Paper-thin aging sewage tanks dumped just in time

Infrastructure testing uncovers contamination risk

  • Tue Nov 1st, 2011 8:00pm
  • News

A decision to test some essential sewage infrastructure proved to be a good catch for the Town of Ladysmith.

During the first week of September, the town hired Acuren Group to test its autothermal thermophilic aerobic digesters (used to store and heat up biosolids to kill pathogens) to see if they would last another two or three years until the next phase of the town’s sewage plan.

The results were not good.

According to Director of Public Works Joe Friesenhan, the company found the wall of one of two tanks was around one-thousandth of an inch thick and a further filling of the tanks could risk contaminating the harbour.

Both were taken out of service immediately.

Friesenhan said in the ATADs, solids sit for a week to get the temperatures to a level that kills pathogens.

“It kills the pathogens so that it’s safe to use for compost,” said Friesenhan.

Public works is left with one large, square ATAD, but it is a little more work to use, said Friesenhan.

Once the pathogen-kill has been completed, Friesenhan said the solids are pumped to the de-watering building to get as much water out as possible.

“That goes back into the system and goes through a treatment process again.”

The solids left over are brought up to the public works yard and mixed with woodchips and grass to make compost.

Friesenhan said the town is in the process of phasing out its made in Ladysmith composting as the Cowichan Valley Regional District makes its own facility to handle biosolids from throughout the district.

That should take a couple of years, Friesenhan said, adding the public works facility is the wrong place to have it.

In the meantime, the Town of Ladysmith is looking at sending its biosolids to a facility in Comox.

However, the facility requires the solids be dewatered to 22 per cent. Currently the town achieves a level of around 15 per cent.

The town has had to push ahead the purchase of a centrifuge for the dewatering process. The purchase was to come later in the process, but council approved doing it now.

Friesenhan said the $500,000 price tag is a high estimate but is the amount remaining in a grant the town received.

There is also a $50,000 price tag to use sodium hypochlorite instead of chlorine gas.

“We want to eliminate the gas,” said Friesenhan, noting the sodium hyochlorite is safer than chlorine gas for staff and the town.

The switch from gas will happen by the end of the year, Friesenhan said, and he hopes a tender for the purchasing will go out in the next couple of weeks.