Don't use the
processed water for two or three weeks after starting the filter. You
should have a bypass valve to divert the first few weeks of water back to
the environment until the schmutzdecke is established. Again, test the
water before use. Tested water should come from the diverter so you don't
get bad water in the clear well.
One of the worst
possible sources of water is collection from rooftops. Among the
contaminants are chemicals leached from the roof, unless it's steel, bird
droppings, wind carried dust, spores, other detritus, and leavings from
other animals that have access to the roof. In tests, rooftop collected
water has high percentages of biologicals and other bad things. However,
also in tests, the use of a slow sand filter removes virtually all of
these nasties, making a collected water supply a viable alternative for
potable water. Processed water from this source also makes it viable for
irrigation, if having E Coli in your veggie garden bothers you at all,
since E Coli is one of those critters usually transferred in scat. Several
cities in the Northeast have begun using sand filters to process runoff
water, making it EPA clean for irrigation and other uses.
It's a very good idea
to use a first flush diverter to remove the first batch of collected
rainwater in such systems. Some diverters use a fast sand filter or
gravel filter to remove larger contaminants. But that's another story, so
we'll leave that for another time.
Here's a picture of a
basic 50 gallon sand filter courtesy of David Tarsi, who has done quite a
lot of research into homestead style slow sand filtration:
For those who wonder
if such filters work, here's a picture of water input to a slow sand
filter, and a close-up of the water out of that filter.
Maintenance of a Slow
Sand Filter
Since this filter uses
only activated charcoal as a manufactured product, the only maintenance
required is to break up the schmutzdecke occasionally, when the water flow
becomes very slow. This is done by opening the top and stirring up the
very topmost layer of sand where the schmutzdecke resides. Since you
don't want this messy water in your potable system, shut off the delivery
valve and open the diverter valve before stirring up the schmutzdecke.
Open the flush valve and run water through gently until the water runs
fairly clean. Don't use a lot of pressure or fast flow so you won't lose
sand. Easy does it is the key. When this rinse is complete, with
relatively clear water flowing from the flush valve output, close off the
flush valve and start the filter once again. You must leave the diverter
valve open and the delivery valve closed until the schmutzdecke is once
again established. This will require at least two weeks, and you don't
want unprocessed water to enter your potable water system. It's also very
important that you never, ever back flush a slow sand filter, since this
will destroy everything you've worked for and the filter must be rebuilt.
The only other
maintenance necessary is to replace the activated charcoal occasionally.
The frequency of this is dependent on the manufacturer of the charcoal and
the amount of chemicals left in the filter processed water. Usually,
manufacturers recommend every six months to a year for replacement of
granulated charcoal. The charcoal is usually manufactured from coconut
shells and isn't terribly expensive if purchased in bulk. If you've made
your own charcoal filter, it's certainly not an excessive cost.
And there you have it:
a method to use natural functions and some activated charcoal to make bad
water into good water. Enjoy!
