Learning from Events: Major Process Safety Incidents from Waste Water in Process Chemical Plants, or, Take Care of Your Waste Water or It Will Take Care of You

Most, if not all chemical industries generate waste water from its processes. This waste water is often pre-treated and then disposed to water courses as agreed with the appropriate authorities. The focus of attention has usually been on the environmental hazards of waste water. This paper illustrates that process safety hazard from waste water treatment can also pose significant risks. Five serious events are described associated with the pre-treatment, storage, reuse or treatment of waste water from chemical production. They are among four different countries and from a variety of businesses. These include one detonation, two confined vapour cloud explosions, one over-pressure from gas evolution and one thermal runaway and fire. In particular, often waste water sumps span an entire plant and have developed explosions over extensive areas. The paper describes the events, lessons learned and some methods and procedures that can be used minimize the risks.