By Gagandeep Ghuman
Published: Aug. 18, 2012
The district has never been required to disinfect the effluent (not to be confused with raw sewage) it dumped in the Squamish River water.
For the past 20 years, the tidal influence on the Squamish River has done the work of for it. The effluent is the water that is returned to the Squamish river after it is processed through the plant.
In fact, the district discharges anywhere between 8,000 and 12,000 cubic meters of effluent into the Squamish River per day, representing a small part of the river’s flow.
In accordance with the Ministry of Environment, Lands and Parks testing protocols, the District regularly submits effluent samples for environmental testing.
Last weekend, however, there was a problem.
The district was informed by the ministry that water tested on July 31 and Aug. 1 had exceeded the allowable amount of Biochemical Oxygen Demand (BOD).
The allowable amount of BOD permitted under our permit is 30 mg/L, the BOD test results showed that this amount had been exceeded with a test result of 48.7 mg/L. T.
The higher BOD was due to the staff starting the old part of the plant in order to do maintenance on a new section.
“Sometimes when just starting up a plant the air that we pump into the process may be too high or too low and this can affect the biological process,” said Bob Smith, the district operations manager.
BOD levels are monitored primarily to protect fish habitat.
Discharging effluent with high BOD increases the burden of the receiving system to provide oxygen to the incoming water source, diluting natural oxygen levels.
BOD, Smith said, does not carry illness, although there were a few sick wind enthusiasts last weekend.
Vancouver Coastal Health said there was no reported case of gastrointestinal sickness.
Smith said the district sends a final effluent sample weekly to be tested for BOD, and does the LT50 toxicity test twice annually.
The operators, he added, also sent a raw sewage sample for testing monthly.
The local waste water treatment plant is a secondary treatment plant that uses the activated sludge method to treat the sewage.
“This method is a biological process that has microorganisms that consumes the biological mass. Prior to this treatment the sewage is screened and pretreated,” he added.