Time to filter, TTF

TTF is determined by using an apparatus shown in   (Method 2710H). A 90-mm Buchner funnel is used with Whatman #1, #2, or equivalent filter papers. After pouring 200 ml mixed liquor, the time required to obtain 100 mL of filtrate is measured at the vacuum pressure of 51 kPa (or 7.4 psi). TTF can be normalized against MLSS, but this normalization is valid only at a narrow MLSS range. Fig. 2 shows the pictures of the required equipment and the setup of the system.

Filter8Fig. 1. Apparatus to measure time to filter, TTF (APHA, 1992)

Filter1Fig. 2. Time to filter (TTF) test equipment and the method (Jeffery, 2005)

Fig. 3 shows one application of TTF that is used to compare the efficacy of various coagulants on improving sludge filterability. In general TTF decreases as the coagulant dosage increases, which suggests slower membrane fouling.

Filter2Fig. 3. Effect of various chemicals on TTF, where MPE50 is a flux enhancing chemical sold by Nalco (Jeffery, 2005)


© Seong Hoon Yoon