Modeling And Simulation Of Alage Uptake Nitrogen And Phosphorus In Water By P-system

With the development of industry and agriculture,a large number of sewage was discharged into the rivers and lakes,the aggravation of water pollution makes China’s lack of resources increasingly tense.At present,there are three kinds of methods are used in sewage treatment:Physical method,chemical method and biological method.The biological method is widely used because of its good sewage treatment effect and low cost.Algae is a new type of aquatic organism which can be used to effectively remove the nutrients such as nitrogen and phosphorus in water,which is widely concerned because of its good removal effect,low cost and two times utilization of algae.The effect of algae removal of nitrogen and phosphorus is affected by many external environment,such as illumination,temperature,nitrogen and phosphorus nutrient concentration,in order to maximize the effect of algae removal of nitrogen and phosphorus,we need to establish a model that can effectively simulate the internal mechanism and macroscopic expression of nitrogen and phosphorus in algae absorption water.In this paper,p system and Gillespie algorithm are used to establish a P-system model of algae uptake water body,and the effects of light intensity and temperature on the removal of nitrogen and phosphorus by algae are considered.Firstly,a random P-system model describing the growth of algae was established,and a 11-day algae culture experiment was conducted,with fixed illumination of 330 μmol · m-2 · s-1,temperature 28 ℃,collecting the algae concentration change data in this 11 days,The parameters of the model are determined by using genetic algorithm.Using MATLAB to simulate the model,the calculated value of the algae concentration is compared with the actual value of the experiment,The results show that the average relative error between the simulated value and the measured value of the algae concentration is between 12%and 14%at all time points.It shows that the algae growth model is effective and accurate.Based on the algae growth model,in this paper,a random P-system model of algae absorption of nitrogen and phosphorus is established,which optimizes and adjusts the algae growth model,modifies the relationship between illumination intensity and temperature on algae growth,introduces the control of time to the model rule execution,and then carries out parallel experiments of 12 groups of algae culture.The illumination was set to 50,100,150,200μmol · m-2 · s-1,the temperature was 20,25,30 ℃,and the variation data of TN concentration and TP concentration in each group parallel experiment were collected.Using some data to obtain a new set of parameters,using MATLAB to simulate the model,the results show that the model of algae absorption of nitrogen and phosphorus can well fit the TP concentration of the track with time.The average relative error between TP concentration and measured value is up to 1.9%,the highest is 26.0%,and most average relative is within 15%in 12 kinds of external environment.However,the fitting effect of TN concentration change is poor,the calculated value of the model can not reflect the changing trend of measured value.At last,a verification experiment is designed,and the reasons for the unsatisfactory fitting effect of TN concentration are analyzed according to the experimental results.