Well, the reference you have really clears it up for me. I'd always thought CaO, aka, the lime pit, was the standard method of treating lab wastes. Virtually all heavy metals in solution precipitate out as hydroxides, and you can safely release your lab water effluent, for certain values of the word, safe. Removing sulfate is new, but I figured the excess NaOH was removed somehow, and your reference says it is, by CO2 addition to "re-carbonate" and reduce pH before effluent release, as sodium carbonate isn't as soluble in a sodium hydroxide solution. But if you're sampling before all steps, then I have no idea.
*EDIT-spelling*