| Abstract | Crossflow microfiltration (CFMF), technically being a very effective
filtration process for separation of both colloidal and suspended particles from
liquid, however, at this stage is found to be commercially viable mainly for
obtaining high value products but not yet in water and wastewater application due
to the high installation and operation costs. And further, the problems of f lux
decline resulting from fouling, deposition and internal clogging of membrane
etc., demand more research in an attempt to improve t he effectiveness of the
process, especially in terms of flu x improvement techniques. In this present
study, different sets of CFMF experiments were carried out to stud y the use of
backflush as a de-clogging technique in enhancing the process performance. The
membranes used in this study were bought from SCT1, France, but the membrane
housing and t he whole experimental set up was designed and fabricated locally.
Synthetic and natural suspensions were tried out. Backflush technique was found
to improve the efficiency of the filtration process when synthetic suspensions
of clay alone and clay together with colloids were used. The effect of backflush
frequency, Tf, and backflush duration, Tb , were studied and it was observed that
for CFMF with clay suspension Tf = 1 min., Tb= 1 sand with clay and colloids
as suspension , Tf = 2 min. , Tb = 1 s were found to be the best operating
conditions. The improvement in productivity, Ipv, of the stabilized productivity
of the two experiments were 290% and 210%, respectively, compared to CFMF without
backflush. In order to study the application of CFMF with backflush technique,
natural water and filter backwash wastewater from water treatment plant were
used. The best operating condition for these two suspensions were Tf = 5 min ., Tb= 5 sand Tf = 1 min., and Tb= 1 s respectively. The Ipy of the stabilized
productivity were 220% and 1,300% respectively, compared to CFMF without
backflush. Thus backflush technique can be effectively used as a de-clogging
technique in CFMF for treating filter backwash wastewater.
Both t he new and used membranes were chemically cleaned and further
subjected to filterability test before using in the experiments. These two
techniques, i .e ., chemical cleaning and filterability test were developed by the
researcher.
Other de-c logging technique, i.e., pulsation cleaning technique was also
tried; but it was found to be less effective compared to backflush technique.
Further, when other f lux improvement techniques like flocculation of suspension
was investigated, it was observed that though this technique has promising effect
in increasing t he performance , the effect of using flocculation coup led with
backflush technique is even more significant, evidenced by t he I of t he
stabilized productivity which is 1,010% compared to that with CFM~ without
backflush and without flocculation. This tremendous improvement in CFMF
performance can thus be said as a breakthrough in membrane technology. |