"At Pueblo, each shell is pierced by a robot arm, and the mustard agent inside is sucked out. The shell is washed and baked to destroy any remaining traces. The mustard agent is diluted in hot water, then broken down by bacteria in a process not unlike the one used in sewage treatment plants. It yields a residue that is mostly ordinary table salt, Mr. Levi said, but is laced with heavy metals that require handling as hazardous waste. “Bacteria are amazing,” Mr. Levi said as he watched shells being destroyed during the last day of operations at Pueblo. “Find the right ones, and they’ll eat just about anything.”"