rev. 8-31-2011
There was a thread with the above name on a popular sailing forum; it was closed long before the conversation was finished. Comments were running counter to Raritan Engineering's party line, and so interested persons stepped in and clipped it short. So much for truly open forums.
Let me add that I'm not anti-Raritan Engineering or anti-type I MSD. Raritan makes good products and type I MSDs have their place. I am opposed to incomplete disclosure and to people that would convince us that the discharge is clean. It amounts to sterilized but poorly treated sewage; the data, not my personal opinion.
I'm only thinking about the Chesapeake, because it's what I know. Other areas have different issues.
rev. 7-22-2024
Maryland has added many more NDZs (places you can't use a Type I MSD) in the past few years. Check before you buy.
Typical raw sewage, as delivered to a sewage treatment plant is only about 200 ppm BOD, due to dilution with shower water and other low strength waste. Holding tank waste is considerably stronger due to reduced dilution.
Is the type I effluent as clean as Chesapeake Bay water? No, the average BOD5 of the Bay is 0.2 to 0.03 ppm, or perhaps 10,000 times cleaner. The primary impact of BOD5 (5-day biological oxygen demand) is to demand oxygen to support the bacteria decomposing the waste, and so each gallon of effluent is capable of lowering the dissolved oxygen of 1000 gallons of water from 4 to 3 ppm, enough to stress marine organism and increase the size of "dead zones." There is also a significant oxygen demand caused by nutrient-fueled (nitrogen and phosphorus) algae blooms, though this is very difficult to quantify. In total, each flush will impact about 20,000 gallons of Bay water, roughly a back yard swimming pool worth. Not so much, given the size of the Bay. On the other hand, in a harbor with poor tidal flushing and thousands of boats (Deale has over 2,000 slips), it could be material if the calculation were taken to its illogical extreme, another sort of logical fallacy and rhetorical insult. In practice, only a small fraction of the boats see their owners on any given weekend, and fewer during the week.
How does this compare to other pollutant loads? A single gallon of glycol antifreeze concentrate (ethylene or propylene), containing about 750,000 ppm BOD5, may amount to more oxygen demand than an entire year of occupancy by a live-aboard. Street storm water run-off typically averages 20-60 ppm BOD5 and is of vast volume; my driveway alone would contribute BOD5 equivalent to 36 flushes. Logically, since a flush is only food we are finished with, a flush can contain no more than the BOD5 of a fraction of a sandwich or a banana peel, a pollutant load that wouldn't offend anyone too greatly. Yes, the pollutant load from a type I unit is tiny.
There are over 300 pump-out stations in the Maryland Chesapeake and nearly as many in the Virginia Chesapeake, the result of a state funded project. The fee is capped at $5.00 and is often waved for slip holders and fuel purchasers. It is difficult to pump-out when the water freezes; harbors typically freeze for 2-6 weeks in the central to northern Bay, and piping may be frozen on some other cold days, though most pump-out stations are open all year. They just don't work on the cold days.
Back to opinion.
Would I use a type I unit if installed on my boat? Not in a NDZ. Not anchored with other boats. Not in a very confined harbor. There is some chance of disinfection failure, as demonstrated by the data, and there no point in presenting the risk of infection. In the main course of the Chesapeake? I suppose I might. Or I might just pump out a few times a month while getting fuel, which is quite painless and often given as a free perk. That's what my kid would want me to do and I would listen. But like recycling, I wouldn't necessarily believe it actually helped in many cases. Would a type I on the open ocean? Absolutely. In fact, I wouldn't hesitate to use a type III closer in-shore than 3 miles. Sit on the beach, watch the dolphins and ponder the vastness of the sea. Toxic waste is one thing--natural waste is another.
Is bleaching poop real treatment? Yes and no. Why don't the manufacturers link to this data or provide other similar 3rd-party performance information? Because the data is not easy to understand and doesn't sell. Is the pollutant load from a few type I units material in tidal waters? Boat US claims it represents 0.0035% of the total load. But it also represent the actions of only 0.006% (guess 1,000 active type I units/17,500,000 people) of the people in the Chesapeake Bay drainage area, so it's material on a per-capita basis.
You judge. Personally, I think it's small beans. I believe every bit helps and that type I MSD users in confined waters (designated NDZ or not) or places they see swimmers should use pump-outs or wait until in more open waters--a reasonable compromise. In open salt water bays and ocean waters, where dilution is vast, whales poop and salt kills human pathogens in minutes or hours, it's small beans.
references:
CWA of 1972. MSDs are in section 312, page 156.
http://epw.senate.gov/water.pdf
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