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On November 5, 2005, at a waste treatment facility located in Rhadereistedt, Germany, a release of H2S resulted in four fatalities, including a truck driver, operator, and two additional personnel attempting to rescue those directly impacted.
A tanker truck containing acidic animal byproducts was unloaded into the feedstock pit and left to sit overnight.
Additionally, a tanker truck containing pig intestine waste stabilized with sulfur containing compounds arrived at the site and was parked overnight near the pit.
The tanker truck containing pig intestine at an elevated temperature was unloaded into the feedstock pit with the pit door stuck open, as the door hoist used to open the pit door was inoperative at that time.
As a result of the difference in pH and temperature between the two sets of materials loaded into the pit, a large cloud of H2S was released from the open feedstock pit into the loading building nearby, resulting in 4 fatalities, including the truck driver, an operator, and two additional personnel who responded to the event in an attempt to rescue those impacted.
Emergency responders were dispatched to the scene due to a call from another truck driver prior to his collapse outside of the loading building as a result of exposure to the H2S that had been released in the incident.
Important Notes
The acidic material in the feedstock pit mixed with the hot sulfur containing waste allowed H2S to vaporize from the solution. The open pit, open due to the inoperable door hoist, with agitators on, contributed to the vaporization of H2S and allowed for the cloud to disperse to the building. The open pit door also blocked the ventilation system in the building.
The operating procedure for truck unloading required that the door remain closed. However, this procedure was not followed because the hoist was broken. Since this deviation from normal operation represented a change to established procedures, an effective Management of Change (MOC) program could have identified and analyzed the potential safety impacts of this change. An analysis of the impact on safety should be performed whenever procedures are altered, to determine whether unintended consequences could result.
Operators must also undergo formal training to identify actions that constitute MOCs and mitigative operator intervention.
The interactions between the waste products were not well understood, and as a result, the potential release of large amounts of H2S was neither anticipated nor adequately planned for.
The hoist to close the pit door was broken and inoperable, which contributed to the ability of the H2S to disperse to the building. An effective Preventative Maintenance and Mechanical Integrity program could have prevented / identified these issues.
In high concentrations, H2S paralyzes the olfactory system, giving no warning to operators. This highlights the need for gas detection systems, actuated mitigative measures, and a formal assessment of operator limitations.
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