Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Tiny Bubbles Clean Oil from Water

17.11.2009
Small amounts of oil leave a fluorescent sheen on polluted water. Oil sheen is hard to remove, even when the water is aerated with ozone or filtered through sand.

Now, a University of Utah engineer has developed an inexpensive new method to remove oil sheen by repeatedly pressurizing and depressurizing ozone gas, creating microscopic bubbles that attack the oil so it can be removed by sand filters.

“We are not trying to treat the entire hydrocarbon [oil] content in the water – to turn it into carbon dioxide and water – but we are converting it into a form that can be retained by sand filtration, which is a conventional and economical process,” says Andy Hong, a professor of civil and environmental engineering.

In laboratory experiments reported online this week in the journal Chemosphere, Hong demonstrated that “pressure-assisted ozonation and sand filtration” effectively removes oil droplets dispersed in water, indicating it could be used to prevent oil sheen from wastewater discharged into coastal waters.

Hong says the method – for which patents are pending – also could be used to clean a variety of pollutants in water and even soil, including:

-- So-called “produced water” from oil and gas drilling sites on land. Such oily water normally is re-injected underground. “If we have technology to clean it, it could be put into beneficial uses, such as irrigation, especially in arid regions where oil and gas tend to be produced,” says Hong.

-- Water from mining of tar sands and oil shale.

-- Groundwater contaminated by MTBE, a gasoline additive that reduces harmful vehicle emissions but pollutes water due to leaking underground gasoline storage tanks.

-- “Emerging contaminants,” such as wastewater polluted with medications and personal care products.

-- Soil contaminated with polychlorinated biphenyls (PCBs, from electrical transformers) or polycyclic aromatic hydrocarbons (PAHs, from fuel burning). Water and contaminated soil would be mixed into slurry, and then treated with the new method.

-- Heavy metals in soil. Instead of ozone, air and metal-grabbing chelating agents would be pressurized with a slurry of the contaminated material.

-- Refinery wastewater and oil spills at refineries or on waterways. The spill could be vacuumed, and then treated with the new method on-site or on a barge.

Hong conducted the study with two University of Utah doctoral students – Zhixiong Cha, who has earned his Ph.D., and Chia-Jung Cheng – and with Cheng-Fang Lin, an environmental engineering professor at National Taiwan University.

Zapping Oily Water with Microbubbles from Ozone under Pressure

Hong says his method uses two existing technologies – ozone aeration and sand filtration – and adds a big change to the former. Instead of just bubbling ozone through polluted water, Hong uses repeated cycles of pressurization of ozone and dirty water so the ozone saturates the water, followed by depressurization so the ozone expands into numerous microbubbles in the polluted water, similar to the way a carbonated beverage foams and overflows if opened quickly.

The tiny bubbles provide much more surface area – compared with larger bubbles from normal ozone aeration – for the oxygen in ozone to react chemically with oil. Hong says pollutants tend to accumulate on the bubbles because they are not very water-soluble. The ozone in the bubble attacks certain pollutants because it is a strong oxidant.

The reactions convert most of the dispersed oil droplets – which float on water to cause sheen – into acids and chemicals known as aldehydes and ketones. Most of those substances, in turn, help the remaining oil droplets clump together so they can be removed by conventional sand filtration, he adds.

In his study, Hong showed the new method not only removes oil sheen, but also leaves the treated water so that any remaining acids, aldehydes and ketones are more vulnerable to being biodegraded by pollution-eating microbes.

“These are much more biodegradable than the parent compounds,” he says.

Hong says the water is clean enough to be discharged after the ozonation and sand filtration, but that some pollution sources may want to use conventional methods to biodegrade remaining dissolved organic material.

Details of the Experiments

Hong conducted his experiments using a tabletop chemical reactor that contained about a quart of oily water made by mixing deionized water with crude oil from the Rangely oil field in northwestern Colorado.

Ozone was produced by passing dry air through a high-voltage field, converting oxygen gas, which has two oxygen atoms, into ozone, which has three.

The ozone was pressurized to 10 times atmospheric pressure, about 150 pounds per square inch, which compares with inflation pressures of about 100 PSI for Hong’s bicycle and 35 to 40 PSI for many automobile tires.

He found oily water was cleaned most effectively by pressurizing and depressurizing it with ozone gas 10 times, then filtering it through sand, then putting the water through 20 more pressurized ozone cycles, and then filtering it again through sand. That was at flow rates of 10 to 20 liters per minute [about 2.6 to 5.3 U.S. gallons per minute] in his laboratory apparatus.

Hong tested how well the ozonation worked by measuring chemical and biological oxygen demands of treated water samples. Both indirectly measure organic contents in the water. Hong also used mass spectrometry to identify what contaminants remained in the water.

He found that his most effective procedure removed 99 percent of the turbidity from the “produced water” – leaving it almost as clear as drinking water – and removed 83 percent of the oil, converting the rest to dissolved organic acids removable by biodegradation.

A Tryout in China

With success in the laboratory, Hong now plans for larger-scale pilot tests.

“It is economical and it can be scaled up,” he says.

One such test will be done in Wuxi, China, where a prototype desk-sized device capable of treating 200 liters [53 U.S. gallons] at a time will be tested at three to five polluted industrial sites that the government vacated for redevelopment, Hong says.

Meanwhile, the University of Utah Research Foundation has entered into options to license the technology to Miracotech, Inc., of Albany, Calif., and 7Rev, L.P., a Salt Lake City venture capital group, so the companies can bring the technology to market.

Hong says other methods of treating oil well “produced water” have met with varying degrees of success. They include centrifuges, membranes, regular ozonation and air bubbles to float off contaminants. But all have drawbacks, such as inability to handle dissolved oil or high levels of oil, or susceptibility to quickly getting fouled by the oil.

Neither ozonation nor sand filtration alone has been able to effectively treat oily “produced water.” Hong says long-chain oil molecules don’t react with ozone easily without his pressure treatment. And sand filters alone cannot remove oil.

For more information on the University of Utah College of Engineering, see http://www.coe.utah.edu

Contacts:

-- Andy Hong, professor of civil and environmental engineering –
office (801) 581-7232, cellular (801) 999-0083, hong@civil.utah.edu
-- Lee Siegel, science news specialist, University of Utah Public Relations –
office (801) 581-8993, cellular (801) 244-5399, leesiegel@ucomm.utah.edu

Andy Hong | Newswise Science News
Further information:
http://www.utah.edu
http://www.coe.utah.edu

More articles from Life Sciences:

nachricht Study suggests oysters offer hot spot for reducing nutrient pollution
17.10.2017 | Virginia Institute of Marine Science

nachricht World first for reading digitally encoded synthetic molecules
17.10.2017 | CNRS

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

Im Focus: New nanomaterial can extract hydrogen fuel from seawater

Hybrid material converts more sunlight and can weather seawater's harsh conditions

It's possible to produce hydrogen to power fuel cells by extracting the gas from seawater, but the electricity required to do it makes the process costly. UCF...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Study suggests oysters offer hot spot for reducing nutrient pollution

17.10.2017 | Life Sciences

Breaking: the first light from two neutron stars merging

17.10.2017 | Physics and Astronomy

World first for reading digitally encoded synthetic molecules

17.10.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>