It is now October 2, 2014. Filter 1, and filter 4 have output water with no (0) coliform and no (0) e coli bacteria present. The cistern water that flows through filter 2, and filter 3, has 4 cfu’s of coliform per 100ml and 20 cfu’s of e coli per 100 ml. See the images below:
These images are of filter 1, filter 4, and the cistern output water tests.
Tests on filter 2, filter 3 and filter 5 will be done in the next couple of weeks.
On September 27 2014, after 6 months of continuous operation since this winter’s extended below freezing weather, a field test was done on the 5 gallon filters 10a and 10b. The tests indicate that filter 10a did not work satisfactorily. In fact, the output of the five gallon filter 10a was hundreds of times worse than its input water, which came from the source which is water collected from the first flush diverter/settling barrel array. Filter 10b, which filters the output water from filter 10a, did show some additional removal of ecoli and coliform bacteria as compared to the output of filter 10a which appeared to actually add bacteria. But both filters’ output was far worse than the input from the source water. These results indicate that .25 mm sand is just too coarse to work in a shallow filter such as these 5 gallon subjects, and that .15 mm effective size sand just barely works, and may not work at all. These results also indicate that having more than one shallow filter is absolutely necessary for even marginal results, and that the water from the first must be fed into the second. This testing is after 6 months of operation. I will post images of the test results sometime today or tomorrow. The 55 gallon filter (filter 1) that has been running here for 8 years has output that is tens of thousands of times better than either one of these 5 gallon filters. It uses the same source water as the 5 gallon filters.
It is important to note that these tests are only valid for this water here at this location. Water in a different area, such as a climate where the temperature is always way above freezing, will have different characteristics, and may very well be filterable by a 5 gallon filter.
These are the test results for filter 10a and 10b. The “source” water is from the diverter output (water taken from the house roof)
Water comes from the “source” goes into filter 10a, flows out (supposedly filtered) and then goes into filter 10b. The water out from 10b, the source water, and the water out from 10a are what was tested. The water out from 10b, is better than its input, so that filter is working somewhat. Filter 10a is not working, it is adding huge amounts of bacteria to the water. The red dots are coliform, and the blue dot in the filter 10a dish is e coli.
The water coming from this filter, filter 10a, is highly toxic and not safe. The filter has been removed from any more testing and is no longer active. The sand has been discarded and the bucket and the sand have been sterilized. The bucket will be reused in a different setup.
What might this test result indicate?
1. A 5 gallon filter using sand with an effective size of larger that .15 mm won’t adequately filter water at this location.
2. Water run through two 5 gallon filters (first one, then out of that and then into the next one ) is filtered better than just going through 1 filter.
3. Filter 10a obviously adds bacteria to the water. It is totally not working and is supplying toxic water output. That is the .25 mm effective size sand. It does not work.
4. Filter 10b filters that bad water from 10a and makes it better, but not good enough.
5. Contaminated water is slipping through the area between the sand and the inside of the bucket where the surface of the bucket was not adequately roughed up with sandpaper.
6. The sand in the bucket is not deep enough to catch all of the bacteria possibly because bacteria predation typically occurs deeper than just a few centimeters down from the top surface of the sand. As this happens over a long time period, in this case 6 months, the escaped bacteria simply build up in the lower regions of the sand. Know that there is only about 10 inches of sand in one of these filters.
7. Filter 10a uses an overflow pipe to allow the excess water added to the top bucket to flow into a reservoir bucket. That water is, occasionally, then poured back into the filter 10a input. It could be that bacteria is multiplying in that reservoir, and then overwhelming the 5 gallon filter.
9. The bucket used to transfer water to filter 10b could be inadvertently adding bacteria to the water. It could be that filter 10b is actually working quite well.
Filter 10b uses .15 mm effective size sand. The flow rate is very, very, very slow. It may be that another filter with .15 mm effective size sand would adequately filter the water. In other words 3 filters in series may work. But, the sand size must be no larger than .15 mm effective size. That will mean an extremely slow flow rate.
All the filters are still functional with the exception of one. The filter connected to the largest pond has been inactivated by damage due to the wildlife present here. We are reasonably sure the damage was caused by raccoons. The output pipes were disrupted and as a result all the water was pumped out into the ground. Re-activation will have to wait until there is enough rain to refill pond. In the mean time the filter remains inactive. This will be an interesting test of the pond filter to determine what happens if the filter stays inactive for over 2 weeks. This has been a warm dry summer with several periods of heavy rainfall, and extended periods of warm dry, sunny weather.
To harvest rain water or use water from the public water supply – what to do? According to a recent article in the New York Times, which mentions the trouble with the Silver Lake reservoir near Los Angeles California, public water is becoming more and more polluted as time goes on. We covered the problem with the Silver Lake reservoir already – bromates were found in the water. These bromates were due to other pollutants mixing and then being chemically altered by sunlight.
Pollutants are all over the place now. Reservoirs that fill using river water, or surface runoff can have up to 60, 000 different chemicals present in the water, yet only 91 are tested for by law. The above mentioned article states (from a citation using EPA records) that there are more than 60,000 chemicals used in the U.S.
We have already shown, on this blog, and our three other websites, that way less contamination exists in rain water than in surface water, or runoff that comes in contact with areas that have been contaminated by urban development, industry, or agricultural activities. The first few hundred gallons of water that runs off of your roof washes away most of the pollution that has settled from the air. All that is left is the petroleum residue from composition roofing. In the case of non-toxic roofing, such as galvalume, little pollution remains after the initial washing from the first few minutes of a moderate rain shower.
It is important to know that some contaminants need only be present in very small amounts to be hightly toxic over long periods of time (years). Trihalomethanes, Haloacetic Acid, Bromate, and Chlorite and microcystins are some examples.
Will a slow sand filter take out microcystin toxins more effectively than conventional water filtration (rapid sand filtration) ? It appears as though the answer is yes:
http://www.ncbi.nlm.nih.gov/pubmed/12203961 (information is in the abstract; access to the entire document requires a log in.)
http://www.who.int/water_sanitation_health/dwq/chemicals/microcystin_sections.pdf (its a 3 page document; read the entire document)
http://www.ibg.uu.se/digitalAssets/164/164676_3bojcevska-hristina-jergil-erik.pdf (page 19 and read the entire document)
Removal of Algae and Cyanobacterial Toxins during Slow Sand and Bank Filtration (page 53 “schmutzdecke”)
www.terrapub.co.jp/onlineproceedings/ec/02/pdf/ERA33.pdf (page 280)
Biological treatment options for cyanobacteria metabolite removal A review (page 1543)
Slow sand filtration is not used in most water treatment facilities in the U.S. , even though it is more efficient, more sustainable, and less expensive than rapid sand filtration. Slow sand water filtration has been around for hundreds of years and has been shown to work. The city of Salem, Oregon is one of the few cities in the U.S. that uses slow sand filtration.
What would you do if you found out that the public water system had been contaminated by powerful toxins that could not be removed by boiling? Setting up a rain barrel or two might be a good idea.
Back in September of last year, we started 3 small 5 gallon slow sand filters. They are still running, and marginally cleaning the water that runs through them. So far, the best water quality is from filter 10b, followed by 10a, and then 10c. They do work, but only just barely. If this were all you had to clean the water you use, they would absolutely be better than nothing, however they are very sensitive to any physical movement, and the flow rate must be extremely slow for these small filters to do any good. If the input water is turbid, they will plug up quickly, as it is necessary to use very fine sand in these small filters. Perhaps a good way to run them is to use 2 in series. The first one should have coarse sand like .65 mm effective size, and the second one much finer sand like .15 mm effective size.
The five gallon slow sand filter experiment, mentioned in September of last year (2013) is still in progress. Due to some unforeseen issues, the EPA tests cannot be done as of yet. We will attempt to start some field tests on the three filters (filter 10a, 10b, and 10c) as time permits. These filters are still in the process of recovering from being totally frozen this winter. Until about early March, there was no water flowing through them.
A summary of what we have observed so far:
These filters will work, but there are some serious issues.
It is necessary to keep the flow rate very, very slow; much like a dripping faucet.
They are very easily disrupted if moved or bumped even slightly as the biofilm seal between the sand and the container may be broken easily – the sand and water in the bucket is so heavy it causes the bucket to flex if even moved slightly. As a result, the output is bad for about a week.
They are inferior to the much larger 55 gallon filters we have running here, but most certainly better than nothing.
As an experiment, they appear to “work” to filter out some turbidity, and we have noted what appears to be some removal of biological contamination. The water that comes out of the roof water diverter and is poured into the top of these little filters is improved by running through them.
If anyone reading this has conflicting information, please post it here in the comments section below.