Sentence:  The BOD of the influent to the pilot plant varied between 110 and 710 mg / l with an average of 350 mg / <WSD>l</WSD> . 
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)