Sep 02, 2016

Two Pipes Are Better Than One

Sewer use continues to evolve in Scandinavia

As Sven Platzer walked through the Water Environment Federation Technical Exhibition & Conference in Miami Beach, Fla., in 1975, his mind was occupied with a unique challenge facing his Swedish construction company.

His isolerlåda (insulation box) could protect water pipes buried above the frost line, but how could he surmount the financial and environmental obstacles of traditional gravity sewers or septic tanks for a development close to the sea with a high water table and rocky terrain?

Upon spotting the ALL-TERRAIN SEWER (ATS) low-pressure system, which had been developed by Environment One Corp. (E/One) four years earlier, Platzer experienced a moment of enlightenment. Because the grinder pump-driven ATS could propel wastewater through a flexible inflow- and infiltration-free pressurized 2- to 4-in. pipe for a distance of more than 2 miles—even uphill—to a force main or treatment plant, he could combine it with the potable water inside the same isolerlåda.

“He instantly saw the use of it back home, enabling him to solve his sewer problem,” said Torbjörn Jansson, director of Skandinavisk Kommunalteknik (SKT, or Scandinavian Municipal Infrastructure). Simultaneously, “He could make a low-cost investment in pressure pipes and laterals and buy the pumps as he was selling the lots. It was good timing to combine the versatility of the E/One grinder pump with the newly developed frost protection system. A perfect match,” Jansson said.

SKT conceived the isolerlåda in the early 1970s. “We designed an insulating Styrofoam box,” Jansson said, requiring only a shallow trench despite Scandinavia’s harsh climate and formidable terrain. “Inside, sand is filled around the pipes, which stores the energy from the flowing water and returns energy. Ideally, with normal use of sewer and water, the box’s dimensions and sand keep the pipes protected with no need for extra energy. When we have no or low flow [e.g., vacation houses idle during the winter], we add an electrical heating cable as insurance.”

The E/One-SKT strategic alliance then dove-tailed nicely with a 1990s European Union (EU) mandate requiring wastewater collection and treatment for all communities with a population of 2,000 or more. It was further enhanced by EU wastewater directives setting high environmental standards for rivers, lakes, groundwater and coastlines. Both decrees spurred significant sewer infrastructure investment throughout Scandinavia.

Sewers’ Spread

The concept has grown tremendously over the last 40 years: “At first,” SKT said, “we were ‘missionaries.’ Pressure sewer was something new, revolutionary and challenged the old ‘truths.’” 

Today, SKT is Scandinavia’s largest supplier of ATS systems, with an installed base of 60,000 grinder pumps—or 60% of the market—in Sweden, Denmark, Norway and Finland, serving more than 200,000 people. SKT installs about 20 miles of frost protection annually.

The tally includes scores of small projects utilizing the high torque of E/One’s 1-hp pump to sewer Scandinavia’s far-flung settlements and isolated vacation retreats. In Skåne, at one of Sweden’s amusement parks and zoos, an ATS spawned modern restrooms throughout the 85-hectare (210-acre) facility. Currently, SKT is installing 800 pumps at almost every home in Årsta Havsbad, a beach town 24 miles south of Stockholm.

In Gävle, a flat seaside area with failing septic systems that are threatening its freshwater supply, “The only way to solve this problem was connecting everything to the city’s sewer pipes,” said project engineer Fredric Eriksson of Gästrike Vatten. “We calculated the most cost-effective design and that was with an ATS system.”

The trophy project is the 16th-century Drottningholm Palace, the private residence of Sweden’s royal family. 

“The system at Drottningholm was built in 1981 to 1983 [after ancient wooden sewers collapsed] and has 65 [grinder] pumps,” Jansson said. “It has operated since then and the pumps are gradually replaced as they become outdated or fail from age. We estimate one-third of the original pumps are still in use after 35 years.”

“Most parts of Drottningholm use the isolerlåda [for water/sewer],” he said. “The main reason is that we were not allowed to dig deeper than 2½ ft. There are too many archeological layers and remains from pre-15th century settlements.”

U.S. Utilidors?

The U.S. and Canadian governments began examining isolerlåda (often referred to as utilidor) applications in Scandinavia and the Arctic in the mid-1970s. One study, “Cold Climate Utilities Delivery,” published in 1979, defined utilidors as “conduits that enclose utility piping which, in addition to water and sewer pipes, may include central heating, fuel oil, natural gas, electrical and telephone.”

In essence, an “all-in-one” installation somewhat heralded the next-generation infrastructure common in Scandinavia today, where developers sometimes piggyback a water-sewer utilidor with electric and fiber optic cables in the same trench. Their omission from the landscape is practical—no downed lines from wind or ice—easy on the eye and more economical than multiple trenches, poles and accompanying labor costs.

“Inclusion of conduits such as electrical power, natural gas, and telephone cables, along with water and sewer lines in utilidors can be cost-effective and aesthetic,” noted the 1979 study prepared by the U.S. Environmental Protection Agency (EPA) and Corps of Engineers and Environment Canada. “This practice is generally recommended wherever practical.”

So why isn’t the utilidor concept incorporated by cash-strapped municipalities and tight-fisted developers in the U.S.? Because, the 1979 report added, “Most public health codes do not allow the proximity of water and sewer pipes.”

Despite Scandinavia’s 40-year-old test lab, this custom—sometimes written, sometimes not—endures state to state, town to town: Water on one side of the street, sewer on the other. Its origin and necessity are open to interpretation.

“When I was a young engineer, I designed sewers that way because that’s how the older engineers said it would be or it was driven by code or standards,” said Keith McHale, a professional engineer and inflow and infiltration project manager for E/One.

“Average citizens give yea or nay votes on developments every evening across the world as sites are submitted to planning commissions and councils,” said Rick Harrison, author of Prefurbia: Reinventing the Suburbs from Disdainable to Sustainable. “Convince these people that putting their water supply inches from the crap (literally) they flush down their toilets is a great idea, and you’ll have a new standard. No science behind it … simply emotion.”

Dr. Neil S. Grigg, a professor of civil and environmental engineering at Colorado State University, is less jocular: “The utilidor concept is interesting, but not widespread. In the 1970s, Herb Poetner wrote about it in a report for the American Public Works Assn. He thought it would revolutionize public works, but alas it didn’t happen,” he said.

“It would be extremely hard to do anything on this,” Grigg said. “The U.S. has a tradition of voluntary (non-governmental) standard-setting and associations such as the American Water Works Assn. are not willing to trample on local prerogatives unless it is a matter that everyone agrees requires a national standard.

“I think that Scandinavia has a much greater tradition of cooperation than we do, and you see that in how they manage local government and public works. That’s one answer to the puzzle of slow innovation. And, industry influence,” he said.

No Stopping in Sweden

Meanwhile, SKT’s evolving creativity extends to a project owned by the Royal Swedish Yacht Club on Telegrafholmen Island east of Stockholm. In a permutation of the isolerlåda, SKT is laying adjacent water and ATS pipes on top of solid rock to access 40 homes with $600,000 price points. The 1 1/4-in. ATS pipe and 1-in. water pipe are polyethylene encased in separate insulated, corrugated polypropylene tubes using an electric heating cable as most are seasonal residences. Artful boardwalks conceal them throughout the isle.

“It’s truly transformational technology,” said Eric LaCoppola, E/One’s president. “And it’s a good example where Sweden has taken U.S. technology and repackaged it to become more innovative. This is one of the dynamics that has made SKT great.” 

About the author

Joseph Harmes is an independent writer. Harmes can be reached at [email protected].

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