Exploring Algae-Bacteria Combined System To Remove Nutrients From Domestic Sewage

With the rapid advancement of industrialization and the continuous improvement of people’s living standards in China,the discharge of large of sewage,especially domestic sewage,has become increasingly prominent.A large amount of domestic sewage will cause the discharge of N,P and organic pollutants,and the discharge of untreated domestic sewage into natural waters will cause eutrophication of water bodies,seriously damaging the use and ornamental value of natural water bodies,which will inevitably aggravate the shortage of fresh water resources and the destruct the ecological balance.Therefore,it is imperative to treat nutrients in domestic sewage.Microalgae is widely used to absorb inorganic salt pollutants and adsorb heavy metal pollutants because of its good treatment effect,simple operation,low cost and no secondary pollution.However,the application of microalgae is limited by slower growth rates and lower resistance to pollutants,especially organic pollutants.Therefore,we have chosen a new algae-bacteria combination system to increase the amount of microalgae organisms as well as enhancing the removal efficiency of N,P and organic matter.In this strategy,bacteria degrade macromolecular organic matter into small molecular organic matter,and absorb oxygen and release carbon dioxide in the process of respiratory metabolism.At the same time,microalgae absorb inorganic salts for the synthesis of their own biomass,and absorb the carbon dioxide released by the bacteria in situ and release oxygen for microalgae utilization via photosynthesis.In the experiment,we used the method of controlling variables to introduce specific microalgae and specific bacteria into the same simulated sewage treatment system,comparing the difference in the removal effect of N,P and organic matter with the microalgae or bacterial single system,investigating the mechanism of the combined action of algae and bacteria and exploring the optimal environmental conditions for the removal of pollutants by the algae-bacteria system.Satisfied results were obtained in the experiment.The algae-bacteria combination system has faster and better treatment effect of N,P and organic matter than a single treatment one.After ten days of treatment,the combined system can reduce the concentration of ammonia nitrogen,phosphate,soluble total phosphorus and COD in wastewater from 9.90 mg/L,1.67 mg/L,5.02 mg/L,150.00 mg/L to 1.40 mg/L,0.14 mg/L,1.32 mg/L,0.00 mg/L,with the removal rate of 85.90%,91.50%,73.75% and 100.00%;The dry-weight of the microalgae and the bacteria in the single treatment system were 323.22 mg/L and 262.50 mg/L,and the dry weight of the microalgae and the bacteria in the mixed treatment system were 416.28 mg/L and 463.82 mg/L;The optimal condition for the removal of nutrients from the combined system the pH= 7,temp 25°C,white led light 12000 lux with maintaining 12:12 hours diurnal condition.