Selamat pagi Amir,

Option 1. consult:

American Public Health Association. Standard Methods for the Examination of Water and Wastewater, APHA, Washington, D.C. Standard Methods for the Examination of Water and Wastewater

Option 2. Go to Google,copy, paste, enter this string and get a rich answer lah:

"Membrane Filter ""avoid the formation of bubbles between the membrane and the agar surface"

all the best

Hi there,

Make sure the filter is dry and make sure the agar surface is dry before placing the filter on it in order to avoid spreading of cells due to liquid lateral diffusion.

Make sure to start with a sterile filter and to work sterile during the filtration and transfer steps.

Finally make sure to respect the filter orientation on the agar plate by keeping the side up all the way. If you put the filter upside down, you encourage cell spreading between filter and agar surface.

There might also simply be too many cells on the filter...

Hi Amir

I had that problem too in the membrane of the second samples I run. Consider to sterilize the equipment you use and for second samples treat with UV radiation the filter of the equipment. And follow tecomendations od APHA revomendations for examination of water.

Best wishes.

Hello,

In addition to Dominique Liger answer, if the water is polluted you can ascetically do a serial dilution of the stock before the filtration in order to reduce the microbial load. This will also help you to obtain discrete microbial (bacterial) colonies.

Thank you everyone .

Hello Mr. Amir, i had the same problem while working. I suggest you to expose all the necessary equipments (including membrane filtration assembly) under UV radiation for 20-30 minutes before performing the experiment. Please make sure to use sterile filter paper. Thank you.