Study On The Removal Of N And P From Domestic Wastewater By Open Reactor Artificial Algae System

The algae system is used for sewage treatment,which can not only effectively reduce N,P and other pollutants,but also the algae can be used as raw material of organic feed.In addition,based on the development and research of the photo bioreactor,it is of great significance to study the algae wastewater treatment system.In this study,two kinds of microalgae,Chlorella vulgaris and Spirulina platensis,which had better removal effect on nitrogen and phosphorus,were selected as experimental algae.The artificial algal system was constructed in open reactor to conduct N and P removal experiments.The experiments mainly included that the start-up and establishment of artificial algae system,the removal effect of N and P in domestic sewage by system and the effects of relevant system parameters and operating parameters,and the system N,P balance and trend in the process of domestic sewage treatment.Based on the above research,this paper provides the support of technical basis for N and P treatment of domestic sewage and the development of recycling and utilization of pollutants.The results showed that:（1）Different algal species and algae proportion effect the start-up of artificial algae system,Chlorella vulgaris and Spirulina platensis artificial algal system suitable algae proportion were 10% at the start-up.（2）When the algae proportion was 10%,Spirulina platensis open reactor artificial algal system start and build completely needs 24 days,Chlorella vulgaris system needs 21 days.When it were build completely,Spirulina platensis system dry weight was 380mg/L,Chlorella vulgaris system dry weight was 349.5mg/L.（3）The system influent and effluent proportion and hydraulic retention time（HRT）have important effect on N,P removal and algal growth.The suitable influent and effluent proportion was 10%,and the suitable HRT for Chlorella and spirulina system treated domestic wastewater was 10 days.（4）When the influent and effluent proportion was 10%,HRT=10d,the phenomenon of NO₃^--N and NO₂^--N generated and the content is higher than influent all occurred at the process of Chlorella and spirulina system treated domestic wastewater.This may be due to the existence of nitrifying bacteria and nitrite bacteria in the system,such as nitrification and incomplete nitrification occurred.The removal rate of domestic sewage NH₄⁺-N by Chlorella and spirulina system treated were above 99%.Chlorella and spirulina system NH₄⁺-N effluent concentration were between 0.05-0.44mg/L.The removal rate of domestic sewage TN by Chlorella and spirulina system treated were 88.50% and 89.57%.Chlorella and spirulina system TN effluent concentration were 5.96-8.67mg/L and 3.87-8.05mg/L.The removal rate of domestic sewage TN by Chlorella and spirulina system treated were 81.37% and 79.28%.Chlorella and spirulina system TN effluent concentration were 0.62-1.23mg/L and 0.78-1.64mg/L.（5）The mass of biological phase nitrogen were accouted for 10% of dry weight in Chlorella and spirulina system,TN/TP were nearly 7.These were consistent with the algal approximate molecular formula C106H263O110N16 P.（6）The contribution rate of Chlorella and spirulina system biological phase（algae bacteria system）absorbing nitrogen for self growth for system TN reduce amount were 44.73% and 33.04%.（7）The contribution rate of Chlorella and spirulina system biological phase（algae bacteria system）absorbing phosphorus for self growth for system TP reduce amount were 75% and 86.67%.（8）The nitrogen conversion in Chlorella vulgaris and Spirulina platensis artificial algal system mainly includes nitrification,incomplete nitrification,ammonia volatilization and Biomass（algal bacteria system）increased absorption.Most of the phosphorus transformation is absorbed by the biological phase（algal bacteria system,mainly algae）,for their own growth.