denser,and the wet density reached 1.134 g/cm³.When the influent COD concentration was 8000 mg/L,the COD removal rate of the test group and the control group was 95.27%and 93.13%respectively.The ammonia nitrogen concentration level of the two reactors was always in a dynamic state.Because UASB reactor cannot provide complete nitrogen circulation conditions,ammonia nitrogen was always in a dynamic balance of consumption and transformation.In terms of gas production,the maximum gas production of the control group in a single cycle was 2250 m L,and the methane content was 47.27%;The maximum gas production of the reactor in the test group with fiber carbon in a single cycle was 2620 m L,the methane content reached 73.06%,and the sludge adaptation period was shorter and the adaptability was stronger.Finally,through the analysis of sludge microbial community diversity and population richness during the operation of the reactor,it is found that with the operation of the reactor,sludge microbial diversity and richness show a downward trend,which is more obvious after adding fiber carbon.Based on the analysis of the community composition at the"phylum"level and"Genus"level of sludge microorganisms,it is found that Firmicutes and Bacteroidota are the main dominant bacteria.After adding fiber carbon,Firmicutes has become the absolute dominant bacteria,accounting for 86.16%.Clostridium has the highest relative content in sludge samples.After adding fiber carbon,the advantage of Clostridium is more obvious,and the relative content of methanogens is low.The functional analysis of the flora shows that compared with the methanogenic stage,the pre-stage such as hydrolysis and acidification in the anaerobic system is the main occurrence stage of the anaerobic system.