| Algae is an important component of photosynthetic organisms,and is also considered as a functional microorganism in sewage treatment.It has the advantages of fast growth and strong adaptability,and is a potential species for sewage treatment and biodiesel production.In algae-bacteria symbiotic systems,the cooperation of algae and bacteria in sewage treatment can reduce the aeration intensity and carbon emission,which has a broad application prospect in sewage treatment and energy saving.In view of the problems such as the difficulty in controlling the biomass and the unstable treatment effect in the traditional algae-bacteria symbiotic system and this paper introduced filamentous algae as the carrier to build the filamentous algae-bacterial symbiotic granules system.In this system,filamentous algae-bacterial symbiotic granules were formed by the coupling of filamentous algae and activated sludge.At the same time,the effects of stirring and aeration on the construction of filamentous algae-bacterial symbiotic granules system were investigated.The efficient and stable operation of the filamentous algae-bacterial symbiotic granules system was realized by adjusting the operating parameters.Firstly,filamentous algae and activated sludge were cultured under static conditions for 15 days to form filamentous algal-bacterial symbiotic granules.The results showed that filamentous algae obtained good enrichment and accumulation in the granules formation process which wrapped around the activated sludge.The average concentration of chl-a increased from 43.78?g·L-1to 248.36?g·L-1.In addition,filamentous algae can produce mucus,which is dispersed around the cells in the form of soluble polysaccharides or mucinous substances.There is not only the exchange and utilization of nutrients and substances,but also the mutual competition of substrates between bacteria and algae in the bottle.The above results preliminarily determined the possibility of the coupling between filamentous algae and activated sludge,and indicated that filamentous algae played a key role in the granulation process due to its unique filamentous structure.Secondly,suspended algal-bacterial symbiotic system was combined with the sequencing batch reactor?SBR?to set up different ways of mixed bacteria and algae,aiming to explore the effects of filamentous algal-bacterial symbiotic granules system on the removal efficiency of pollutants in domestic sewage,to investigate the effects of stirring and aeration on the treatment efficiency and operation of the reactor.The results showed that the average removal efficiency of COD and NH4+-N were 71%,65%and82%,66%,respectively.The amount of oxygen produced by algae alone was not enough to support the removal of organic carbon and ammonia nitrogen.Finally,filamentous algae-bacteria symbiotic granular system?R2?were developed in a photo-sequencing batch reactor?PSBR?.Meanwhile,the characteristics and performance of the mature granular consortia were investigated,and was compared with those of activated sludge?R1?under the similar operating conditions.After 60 days operation,the filamentous algal-bacterial symbiotic granules with smooth appearance and clear outline could be observed in the symbiotic system.The average removal efficiency of COD,NH4+-N,and TN in R1 and R2 were 88%,71%,69%and 94%,86%,76%,respectively.The results of microbial structure analysis showed that the microbial diversity of the filamentous algae-bacteria symbiotic granules system was higher than that of the activated sludge system and the microorganisms enriched in symbiotic system were mainly the Comamonadaceae and Rhodobacteraceae.The above results show that the introduction of algae into the activated sludge system is conducive to the aggregation and formation of granules.In fact,under the effect of low aeration and selective pressure,algae are more likely to attach to the periphery of activated sludge and form filamentous algal-bacterial symbiotic granules. |
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