Residents in the south end of the city have had to endure a pungent smell resembling rotten eggs at times over the last year.
“Depending on the way the wind is blowing, during those times, we will certainly get calls from people on Michelle Drive or Barrie Road complaining of the smell,” said Greg Preston, the manager of waste management for the city. “We really feel for those folks who may be wanting to be out in their backyard enjoying a barbecue … we don’t want to be doing that.”
While there is a certain natural, albeit nasally unfriendly odour that results where waste is stored and treated, what happened at times last fall and this spring was not entirely natural.
And, believe it or not, you and I may be to blame – at least partially.
During a guided tour of the wastewater treatment facilities that sprawl behind a modest administration building on Kitchener Street, city staff explained to Mayor Steve Clarke and media members how the process works and why the rank odour occurred.
Basically, it was a perfect storm of sorts, explained Preston, who said the main culprit was what he called ‘digester upset.’
The problem began when staff started its regular maintenance on the primary digester – one of two large silo-like buildings partially built into the ground where bio-solids are stored after being treated.
Every five years, staff drain the massive digester to clean it “because we get this garbage buildup on the bottom,” said Preston. “When we started filling the tank back up, we ended up with what we call a sour digester. Basically, the material in there was too acidic and we couldn’t generate that methane gas which helps treat and reduce the odour when biosolids went from the digester to the lagoons – that was the primary cause of the odour.”
He said the process is quite scientific and it’s not easy to properly balance the acid and alkaline levels in the huge tanks. “Basically, it took staff from September to December to get the pH level balance right and to get the environment correct. You have to have the right temperature, we had to keep adding more base … it was quite frustrating.”
But that was compounded in the lagoon. Because of the problems in the digester, the solids did not settle to the bottom of the lagoons. Instead, some floated to the surface, where they mixed with items that should not have been there – plastic hygiene applicators, condoms, wet wipes, rags and other materials that people flushed down their toilets.
“Those items get covered in waste water and when they float on top of these lagoons, the wind catches it and you can smell it,” explained Preston. “There will always be some odours – you can’t avoid that. But keeping those floatables out of the (system) would really help reduce those odours.”
Preston pleaded with residents to do their part. “The only thing that you should flush down the toilet is toilet paper,” he said. “It might say on wet wipes containers that they’re flushable, but they’re not. We really urge people not to flush anything but toilet paper.”
That’s the primary message city staff wanted to impart to residents. But, it was fascinating to tour the facilities, to see the grinder that gnashes its way through the incoming wastewater from the James Street Pumping Station, before it goes through six cells where micro-organisms treat the liquid part of wastewater.
“It is a rather fascinating process …(and) it’s kind of a hidden service that most people don’t realize occurs,” said Preston.
After flowing through the cells, the wastewater goes to a clarifier before being pumped into the digesters; the whole process takes, approximately, 30 hours, explained Ben Smith, the city’s superintendent of waste water treatment.
The material, he said, is then stored in the primary digester for 14 days, is moved into a secondary digester for 14 days and then pumped into one of the two massive lagoons.
One lagoon is 48 metres by 134 metres by 1.7 metres deep; the other is 48 metres wide, 151 metres in length and has a depth of 1.9 metres. Together, the two lagoons can hold almost 5.5 million U.S. gallons of wastewater.
In 2015, a rubber liner was added to each of the large lagoons that were formerly lined with clay. The new liner is superior and helps ensure there’s no leakage, said Preston.
And while every effort is made to keep plastic floatables out of those lagoons, some still end up there. Because of that, staff regularly use what is basically a pool screening tool to fish the nasty items out of the water.
In the spring and fall, the biosolids in the lagoons are sucked out by a pumper truck, which mixes up the material before it is transported to approved farm fields where it is used as fertilizer. “The farmers get the fertilizer at no charge and it’s good for us, because we don’t have to send it to a landfill or anywhere else.”
