Tests on a slow sand filter after freezing and thawing
Filter 5 was frozen solid and not running for 2 weeks in January of this year (2013). Before that for 5 days the filter froze at night, and then ran for 6 hours each day. As of Jan 25 the filter was running 24 hours a day. The samples were taken on the 25 th. The pre-filter water was taken from the water in the top of the filter – the water from the source that has been running through it for 3 days. The post filter water was taken from the output pipe of the filter . The images below confirm that being frozen for 2 weeks causes this filter to produce poor quality water. Another test will be done in 2 weeks, providing the filter does not freeze again.
These images show the reduced abilty to remove pathogens due to the filter being frozen. This test is from filter 5. The colored dots are ecoli, and coliform bacteria. This test was done the same day the filter started flowing again.
Test results on filter 5 from 2 weeks of running time after this filter had been frozen at night for 1 week and then frozen solid for 2 weeks .
This image shows the results of the most recent tests done on filter 5. It has been thawed out and running for 2 weeks as of the date of this test. Before this it was frozen at night for 1 week, then totally frozen for 2 weeks.
These are the results of the most recent tests on filter 5 Feb. 19 2013