| Energy shortage is the first major crisis faced by mankind in the21st century, anothermajor crisis in parallel with the energy crisis is a crisis of water resources and water quality.Using microalgae can take advantage of pollutants in domestic sewage as their own nutrients,to achieve effective removal of pollutants, microalgae can also be used as a green energy by alarge number of recycling. In this paper, mixed microalgae was obtained from the naturalenvironment to high-density enrichment culture. The impact of environmental factors onmixed microalgae extracellular carbonic anhydrase activity was explored, the effect of mixedmicroalgae treatment domestic sewage was examined, and an algae-bacterial symbioticsystem was set up to determine the optimum operating conditions, to examine daily andcontinuous running effect of algae-bacterial symbiotic system for wastewater treatment.In this paper, under optimal growth environment, microalgae enrichment cultureexperiment was conducted firstly. Appropriate additional nutrients can promote mixedmicroalgae continue to grow by a certain extent; fed-batch culture, particularly variable speedfed-batch culture is more suitable for the growth of mixed microalgae than one-time nutrient.The extracellular carbonic anhydrase plays an important role in the mechanism of mixedmicroalgae using inorganic carbon. It can promote the conversion of HCO3-and CO2, whichis an integral part of the CO2concentrating mechanism. Studies have shown that nitrogen,phosphorus, Zn2+, inorganic carbon （HCO3-and CO2）, light intensity, temperature, pH, andglucose and other factors can regulate and influence the expression of extracellular carbonicanhydrase activities. In addition, studies also found that mixed microalgae cells′plasmamembrane redox activity can stimulate cells′extracellular carbonic anhydrase activity.This article examines the effect of of mixed microalgae on the treatment of domesticsewage, COD, TN and TP removal rate reached80%,67.18%,80%respectively. Theoptimum operating conditions of the algae-bacterial symbiotic system were determined as:temperature23°C; average light intensity8200lux; light/dark ratio12:12; light interval12h;shaker regularly shake; the aeration intermittent exposure gas; aeration interval12h; theaeration time from8:00p.m to8:00a.m; the volume ratio of activated sludge and mixedmicroalgae2:3; the hydraulic retention time24h. In this paper, the system daily running experiments showed that COD removal rate up to89%, TN, TP removal rate reached and stabilized at around80%, HCO3-removal was mainlyconcentrated in the light stage, light stage average removal rate reached about80%, darkphase had to be reduced by20percent; system continuous running experiments showed thatunder optimal conditions, the system can be stable running. COD, TN and TP removal ratereached and stabilized at about80%. The system can make the influent COD600to700mg/L,TN concentration40to50mg/L, TP concentration11to12mg/L and HCO3-concentration300to350mg/L of domestic sewage reduced to100mg/L,20mg/L,2mg/L and150mg/L,to reach sewage discharge standard. System can maintain pH close to neutral in the reactor,DO was stable in23mg/L, effluent water algae concentration below30mg/L, it caneffectively avoid the loss of algae. |
