Clear ambition

“Reliability is No. 1,” says Fernandes, manager of treatment
capital works in the wastewater division of Peel’s Lakeview facility, which has just undergone a massive expansion costing 260 million Canadian dollars.

That expansion has turned Lakeview, situated in the City of Mississauga, into one of the largest wastewater treatment plants in the province. The largest is in Toronto, next door to Mississauga on the north shore of Lake Ontario. Lakeview, which opened in 1961 as a tiny operation with rudimentary systems, is also now one of the most modern and efficient such plants in North America. It has a capacity to handle 448 million litres of raw sewage per day and services about 800,000 residents, plus businesses, in the Peel Region.

Yet despite its massive size and the impact of its operations, it co-exists with nature. Mute swans, double-crested cormorants and various dabbling and diving ducks skim across the waters of the lakeshore in front of the plant. The treated water flowing into the lake through a pipe stretching 1.4 kilometres out is clear and odour-free. A nature path is being discussed for the facility’s eastern perimeter.

The treatment of biosolids, or activated sludges, is the most dramatic part of the plant’s modernization, and Alfa Laval technology is an integral part of the process.

“No matter what you do,” Fernandes says, “sewage keeps coming. You can’t stop it. And the environment has to be protected. Reliability is critical. It’s extremely useful to have a company like Alfa Laval only a phone call away to help us maintain the plant at peak efficiency.”

Alfa Laval has a relationship with Lakeview dating back to a 1984 installation by Sharples, a company Alfa Laval bought in 1989. Alfa Laval technicians took over service of the Sharples equipment, and that relationship gave the company a chance to showcase its reliability at Lakeview.

Since then, Alfa Laval has earned the right to install two rows of large thickening centrifuges and dewatering centrifuges. These processes produce “the cake.” It is the sewage sludge that, once it has been concentrated to between 26 and 28 percent solids, goes to Lakeview’s fluid bed incinerator for disposal.

“Dewatering sewage sludge is largely the way of the future for major municipalities,” says Marc Hunt, technical sales manager for Alfa Laval. “Centrifuge technology is the leader in that end of things because it’s enclosed. And it’s automatic,
so it doesn’t need much supervision because the centrifuges
run on computer controlled programs. So there is a huge advantage to it.”

THE PUBLIC IN THE REGION OF PEEL agrees, even if most people don’t know or care about engineering. Their concerns are focused on the environment and even more on foul odours that once emanated from the plant, before Alfa Laval technology fully took over treatment of the sludges. “Of primary importance was the need to reduce the impact on the local community,” Elaine Moore, chair of the public works section at Peel regional council, said in a public statement about the expansion project.

The Lakeview Wastewater Treatment doesn’t only service residents and businesses in the Peel Region, but it also has an agreement with the Region of York, to the northeast, to accept its untreated sewage.

The key factor in the odour problem was urbanization. When it opened in November of 1961, the operation was so modest and so remote, that the few people who lived nearby barely noticed. That, of course, has changed.

“The evolution of the plant has to do with the evolution of the region and evolution of industry within the region, as well as the population growth,” says Mitch Zamojc, commissioner of Environment,
Transportation and Planning services for the region. “So these plants, both here at Lakeview and at Clarkson [the sister plant], have necessarily undergone several expansions over the years.

“As the population grew, people came to be living closer and closer to the plant,” Zamojc explains. “So the need to take the neighbourhood into account became more and more significant.”

There was a problem. For years, Lakeview used the Zimpro process to treat biosolids. “The Zimmerman process takes sludges and heats them up to allow the separation of liquid and solid,” says Fernandes. “But when you heat sewage, you get odours. It is unavoidable.”

Public complaints were constant, especially on muggy summer days when odours hung over nearby neighbourhoods.
At the same time, the six Zimpro streams could not handle the increasing loads.

“We needed growth, and we needed it fast,” says Fernandes.
He and the consulting engineers, as well as politicians
at Peel, recognized that the evolution of the centrifuge technology meant that Lakeview could replace thermal treatment of sewage sludges and achieve the same results without foul odours.

“So, in 2001, we decided to put in dewatering centrifuges,” says Fernandes. In 2002, Alfa Laval won the evaluated bid process. Five Alfa Laval dewatering centrifuges were ordered in 2003 and commissioned in 2006. Two more are in operation at Clarkson, which now has a capacity to handle 200 million litres of raw sewage per day.

“Effectively,” says Ric Robertshaw, director Wastewater Services
for Peel, “you could say that the entire Region of Peel is serviced by Alfa Laval, as far as the dewatering of biosolids is concerned.” That means there is a total of 1.2 million residents served by the process.

“And odour complaints have been virtually eliminated,” says Fernandes. Indeed, on a visit on a warm spring day, Lakeview is undetectable from the nearby main road.

The Region of Peel is extremely happy so far with the Alfa Laval centrifuges, says Fernandes, but he says it is difficult, if not impossible, to quantify the savings that have resulted from the dramatic switch to the centrifuge process. That is true even though some benefits, such as odour abatement, are obvious.

“Quantification of savings is always an issue because you have to compare something with a base line,” he says. “If you change the entire process – which we have by going to centrifuge process – what is the base line to compare it to? But, in the overall scheme of things, yes, this plant is more economical now. This plant is state-of-the-art as far as sewage treatment is concerned.”

ONE OTHER BENEFIT, however, is reduced truck traffic from Clarkson to Lakeview. Before the switch to Alfa Laval’s centrifuge technology, Clarkson sent 35 trucks of liquid sewage a day to Lakeview for further treatment. Now it sends just three, each containing 40 cubic metres of biosolids heading to the Lakeview incinerator.

“There are cost savings and environmental benefits to trucking only the cake,” Fernandes says.

Overall, Fernandes supports the benefits of centrifuges in the treatment of sewage sludges. “In the Region of Peel, the biosolid master plan showed that centrifuge technology, when coupled with incineration, has the lowest life-cycle cost, is the most environmentally friendly and is the best with regard to suppression of odour,” he says. “I believe that this technology is going to go far.”

Sewage management the centrifuge way

Sewage in, clean water out.

And burn the biosolids.

It sounds simple but a modern wastewater treatment plant such as the Lakeview Wastewater Treatment Plant in Ontario, Canada, is a complex facility that is literally a living organism. It depends on technology, nature and human intervention to maintain an efficient operation.

All sewage is channelled through the headworks, with its mechanical screens, washer compactors and grit chambers. The sewage then goes to primary settling tanks, where sludge separates to the bottom. The primary effluent heads to aeration and secondary settling tanks. Settled material – the waste-activated sludge (WAS) – is sent to the Alfa Laval thickening centrifuges. Then, as thickened WAS, it goes to blend tanks where it is mixed with more sludge from the primary tanks.

The blended sludge then moves through the Alfa Laval dewatering centrifuge machines, where it is ideally concentrated to between 26 and 28 percent solids. It falls into a collection silo and is pumped to the fluid bed incinerator. When conditions are right, no additional fuel is necessary for incineration.

Alfa Laval technology has dramatically improved the system, according to Lakeview executive William Fernandes. “In the previous process, it was a long chain with many links in it, and if any link broke you were out of that process,” he says. “But in this process, you’ve got the centrifuges, the pumps and the incinerator. The number of links is small.

“Any chain is only as good as it weakest link,” Fernandes continues. “By reducing the number of links, you reduce the number of breakage points. So the efficiency of the plant in terms of reliability has gone up significantly. And we are in discussions with Alfa Laval all the time about how to improve further in the future.”

Marc Hunt, technical sales manager for Alfa Laval Canada, says, “A good part of our success is having good local service. That is a big thing for us.” With regular contact and an exchange of information with its customers, Alfa Laval technology will continue to evolve, he says.