We are currently dealing with a similar situation for a water well in Texas. The producing sands are very fine. Turbidity remains in the water that makes it through the gravel pack that we have determined to be associated with very fine solids. The solids are fine enough that they don't settle out when a sample produced from the well sits for weeks. These fine solids are removable with a 0.45 um filter. Analyses indicate that the chemical quality of the water is suitable for potable use according to US EPA primary standards. However, the turbidity and color exceed the secondary standards and are issues with the Owner. Turbidity is 5 NTU, color is 20 CU, total suspended solids is 3 mg/l. Our approach to removal of the fine solids is to add a coagulant (alum or polymer) and filter using direct filtration with a sand filter. This approach has been verified by bench scale testing, and we are planning pilot scale testing soon. Final design and construction of the treatment system will occur after the pilot testing, so we have not verified this approach with the full scale system. Nonetheless, I doubt that your problem can be resolved without the use of a similar approach.
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Walter Winn P.E., D.WRE, F.ASCE
President
Winn Professional Engs & Cons LLC
Longview TX
(903) 553-0500
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