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3 votes
In what stage of wastewater treatment is 90 percent of the oxygen-demanding substances removed from the waste by microbes? primary treatment. secondary treatment. tertiary treatment. septic tank treatment.

2 Answers

4 votes
i need an answer for this question. here are the choices

primary treatmentsecondary treatmenttertiary treatmentseptic tank treatment
User Sjeijoet
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8.2k points
1 vote
I think the correct answer would be secondary treatment. Oftentimes at this stage, microbes are being used to treat the wastewater. It is the heart of the process since a big part of the harmful substances are lowered at this stage. Hope this helps.
User Dod
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8.4k points
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