Sunday, August 21, 2011

Poo Pumping Protecole: Type I MSDs

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.


Most of boaters use type III MSD (a simple holding tank) and either pump-out off shore (the regulations require 3 miles) or at a pump-out station. Perhaps 15% cheat and pump-out where ever they please (MD DNR survey). If we install a type I devise, we can discharge at any location except EPA designated no discharge zones (NDZ). Please read that link; there may be one near you--we moor in one (Herring Bay, MD).

What is a type I MSD? The Raritan Engineering unit, pictured above, macerates the waste and then treats with bleach. The bleach is derived from electrolysis of seawater. Groco also makes a type I unit (ThermoPure II) which treats by cooking the waste. The unit is very battery hungry (20 AH/flush) and is not too popular among sailors.

How effective are they? Read this EPA evaluation of type I MSDs, if you like detail. You won't find this sort of information on manufacturer web sites--unfortunately, it doesn't help sell.

EPA Summary Data (results in mg/L)
Annalyte     After Treatment Result     EPA Sewage Treatment Standard
BOD5                   780                         45
TSS                     1,000                      45
Fecal Coliform       < 82                     200 (swimming areas)

The data was quite variable, with standard deviations over 100%.

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 this good enough? With any reasonable mixing model, yes. Certain vocal Raritan boosters redirect any criticism by pointing fingers at sewage spills, bird poop, storm run-off, and spilled chemicals--a rhetorical approach which insults the reader. They claim NDZs increase illegal dumping of untreated sewage, which is silly since the Bay has been no-discharge for untreated waste for many years. They claim that the effluent is as clean as Bay water, but present no data. I suppose we should take this on faith. Would the owners go swimming in the plume while they are pumping out? Probably not, and that presents an interesting double standard. It comes back to the mixing model.
Enough personal opinion. Back to facts.

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.



CWA of 1972. MSDs are in section 312, page 156.

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