Use of human urine in phytoplankton production as a tool for ecological sanitation

Measurements of primary productivity of phytoplankton and enumeration of the counts of coliform and heterotrophic bacteria (HB) were made in the water of 12 experimental tanks used for 3 treatments and control in triplicate as follows: (a) fresh human urine (0.02%), (b) stored human urine (0.02%), (c) mixed urine of fresh and stored human urine (0.02%) and (d) control without input of urine. The gross primary productivity of phytoplankton was highest in the stored urine treated tanks (508 mg C m⁻² h⁻¹) followed by fresh urine (353 mg C m⁻² h⁻¹), mixed urine (303 mg C m⁻² h⁻¹) and control (215 mg C m⁻² h⁻¹). Similar was the response of net primary production of phytoplankton. The mean count of HB observed in stored urine fed tanks was significantly higher (59–184%) than the remaining urine fed treatments. The mean count of Escherichia coli did not differ from urine treated tanks to control implying the good quality of water. The concentration of dissolved oxygen of water (7.6 to 12.8 mg L⁻¹) in these tanks remained satisfactory for aquaculture. The mean concentration of ammonium-N observed in fresh urine treated tanks was more than 10 times higher than the remaining treatments employed. In contrast, the level of phosphate and electrical conductivity in the stored urine treated tanks were significantly higher than the remaining treatments. It is proposed that stored urine with a significantly reduced load of E. coli might be an effective low cost liquid fertilizer for algal biomass production.