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- Cannot remove color or dissolved compounds (same as all other filters)<br>
- Can be difficult to move (weigh 170 lbs / 77 kgs)<br>
- Cannot ensure pathogen free water <br>
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The flow rate through the filter will slow down over time as the biolayer develops and sediment is trapped in the upper layer of the sand. For turbidity levels greater than 50 NTU, the water should first be strained through a cloth or sedimented before using the BSF.
The treated water following should be collected by the user kept in a safe storage container placed on a block or standmind, so that to ensure correct operation:- water from the container opening same source is just under used, regularly <br>- water supplied from shallow wells and surface waters will develop a faster and stronger biolayer <br>- water from rain water and deep wells may result in less of a biolayer however the outletquality from these sources should be better <br>- water containing VOC’s, insecticides, minimizing herbicides, heavy metals, lead, mercury, industrial pollutants, algae, plankton, chlorine and salt should not be used in the risk for recontaminationfilter <br>- water with a turbidity of less than 100 NTU will still work with more frequently cleaning, water with a turbidity of < 50 NTU is preferred <br>- maximum flow of 0.6 liters per minute when filter reservoir is full <br>- pause period <br>- intermittent cleaning to restore flow rate- proper “swirl and dump” cleaning process
====Treatment Efficiency====
Working with cement and heavy molds is potentially hazardous and adequate safety precautions should be used. Concrete filters are heavy and difficult to move and transport.
Correct manufacturing and installation, to ensure a long and succesful life, of the biosand filter requires:
- that the box that doesn’t leak <br>
- screened and washed sand, (organic free, Uniformity Coefficient of 1.5 – 3.0 and an Effective size of 0.15 – 0.30 mm - a sieve analysis is required to determine these numbers) <br>
- well washed under-drain and separating gravel <br>
- diffuser plate and lid <br>
- safe storage container <br>
- maximum standing water level of 5 cms <br>
- start-up (maturing) time of 14-21 days <br>
====Estimated Lifespan====