A method for treating a waste product from a chemical processing plant. Chemical processing plants such as oil refineries produce sour water waste that includes ammonia and hydrogen sulfide. The sour water is typically steam stripped to form a vapor stream including water, the ammonia and the hydrogen sulfide. The vapor stream is converted into a concentrated ammonium sulfide solution using a scrubber unit that includes a cooling and quenching column. Concentrating the byproducts provides for more efficient transportation of the concentrate from several refineries to a remote, centralized purification facility.