Drought, temperature swings extend drinking water 'inversion'

BETHLEHEM, Pa. — If you think you've noticed a change in the taste or smell of your drinking water, you are not imagining things.

It’s caused by a seasonal phenomenon known as inversion, officials said.

“The water turnover in the reservoirs happens every spring and fall," Bethlehem Water and Sewer Resources Director Edward Boscola said.

"The bottom water [and particles] comes up to the top, and the [clear] topwater goes to the bottom, stirring the pot, if you will, and a lot of impurities at the bottom get mixed up and end up passing through our filters.

“They’re microscopic particles. It happens every year, but some years are worse than others.”

This fall, it’s more pronounced than usual, Boscola said.

“Probably due to the current weather situation,” he said, referring to the drought conditions the area is experiencing.

Like oil and water

Think oil and water.

In winter, the sun is less intense, so the water surface is colder. That forces the warm air down.

The opposite happens in spring, as the sun warms the water surface.

“It’s dry, and it’s been warm," Boscola said. "Warm during the day but cool at night. So these big temperature swings for the last month or so,” aren’t helping particles to settle and filter once and for all.

Since late October, residents in one northeast Bethlehem neighborhood have noticed and were concerned enough to post about it on social media.

“Does anyone else have water that tastes like dirt straight from the tap?” posed one member of the Facebook group Elmwood Park Historic District (Bethlehem, PA).

“Yes! The past few weeks it’s had a dirt smell and taste,” replied another, to which the first replied, “Lol good, at least I’m not going crazy about this.”

Then it was 15 to 20 residents from "randomly scattered" areas who started contacting the city from Oct. 25.

So Bethlehem’s public works department on Oct. 30 made a Facebook post of its own.

“The City of Bethlehem drinking water system is currently experiencing taste and odor issues," the post said. "This is due to seasonal turnover, or inversion, of our reservoirs, which occurs every spring and fall.

"The turnover stirs up impurities in the reservoirs that can make the water smell or taste 'stale,' 'musty,' or 'metallic.'"

The path of Bethlehem water

Two reservoirs feed the city’s drinking water supply. Penn Forest and Wild Creek are in Carbon County, about 25 miles due north of Bethlehem’s pipelines, called transmission lines.

Wild Creek was built in 1940, and its main runs from the reservoir to the city. Penn Forest was built in the 1950s, Boscola said, and is upstream of Wild Creek, with a filtration plant in Lehigh Township.

“Penn Forest feeds Wild Creek, the one we keep full, and Penn Forest is where the level drops," Boscola said. "It’s currently at 60 percent capacity."

There’s a 20-acre watershed up in Carbon County, so all the land is protected, and there are a lot of streams and runoff. That runoff eventually ends up passing through Wild Creek.

The filtration system is sand, stone and charcoal, which Boscola said is a pretty basic technology that’s been around for a hundred years.

It's able to filter out not only large particles but all biologicals, which then killed with chlorine, he said.

“It keeps the clarity of the water,” Boscola said. “Unfortunately, it’s not very good at filtering out these microscopic particles that can cause taste and water issues.”

Turnover and low water levels, he said, can increase levels of geosmin and MIB (2-methylisoborneol) which are compounds known to cause taste and odor issues, but are not harmful.

They’re produced by certain types of algae and bacteria, but it's not a harmful algal bloom, which are known to cause health issues.

“The upper reservoir, Penn Forest, feeds the lower, and we keep the lower reservoir full. So the level of the upper drops," Boscola said.

"That means a smaller volume of water coming from the top to the bottom, but the same amount of impurities.

“Impurities are technically algae, but it’s benign algae. There are lots of different kinds, and some are more harmful than others.

"Most of the algae gets treated or killed via our disinfection, but what’s left, the microscopic, are so small you can’t see them."

'We'll get through'

Disinfection kills those organisms, but the byproduct chemicals from the dead algae and bacteria cause the foul taste and odor, he said.

“It doesn’t change the color of the water, but it does give a stale taste,” Boscola said.

“My taste buds aren't that good, so I don't really notice it. Some people’s taste buds are more sensitive. But it’s a naturally occurring phenomenon.”

Even if the reservoirs were full, he said, the turnover still takes place every spring and fall, which he called the "shoulder seasons."

The steps to your drinking water:

• Reservoir water is filtered and passes through the outlet of the filtration plant in Lehigh Township. It's then considered potable (safe and taste- and smell-free).
• It enters the distribution network and travels to homes in Bethlehem and surrounding municipalities, including townships of Allen and East Allen and both Hanovers, Lower Saucon, parts of Upper Saucon and Bethlehem townships, and the boroughs of Freemansburg and Fountain Hill.

“Normally, these are transient events that occur for a couple of weeks and don't last this long, so we’ll have to just wait and see what happens,” Boscola said.

“It’s been warm and no rain. There’s not much we can do about it. Mother Nature has to run its course.

“We’ll get through.”

"Once the temperature changes permanently to cold, the inversion is over, and things go back to normal," Boscola said.

Until then, residents can buy bottled water or their own home filtration system, which some, as their posts on Facebook reflect, have started to do.