Sentence:  The maximum rate of <WSD>oxygen</WSD> transfer at 1.0 mg / l dissolved oxygen was calculated as 220 lb / day at a maximum rate of 9.3 mg / l / hr . 
Meaning of the word marked with <WSD> tags:  a nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gas; constitutes 21 percent of the atmosphere by volume; the most abundant element in the earth's crust