A local study recently found household wastewater (gray water) as a good liquid fertilizer for tilapia and vegetable production.
Researchers from the Aquatic Biosystems (ABS), a private research and development firm, found laundry wastewater, applied at 1.28 liters per cubic meter per day, was good liquid fertilizer for tilapia production (0.87 kg/m2 per day) in a backyard pond.
The study was monitored by the Philippine Council for Aquatic and Marine Research and Development (PCAMRD) of the Department of Science and Technology.
Results of the ABS study on the use of human urine and kitchen wastewater for vegetable production showed that fertilization of pechay (Brassica compensis) with 10 percent human urine and 90 percent tap water gave a higher yield compared to that of tap water only, the PCAMRD said.
“The use of kitchen wastewater only and a combination of kitchen wastewater (90 percent) and human urine (10 percent) had a similar and better yield than that of the control, respectively, for sweet potato vegetation after a month of culture in pots,” the agency said.
PCAMRD said household or domestic wastewater is a major pollutant of freshwater bodies (lakes and rivers) in areas of the country that lack adequate wastewater treatment facilities.
“The reuse or recycling of gray water will not only minimize aquatic pollution but will also enhance food production and reduce the consumption of potable water in households,” the PCAMRD said.
PCAMRD said each urban household uses at least 100 liters of water for drinking, washing and bathing a day. Of this volume, about 90 percent is disposed off as wastewater into the environment. – Helen Flores