Recycling sewage water has helped free Israel, a desert country, from depending on rain.
Treated sewage water provides close to a quarter of Israel's demand for water, right behind desalination, the other major process that has eased Israel's fear of drought.
But making that water — from toilets, showers, and factories — clean enough to use is challenging.
One of the first steps is removing garbage from the sewage system. At Israel's biggest wastewater treatment plant, called Shafdan, three-quarters of that garbage is one thing: wet wipes.
"Every day we're dealing with 30 tons of wet wipes," says Meir Ben Noon, chief tour guide at the plant.
That's not all.
"We also have a lot of weird things, like earrings, rings, and even cell phones, that people lose every day in our pipes," Noon says.
The jewelry goes to the Israeli treasury. Cell phone components get recycled or trashed.
Only then does the real cleaning begin.
That work is done by sewage-munching microbes. They're too small to see in the big concrete ponds outside the Shafdan facility, but slowly they turn the water from muddy to clear.
The microbes need air as well as food, so pumps steadily churn air into the ponds. The pumps require energy — a significant cost of cleaning sewage water.
Cutting The Power Bill
To save money and make the system more environmentally friendly, Shafdan is now building a system to trap methane from decomposing microbes, known as sludge, and use that gas to power the plant.
The sludge is heated slowly to kill the microbes and any remaining pathogens, like viruses. It is then used as compost.
"The gases coming out from the same process will give power, which is the energy, the electricity, that will supply most of this facility," Noon says.
Israel's water authority says Israel uses a much higher percent of its treated sewage for irrigation than any other country — 86 percent, with Spain next at 19 percent.
So entrepreneurs are also experimenting with other ways to cut the energy bill.
About 40 miles north of the huge Shafdan plant, 10 white tanks hold microbes eating sewage water.
This is an experimental sewage treatment site. The basic process is the same as at Shafdan — microbes munching sewage solids — but this process uses much less energy, says Eytan Levy, CEO of the startup, Emefcy, which runs this pilot project.
Levy's company has developed a way to diffuse oxygen into the water through a thin plastic membrane that lets air pass through, but not liquid.
"It lets air in without the need to blow bubbles" into the water, Levy says.
This cuts the energy bill.
In addition, Levy's company is trying to capture electricity, not through methane from decomposing microbes, but from the live microbes as they eat.
"It starts from the idea that the organic contamination in the waste water is in fact a fuel, Levy says. "We spend a lot of electricity getting rid of this fuel. And you ask yourself, why can't we utilize this energy?"
He admits the concept is futuristic. But in Israel, efficient treatment of sewage water is a current issue. Half the water for Israel's farms comes from treated sewage water.
Keeping Pharmaceuticals Out Of Crops
The Shafdan plant sends all its water to the Negev desert, where the government has long promoted agriculture development. Farms elsewhere depend on water from smaller treatment plants.
Near an almond grove at the Kibbutz Netiv HaLamed He in the hills south of Jerusalem, Efi Cohen shows off the communal farm's local sewage treatment plant.
It's a big concrete tank with a red pipe coming out. The pipe dumps water into a pond, making a frothy foam.
Red pipes show this is not drinking water, Cohen says. But it is water for crops. The water comes from the toilets, showers, sinks and even chip manufacturing plants in nearby communities.
The treatment process here is less sophisticated than at the Shafdan plant, and government regulations allow Cohen to use this water only on "dry" crops, meaning those — like almonds — that don't come into direct contact with the treated water.
For watermelon or cucumbers, he still needs rain or water that is safe for drinking.
Cohen likes the price of recycled sewage — it's cheaper than piped-in potable water. But soil chemist Benny Chefetz says even the highest quality recycled sewage has trace pollutant elements that are not regulated.
At Hebrew University's Smith Faculty of Agriculture, Chefetz studies the effect that elements from pharmaceuticals and personal care products in treated sewage have on soil and food when used for irrigation.
In a small lab, he is dosing cucumbers with anti-epilepsy medications that break down very slowly in the soil. Chefetz says how trace chemicals in water move into food depends on the chemical, the crop and the soil quality.
There is a lot to learn, he says.
"We have no idea what [are] the consequences," he says, if a child is continuously exposed to even tiny amounts of medications by eating carrots or cucumbers.
He says it's important to figure out what's safe, because using treated sewage water is important.
"I'm not saying we need to stop irrigating with treated waste water," he stresses, noting agriculture in Israel and other Mideast countries is dependent on this source. "We don't want to stop irrigation, we want to continue, knowing that it's safe."
RACHEL MARTIN, HOST:
Israel is a desert country and as a matter of survival has had to become a pioneer in water technology. Last week, NPR's Emily Harris brought us a story about how Israel is building a desalination plant in San Diego. Today, Emily digs deeper into Israel's water treatment systems for agricultural use and finds that can be kind of a messy job.
EMILY HARRIS, BYLINE: One of the first challenges is wet wipes says Meir Ben Noon, chief tour guide at Israel's biggest sewage treatment plant.
MEIR BEN NOON: You have wet wipes. You love them. It says premoistened, flushable or biodegradable. And you believe that you can throw to the toilets.
HARRIS: Three quarters of the garbage hauled out here is wet wipes.
BEN NOON: Every day, we are doing with 30 tons of wet wipes in our pipes that creating blockage.
HARRIS: Once the big garbage is out, the real cleaning begins. That's done by microbes munching sewage in big ponds outside. But they need air to live, and pumping that air takes energy. So this plant is building a system to trap methane from decomposing microbes known as sludge and use that gas for power.
BEN NOON: The idea is to take the sludge, basically to kill it slowly with high temperature. And the gases coming out from the same process will give power, which is the energy, the electricity that will supply most of this facility.
HARRIS: That's a fairly standard practice around the world, but because Israel uses a much higher percentage of its treated usage for irrigation than any other country, according to Israel's Water Authority, entrepreneurs are also experimenting with new ways to cut the energy bill.
At a small experimental sewage treatment site, I climb above a tank of bubbling brown water with Eytan Levy, CEO of a startup called Emefcy.
EYTAN LEVY: It's being mixed right now for a few seconds. It's stopped.
HARRIS: The bubbling is settling down. It's defusing.
LEVY: And now it will settle. And in a few seconds, you will see that the upper layer becomes clear.
HARRIS: Levy's company is trying to capture electricity from the live microbes as they munch.
LEVY: It starts from the idea that the organic contamination in the wastewater is, in fact, a fuel. Now we spent a lot of electricity getting rid of this fuel. And you ask yourself, why can't we utilize this energy?
HARRIS: He admits it's futuristic, but it's a current issue. Half the water for Israel's farms comes from treated sewage water.
It smells a little bit like rotten eggs out here.
I've traveled to a kibbutz almond orchards south of Jerusalem. Efi Cohen is showing me the communal farm's local sewage treatment plant. It's a big concrete tank with a red pipe going out of it.
Why is the pipe red?
EFI COHEN: Because red - it's not water for to drink.
HARRIS: But it is water for crops. The red pipe dumps into a pond making a frothy foam. The water comes from the toilets, showers, sinks and even chip manufacturing plants of nearby communities. Government regulations allow Cohen to use this water only on some crops.
COHEN: The almond, it's dry, right. Every food, when it dry, you can use this. But I don't allow to irrigate watermelon for the food.
HARRIS: The rule is recycled sewage cannot come into direct contact with food. Soil chemist Benny Chefetz studies pollutants in his lab.
Wow it's bright in here.
BENNY CHEFETZ: Yeah. Those are cucumbers.
HARRIS: Chefetz researchers what happens to drug residues left in treated sewage water used for irrigation. Some, like epilepsy medications, can be found in trace amounts in certain crops. Chefetz says that raises important long-term questions.
CHEFETZ: We have no idea what is the consequences of a two-year-old child that will start to be exposed to those antiepileptic drugs when he was eat cucumbers, carrots etc. for the entire life.
HARRIS: He says it's important to figure out what's safe because using treated sewage water is important.
CHEFETZ: We must continue to irrigate with treated wastewater because there is no future for the cultural activity in places like Israel because there's not enough water, freshwater, high-quality water to support intensive agriculture.
HARRIS: He says that's true around the Mideast now and perhaps in other countries in the future. Emily Harris, NPR News, Jerusalem. Transcript provided by NPR, Copyright NPR.