Degradation Of Nitrogen,Phosphorus And Organic Matters For Black Odorous Water By Microalgae In The Algae-bacteria Symbiotic System

With the acceleration of urban development,the treatment of black odorous water has become a main problem in the restoration of the water environment.To restore the river habitat and realize the resource utilization of black odorous water,black odorous water was employed as the research object,and Haematococcus pluvialis（H.pluvialis）M1 were inoculated as the dominant species in the treated water samples.Culturing indigenous microorganisms for synergistic biological contact oxidation（BCO）as well as ultraviolet photolysis of black odorous water was used for the pretreatment comparison process.The algae-bacteria symbiotic culture conditions were optimized,and then analyzed the changes of the structure for the biological community under different light sources.A high efficient algae-bacteria symbiotic system was constructed to achieve the effective migration and transformation of organic matter and nutrients such as nitrogen and phosphorus.Firstly,the black odorous water was preliminarily degraded through pretreatment.Then,the physiological and biochemical characteristics of microalgae were explored,rules of microbial degradation were understood,and the effect of the algae-bacteria symbiotic system on black odorous water was analyzed.In addition,the biological activated carbon（BAC）column was deemed as a carrier to construct an algae-bacteria symbiotic system.The treatment of black odorous water was reflected by the adsorption of the algae-bacteria symbiotic system combined with BAC in a simulated flowing state.The biofilm was formed in the BCO pond and the BAC column,and meanwhile,the growth status of the biofilm was observed by scanning electron microscope（SEM）.For different treatment processes,three-dimensional excitation and emission matrices（3DEEM）spectra were used to detect dissolved organic matter（DOM）in water bodies.The main research results were as follows:（1）The pretreatment method of culturing indigenous microorganisms for synergistic BCO was adopted for the black odorous water.Different carbon sources had all promoting effect on the growth of indigenous microorganisms in the water.The effect decreased in the following order:glucose>peptone>control group.（2）UV photolysis could breakdown macro-molecular organic matters into small molecules substances that were easily metabolized by bacteria.Furthermore,malodorous substances were generally organic substances containing nitrogen and sulfur.There were low bond energies in C-N and C-S bonds and were easily dissociated by ultraviolet light.Therefore,the odor weakened gradually or even disappeared.（3）A algae-bacteria symbiotic system was formed to further purify water quality via inoculating mutant strain M1 through ultraviolet-B radiation.The algae strains with directional screening had more accumulation of astaxanthin and a significant ability to treat black odorous water.According to the living conditions of microalgae,a single factor comparison test was carried out.At the dissolved oxygen（DO）concentration of 5mg/L,light intensity of 3000Lx and inoculum size of 125,000 cells/m L,black odorous water treated by the combined treatment met the demand of landscape water in the urban river.（4）According to the growth curve and biomass of microalgae,compared with the flow state,the static state under the LED light source was most suitable for the growth of microalgae,which conformed to the static hydrodynamic characteristics of black odorous water.The measurement of biodiversity revealed that the community structure of bacteria in different light sources has changed.（5）After combining the BAC column with the algae-bacteria symbiotic system,the values of chemical oxygen demand（COD）,UV₂₅₄-pollutants,total nitrogen（TN）,ammonia nitrogen（NH₃-N）,and total phosphorus（TP）were reduced by 83%,69%,63%,70%,and 75%,respectively.3DEEM spectra suggested that both UV photolysis and activated carbon adsorption were beneficial to the removal of aromatic protein I pollutants.After the combined treatment,all peaks in five regions of the 3DEEM spectra disappeared,thereby the pollutant intensity decreased,indicating that the combined treatment process was of great significance for the study of the algae-bacteria symbiotic system to repair the black odorous water.