Study On Treatment Of Livestock Wastewater By Microalgae And Bacteria Symbiotic System Based On Glucose Co-metabolism

The pollution of livestock wastewater is the third major water pollution after industrial and domestic wastewater currently.The existing treatment technology of livestock wastewater is high in cost and the procedure is complicated.It is necessary to find a new and harmless treatment technology for the treatment of livestock wastewater.Microalgae and bacteria symbiosis system is considered as a treatment technology with application prospects for livestock wastewater.In this thesis,a microalgae Chlamydomonas reinhardtii CC-125 and multiple strains of Bacillus were used to establish microalgal and bacterial symbiosis systems respectively.The removal efficiency of nutrients from wastewater with the system by adding glucose and spore germination agents was investigated,and the growth of the Bacillus and the photosynthetic characteristics of algae were preliminary studied.The research contents are as follows:Four strains of Bacillus spp.which can grow in livestock wastewater are selected.They were Bacillus cereus YS,Bacillus cereus SLK,Bacillus pumilus BSK9 and Bacillus coagulans BS32,which constitute microalgal and bacterial symbiosis system with C.reinhardtii CC-125 respectively to treat livestock wastewater of different nutrient concentrations.Compared with the pure algae system,four kinds of algal symbiosis systems did not show an advantage in the removal of nutritive substances,and the removal efficiency of TP was reduced by 20% in the wastewater with an initial COD concentration of 1000 mg/L.ECO micro plates was used to explore the ability of microalgae and bacterial symbiosis systems to utilize different carbon sources.Glucose was used as the carbon source to establish a symbiosis system with co-metabolism to facilitate the removal of livestock wastewater.The purification of the livestock wastewater with the addition of 0.5g/L and 1 g/L glucose was studied.It was found that the removal efficiency of the experimental group with 0.5 g/L glucose was significantly increased.The symbiotic system of B.coagulans BS32 and C.reinhardtii in the four symbiotic systems was remarkable.Compared with the pure algae system,the removal efficiencies of ammonia nitrogen,total nitrogen,total phosphorus and COD increased by 16.58%,28.38%,8.90% and 23.04%,respectively.L-alanine is a common agent to promote the germination of Bacillus.0.5 g/L glucose and 100 ?M alanine are added in the symbiosis treatment system at the same time.It is found that the removal efficiency of nutrient substances from livestock was further improved.The removal efficiency of B.coagulans BS32 and C.reinhardtii CC-125 symbiosis system was significantly improved.Compared with the pure algae system,the respective removal efficiencies of ammonia nitrogen,total nitrogen,total phosphorus and COD increased by 18.16%,39.51%,19.84%,and 39.56%,respectively.Two antibiotics containing sulfamethazine and enrofloxacin were detected in livestock wastewater using LC-MS with concentrations of 127.47 ?g/L and 219.54 ?g/L,respectively.The symbiotic system has a very significant degradation of sulfamethazine,with a degradation rate of 61.22% in 5 d.However,the degradation effect of this system on enrofloxacin is slightly poor.The addition of glucose and alanine does not increase the degradation of enrofloxacin.In summary,the symbiosis system based on glucose co-metabolism not only promotes the removal of nutrients in livestock wastewater,but also promotes the degradation of sulfamethazine in wastewater.The growth of bacteria and photosynthetic characteristics of algae in C.reinhardtii CC-125 and B.coagulans BS32 symbiotic systems were analyzed.It was found that symbiotic system based on glucose co-metabolism significantly promoted the chlorophyll content of C.reinhardtii.The simultaneous addition of glucose and alanine can promote the growth of Bacillus initially and the photosynthesis of C.reinhardtii,but the effect on respiration is not significant.The maximum photosynthetic quantum yield(Fv/Fm)of C.reinhardtii remains at about 0.75,which showed the presence of B.coagulans BS32 was beneficial to maintain the higher photosynthetic activity of C.reinhardtii CC-125 in the symbiotic system.