INTRODUCTION Until recently the main purpose in stripping refinery sour waters was to keep sulfides out of the wastewater. In the last few years@ however@ ammonia has also become recognized as a serious pollutant. The Federal Environmental Protection Agency has placed stringent limits on the quantities of ammonia that refineries may discharge to receiving waters. Since sour waters are the source of nearly all of the ammonia in refinery waste waters@ there is now much interest in stripping out 99% and more of the ammonia@ as well as the hydrogen sulfide.