Microalgae Screening And Mutagenesis Breeding For Purifying Wastewater

The treatment of wastewater by microalgae can not only effectively remove nitrogen,phosphorus and other pollutants,realize the advanced treatment of wastewater,but also can be used to prepare biodiesel as animal feed after harvest,which has certain economic benefits.In this thesis,microalgae with good absorption of nitrogen and phosphorus were isolated and screened from natural water,and the microalgae were mutated by atmospheric and room temperature plasma（ARTP）mutation breeding technology,in order to obtain high-quality mutant microalgae strains with strong wastewater purification ability,and the wastewater treatment effect of algae-bacteria symbiosis system constructed by high-quality mutant microalgae strains was investigated.Three strains of microalgae were isolated and purified from the local natural water body of Jinan by dilution plate method and plate scribing separation method.Through microscopic observation and morphological judgment,it was confirmed that microalgae strain SDJZ-A was Chlorella,microalgae strain SDJZ-B was Scenedesmus,and microalgae strain SDJZ-C was Chlorella.By comparing the growth,nitrogen and phosphorus removal capacity and biomass accumulation of different microalgae,a microalgae strain SDJZ-A with the best performance was obtained.The microalgae strain SDJZ-A the removal rate of NH₃-N,TP and TN in synthetic wastewater was 87.02%,79.02%and 80.56%respectively,and the contents of total lipid and protein was 16.89 mg/100mg and 35.75 mg/100mg respectively.The microalgae strain SDJZ-A was mutated by ARTP mutation breeding technology,and a high-quality mutant microalgae strain SDJZ-A14 with the best performance was selected by investigating the nitrogen and phosphorus removal ability and biomass accumulation of different mutant microalgae strains.Mutant microalgae strain SDJZ-A14 has great genetic stability,and the removal rate of NH₃-N,TP and TN in synthetic wastewater was 98.79%,91.12%and92.85%respectively,which increased by 11.77%,12.10%and 12.29%compared with the SDJZ-A of wild microalgae strain respectively,and the contents of total lipid and protein was24.54 mg/100mg and 52.73 mg/100mg respectively,which increased by 45.29%and 47.50%compared with the SDJZ-A of wild microalgae strain respectively.ARTP mutagenesis did not change the morphological size of the SDJZ-A14 of the mutant microalgae strain,but increased the number of algal cells produced per unit time.The algae-bacteria symbiosis system was constructed by combined culture of mutant microalgae strain SDJZ-A14 and activated sludge,and the wastewater treatment effect of the algae-bacteria symbiosis system was investigated,and compared with the pure algae system composed of mutant microalgae strain SDJZ-A14.The algae-bacteria symbiosis system removed NH₃-N of 99.80%in two days and removed TP,TN of 92.82%and 93.75%in four days respectively.The removal rate of NH₃-N,TP and TN by algae-bacteria symbiosis system is 10.69mg/L/d,2.20 mg/L/d and 16.21mg/L/d respectively,which is 51.68%,26.15%and 26.05%higher than that of pure microalgae system respectively.