| Self coupling microalgae bacterial granular sludge（ABGS）is a new type of granular sludge.It is inoculated with algae on the basis of aerobic granular sludge.Through the characteristics of algae like attachment and growth,it becomes a symbiotic spherical combination of algae and bacteria.Algae and bacteria can co-exist in the water body.Bacteria convert organic matter into CO2 and release it.CO2 is the substrate of algae photosynthesis.At the same time,oxygen generated through photosynthesis is an essential condition for the survival of aerobic bacteria.They complement each other and give full play to their advantages.They can achieve excellent water treatment effect and energy conservation and emission reduction effect.They have broad application prospects and are one of the research hotspots in the field of water treatment.After ABGS is cultivated in this paper,we can infer the reason why algae and bacteria can combine independently by comparing the electron microscope scanning photos of ABGS and ordinary aerobic granular sludge.At the same time,combined with the results of microbial community analysis of them,we can explore how the existence of algae affects bacteria.The optimal operation conditions of ABGS treatment system were studied by changing the aeration volume and light intensity.Finally,the environmental benefit of the treatment system is analyzed by estimating the power saving capacity,and a specific case is used to illustrate it.The main research contents and conclusions are as follows:（1）ABGS was cultured by inoculating algae in aerobic granular sludge for 130 days.It has the characteristics of large particle size and high compactness,which is better than ordinary aerobic granular sludge.Cultivating mature aerobic granular sludge and then inoculating ordinary freshwater Chlorella into the system can minimize the impact of algae on the sludge,especially the interior of the particles.By measuring the indicators that can reflect the characteristics of the particles and comparing with the ordinary aerobic granular sludge cultured in the same period,it is found that ABGs is superior to the ordinary aerobic granular sludge in terms of particle density and particle size,Dense particles can ensure the system to maintain a stable state in long-term operation,and the high particle density of ABGS is also the main reason for its excellent settlement performance.（2）Changing the two external conditions of aeration and light,it is found that when the aeration is 0.2L/min and the light intensity is 5klux,the system can achieve the dual effects of excellent water treatment capacity.Under the condition that algae photosynthesis provides oxygen completely instead of mechanical aeration or blast aeration,the water treatment efficiency of the system is low,which is contrary to the purpose of energy conservation and emission reduction in this paper,so it is not suitable to be implemented in the actual situation.It is found that the aeration system can achieve one of the best energy-saving effects of 94.0%of total nitrogen and 87.0%of total phosphorus required by the aeration system under the condition of 22.0%of total nitrogen and 27.0%of total phosphorus required by the ordinary aeration system.On this basis,by changing the light intensity of simulated natural light,it is found that the removal rate of COD and total phosphorus is directly proportional to the enhancement of light intensity,but there is an abnormal situation of total nitrogen.The stronger the light is,the more oxygen is,and the total nitrogen removal rate decreases.Further analysis of various forms of nitrogen shows that the accumulation of nitrite nitrogen will occur under the excellent aerobic environment,resulting in the decrease of total nitrogen removal rate.On the premise of ensuring that the effluent can meet the first-class a standard,taking into account the environmental benefits,it is considered that the simulated light intensity of 5klux is the best light intensity condition for the system,and the removal rates of COD,total nitrogen and total phosphorus can reach 94.01%,81.28%and 92.98%respectively.When the system has good water treatment effect,explore the role of algae in it.It is found that algae absorb less nitrogen and phosphorus under the best conditions that bacteria can adapt,with a removal rate of only 20-30%,indicating that the existence of algae promotes the absorption of pollutants by bacteria.（3）The formation mechanism of ABGS and the structure of biological community were investigated.Comparing the scanning electron microscope photos of ABGS and ordinary aerobic granular sludge,it is found that there are great differences in the outer structure between them.On the surface of ABGS,a large number of filamentous algae cells are intertwined and some spherical or rod-shaped bacteria are attached,while the surface of ordinary aerobic granular sludge is the extracellular polymer secreted by spherical bacteria and bacteria.Therefore,the existence of algae mainly affects the outer surface structure of particles,and the combination of the two is mainly through the intertwining of filamentous algae cells Connecting to form a shell and wrapping the original aerobic granular sludge inside;The difference of internal structure is small,and most of them are aggregated spherical bacteria.Through microbial community analysis,it is found that the existence of algae reduces the biodiversity of the system,the content of Proteobacteria related to nitrogen and phosphorus removal in ABGS decreases,and algae accounts for 22.2%of all species.Therefore,the proportion of algae and bacteria in ABGS is roughly 1:4.（4）The energy saving capacity of ABGS treatment system under laboratory conditions is estimated,and the annual power consumption of Tangwang sewage treatment plant can be reduced by about 26%through oxygen supply capacity.The results show that compared with ordinary aerobic granular sludge treatment system,it can save 0.06kw·h power consumption in one operation cycle under laboratory conditions and 5780 kW·h power consumption per cubic meter per year.For Tangwang sewage treatment plant,which processes 180000 cubic meters of sewage per day,using ABGS treatment system can save 0.27*107 kW·h of power consumption every year,which is equivalent to saving 26%of power consumption every year,and the environmental benefits are very considerable. |
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