| The main bottleneck for the large-scale development of the pig industry is the environmental pollution issue brings by discharge of fecaluria and washing wastewater from the aquaculture wastewater.At present,the treatment of the swine wastewater focus on the removal of pollutants including nitrogen and phosphorus instead of resource utilization.Meanwhile,the above treatment is limited by high cost,insufficient space and low efficiency.On the one hand,resource of nitrogen and phosphorus from wastewater is ignored.On the other hand,it is uneconomical to cultivate microalgae because of the high cost of nutrients.Therefore,aquaculture wastewater used for microalgae cultivation not only decreases nitrogen and phosphorus pollution but also realizes cost saving with the advantages of environmental protection and resource conservation.However,treating wastewater by microalgae only is inefficient.But,the removal rate of pollutants such as nitrogen and phosphorus is higher when microalgae coupling with bacteria system is used.Based on this background,the main objective of the present study was to construct algae-bacteria symbiotic system with high efficiency to remove nitrogen and phosphorus from piggery wastewater.This study was designed to(1)investigate the effects of various bacteria on the wastewater purified by microalgae;(2)explore the optimized reaction conditions for algae-bacteria symbiosis system with nitrifiers and Desmodesmus sp.CHX1;(3)set up an efficient algal-bacterial symbiosis system to treat the digested piggery wastewater of pig farm from Hangzhou,Zhejiang.The results obtained here can provide practical technical support for the management of aquaculture wastewater in actual production,which was as follows:1.The growth condition of microalgae and the removal efficiency of pollutants were considered in the trails of treating simulant digested piggery wastewater by Desmodesmus sp.CHX1 with or without COD(COD represents chemical oxygen demand)degradative bacteria,compound bacteria,nitrifier.The results showed that the removal rate of ammonia nitrogen,total nitrogen and total phosphorus as well as microalgae biomass were all the highest in the algal-bacterial symbiosis system composed by microalgae with the amendment of nitrifiers.Consequently,nitrifiers were chose to constitute algae-bacteria consortium with Desmodesmus sp.CHX1.2.Research on the optimization of algal-bacteria consortium with Desmodesmus sp.CHX1 and nitrifiers showed that optimized operational conditions were microalgae and bacteria with a ratio of 1:1,culture temperature of 30?,initial ammonia concentration of 550 mg/L.3.Algal-bacteria consortium with Desmodesmus sp.CHX1 and nitrifiers can grow normally in anaerobic digestion piggery wastewater,accompanied by the excellent removal of ammonia nitrogen and total phosphorus rather than COD.The growth of microalgae and the removal efficiency of ammonia nitrogen in wastewater were obviously improved as the dilution of the initial ammonia nitrogen concentration.When the R(R=Volume of anaerobic digestion of piggery wastewater/Total volume of solution in the reactor)was 0.5,the content of chlorophyll,carotenoid and the ammonia nitrogen removal amount were the highest.Nitrite nitrogen and nitrate nitrogen had no significant accumulation in the wastewater,and they kept values below 0.1 and 7 mg/L,respectively.The total phosphorus removal amount was highest in wastewater with R=1.0.In conclusion,Desmodesmus sp.CHX1 and nitrifiers were in favor of constructing algae-bacteria symbiotic system to treat digested piggery wastewater. |
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