[permaculture] any biologists out there?

Lawrence F. London, Jr. venaurafarm at bellsouth.net
Sat Dec 19 15:49:52 EST 2009


paul wheaton wrote:
> When heating water with solar or the jean pain method or .... whatever
> ... it seems wise to consider legionnaires disease.  But in order to
> consider it, it seems we need to know the enemy.  And we're coming up
> short on a few things.
> http://www.permies.com/permaculture-forums/2607_0/alternative-energy/alternative-hot-water-and-legionnaires-disease
> The question is:  what is the reproduction rate of legionella?  Would
> they reproduce faster in pond water than in, say, well water?
> Distilled water?

Kevin Topek, in this list, might have an answer as he seems 
knowledgeable about health and safety issues. Misha Gale-Sinex, once in 
this forum (see the archives) and occasionally in sanet-mg list will 
probably have a quick answer for you. Of course, Google it.

I never thought about the possibly of legionella on the farm or 
homestead. How did this subject come up in the first place? If you're 
heating DHW for dish wash, heat, bathe etc. then it would seem the only 
issue would be getting water on you rather than in you or on washed 
dishes used wet or breeding in clothes as well as airborne pathogens 
from dried particles (does it need a moist environment to survive?) or 
from water vapor, humidity, condensation on objects and steam.

Do I assume correctly that it presents a risk from external contact
or only from internal contact, including breathing the contaminants as 
airborne dry particles or moist, in steam, mist, spray?

What environment does it need to survive and propagate? What nutrients 
does it need? Where is is usually found?

There is also the known risk of pathogens breeding in hot tub water.
The Japanese obviously figured out how to avoid this problem over the 
centuries of bath house use.

One way to avoid the problem, just as with common hot water heaters,
used, of course, for storage, long term, might be to use solar or Jean 
Pain apparatus to transfer heat to your DHW
by way of a heat exchanger located in the actual DHW storage tank, 
heating a continual source of clean water. Instead of running your clean 
cold water infeed through the actual heating apparatus you run it into 
your storage tank and heat it with a heat exchanger carrying hot water 
from the collector, recycling that fluid continuously while your 
pressurized DHW cycles from its source (city, cistern or well) through 
your storage tank to where you use it, never in contact with the heating 
  equipment. Remember the sludge buildup inside conventional hot water 
heaters (minerals and microorganisms, if I am correct)? Most of this 
could probably be avoided using a heat exchanger as a DHW heat source.
Or just use hot water direct from the source for house or greenhouse heat.

Another option is using a solar closet, heating water in barrels located
in a super insulated room with hot air from a collector inside a glazed 
case. Cycle hot water from your Jean Pain equipment or solar collector 
through the barrels also. Extract the heat by way of a heat exchanger to 
generate DHW, stored in its own insulated tank or figure out a way to do 
demand batch DHW generation in a hot box of some sort. The heat 
exchanger itself, if it can contain an adequate volume of water, might 
serve that purpose by default. Google "solar closet" and "Nick Pine"
for more info on solar losets or read the Usenet newsgroup 
alt.solar.thermal or alt.energy.renewable. I have archives of saved 
Usenet posts on Nick and his solar closet technology here:
Top level directory:
http://www.ibiblio.org/ecolandtech/alternative-energy/
http://www.ibiblio.org/ecolandtech/alternative-energy/solar/
This is solar closet central:
http://www.ibiblio.org/ecolandtech/alternative-energy/solar/Nick.Pine/



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