Abstract: In order to cultivate Chlorella effectively with domestic sewage in villages and towns in northern China, the growth environment (initial sewage concentration, ambient temperature, illumination intensity and illumination time) for Chlorella was studied by single factor and orthogonal experiments in this study. The results showed that the initial sewage concentration, ambient temperature, illumination intensity and illumination time of sewage have respectively a significant effect on the growth of Chlorella under single-factor environmental conditions. The optimum initial sewage concentration is two times dilution of raw sewage, an ambient temperature of 30 ℃, an illumination intensity of 12 000 Lux, and a illumination time of 20 h. The results of orthogonal experiments showed that the optimal culture conditions of Chlorella are not a simple overlay of environmental factors, but controlled by the coupling of environmental factors. The dominant environmental factors are the initial sewage concentration and illumination time. Two times dilution of the raw sewage, the ambient temperature of 30 ℃, the illumination intensity of10 000 Lux, the illumination time of 16 h, the sewage culture Chlorella reaches the highest efficiency at this time.

Key words: domestic sewage, Chlorella, environmental factors