Ole manaoga ole okesene ole vaila'au e ta'ua foi ole manaoga ole okesene kemisi (chemical oxygen demand), e ta'ua ole COD. O le faʻaaogaina o vailaʻau faʻamaʻi (e pei o le potassium permanganate) e faʻamaʻi ma faʻaleagaina mea faʻamaʻi i totonu o le vai (e pei o mea faʻalaʻau, nitrite, masima ferrous, sulfide, ma isi), ...
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