in cities equipped with water-borne sanitation and where wastewater is treated to high standards, environmental wastewater pollution is minimized but nutrients are contaminated and lost in minimized but nutrients are contaminated and lost in sludge. here, only huge investments in sludge processing and treatment facilities could
make wastewater nutrients available for agricultural production. A few countries can สัตว์น้ำ such investments. another possibility, that is tested in many countries, is gradual change of sanitation type