Dear Muhammad, you can concentrate your water samples by ultrafiltration. The volume should be large enough to give you the minimum DNA yield of 5ug/ul required for pyrosequencing. If your DNA yield is not enough, you can do a random genome amplification to increase the yield. Before the concentration, it is expected that treatments involving flocculation, settling, pH adjustment, sand filtration and chlorination (depending on the nature of your water sample) must have been made. The retentate after ultrafiltration can be filtered onto 0.2-m polycarbonate membranes. Details could be found in the attached documents. Article Metagenomic Analyses of Drinking Water Receiving Different D...

Article Use of competitive DNA hybridization to identify differences...

Thank you sir for your nice cooperation.

I appreciate the time taken by Dr Maurice, and his suggestions are really valuable.

In addition to it, I would like to add, if your interest in metagenomics, you no need to have higher concentration of DNA (More than 100 ng is enough).

Any metagenoics will do amplification of ribosomal RNA. so, the enrichment step during library preparation will make your study success.

All the best

Murugan N