Introduction
Please note: I strongly suggest reading
the terms of
use and license regarding the content of this site.
The slow sand filter projects documented on this website have taken
place in the pacific northwest area of Washington state, USA. The
first filter project (filter one) was started in early 2007. All of
the projects are ongoing and will continue as long as the author is
able. The water quality tests that have been done by epa certified
testing laboratories are noted as such. The preliminary field tests
are done onsite and are also noted as such. The researcher has a
four year degree from the University of Washington (class of 2006)
in environmental studies plus 35 years of experience in
non-academic work. Chemicals used for drinking water treatment such
as chlorine, or ozone that produce toxic cancer causing byproducts
are not used in these filters. The longest running slow sand water
filter project this site documents has been ongoing for 17 years
(it was started in the summer of 2007). It is still running and
will continue as long as possible.
We are in the process of updating
the old lit cited links.
As of 08-21-2024; all links that are still availble have been
updated.
Some of the content for several links has disappeared permanently,
and we are searching for info.
please note: this page was first written 16 years ago and is still
here. We are still working on slow sand filters; and continuously
making improvements on them.
Keep in mind that "Backwashing" a biological sand filter
will destroy it.; and that a biological sand filter is
constantly full of water up
to and covering the top surface of the sand inside by at least
1 inch or more - the sand must
not be exposed to air.
Know that the content of this site will change considerably as
this study continues.
Rain barrels are now legal in Washington
state! For over 90 years it has been illegal to catch rainwater in
Washington state.note 2
As of October 9 2009, catching roof water is no longer a crime!
The
department of Ecology in Washington state (the D.O.E.) has finally
clarified the law so as to allow individuals to catch rainwater for
their own use. (from this preceding link, click on the links at
the D.O.E. site on the upper right hand side of their page that say
"new" highlighted in yellow.)
As of December 2014, research and development has been done on 5
separate slow sand filter designs:
FLOW SUMMARY FOR TESTED SUCCESSFUL DESIGNS OF SMALL
SLOW SAND WATER FILTERS
See faq 31 for an explanation of flow
rates
or
the U.S.D.A. site has a good explanation of water flow through
sand
|
Filter 1 (fourth
configuration)*
input: roof water
using first flush diverter. 3 tab comp. roof.
top layer of sand .15mm effective size
bottom layer of sand:
non-graded. approx. .65mm effective size
electric pump recirculation at less than 1 L/hr.
container diameter: 23 inches
sand surface area .26791 sq m
container depth: 30 inches
|
Filter 2*
input: pond water
top layer of sand: .15mm effective size
bottom layer:
non-graded "fine" sand approx .30mm effective size
container diameter: 22 inches
sand surface area .2452 sq m
container depth: 40 inches
2010-09-16: this filter now
has a float valve installed
|
Filter 3 (with float valve flow
control).
input: shallow well water
top layer of sand: .25mm effective size
bottom layer: 35mm effective size.
container diameter: 22 inches
sand surface area .2452 sq m
container depth: 40 inches
|
Date.
|
| 12 L/hr (10 cm supernatant
water depth) (.045 meters/hr) |
no measurement |
no measurement |
2008-01-02 |
| 3 L/hr (10 cm supernatant water
depth) (.011 m/hr) 12 months continuous operation |
no measurement |
no measurement |
2008-12-01 |
| no measurement |
72 L/hr (20cm supernatant water
depth) (.286 meters/hr) |
90 L/hr (16.5cm supernatant
water depth) (.358 meters/hr) |
2009-02-08 |
14.1 L/hr (10 cm supernatant
water depth) (.053 meters/hr) 2 months running time
was totally frozen in Dec 2008 / Jan 2009. |
42 L/hr (20cm supernatant water
depth) (.167 meters/hr) |
45 L/hr (16.5cm supernatant
water depth) (.179 meters/hr) |
2009-04-08 |
| 13.84 L/hr (14cm supernatant
water depth) (.052 meters/hr) |
40 L/hr (20cm supernatant water
depth) (.159 meters/hr) |
48 L/hr (18.5cm supernatant
water depth) (.191 meters/hr)** |
2009-04-26 |
| 13 L/hr (14cm supernatant water
depth) (.049 meters/hr) |
36 L/hr (20cm supernatant water
depth) (.146 meters/hr) |
45 L/hr (18.5cm supernatant
water depth) (.183meters/hr) |
2009-05-11 |
| 12 L/hr (14.5cm supernatant
water depth) (.045 meters/hr) |
36 L/hr (20cm supernatant water
depth) (.146 meters/hr) |
36 L/hr (18.5cm supernatant
water depth) (.146 meters/hr) |
2009-08-07 |
| 12 L/hr (14.5cm supernatant
water depth) (.045 meters/hr) |
36 L/hr (20cm supernatant water
depth) (.146 meters/hr) |
25.7 L/hr (18.5cm supernatant
water depth) (.104 meters/hr) |
2009-09-04 |
| 9 L/hr (14.5cm supernatant
water depth) (.034 meters/hr) |
22 L/hr (20 cm supernatant
water depth)(.09 meters/hr)
added 48 liters of roof water from diverter output |
28.8 L/hr (18.5 cm supernatant
water depth) (.117 meters/hr)
added 48 liters of roof water from diverter output |
2009-09-21 |
| 10.74 L/hr (14.5cm supernatant
water depth) (.040 meters/hr) added 12 litres of undiverted roof
water |
22 L/hr (20cm supernatant water
depth)(.09 meters/hr) (no significant change)
added 48 liters of roof water from diverter output |
25.7 L/hr (18.5cm supernatant
water depth) (.103 meters/hr)
added 48 liters of roof water from diverter output |
2009-10-08 |
| 9.24 L/hr (14.5cm supernatant
water depth) (.035 meters/hr) |
21 L/hr (20cm supernatant water
depth)(.086 meters/hr)
|
21.81 L/hr (18.5cm supernatant
water depth) (.089 meters/hr)
|
2009-10-12 |
| 10.58 L/hr (14.5cm supernatant
water depth) (.039 meters/hr) |
20.57 L/hr (20cm supernatant
water depth)(.0839 meters/hr)
source water changed to surface well
|
21.17 L/hr (18.5cm supernatant
water depth) (.086 meters/hr)
source water changed to surface well
|
2009-11-05 |
| 9.00 L/hr (14.5cm supernatant
water depth) (.0335 meters/hr) |
18.95 L/hr (20cm supernatant
water depth)(.077 meters/hr)
|
19.46 L/hr (18.5cm supernatant
water depth) (.079 meters/hr)
|
2009-12-04 |
| 0 L/hr Filter
frozen*** by below 0°C weather |
0 L/hr Filter
frozen*** by below 0°C
weather
|
0 L/hr Filter
frozen*** by below 0°C
weather
|
2009-12-07 |
| 11.25 L/hr (14.5cm supernatant
water depth) (.042 meters/hr) |
35 L/hr (20cm supernatant water
depth)(.142 meters/hr)
|
30 L/hr (18.5cm supernatant
water depth) (.122 meters/hr)
|
2010-01-01 |
| 11.25 L/hr (14.5cm supernatant
water depth) (.042 meters/hr) |
27.7 L/hr (20cm supernatant
water depth)(.113 meters/hr)
|
28.8 L/hr (18.5cm supernatant
water depth) (.117 meters/hr)
|
2010-01-09 |
| 8.37 L/hr (14.5cm supernatant
water depth) (.031 meters/hr) |
32.7 L/hr (20cm supernatant
water depth)(.133 meters/hr)
|
27.7 L/hr (18.5cm supernatant
water depth) (.112 meters/hr)
|
2010-02-07 |
| 9.47 L/hr (14.5cm supernatant
water depth) (.035 meters/hr) |
24 L/hr (20cm supernatant water
depth)(.098 meters/hr)
|
25.74 L/hr (18.5cm supernatant
water depth) (.105 meters/hr)
|
2010-03-01 |
| 8.47 L/hr (14.5cm supernatant
water depth) (.032 meters/hr) |
24 L/hr (20cm supernatant water
depth)(.098 meters/hr)
|
25.74 L/hr (18.5cm supernatant
water depth) (.105 meters/hr)
|
2010-03-26 |
| 8.47 L/hr (14.5cm supernatant
water depth) (.032 meters/hr) |
24 L/hr (20cm supernatant water
depth)(.098 meters/hr)
|
24.25 L/hr (18.5cm supernatant
water depth) (.099 meters/hr)
|
2010-04-30 |
| 10.3 L/hr (14.5cm supernatant
water depth) (.038 meters/hr) |
29 L/hr (20cm supernatant water
depth)(.118 meters/hr)
|
34 L/hr (18.5cm supernatant
water depth) (.139 meters/hr)
|
2010-09-16 |
| 11.15 L/hr (14.5cm supernatant water depth) (.0416
meters/hr) |
26.4 L/hr (20cm supernatant
water depth)(.108 meters/hr)
|
28.2 L/hr (18.5cm supernatant
water depth) (.115 meters/hr)
|
2010-12-19 |
| 16L/hr (14.5cm supernatant
water depth) (.0597 meters/hr) |
28 L/hr (20cm supernatant water
depth)(.1142 meters/hr)
|
33 L/hr (18.5cm supernatant
water depth) (.1346 meters/hr)
|
2011-02-06 |
| 12.2L/hr (14.5cm supernatant
water depth) (.0455 meters/hr) |
22.29 L/hr (20cm supernatant
water depth)(.091 meters/hr)
|
27.23 L/hr (18.5cm supernatant
water depth) (.111 meters/hr)
|
2011-03-08 |
| 13.56L/hr (14.5cm supernatant
water depth) (.0506 meters/hr) |
26.67 L/hr (20cm supernatant
water depth)(.1087 meters/hr)
|
28.24 L/hr (18.5cm supernatant
water depth) (.115 meters/hr)
|
2011-04-16 |
| 10.64L/hr (14.5cm supernatant
water depth) (.040 meters/hr) |
32.21 L/hr (20cm supernatant
water depth)(.131 meters/hr)
|
31.86 L/hr (18.5cm supernatant
water depth) (.130 meters/hr)
|
2011-07-02 |
| 16.14L/hr (14.5cm supernatant
water depth) (.060 meters/hr) |
38.71 L/hr (20cm supernatant
water depth)(.158 meters/hr)
|
41.62 L/hr (18.5cm supernatant
water depth) (.170 meters/hr)
|
2011-09-14 |
| 12 L/hr (14.5cm supernatant
water depth) (.0448 meters/hr) |
28.685 L/hr (20cm supernatant
water depth)(.117 meters/hr)
|
32.8 L/hr (18.5cm supernatant
water depth) (.1337 meters/hr)
|
2011-11-25 |
| 10.48 L/hr (14.5cm supernatant
water depth) (.039 meters/hr) |
44.31 L/hr (20cm supernatant
water depth)(.181 meters/hr)
|
31.86 L/hr (18.5cm supernatant
water depth) (.130 meters/hr)
|
2012-03-06 |
| 15 L/hr (14.5cm supernatant
water depth) (.056 meters/hr) |
58.42 L/hr (20cm supernatant
water depth)(.238 meters/hr)
|
37.9 L/hr (18.5cm supernatant
water depth) (.177 meters/hr)
|
2012-08-09 |
| 13.14 L/hr (14.5cm supernatant
water depth) (.049 meters/hr) |
42.85 L/hr (20cm supernatant
water depth)(.174 meters/hr)
|
43.9 L/hr (18.5cm supernatant
water depth) (.179 meters/hr)
|
2012-10-03 |
| 10.98 L/hr (14.5cm supernatant
water depth) (.041 meters/hr) |
48 L/hr (20cm supernatant water
depth) (.196 meters/hr)
|
28.57 L/hr (18.5cm supernatant
water depth) (.117 meters/hr)
|
2013-04-30 |
| 10.00 L/hr (14.5cm supernatant
water depth) (.037 meters/hr) |
51.4 L/hr (20cm supernatant
water depth) (.192 meters/hr)
|
42.4 L/hr (18.5cm supernatant
water depth) (.158 meters/hr)
|
2013-08-27 |
| 12.32L/hr (14.5cm supernatant
water depth) (.046 meters/hr) |
33.96 L/hr (20cm supernatant
water depth) (.139 meters/hr)
|
37.8 L/hr (18.5cm supernatant
water depth) (.154 meters/hr)
|
2014-03-13 |
| 25L/hr (14.5cm supernatant
water depth) (.093 meters/hr) |
36 L/hr (20cm supernatant water
depth) (.147 meters/hr)
|
37.5 L/hr (18.5cm supernatant
water depth) (.153 meters/hr)
|
2014-10-09 |
| 26.86L/hr (14.5cm supernatant
water depth) (.100 meters/hr) |
34.6 L/hr (20cm supernatant
water depth) (.141 meters/hr)
|
30 L/hr (18.5cm supernatant
water depth) (.122 meters/hr)
|
2015-04-05 |
FLOW SUMMARY FOR FILTER 4 AND FILTER 5 *
|
Filter 4
(3rd configuration)
.45 mm effective size bottom sand 600 lbs
.24 mm effective size top sand 80 lbs
dc pump is used to recirculate water
filters roof water from composition roof
sand surface area: .26791 sq. m.
container depth 32 inches
started 2011-11-01 |
Filter
5
.25 mm effective size bottom sand 700 lbs
.15 mm effective size top sand 150 lbs
filters roof water from composition roof
sand surface area: .2452 sq. m.
container depth 40 inches
started 2012-05-01 |
Date |
| 30 L/hr (18cm supernatant water
depth) (.112 meters/hr) |
37.9 L/hr (22cm supernatant
water depth) (.154 meters/hr) |
2012-08-09 |
| 31.101 L/hr (18cm supernatant
water depth) (.116 meters/hr) |
28.4 L/hr (22cm supernatant
water depth) (.1158 meters/hr) |
2012-09-27 |
28 L/hr (18cm supernatant water
depth) (.105 meters/hr)
first day of temps below 4° C (40° F) at night this season |
29 L/hr (22cm supernatant water
depth) (.118 meters/hr)
first day of temps below 4° C at night this season |
2012-10-03 |
| 40 L/hr (18cm supernatant water
depth) (.149 meters/hr) |
3.7 L/hr (22cm supernatant
water depth) (.015 meters/hr) first flush diverter malfunction;
turbid water clogged filter |
2013-04-30 |
| 92 L/hr (18cm supernatant water
depth) (.345 meters/hr) sand changed. .30 mm effective size. May
2013 |
24 L/hr (22cm supernatant water
depth) (.099 meters/hr) sand changed, .25 mm effective size. May
2013 |
2013-08-27 |
| 75 L/hr (18cm supernatant water
depth) (.280 meters/hr) sand changed. .30 mm effective size. May
2013 |
13.35 L/hr (22cm supernatant
water depth) (.054 meters/hr) sand changed, .25 mm effective size.
May 2013 |
2014-03-13 |
| 45 L/hr (18cm supernatant water
depth) (.168 meters/hr) sand changed. .30 mm effective size. May
2013 |
16.98 L/hr (22cm supernatant
water depth) (.069 meters/hr) sand changed, .25 mm effective size.
May 2013 |
2014-10-09 |
| 56.25 L/hr (18cm supernatant
water depth) (.210 meters/hr) sand changed. .30 mm effective size.
May 2013 |
9 L/hr (22cm supernatant water
depth) (.037 meters/hr) sand changed, .25 mm effective size. May
2013 |
2015-04-05 |
| *Filter 4
and 5 are the newest filters. |
|
Notes:
2009:
*Filter 2 and Filter 1 stopped flowing
for three days due to below 0° C. temperature. 2009-03-11. All
filters were restarted at the beginning of 2009, as they were
frozen and the biolayer in each was destroyed.
**The supernatant water depth was
increased in filter 3 due to a change in the float valve setting
after the measurement taken 2009-04-08.
**48 L/hr at 18.5 cm actually
represents a decrease in
flow rate of L/hr per cm of water depth.
*** The temperatures have ranged from
-2° C (28°F) during the day to -11°C (12°F) at night. The below
freezing weather actually started (2009-12-04) but the filters
continued to flow until 2009-12-07.
2010 (including POND FILTER):
As of November 23 2010, All filters - filter 1,2,3 and the
pond filter are frozen and have ceased operation. Some damage is
expected. The temperature is at minus 9.5 degrees Centigrade night
(15° F) and minus 5.5 degrees Centigrade day (22° F) with 7.6 cm (3
inches) of snow on the ground.
As of December 8 2010, All filters - filter 1, 2,3 and the
pond filter are back on line and operating. The pond filter stayed
inoperative the longest. Possibly because the output pipe runs
right through the frozen water on the inside of the filter
thus making it take longer to thaw out.
2011:
As of Jan 5 2011,Filter 1 and the pond filter are frozen and
have not been running for 8 days. The temperature at night has been
minus 8 degrees Centigrade (17° F) and during the day 0 degrees
Centigrade (32° F). Additional snowfall was 10 cm ( about 4 inches)
as of December 28. Filter 2 and filter 3 are still running with
water from the shallow well continuing to flow and filling the
cistern which also has not frozen.
As of Feb. 06 2011 the pond filter is flowing at 144 l/hr.
which is .553 meters per hour. (the sand surface area is .2600 sq
meters. This flow rate is probably just slightly too high for good
purification, so the water will not be ok for consumption (see link
below).
As of March 8, 2011 the pond filter is flowing at 128 l/hr.
which is .492 meters per hour.
As of April 16, 2011 the pond filter is flowing at 138 l/hr.
which is .530 meters per hour.
July, 2011The filters 1,2,and 3 were inactive for 5 days in
the first of July
2012:
Filter 1 was frozen and inactive for 1 week starting Jan. 15. There
was a massive snow storm / ice storm here - many trees down and the
power was out for 2 days. 14 inches of snow with a 1/8 inch coating
of ice was the total. A state of emergency was declared by Governor
Christine Gregoire. Filter 2 and 3 did not freeze and kept
operating throughout the entire time. Temperatures averaged 25
degrees F for 5 days. All filters are now operating as of Jan. 24,
2012. Both pond filters were frozen for 4 days.
Originally, flow
measurements were taken by recording the number of minutes required
to fill a 12 litre container.
Most recently (2010-12-19) we are using a 4 litre container, as it
is more indicative of instantaneous flow volume when measuring the
flow from a filter that is not fed by a steady flow of water.
The 4 litre container was tested against the 12 liter container
using filter 2 which has a steady flow (its input is controlled by
a float valve and pressurized water). The 4 litre container was
found to result in flow measurement precision and accuracy equal to
the 12 litre container when the flow volume totals were
averaged.
1 cubic meter = 1000 litres 1 litre = .001 cubic meter
We use flow rate per unit area per unit of time because we are
interested in quantifying how fast the water flows past a given
level in a given area. Simply measuring liters per hour does not
give the full story. For example; 20 liters per hour from a 25 cm
diameter container does not allow the same sand particle contact
time as 20 liters per hour from a 75 cm diameter container, and
sand particle contact time is critical for allowing maximum
purification.
flow
rate should be between .1 and .4 meters per hour (ideally between
.1 and .3 meters per hour for the best results
This is how to figure the flow rate by just measuring how many
litres flow per hour:
flow rate in meters per 1 hour = [(liters per
1hr)÷1000]÷(area of sand bed surface in square meters)
Explanation:
Here we will use X to mean multiply; and / to mean "per" as in per
hour; and the ÷ to mean divide
L means litres and m means meters
In this formula, a cubic meter is represented by meters cubed or
just: m3
(in other words meters X meters X meters or think of length X width
X height the way we find volume)
And the area of the sand surface is represented by meters squared
or just m2
meters X meters (length X width the way we find area)
Now, know that 1 cubic meter = 1000 Litres, or more simply:
m3 = 1000L
Divide litres by 1000 to get cubic meters; or multiply litres by
.001 to get cubic meters
If m3 = 1000L, then cubic meters/hour = Litres/hour
÷1000
(the per hour thing is there because we need to have a concept of
motion over a time period
since it is 1 hour it does not change the result division by 1 or
multiplication by 1 is identity)
or more simply: m3 per hour = (L per hour)÷1000
Now; m/hr = [(L/1hr)÷1000]÷m2
or just m/1hr = (m3/1hr)÷m2 (the
m3 and m2 cancel out into just m so we end up
with m/1hr)
Now, the above translated into language:
flow rate in meters per hour = volume in cubic meters per hour ÷
sand surface area in square meters
and finally back to where we started:
flow rate in meters per 1 hour = [(liters per
1hr)÷1000]÷(area of sand bed surface in square meters)
A simplified version of the above is:
For the shorter large barrel with a sand surface area of .26791 sq
meters (23 inch diameter):
flow rate in meters per 1 hour = (53.75) ÷ (time in seconds to fill
a 4 litre container)
For the taller smaller diameter barrel with a sand surface area of
.2452 sq meters (22 inch diameter):
flow rate in meters per 1 hour = (58.73) ÷ (time in seconds to fill
a 4 litre container)
|
HYDROCARBONS
(TPH) IN ROOFWATER ARE SIGNIFICANTLY REDUCED BY A SLOW SAND FILTER
SYSTEM
The most recent tests on fiter 1 show that a slow sand filter
system of this design is capable of significantly reducing TPH
(Total Petroleum Hydrocarbon) contamination in the water that
passes through it. In this case the pre-filter system contamination
is
2.9 milligrams per liter in the winter from water directly
off of the roof. When we are talking about clean water, this is
an unacceptable level for use as a water source without proper
filtering.
The slow sand filter system described here, which is
in use with filter 1, has been in operation for 2 years without
changing or cleaning the filter media. This system reduces these
petroleum hydrocarbons from the roofing material (heavy oils), and
(possibly) from air pollution (Diesel), down to less than one tenth
of a milligram per 1 liter of water each (2 tenths of a miligram
total); and this is when the filter is LEAST effective at 32
degrees F. This exceeds the
MTCA
Method A cleanup level for TPH in ground water as per the
Washington State Department of Ecology 54 (page 4) by a factor of 10.
The tests also show that petroleum hydrocarbons are removed by the
first flush diverter to a level of less than 1 part per million
(this exceeds the MTCA Method A requirement for groundwater which
is 1mg/L). Also we know from the tests that over 40 percent of the
hydrocarbons are Diesel. We do not know exactly how much
hydrocarbon comes from local air pollution, which is significant in
this area. The test for how much is due to the roofing material and
how much is due to air pollution will have to wait. Funding is
limited, and these tests are extremely expensive. The US EPA
considers petroleum hydrocarbons (oil and grease) one of 46 other
"non-priority pollutants"
55. There are not any
"official" specific regulations for levels of TPH contamination in
water set by the EPA. One of the reasons is that there are hundreds
of compounds in petroleum and it is extremely difficult to identify
each one and the effects each has on living organisms . We do know
that there are between 5 and 10 million metric tons of oil entering
the marine environment every year (as of 1986), and that oil spills
are lethal to most forms of life. In spite of that, the EPA has yet
to establish strict guidelines for TPH in water; and the studies
they have done fail to show toxicity to humans. However,
concentrations of some individual elements in TPH pollution above
.001 mg/L have been shown to be harmful to aquatic life.
56 (p 203-206), 57
(p 220)
In addition to removing TPH contamination, Filter 1 removes
coliform bacteria from 30,000 cfu per 100 ml down to 10 cfu per 100
ml (log credit of 3.477).This exceeds the
Washington state Class AA (extraordinary) surface water
requirements for the absence of coliform by a factor of 5, and
this is when it is operating at minimum efficiency in 32 degree
(Fahrenheit) weather.
Update, 2015-02-21:
Filter 1, 2, 3, 4, and 5 are still running and producing clean
water. More tests will be done as time and finance permits. Filter
1 has not had the sand changed for 7 years; and has only been
wet-harrowed (cleaned) once in that time. The flow rate on filter 1
has stabilized to approximately 12 liters per hour overall average.
Of the 3
original five gallon filters set up here only one system is now
running (as of February 2015);
the other two systems
failed miserably.
Update, 2014-06-15:
Filter 1, 2, 3, 4, and 5 are still running and producing clean
water. More tests will be done as time and finance permits. Filter
1 has not had the sand changed for 6 years; and has only been
wet-harrowed (cleaned) once in that time. The flow rate on filter 1
has stabilized to approximately 12 liters per hour overall average.
There are now
three 5 gallon slow sand filters running here. They have been
in operation since September of 2013. There are also 3 pond filters
in operation here. All of the filters, including the experimental 5
gallon filters improve the quality of water that runs through them.
Filter 1 is the best so far. The 5 gallon filters are the least
effective, but they do work marginally.
2011-01-13: The pond
water filter test shows fecal coliform at less than 2 MPN per 100
ml.(less than 2 organisms per 100 ml of water. MPN means Most
Probable Number)
see this website for a good expanation of "MPN" per 100ml Not
bad considering birds, squirrels, and other wildlife use the pond
daily.
Build a Cistern and store water for the
summer!
or Use a slow sand filter to keep a pond
or fountain clean
NEW A summary of roofwater
harvesting procedures
2010-01-05 Tests to determine total petroleum hydrocarbon pollutants
in roof water from a composition roof are now available
2010-01-05: Total Petroleum Hydrocarbons (heavy oils
and Diesel together) are significantly reduced by the slow sand
filter down to less than 2 parts per ten million. Read the
details
below: See a
YouTube
video of the roof water filter here
2010-05-18 Tests on filter
2 and 3 to determine total organic carbon content and on filter 1
to determine Snohomish county water quality standards compliance
and total organic carbon content have gone in. The results will be
posted when received.
2010-06-15: The filters passed all the tests by
comfortable margins. The TOC was a little on the high side, but
still acceptable, and was much better in filter 2 and 3 actually
being reduced.
1. The first filter
(filter 1 2007-08-13)
configuration was put together with very casual attention to detail
and operated with only "human" power (10 gallons of water was added
manually each day). This was done deliberately to verify the
validity of this question: Can a working biological sand filter be
put together with mostly recycled material at very low cost (under
25 dollars) using construction grade sand and average skills? The
answer - partially. The test results showed no fecal coliform
bacteria from stagnant roof water runoff but some coliform present.
This water would be ok for everything except consumption and better
than water straight from a "rain barrel".
2. The second configuration of
filter 1
2007-10-09 was the addition of graded sand (.15 mm effective
size) to the top layer of this filter and ungraded "fine" sand to
the bottom layer. These were the only changes to the filter detail.
This filter removed 99.9 percent of all coliform bacteria
(including ecoli and fecal coliform) and removed more of the color
from the roof water runoff - still not ok for drinking on a regular
basis but 99.9 percent better than the rain barrel water and much
safer. With only close attention to the detail of the size of the
top layer of sand, the filter is now functional.
3.The third configuration of
filter 1
2008-02-12 was the addition of a first flush diverter to the
system. This allowed for significant improvement of turbidity (as
determined by visual inspection) and some reduction of the bacteria
(as determined by laboratory tests) before the water was put into
the filter. Still the same result - removal of 99.9 percent of all
coliform bacteria.
4. The fourth
configuration of filter 1 2008-02-12 involved the
addtion of a small dc powered pump to recirculate the water through
the filter. This was an attempt to keep the biofilm alive without
having to manually add water each day. The dc pump is operated with
a very small amount of power and can be run by a solar panel. This
worked. The filter still removed 99.9 percent of all coliform. As
of 2008/12/01, this configuration of Filter 1 has been in
continuous operation for 14 months without disturbing the biolayer
(schmutzdecke). The flow rate is 3 liters per hour as of
2008/12/01. The reason for this long undisturbed run is to
determine if a slow sand filter becomes more efficient at removing
contaminants as it ages. The compromise would be in flow rate:
significantly reduced flow rate to obtain significantly increased
water quality. This filter uses water from a composition roof as
its source. This water should contain unacceptable amounts of
hydrocarbons from the roof surface. The question is: will the aged
slow sand filter remove enough chemicals
and pathogens to
produce potable water?
Update 12/18/2008: Two samples
of water were taken from this filtering system (the fourth
configuration of
filter 1) just before the freezing weather
hit: Filtered water and unfiltered water. The filtered water had
been through the slow sand filter and the unfiltered water was
taken from the storage container that provides the raw water source
for the filter.(
filter 1) The samples were put into two
separate containers which were identical and were cleaned and
sterilized. These containers were put in a building where the
temperature was 32 degrees F. The filtered water froze and the
unfiltered water did not freeze. It is a known scientific fact that
water containing dissolved substances freezes at a lower
temperature than water with less dissolved substances. (this is
why salt is put on roads to "thaw" out the ice - the salt slowly
lowers the freezing point of the ice and causes it to
"melt".) Since the filtered water froze and the unfiltered water
did not freeze (the surrounding temperature was not low enough to
freeze the unfiltered water - it's freezing point was lower than
the filtered water - for some unknown reason),
did the filter remove dissolved
chemicals? A test will go in as soon as money, time and weather
permit.
5. Filter 2 2008-05-24 is 12 inches deeper
than filter 1 with more graded sand (.15mm effective size), and the
water input is from a shallow well. This filter uses the dc pump
modification and is fully functional - it removes 99.9 percent of
all coliform bacteria and the water has no roof chemicals in it.
This is potable water with one (albeit only slight) caveat:
chemicals or pollutants present in the sand will be in the output
water. This condition can be checked with a thorough water quality
test, if no poisons are found in the water then it is potable and
probably the best water around.
6.Filter 3
2008-10-09 is now in the process of becoming fully
operational. This filter contains all NSF/ANSI 61 - AWWA 100
approved (the two standards for potable water) sand. This means we
know there are not poison chemicals in the sand. The top layer of
sand is .25 mm effective size and the bottom layer is .35 effective
size, however these sands have known uniformity coefficients of
less than 2. The container and all the pipe are also ok for potable
water. A test will be done on the water in about 3 weeks. (3 weeks
from Sept 19 2008). As of Sept 23 the flow rate is 38 liters per
hour (approximately 10 gallons per hour.)
2008/11/07
Update: An excessive amount of alge has formed on
top of the sand in this filter. This has drastically slowed down
the flow rate - from 10 gallons per hour to 3.6 gallons per hour.
It only took 4 weeks for this algae to build up. The cleaning
process, however is very simple. This is a description of what was
done ( it is called "wet harrowing"):
I removed the top of the filter and GENTLY ran my hand over the top
1/4 to 1/2 cm of sand until all the surface of the sand had been
agitated. The water became cloudy with fragments of algae. This
part of the water was drained off. There was an almost immediate
change in the flow rate, although I would recommend plugging the
output while the filter is being cleaned. I installed a drain pipe
on the top of the filter so water can be run through the input
baffle pipes while the excess cloudy water is drained off. When the
water draining off became reasonably clear, the top cleaning
drainpipe was closed and the filter was allowed to resume
operation. The flow rate measured 48 hours after this procedure was
28.965 litres per hour (7.65 gallons per hour). The biolayer must
have time to re-grow however, so the water will not be safe for
several weeks.
7.2009/02/17: Added a
float valve to
filter 3.
2008/11/10
Update: The test
that went in 2008/10/29 has come back on filter 3.
All coliform bacteria are removed by the
filter.
2008/12/18
Update: Due to extremely cold weather (for this
location) all the filters have completely frozen and stopped
operation. The temperature has been below freezing since
2008/12/12
2008/12/27
Update: New information from the results of
research regarding the viability of composition roofing material
for water collection are posted on the
FAQ page.
2009/01/16
Update: The filters are now running again. The
below freezing weather lasted until the first few days in January
2009. In this location, temperatures were below 20 degrees for
nearly one week, and dropped to below 15 degrees F for several
days. There was 16 inches of snow on the ground. All the filters
were inactive and frozen for 3 weeks. Pipes were cracked and brass
valves were destroyed. All the pipes were wrapped with insulation,
but that did not help because the water inside the filters froze.
In climates where below freezing temperatures occur, these filters
MUST be kept from freezing.
2009/01/26
Update: The filters have frozen again. There was
an inch and a half of snow last night. Below freezing weather
finally froze all the filters as of today. Operation has been
sporadic for the past nine days - night temps have been near or
below 32 deg F. .
2009/02/08
Update: Both filter 2 and filter 3 were damaged
because of the cold weather. They have been disassembled checked
and put back together. This meant carefully removing all the sand
and gravel from each filter cleaning the container, replacing
cracked drain pipes and putting the sand back in. Each filter
contains approximately 900 lbs of sand and gravel. This is VERY
labor intensive work. The re-assembled filters are now running.
Filter 2 has been running since Feb 3 2009 and has a maximum flow
rate of 72 litres per hour (19 gallons) with 20 cm (7.5 inches) of
water covering the surface of the sand. Filter 3 has a maximum flow
rate of 90 litres per hour (23 gallons) with 16.5 cm (6.5 in.) of
water covering the surface of the sand and has been restarted again
on Feb 13 2009.
2009/03/11
Update: All the filters except filter 3 with the
float valve have stopped operation, are frozen and have been for 3
days ( this is the fourth day ). Record low temperatures here were
below 19 degrees F. and there has been a total of 5 inches of snow
at this location in the past week.
2009/03/13
Update: All the filters are now back in
operation.
2009/04/07
Update: Filter 3 flow rate: .75 litres per minute
(45 litres per hour) with 16.5 cm water depth over the top of the
sand. (11.89 gallons per hour)
Filter 2 flow rate: .71 litres per minute (42 litres per hour) with
16.5 cm water depth over the top of the sand. (11.25 gallons per
hour)
2009/12/08
Update: All filters are frozen. The temperature
has been below freezing for five days, and below 18 degrees F the
past two nights.
2009/12/22
Update: All filters are now in operation.
2009/12/27
Update Temperatures the past 4 days have been
below freezing at night (25 degrees F), however the water in the
filters has not frozen.
2011/01/03
Update The pond filter output water went in for a
Coliform test, and a turbidity test December 27th. We expect
results back within the next two weeks.
2012/01/16
Update The pond filters have frozen as of Jan 16.
Filter 1 and the newest, Filter 4, have also frozen as of Jan 16.
Snow total so far for this storm is 9 inches at this location.
Filter 2 and 3 are still in operation.
2015/03/29
UpdateAll of the above mentioned filters are
still in operation and fully functional.
2017/05/19
UpdateAll of the above mentioned filters are
still in operation and fully functional. This winter was cold and
all the filters were frozen solid for 5 weeks in December 2016
/January 2017 . Some damage occured but only to the pressure tank
system on filter 4.
Clean water is necessary for life, without it people cannot live.
As the population of any given area increases the demand for clean
water increases. At the same time more water becomes unsuitable for
human consumption. Aquatic life, including many species of fish
that support human life also suffer. To prevent human suffering and
conflict, clean water must be freely available to all people. In
most areas of the world today clean water is not freely available
to anyone. In fact, in most parts of the world clean water is
available only for those who can afford it. Polluted water is the
only option for billions of people. This must change. Clean water
must be freely and unconditionally available to all people. If it
is not, there will be dire consequences that will make our current
warfare over petroleum resources seem insignificant. The solution
to water availability lies not in expensive corporate distribution
systems, but in individual or small scale water filtration systems,
and the knowledge of how to build and safely maintain these
environmentally sustainable systems to provide uncontaminated
water.
note
1: Water can be contaminated by many different
things: inorganic chemicals, organic chemicals and compounds; and
many different types of viruses and bacterium and it is impossible
to test for all of these contaminants without access to expensive
elaborate testing facilities.
This website
and this study must not be interpreted as a cure-all for the ills
of water supply problems. The water that goes through these filters
is NOT being consumed, and they are NOT part of the plumbing in the
dwelling unit nearby; and furthermore, consuming water that goes
through any filter is NOT RECOMMENDED without full knowledge of the
source of the water and EXACTLY what may or may not be in the
source water; and a complete EPA approved test on the water before
and after any filtering system used to determine the safety of the
water. That said, it must be recognized that even
public
water supply systems are subject to contamination,
22 40,41 although these systems are
continuously monitored for harmful substances by highly qualified
technicians. Biological sand (slow sand) filtering is not used in
most public water supply systems. Slow sand filters are very
efficient at purifying water (they actually remove pathogens) and
they are the best and most efficient way of removing
cryptosporidum
cysts from water without adding chemical poisons. Most public
water supply systems in the U.S. do NOT use slow sand filters, they
use Chorine or Ozone combined with highly complex mechanical
filtration systems to remove particulate matter and inactivate and
/ or remove pathogens. However, chlorine and Ozone react with
organic matter in water and produce cancer causing substances:
trihalomethanes (from chlorine), halacetic acid (also known as
Acetic acid, dichloro; bichloracetic acid; DCA; dichlorethanoic
acid; 2,2-dichloroacetic acid; dichloroethanoic acid; kyselina
dichloroctova or Urner's liquid) (also from chlorine)
51 and formaldehyde and
ketones (from ozone)
23,
24 that are still in the water (at low concentrations)
when it arrives at the consumer's plumbing and are VERY harmful if
consumed over long periods of time even at low concentrations.
Bromide (present in ground water) and chlorine added to kill
bacteria plus sunlight equal bromate - a cancer causing chemical.
This situation occurred in 2007 in Los Angeles. The Sliver Lake and
Elysian Reservoirs had to be drained, refilled and black plastic
balls put on top of the water to keep sunlight out.
42
note
2 Why is this "good" news? I wasn't going to get
political here, but this is so important and teaching is, after
all, a political act (Paulo Freire) . . . . Four reasons stand out:
One; Enough water for survival should be free for
everyone. It is as necessary for life as air - that one is sort of
a no brainer.
Two; If enough people in the city catch rainwater in rain
barrels, the load on the storm drains is reduced considerably - and
there is less chance of the drains overflowing and spreading
contaminated water into the environment before it is treated. This
is good news for everyone, as less pollution is washed into
streams, rivers, lakes, and oceans during a significant rain
event.
Three; In the summer, water can then be conserved by
using the stored water for flower gardens, lawns, and if filtered
by a slow sand filter, vegetable gardens; thereby significantly
reducing the load on the public water supply.
Four (and probably the most important); It appears as
though government is finally getting a clue. . . hopefully I'm not
wrong about this. Good job Wa. state gov., thank you! Tax dollars
well spent this time!
And, speaking of political
stuff, who is funding this site, and why is it on the
internet? There are no multinational corporations, environmental
groups, universities, or political groups involved in the funding
of this site. The funding is private, unconditional, and limited to
maintaining the domain name and hosting, paying for the epa
certified tests; and purchasing parts used to build the filters. If
any outside funding, or donations are offered, the conditions will
not change - the funding must be unconditional. The website coding,
physical work and research are done without any monetary
compensation. Every effort is made to assure that unbiased results
based on factual evidence and professional testing are presented.
Hazards are noted. No guarantees are offered or implied. The
creation, maintenance, and content of this site have no connection
to any political group. Additionally, this website has no
connection whatsoever to any religious group. This site is here
because it may be helpful to others.
IMPORTANT: Most raccoons carry a type of
parasitic roundworm called Baylisascaris procyonis 43, 44, 45, 46, that causes
very serious illness in people. If there are raccoons in your area
be aware that your yard may be contaminated. Children are highly at
risk. DO NOT use water from a rain barrel, pond or creek unless you
are absolutely certain that it is not contaminated. Read the
literature cited from the link above (43, 44, ,45) on this issue
completely. You have been warned.
Before any water from a
non-public utilty monitored
slow sand filter is used for drinking on a regular basis, it is
HIGHLY recommended that a UV filter
be installed permanently in the water line to the point of use, and
approval from your local health authority be confirmed. Note that
none of the filters described on this website are being used to
supply potable water. The water from these filters is NOT being
used as drinking water, and furthermore, the operation of any
filter is totally the responsibility of the owner/operator. Know
that ANYTHING CAN BE IN WATER, and water quality will vary
considerably depending on the surroundings. Note: In the past seven or eight months websites
describing biological sand filters / slow sand filters have been
appearing with instructions recommending BACKWASHING a biological
sand filter when the flow rate slows down. Forcefully backwashing a
slow sand filter, particularly a small slow sand filter with layers
of different sizes of sand, will destroy it. The flow rate is
slowed by a buildup of material on the TOP FEW CENTIMETERS of sand.
Simply gently agitating this layer and DRAINING OFF the cloudy
water is all that needs to be done. These well meaning people have
apparently confused rapid sand
filtration with biological sand filtration. There are small
scale biological sand filters that have been carefully
engineered to allow reverse flow of water to clean the
filter, but the sand bed is not "fluidized" as it is in the process
of "backwashing". 52
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