Studies on the purification of wastes from the nitrogen fertilizer industry by intensive algal cultures. IV. growth of Chlorella vulgaris in wastes with high nitrogen content in continuous and intermittent light.

The growth and utilization of nitrogen by intensive Chlorella vulgaris in wastes from production of urea, containing 1300 mg NH4+-N and 4000 mg urea-N/1, was investigated. In these conditions only Chlorella vulgaris AA strain, adapted to high concentrations of ammonia nitrogen, was able to grow. The elimination of nitrogen by continuous cultures was 750 mg urea-N/1 with 5-day flow rate. A considerable part of the urea was hydrolized by urease bacteria and removed in the form of NH3. The effect of intermittent light on the growth of algae was also studied. The better growth than in continuous light, was obtained with alternate one hour periods of light and darkness. Good results were also obtained with the use of 12 hour light and 12 hour darkness.