Where does the waste go?

Wednesday, 15 August 2007

Sanitary wastewater contains three basic waste products: urine, feces, and paper products. The traditional image of a wastewater treatment plant includes truckloads of solids taken to landfills and outfall pipes of un-pleasant water. Modern technology has eliminated the truckloads of waste solids and made the outfall water reusable for lawn sprinkling. Agrimond has micro-sized and improved this technology to the point where even the outfall is eliminated. This proprietary and patented process in the DragonflyTM treatment plant sterilizes and continuously recycles the water.

Where does the waste go? Solids make up only a small percentage of the wastewater, by volume and by mass. A continuously recycling biological material called biomass converts incoming wastewater into clarified water and a variety of gasses that are natural components of the air we breathe: nitrogen gas makes up 79 percent of our atmosphere, water vapor is an essential part of air, and carbon dioxide is necessary for plants to grow.

The first step in the process is to grind the wastewater to a uniform liquid and mix it with highly concentrated biomass, consisting of billions of various bacteria cultures capable of breaking down the entering waste. A pump mixes this “cocktail” by the spinning action of the pump’s impeller and transfers it to the aerobic (oxygen present) treatment tank. The odor disappears as soon as the waste is mixed with the biomass, eliminating the offensive vent pipe.

In the aerobic treatment step, air is diffused into the liquid to allow certain species of bacteria to metabolize the organic waste. To a chemist, organic matter contains carbon, oxygen, hydrogen, and nitrogen, the elements of the gasses listed above. The aerobic treatment releases the carbon dioxide and water, but the nitrogen remains. It was converted from ammonia and uric acid into simple nitrogen/oxygen compounds.

The second treatment step is anoxic (oxygen deficient). At this point, anaerobic bacteria break down the simple nitrogen compounds and release nitrogen gas. After this step, the raw waste products are gone and the biomass tends to settle to the bottom of the slightly yellow-brown water. The odor producing nitrogen compounds have been turned into odorless gas.

The third treatment step is called “clarification.” The biomass is allowed to settle to the bottom of clarifier columns. The clear liquid is pumped out for advanced treatment and the biomass is returned to the treatment tanks. The clear liquid still contains some bacteria at this point. Our proprietary process sterilizes it with ozone gas (activated oxygen) and filters it to remove the haze. The sterilizing properties of ozone are well documented and the ozone converts back into oxygen gas in the process. The result is odorless re-use water that is sent back to flush toilet and urinal fixtures.

If potable water from the sink is added to the wastewater stream of urine and feces, why doesn’t the system fill up and need to be drained? The answer is in two parts. First, the biomass is processed 24 hours per day. If there is no incoming waste, the biomass bacteria digest each other. Virtually, everything is converted to nitrogen gas, water vapor, and carbon dioxide gas. Second, the excess water is vaporized by the aeration process; the air bubbles carry water vapor up the vent.

The most modern municipal wastewater treatment plants use these principles, but they have no true recycle use for the treated water. The MeadowhawkTM Portable Restrooms units provide a recycle path for the treated re-use water. It is not magic...it is technology. Our team of chemical engineers, microbiologist, environmental engineers, mechanical engineers, civil engineers, and computer programmers have simplified and downsized the process to make it fit in a small space...and it works!

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