Healthy Boat

NDZs & MSDs

The EPA-designated No Discharge Zones (“NDZ’s”) refer to the areas where the discharge of sewage even after it is treated using MSD I and II type waste management systems. In concert with the relevant states, the EPA has created NDZ’s to protect particularly vulnerable areas from even treated discharges. And it is expanding the number and coverage of those NDZs as sufficient pump-out stations become available.

MSDs are onboard Marine Sanitation Devices. Type 1 and Type II MSDs are macerator-type waste treatment systems that grind up the solids and disinfect the waste – by reducing the coliform count to levels low enough to not pose a health hazard. These MSDs use chlorine-based products that need regular replenishment. Type III MSDs are just blackwater holding tanks without any treatment - what one finds on most pleasure craft. Portable toilets found on very small boats are just mini holding tanks that need to be physcially dumped ashore.

A Little of the Science that Supports Holding Tanks

Some boaters act on the belief that the contents of one little holding tank won’t make much difference in their body of water, especially since the tide “flushes” it daily. But the truth is, it can make a very significant difference, and it’s one that we can control. While, for instance, more than a billion gallons of oxygen-demanding, treated effluent flows into Long Island Sound every day, it is the untreated sewage – and vessel discharge is a primary source – that infuses the waters we play in with disease-causing pathogens.

The three major reasons for using your boat’s holding tank are:

o Visually Distasteful - Although “aesthetic revulsion” is the most obvious of the three effects, it is the least important ecologically. The absence of floating waste does not mean that the surrounding waters are safe from the harmful effects of sewage discharge.

o Health Hazard - Invisible microorganisms contained in human sewage can cause infectious hepatitis, diarrhea, bacillary dysentery, skin rashes, typhoid and cholera. The most common organism is coliform bacteria, which is found in the intestines of all warm-blooded animals. Fecal coliform, including E. coli bacteria, can increase from one bacterium to over 10 million in the 12-18 hour normal digestive time. Pathogen contamination has closed beaches and shellfish beds(note that although onboard treatment facilities can reduce bacteria, they do nothing to control nutrients).

o Nitrogen Pollution - Oxygen depletion caused by an overabundance of nutrients poses a serious threat to plant and animal sea life. A major indicator of pollution by organic materials is Biological Oxygen Demand (BOD), the amount of oxygen that bacteria take from water to oxidize organic matter into carbon dioxide and water. In both air and water environments, oxygen produced by plants is offset by the oxygen consumed by animals, and the reverse is true of carbon dioxide. At its worst, as in the western end of the Sound from July through September, this low dissolved oxygen state is called hypoxia. The marine ecosystem goes out of balance as soon as an external source of oxygen demand is added, such as direct discharge of human waste. At its most extreme, it results in the death of some organisms and the escape of others