Analysis Of Standing Settling Process And Curves Of Activated Sludge

In recent years,with the development of urbanization leads to the increased amount of sewage,as well as sewage treatment plant effluent discharge standards more stringent,sewage treatment plant construction and transformation needs to achieve "land-saving" and "reaching the standard" two requirements.The second settling tank is an indispensable part of the sewage treatment,and it covers a large area and has a great impact on the water quality of the effluent,so many researchers have conducted in-depth research on the secondary sedimentation tank.According to the theory of solid flux,in stable condition,the hydraulic load is equal to two clarifier sludge sedimentation rate,so many scholars have conducted a lot of dynamic and static precipitation experiments on settling velocity were analyzed,established many settling velocity model.Influenced by the experimental conditions at that time,the researchers could not record the precipitation process in detail.In this paper,the method of photo taking is used to record the process of static precipitation,which can be used to carry out many experiments of static precipitation at the same time.This paper carried out static precipitation experiments on four batches of sludge,got a total of 710 concentration range of activated sludge 0.6-22g/L static precipitation curve,through the static analysis of the precipitation curve,obtained the following conclusions:1?The static precipitation process can be divided into three categories: the first category is the characteristics of the precipitation process and no buffer period,the concentration ranges of 364.4~6425.6mg/L;second kinds of precipitation process,the characteristic is obvious,the concentration ranges of 2186.4~16287.3mg/L;third kinds of precipitation process,the characteristic of the period is not obvious,the concentration range of 8195.6~21782.0mg/L.The precipitation process can be divided into 4 periods: the buffer period,the maximum sedimentation rate,the deceleration period and the compaction period.2?The settling velocity curve is divided into 3 periods: rising period,stable period and decline period of time the stable period of precipitation in the first and the second kind of short,appeared in third kinds of precipitation process in a long time.From the first maximum precipitation settling velocity model,power function and exponential function have good fitting effect;exponential function as settling velocity model in second was the best fitting degree,at the same time,cracks are the main reasons of uncertainty phenomenon,and the relationship between buffer duration and sludge concentration was regional distribution;third kinds of precipitation process of settling velocity empirical model for power function,has a good fitting effect.3?In the second types of precipitation curve,the precipitation curve is a piecewise function curve,buffer period empirical model for quadratic function,combined with empirical model deceleration time and compaction period for power function,third kinds of precipitation curve,empirical model of the precipitation curve is cubic function.The determination limit of SV30,SVI in the description of high concentration sludge sedimentation performance is not accurate,the sludge diluted to less than 2000mg/L,and thus the measured SV30 can be obtained through calculation,can accurately describe the settlement performance of SVI.At the same time,the relationship between the height of the settling column and the sludge concentration in the compaction period tends to a primary function.Under the condition of sufficient precipitation time,the minimum water content of activated sludge is mainly concentrated in the range of 96.2% to 97.2%.