Meat-packing plants dump blood, the contents of entrails 内脏, and other animal wastes.
Other food-processing plants discharge fruit and vegetable skins, seeds, leaves, stems, and other vegetable wastes.
Oil spills from tankers at sea or leaks from underground storage tanks on land are very difficult to control
Oil spills at sea decrease the oxygen level in the water and cause grave harm to the creatures living in the sea.
2021/3/10
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As water moves along or beneath the surface of the Earth, it dissolves minerals and matter from decaying plants and animals.
The principal positive ions (cations) in natural water are sodium (Na+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), and sometimes iron (Fe2+ or Fe3+).
Domestic sewage contains a wide variety of dissolved and suspended impurities: a. organic materials-food and vegetable waste b. plant nutrients- chemical soaps, washing powders c. disease-causing microbes微生物