Study On Treatment Of Municipal Sewage By Algae-Bacteria Symbiotic System

Compared with the general sewage treatment measures,microalgae can not only effectively absorb nutrients,decompose toxic pollutants,absorb heavy metal ions,improve pH and dissolved oxygen in water,but also promote circulation of elements such as N and P.But nowadays,there exist several problems in microalgae treatment of urban domestic sewage,such as long treatment time and low yield of microalgae.In order to improve the efficiency of sewage treatment and the biomass of algae,this paper studied the effects of different dilution rates on the growth and sewage treatment of chlorella zofingiensis?C.zofingiensis?,chlorella-activated sludge and chlorella-proteus in continuous photobioreactors.Provides theoretical basis and technical support for large-scale treatment of municipal sewage coupled chlorella production,and provides new methods and new ways for sewage treatment.This research has obtained the following main research results:1.In order to optimize the condition and efficiency of continuous domestic wastewater treatment by Chlorella zofingiensis and obtain the effects of different dilution rates.Six different dilution rates 0.2,0.3,0.4,0.5,0.6 and 0.7d^-1 of sewage were set.This paper use chlorella to continuously treat sewage in photobioreactors,and establish parabolic regression curve of dilution rates,cell yields,nitrogen consumption rates and phosphorus consumption rates.The extreme values of dilution rates obtained by curve fitting are all 0.45,which can be considered as the optimal sewage dilution rate.And the harvested algal cell concentration is 0.53?dry weight?g·L^-1.2.In order to improve the treatment effect of sewage and the production of chlorella,sewage was treated by chlorella activated sludge symbiotic system in batch reaction and continuous reaction.The results showed that when the sewage dilution rate was less than 0.55d^-1,continuous reaction to remove nutrient salts is better than batch reaction.In this dilution rate,TN,TP,NH₄⁺-N,and COD are all lower than the GB18918-2002 A emission limits.3.Based on the diversity of activated sludge flora,proteus was selected as the dominant strain for continuous symbiosis experiment of chlorella-proteus.In the chlorella-proteus symbiosis system,the optimal algae ratio is 10:1.When the sewage dilution rate is 0.65d^-1,nutrient consumption is larger and the removal effect is more stable.The TN,TP,and NH₄⁺-N can meet the GB 18918-2002 A emission limits,and the harvest of algal cell concentration is 0.55?dry weight?g·L^-1.4.After accounting,the 1 m³ processing system of chlorella(sewage dilution rate0.45d^-1),chlorella activated sludge bacteria(sewage dilution rate 0.55d^-1)and chlorella-proteus(sewage dilution rate 0.65d^-1)can treat sewage 0.45m3,0.55 m3and0.65 m3,harvest 238.5g,285g and 325g dry weight,gain output value 2.277,2.962 and3.432 yuan separately one day.