Wednesday, August 29, 2012

Converting sewage into potable water


The idea of drinking water recycled from sewage or wastewater is indeed unsettling if not outright revolting to most folks.  However, in the States, some communities have no other recourse but to resort to recycled wastewater – El Paso, Texas and some parts of Los Angeles County and Orange County, California.

Moreover, according to a Wall Street Journal article by Paul Kix, Orange County's Groundwater Replenishment System, which opened in 2008, produces over 70,000 gallons of water every day. It is modeled to a degree on NASA's space station breakthrough: The wastewater goes through a micro-filtration process and then reverse osmosis (in which chemicals, viruses and pharmaceuticals are removed) before being exposed to high-intensity ultraviolet light to destroy any lingering compounds. Over two-thirds of the county has been served by the recycled water system since it went online four years ago, says Michael Markus, the general manager of the Orange County Water District.

Meanwhile, here in Panglao Island, with its salty water supply, many residents and business establishments have to buy mineral or purified bottled water for drinking and cooking purposes.

From what I was told, every local barangay must have its own water purification system, or get its supply of fresh water from Tagbilaran City.  Supposedly, this issue triggers intense political debates; hence, many barangays, to this day, are still without a steady supply of fresh water.  However, there are residents who are fortunate enough to have a deep well of fresh water within their property.

Even the prominent resort hotels and various dining establishments in Panglao are coping with this issue.  Most have no alternative but absorb the additional overhead expense of hiring tankers to deliver fresh water to fill their water tanks.  As for the employees of the island’s hospitality industry – who rent bed spaces to be near where they work – a higher fee they must shell out if the boarding house provides fresh water.  But such boarding houses are a rare find.  Salty water is all they can offer.

Desalination – turning seawater into drinking water – seems the potential solution, but estimated costs can run one-half to two-thirds more than for a recycled wastewater facility. That is largely due to the amount of filtration required: Wastewater has roughly 1,000 parts per million of salt, but seawater has roughly 35,000 parts per million. Desalination is also, of course, limited to areas near seawater.  Hence, Panglao Island is suitable for such.

The WSJ article further points point out that where the programs of recycled wastewater exist, they are born out of desperation -- which is precisely how the idea got its start:

Quote

It began in the tiny capsule of the Mercury rocket, on May 5, 1961, with Alan Shepard looking out his periscope viewer at the morning clouds. It was 15 minutes before his launch, before he was to become the first American sent into space, and he was nervous, according to "Moon Shot," the book that he later co-wrote. The launch director came on and told Mr. Shepard that there was an electrical glitch; the flight would have to wait.”

Another problem emerged during the nearly 90-minute delay: "Man, I got to pee," Mr. Shepard told astronaut Gordon Cooper, who was in ground control. The flight was only supposed to last 15 minutes, and the rocket wasn't equipped with a toilet. Mr. Shepard was told to hold it.

"Gordo, I've got to relieve myself," Mr. Shepard said, getting angrier. "Tell 'em I'm going to let it go in my suit." But Mr. Shepard had electronic biosensors up and down his legs. Mr. Cooper said, "The medics say you'll short-circuit all their medical leads."

"Tell 'em to turn the power off," Mr. Shepard said.

And so the medical team did. A short while later, Mr. Shepard was launched into his suborbital flight, a brave, relieved man.

As space flights became longer, the problem of discarding waste persisted. Neil Armstrong walked the moon in diapers. It wasn't until the era of the International Space Station, with astronauts on six-month missions, that NASA engineers began to think creatively about waste. "We didn't think that we could resupply [the astronauts] with water up there," says Monsi Roman, a microbiologist at the Marshall Space Station, who has worked at NASA for 25 years. "And that's when we began to think about recycling urine for drinking purposes."

Another problem emerged during the nearly 90-minute delay: "Man, I got to pee," Mr. Shepard told astronaut Gordon Cooper, who was in ground control. The flight was only supposed to last 15 minutes, and the rocket wasn't equipped with a toilet. Mr. Shepard was told to hold it.

"Gordo, I've got to relieve myself," Mr. Shepard said, getting angrier. "Tell 'em I'm going to let it go in my suit." But Mr. Shepard had electronic biosensors up and down his legs. Mr. Cooper said, "The medics say you'll short-circuit all their medical leads."

"Tell 'em to turn the power off," Mr. Shepard said.

And so the medical team did. A short while later, Mr. Shepard was launched into his suborbital flight, a brave, relieved man.

As space flights became longer, the problem of discarding waste persisted. Neil Armstrong walked the moon in diapers. It wasn't until the era of the International Space Station, with astronauts on six-month missions, that NASA engineers began to think creatively about waste. "We didn't think that we could resupply [the astronauts] with water up there," says Monsi Roman, a microbiologist at the Marshall Space Station, who has worked at NASA for 25 years. "And that's when we began to think about recycling urine for drinking purposes."

Urine consists of salt, water and contaminants, and on the space station today, the salt and contaminants are distilled and thrown away. The remaining water goes into a processor that burns away any lingering bacteria, and then iodine further cleans it. "It's a closed loop," Mr. Roman says—and an inspiration for wastewater treatment plants back on Earth.

Unquote

Incidentally, about a week ago I posted a blog article on the success of a team of engineers at Oregon State University  in their study of microbial fuel cells that generate electricity from wastewater.  They have developed a technology that uses bacteria to harvest energy from the biodegradable components of sewage at a rate that is 10 to 50 times more efficient than previous methods.

In essence, they are harnessing biodegradable material in wastewater to feed aerobic bacteria, which digest the substances with the use of oxygen. When the microbes oxidize these components of sewage – and, in turn, clean the water -- they produce a steady stream of electrons.

As the electrons flow from the anode to the cathode within a fuel cell, they produce an electrical current, which can be directly used as a power source. Additionally, this process cleans the water more effectively than anaerobic digestion and doesn’t produce unwanted byproducts.

Electricity and potable water, in the near future, might become the most expensive commodities in the worlf if we do not do something about them now.


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