Any E. coli remaining on the filter after the
disinfection experiment was transferred to a Tris-buffered saline
(TBS) solution, a mixture of 0.15 M NaCl and 0.05 M Tris–HCl at pH
7.5. TBS solution (100 l) containing E. coli bacteria was spread onto
an agar plate, which was kept for 8 h at 37 ◦C, in order to count the
bacterial colonies