Boat Waste-Treatment TechnologyBy Tom Neale
Published: April/May 2012
Developments in onboard waste-treatment technology have created a more effective MSD.
Onboard treatment technology has developed significantly over the past two decades, far from the era of marine-sanitation devices (MSDs) with performance and fail-safe protection issues, and systems that used chemicals. But starting in the 1990s, as pumpout stations began to proliferate, and additional No Discharge Zones (NDZs) were permanently established (where it is illegal to use MSD treatment systems), funding for MSD research and development dried up.
One American-owned company, Raritan Engineering based in Milleville, New Jersey, continued to develop and improve their Lectra/San MSD, a treatment system based on technology first developed in the 1970s. New test results on their latest MSD, called Electro-Scan, have been released by the Environmental Protection Agency (EPA).
In Raritan's patented new system, sewage is pumped, on a flush-by-flush basis, into the first of two treatment chambers, and macerated into fine particles. Electricity (from rare-earth titanium electrodes with a proprietary coating) is introduced into the salt water, which separates the sodium from the chloride, creating free-standing chlorine ions, which neutralizes and disinfects the waste. At the end of the electric charge, the sodium and chloride recombine naturally within the unit so no chemicals are discharged. The particles then move into the second chamber during the next flush where the process is repeated. When discharged, the effluent particulate can best be described as light dust and, in extensive testing, the fecal coliform (FCU) content was found to be only 2.43FCU/100mL; by comparison, 14FCU/100mL is the shell-fishing-approved standard. (The current standard for Type I MSDs is less than 1000FCU/100mL.)
These new results were established in extensive testing conducted by the EPA in 2007, and announced in 2010. The EPA Executive Summary of that test determined: "…The Electro Scan device removed almost all pathogen indicators (99.99% or greater)." This is the first time an independent and thoroughly conducted test, sponsored by the EPA, has validated the results of this technology. Raritan, too, has had the product independently tested periodically for recertification, but the EPA-sponsored test was the most thorough. To see a table of results, and the EPA Executive Summary, visit www.BoatUS.com/Magazine.
Over the past decade Raritan has worked to solve former fail-safe concerns: Their current Electro Scan has a microprocessor and display that tells the user if the device isn't operating properly. It gives the historical data of each flush of the unit for enforcement purposes, uses up to 36 percent less electricity, tailors electrical input to properly treat waste, and shuts down should the unit not be operating within required parameters. Buoyed by their product's performance, Raritan and various boating interests, including BoatUS, have requested that the EPA make its standards for onboard treatment devices substantially more stringent than those on the books today, which were formulated 35 years ago. This change could prohibit onboard devices that don't work as well from ever becoming certified. That request is still awaiting EPA action.
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Running The Numbers
Any treated sewage, regardless of the source, contains nutrients that contribute to water-quality issues including algae blooms. While the existing standards for treatment MSDs on boats only require pathogen reduction, the EPA nonetheless monitored, recorded, and reported on nutrients discharged by the Electro-Scan as part of their testing. The EPA results yielded an average of 0.000375 pounds of nitrogen per gallon of treated discharge (about two flushes). That number is too small to easily conceptualize, but extrapolating it out to an average boating family's annual usage leads to an amount that can be compared to other sources.
If a family of four spends 20 weekends aboard per year (two days aboard X four persons X five flushes per day per person = 40 flushes per weekend) that adds up to 800 flushes per season. The average volume of a flush for a marine head ranges from half to three quarters of a gallon. Using the larger number results in 600 gallons of treated discharge. Multiply that by 0.000375 pounds per gallon and you get 0.225 pounds of nitrogen released, or 3.6 ounces for the year. That's about the same amount of nitrogen in 11 ounces of lawn fertilizer (volumetric measure coming).
Did You Know?
Once the EPA designates a No Discharge Zone, outlawing the use of marine sanitation device treatment systems, it's permanent, regardless of advancements in MSD technology.