Sentence:  The effluent BOD averaged 34 mg / <WSD>l</WSD> , a little lower than that of the study at Fayette indicated for a loading of 60 lb BOD / day / acre . 
Meaning of the word marked with <WSD> tags:  a metric unit of capacity, formerly defined as the volume of one kilogram of pure water under standard conditions; now equal to 1,000 cubic centimeters (or approximately 1.75 pints)