Study On The Effect Of Carbon Source On The Treatment Of Aquaculture Wastewater By Biofloc

In recent years,with the increasing demand for aquatic products,aquaculture industry has developed rapidly.The residual bait in water and ammonia nitrogen released from the feces of aquaculture animals cause serious water pollution.Due to the high ammonia concentration in most aquaculture industries,ammonia nitrogen is generally converted into nitrogenous nitrogen by adding nitrifying bacteria,which leads to the high concentration of nitrogenous nitrogen in aquaculture water and secondary pollution.For nitrogen load in aquaculture water,one treatment method is to change water,but it will consume a lot of water resources.Another method is circular aquaculture,in which water used for farming is treated and recycled,but this aquaculture model increases costs.Biofloc technology is gradually regarded as an effective alternative technology to solve the environmental problems and cost problems faced by the aquaculture industry and to improve the utilization rate of feed.In this study,a new aquaculture model with good economic and ecological benefits was developed by using biofloc technology to purify aquaculture water bodies and realize double utilization of feed in order to solve the problem of high concentration of nitric nitrogen in the aquaculture water bodies of white prawn in South America.Carbon source is an important factor in the process of culturing biological flocs.By adding carbon source,the structure of heterotrophic microbial community in water body can be changed.While using organic carbon,microorganisms can assimilate dissolved nitrogen in water body to form flocs,so as to achieve the purpose of purifying water environment and reusing food.Different carbon sources will form different dominant flora,resulting in different purification effects.Different carbon source addition methods will affect the activity of heterotrophic microorganisms,and thus affect the purification effect of microorganisms on water.This experiment mainly investigated the effects of batch addition of carbon source,real-time supplement of carbon source and seawater on the treatment effect of aquaculture wastewater under different carbon source culture conditions,and clarified the difference of treatment effect of each reactor system,providing reference data and technical support for practical production.The main conclusions obtained in this paper are summarized as follows:(1)The experiment results of culturing flocs to treat the culture wastewater by adding carbon source in batches showed that the reactor with brown sugar as the carbon source had the best treatment effect,but the nutrition supply was not timely in the late stage of the experiment,which led to the death of a large number of heterotrophic microorganisms,and the effect of removing nitrite nitrogen decreased sharply.(2)In the second phase of the experiment,the added carbon source was replaced with a real-time supplement to ensure that the carbon-nitrogen ratio was greater than 20.The results showed that the reactor with added glucose as carbon source could remove nitrite nitrogen in three stages,and the removal rates were 30.36 mg/l·d-1,4.28 mg/l·d-1 and 3.23 mg/l·d-1 respectively,which were the best in all carbon source culture flocs.In the glucose bioflocculation reactor,microorganisms were the most active and DOC utilization was the strongest.However,the crude protein content in the glucose group was slightly less than that in the brown sugar group.(3)The results of the analysis on the structural diversity of the microbial community showed that proteobacteria were dominant in each reactor.The relative abundance of heterotrophic bacteria was the highest in the first 20 families of dominant bacterial communities in the glucose group.(4)The results showed that flocs cultured in seawater were less effective in purifying aquaculture wastewater than in fresh water,and microorganisms were not easy to grow and reproduce in seawater.There was no significant difference in the treatment effect between the glucose group and the brown sugar group.The removal rates of nitrogenous nitrogen were 0.14 mg/l·d-1 and 0.18 mg/l·d-1,respectively.The peak concentrations of DOC were 408.9 mg/1 and 383.3 mg/l,respectively.