Establishment And Nitrogen Removal Characteristics Of Bacterial-algal Co-culture System

In recent years,due to the rapid development of aquaculture industry,aquaculture density has increased,which resulted the nitrogen pollution of water has increased.The traditional biological denitrification method has the disadvantages of long denitrification cycle and high occupation of space resources.In order to find a method for denitrification of water with more efficient,an aerobic denitrifying strain was isolated from intensive culture ponds,through morphology observation,physiological and biochemical test and combining with molecular biology methods for strain identification,a bacterial-algal co-culture system has constructed with the strain and Chlorella,and applied to simulated wastewater and culture wastewater,achieved good nitrogen removal results.The main research results are as follows:1.A strain of aerobic denitrifying bacteria TC-1 with good denitrification ability was isolated from intensive culture ponds.Through morphological observation,physiological and biochemical indexes determination,and combined with 16S r DNA sequence analysis.The strain TC-1 was identified as Pseudomonas toyotomiensis.2.The co-culture of strain TC-1 with Chlorella showed a better nitrogen removal performance than that of single strain or single algal strain.The removal rate of NO₂^--N was96.89%and the removal rate of total nitrogen was 90.98%in 48 h when NO₂^--N was used as the nitrogen source.The removal rate of NO₃^--N was 96.42%and the removal rate of total nitrogen was 89.47%in 48 h when NO₃^--N was used as the nitrogen source.3.The bacteria algae co-culture system were investigated using a single factor test.The effects of the addition of nitrogen source,carbon sources,ratio of carbon source,inoculation amount,initial p H value,culture temperature and rotating speed of shaking table were studied.The optimal nitrogen removal conditions were as follows:addition of NO₂^--N 100mg/L（addition of NO₃^--N 140mg/L）,0.25%sodium succinate and 0.75%glucose as carbon source,total inoculum volume 2%,initial p H 7.0,culture temperature 30℃,rotation speed 170 r/min.The removal rate of NO₂^--N and total nitrogen was 99.14%and 95.07%when NO₂^--N was used as the nitrogen source.The removal rate of NO₃^--N and total nitrogen was 96.31%and 93.95%when NO₃^--N was used as the nitrogen source.4.According to the results of single-factor test,the nitrogen removal conditions of the bacterial algal co-cultures were optimized by response surface method,and the initial p H,total inoculum and rotational speed were selected as the influencing factors with nitrite nitrogen as the nitrogen source and total nitrogen as the response value,and the optimal conditions of initial p H 7.05,total inoculum 2%and rotational speed 169 r/min were obtained.The maximum removal rate of total nitrogen reached 97.06%after the model validation test.The results of applying the bacterial algal co-culture system to simulated wastewater treatment showed that the removal rates of NO₂^--N,NO₃^--N and total nitrogen could reach 98.41%,95.63%and 92.97%,respectively,within 36h.The results showed that the bacterial algal co-culture system can achieve rapid denitrification by adding carbon source in the wastewater denitrification,while it still has good stable denitrification ability without adding carbon source.