How wastewater comes clean at the Burnaby Refinery

Aug 11, 2016   | Categories: Energy, Environment, Fossil Fuels, Lower Carbon Future
Every refinery requires a lot of water for processing crude oil. Water is needed for cooling exchangers, and for the boilers that generate steam for production.

Through the process, hydrocarbons, metals and other contaminants may leach into the water and refineries must find ways to clean the water it uses before discharging it.

In a recent blog, we examined the new wastewater recycling system used at the Co-op Refinery Complex in Regina, Saskatchewan – a first for refineries in North America. Recycling is one way to ensure that refinery water does not find its way back to the general wastewater system.

Another wastewater management “first” was launched by Chevron’s Burnaby Refinery, called the Deep Shaft Wastewater Treatment System.

“We are perhaps the first refinery in North America to use a deep shaft bio-remediation system for treating our wastewater,” said Kel Coulson, one of the process engineers at the Burnaby Refinery, in a Chevron newsletter story.

“The refinery has a relatively small footprint that cannot accommodate a traditional water treatment facility. Instead, in the 1990s, we installed the deep shaft to provide an extra layer of secondary treatment.”

How it works

The Burnaby Refinery collects all water from steam generators and recirculating cooling systems. In fact, every process unit in the entire refinery ties into an underground sewer system.

From there, all the liquid is diverted into three retention ponds and pumped from there into a shaft.

Once there, the water goes through a secondary treatment process in which aerobic bacteria “eat” the contaminants in the water.

“The mixture of oxygen and ‘bugs’ is called ‘activated sludge’ and is the heart of the plant,” said Coulson. “We add oxygen to the water in the shaft which creates an environment good for our bugs to effectively treat and remove the contaminants.”

As the water is returned to the surface, it flows over gravel for yet another layer of cleaning.

Then, Coulson explained, “We ensure it meets our regulatory requirements before the treated water is discharged.”

Now free of contaminants, the water is released into a municipal sewer system before moving on to Metro Vancouver’s sewer system, where it is treated again.

The wastewater is monitored for substances that could be harmful to fish and other aquatic life; indeed one of the first thing Coulson and his counterpart Mack Atkinson do every day is monitor the water’s quality.

An efficient system

The wastewater system is big and complex; but it’s relatively lean compared to other systems that require more land and power.

The shaft is over 100 metres deep. The treatment plant covers 697 square metres, and is powered by 56 kilowatts at peak load. However, a traditional aerobic water cleaning system would cover an area about five times as large and require twice the energy to operate.

“It’s our solution to the challenge of being located where land is in short supply and where the only real direction we could expand was down,” said Atkinson.

Burnaby’s wastewater system is just one of the ways Chevron is taking care of the environment. Check out last week's blog on how special recovery units keep gasoline fumes out of the air.
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