The human waste was used as the manure formerly, and the silicate in the soil composes the skelton of diatoms. It is presumed that multiplication of diatoms is activated by human waste as a nutrient and the soil. In this study, the effects of the human waste and various soils on multiplication of diatoms were investigated.
Diatoms in the seawater was multiplied by the addition of the human waste. After 15 days, multiplication rate increased depending on the concentration of the waste. Diatoms in the seawater containing the human waste was multiplied by the addition of sodium silicate. The multiplication ratio of diatoms was the highest when sodium silicate of 8 SiO2 mg/l was added. When various soils were added into the seawater containing the human waste, green algae and rotifers multiplied markedly in comparison with those without the soil addition. Moreover, life times of green algae and rotifers were extended by the addition of various soils.