Pilot Test On Nutrients Removal Eifficiency Of Domestic Wastewater By Using Photobioreactor System

Water pollution is a hot issue in the society,especially the utilization of wastewater resources.Because of unique metabolic way of algae,it provides a feasible method for wastewater ultilization.It not only can efficiently remove the nutrients of wastewater,but also recycle the algae biomass as a valuable by-products.In addition,based on the research and development of photobioreactor in wastewater treatment,the application of algae technology in wastewater treatment has a broad prospect.Spirulina,a kind of microalgae with considerable proteins,was selected as experimental specie for wastewater treatment in the present study.The construction of photobioreactor system was completed by using artificial sewage for the cultivation of Spirulina.The research experiments on the treatment of wastewater were carried out by adding anaerobic domestic sewage when the system reached stable.The effects of water filling ratio on the removal efficiency of pollutants and the system stability were investigated.The changes of microbial diversity in the system and seasonal variation of nutrients removal in wastewater were investigated under the optimal water filling ratio.At the same time,the assimilation of nutrients in wastewater treatment process under the optimal water filling ratio was studied.Based on the above research,this paper can provide technical support for the resource utilization of wastewater.Some conclusions are obtained in this study as follows:(1)The Spirulina can grow well in Zarrouk culture medium and artificial sewage.Finally,the microalgal biomass and chlorophyll-a was 810.5mg/L and 6.51mg/L in artificial sewage respectively,which was slightly less than that of 942.5mg/L and 7.18mg/L in Zarrouk culture medium.(2)The Spirulina could effectively assimilate the nutrients from artificial sewage,which had great importance for the construction of the microalgal photobioreactor system.The biomass in the photobioreactor system reached 810.5mg/L,and the TN and TP removal efficiency was 74.56% and 71.55%,respectively when the system reached stable.(3)The water filling ratio significantly influenced the stability of photobioreactor system and pollutants removal from wastewater.The system stability and the nutrient removal efficiency were best when the water filling ratio was 10%.The TN,TP and COD removal efficiency were 75.67%,71.38%,and 66.8%,respectively.(4)Due to the variation of wastewater components,the nitrogen source changed greatly in wastewater.It was found that the photobioreactor system preferentially assimilated ammonia nitrogen,followed by nitrate nitrogen and nitrite nitrogen.(5)With the best water filling ratio,the growth of Spirulina and the removal of nutrients in the photobioreactor system were significantly affected by the seasonal changes.(6)The nutrients in wastewater were removed synergistically by bacteria and microalgae in the photobioreactor system.The relative abundance of the bacteria had significant changes before and after the operation with the best water filling ratio.The dominant bacteria families were mainly Cyanobacteria,Proteobacteria and Bacteroidetes.(7)The assimilation of carbon,nitrogen and phosphorus from the removed nutrients was 41.73%,41.93% and 67.94% respectively in the photobioreactor system under the best water filling ratio.Besides,the nutrients in wastewater was mainly removed by microalga Spirulina rather than other bacteria.