2011 Invention Awards: From Waste To Water

A machine that uses exhaust heat to treat onboard sewage

By Bjorn Carey Posted 06.10.2011 at 11:30 am 14 Comments

Clean Machine After a weeklong cruise, a typical 3,000-passenger cruise ship may hold nearly 200,000 gallons of wastewater in toilets—a problem, inventor Namon Nassef says, that the ZLD could easily eliminate. John B. Carnett

When Namon Nassef had to buy a new engine for his boat, he saw an opportunity. He could finally install the invention he had been working on, a machine he calls the Zero Liquid Discharge Sewage Elimination System (ZLD). The device uses engine heat to oxidize and evaporate toilet, shower and galley waste.

A typical combustion engine makes use of only 30 to 35 percent of the energy contained in fuel; the rest escapes as heat through the radiator or the exhaust. The microwave-oven-size ZLD puts that exhaust heat to work. When a passenger flushes a boat’s toilet or drains the waste-containment tank, the wastewater runs through a pipe to the ZLD, which can be installed anywhere in the craft. First the waste enters the machine’s equalization tank, which grinds it into pieces a quarter of an inch or smaller in diameter. Next it moves to the homogenizer, a container with three sets of blades that dissolve solids into 0.002-inch-diameter particles. Then an injector pump pressurizes the waste stream and sprays it through a nozzle into the engine’s exhaust system as a fine aerosol.

The exhaust of an idling engine is at least 550°F, which is hot enough to flashevaporate the waste and thermally oxidize the organic materials. Quite simply, the device can break down anything organic that’s put into it. The process eliminates all odors, Nassef says, and the main by-products are carbon dioxide and clean water vapor.

How It Works: Zero Liquid Discharge: Waste flows from the boat’s toilet to an equalization tank, which breaks it into small pieces. The material next moves into the homogenizer, a container where it gets chopped into particles. The injector pump pressurizes the material and sprays it through a nozzle into the engine’s exhaust system, where the heat cleans it. Blanddesigns.co.uk

Nassef built a ZLD prototype in 2004 from washing-machine parts and a five-gallon paint bucket. The current version, his 11th update, uses only as much energy as ten 100-watt lightbulbs, sterilizes waste without any of the harsh chemicals of other portable toilet-waste-disposal systems, and can be scaled up or down. In 2007 it earned a certificate of approval from the U.S. Coast Guard for marine sanitation devices.

Nassef is starting with boats, but the ZLD has the potential to work in just about any vehicle with hot-enough exhaust and a toilet. He’s drawn interest from RV manufacturers and the U.S. military, which often resorts to burning waste with jet fuel (at a total cost of $400 per gallon) at its forward operating bases. Another promising market is airlines, which could plug the ZLD into existing toilets, allowing some planes to shed up to 500 pounds of wastewater weight over the course of a flight.

Name: Zero Liquid Discharge
Inventor: Namon Nassef
Time: 7 years
Cost: “Hundreds of thousands of dollars"

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14 Comments

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allenm1364

05/20/11 at 11:40 pm

A similar product was made for Motorhomes in the 1970's by a company named Thermasan which incinerated waste @ 1000F in the exhaust pipe stream. Didn't have the very fine macerator that was needed and could clog. Killed by fuel prices and failed about 1980 along with the Motorhome market.

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JOHN GOLDEN

05/24/11 at 12:51 pm

At last, an answer to the most distasteful part of "living your dream" in a motorhome. Now if the motorhome industry would only embrace this amazing invention and include the ZLD as an OEM accessory, all of us motorhome owners would lined up at the door to finally put an end to the black & gray waste tank nightmares we all have experienced. Thank you Namon for hanging in there for 7 years of research.

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Brian H

05/27/11 at 7:37 am

John;
Looks like this could readily be retrofitted. The only part that would intrude into the exhaust system etc. is the hose that sprays the mixture.

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JOHN GOLDEN

05/27/11 at 2:53 pm

Brian:

It is my understanding there is a 1/2" long X 1/8" in diameter temperature sensor and a 1/2" long X 1/2" in diameter injector nozzel mounted close to the engine exhaust discharge. These two items are the only two components that are mounted to the exhaust system.

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jefro

06/09/11 at 3:51 pm

The US Navy have been burning sewage in turbine ships for decades.

It gave a new meaning to stack gasses.

Hope they didn't give a patent for this.

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jwrodman

06/10/11 at 11:53 am

Is it just me or does anyone else find it annoying that the article states "uses only as much energy as ten 100-watt lightbulbs". Is it too hard for the target market of Pop Sci to understand 1000 watts, I doubt it.

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CodeZero

06/10/11 at 12:45 pm

Talk about the mother of all misleading titles! I was gagging halfway though reading this as I kept thinking that this guy was pulping up waste solids to "magically" turn into water to drink.. my relief when I got past the 1/2 way mark and it became obvious that it was meary to reduce waste storage. *wipes brow*

And jwrodman, agreed. A tech publication, and the author resorted to using a horrible analogy.

Playing Devil's Advocate since 1978

"The only constant in the universe is change"
-Heraclitus of Ephesus 535 BC - 475 BC

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Boramir007

06/10/11 at 1:58 pm

"The exhaust of an idling engine is at least 550°F, which is hot enough to flashevaporate the waste and thermally oxidize the organic materials." This statement is not accurate. If vehicle exhaust is hot enough to thermally oxidize organic materials, why do cars have a catalytic converter? In the absence of a catalytic converter, temperatures of 1400-1500°F are required to efficiently convert organic matter into carbon dioxide and water. All this system would provide is dried waste dust. Instead of solid/liquid waste, it is just adding air pollution (VOCs and particulate matter).

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BubbaGump

06/10/11 at 2:04 pm

I applaud this gentleman for his ingenuity and can do spirit. He had an idea and put it to work! CONGRADUALTIONS!

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jefro

06/10/11 at 6:50 pm

This is not a new idea at all.

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Dr.Zoidberg

06/13/11 at 8:31 am

Wow..

So it only consumes the inequivalent energy of 25,000 mobile phone chargers?! That's amazing!!

Or 1/846,000,000ths of the typical mean output of a nuclear power station...

But, what happens if someone flushes a sanitary towel? The're a known killer of any kind of maceration toilet system, then, instead of calling a plumber you would need the services of a mechanical engineer to open up the gizmo and fish out any un-mashable matter.

I don't mean to just poke holes in his idea, but you also have to think how long the jet is going to stay clear, with a constant stream of carbonised poo on it..

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Icaticus

06/27/11 at 5:21 pm

Nice miniturization of a previous technology. Its also improved upon.
The angle on using it on aircraft is great. On larger boats however it might be more cost effective to further develope the waste to energy convertion tech.

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