A DUCK-processing plant run by Charoen Pokphand Foods (CPF) in Bangkok will likely have to suspend manufacturing operations in the wake of the tragic accident that saw five people die in its wastewater treatment pond.

The Industrial Works Department (IWD) has ordered the pond closed for 30 days for improvements.

The closure will require the suspension of manufacturing operations, IWD head Mongkol Pruekwatana said yesterday.

On Friday, a Chulalongkorn University student on her third day of an educational visit to the CPF plant in Bang Na district died after falling into a wastewater pond – along with four CPF employees who attempted to rescue her.

Hydrogen sulfide, a poisonous colourless gas, may have contributed to their deaths. But questions remain about the cause of the incident.

“There was no lid over the pond. When we checked the scene, we found that the lid was in the pond,” Mongkol said.

It is still not clear how the student fell into the pond, which was meant to have a cover over it at all times. The three-by-four-metre pond is about 2.5 metres deep.

Both the Department and |police are investigating the |incident.

“We must gather circumstantial evidence to determine what caused this tragic accident,” Metropolitan Police Commissioner Pol Lt General Sanit Mahathavorn said yesterday. “There is no CCTV at the spot.”

Police were awaiting expert advice before consider if charges should be filed against anyone.

Police have interviewed more than 10 relevant people. “We will also take into account the opinion of the IWD,” Sanit said.

CPF ‘violated regulations’

CPF violated IWD regulations by allegedly failing to keep the area around the pond tidy, however. “Such failure raises the risk of accidents,” Sanit said.

Mongkol said the plant insisted the lid was in place between 7am and 8am last Friday. “It could not say who entered the area and removed the lid later that day,” Mongkol said. “But the lid weighs more than 30kg. It would take at least two people to remove it.” He said the inspection showed there was a “No Entry – Authorised Persons Only” sign in front of the pond.

“The student was at the spot with an environmental officer of the plant.

“Given that the officer started work there just six months ago, she might have not been experienced enough,” Mongkol said.

An air-quality check at the scene showed oxygen was at a safe |level, but circumstances at the time of the incident might have been different. “When the department’s officials arrived, it was already five hours after the incident,” he said. “We will investigate further.”

The Environmental Engineering Association of Thailand’s president Prasert Tapaneeyangkul praised the CPF employees who rushed to the students’ rescue for their bravery, but he stressed that in such |circumstances only people with the right knowledge should deliver help.

“The scene is a confined space and has hydrogen sulfide, which can prove fatal,” Prasert said.

He said when designing wastewater treatment ponds, the plant owner and engineer should ensure there is enough space to rescue anyone in trouble.

“But as a safety precaution, a locked lid should be in place at all times. Communication devices and protective gear should be available to facilitate a timely rescue.”

If the amount of hydrogen |sulfide exceeded 50 parts per |million in the air, people might lose |consciousness after 10 minutes of exposure.

“If the amount goes past 100 parts per million, people exposed to it will die immediately,” he said.

Prasert said his association was willing to educate officials working at plants about safety measures.

“We hope no such tragedy ever takes place again,” he said.

Hydrogen sulfide is a colourless gas with the characteristic foul odour of rotten eggs. It is very poisonous, corrosive and flammable.