A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Environment, Resources and Development

Thesis (M.Eng.) - Asian Institute of Technology, 1990

Detailed experimental studies on backflush technique in crossflow microfiltration is reported. Experiments were conducted at varying backflush frequency and duration and different nature of different suspension. The 1 min. of backflush frequency and 5 sec. of backflush duration were found to be optimum a nd this improved the flux by 200% in the case of Kaolin clay suspension. The application of various of filtration laws proposed by Hermans and Bredee to describe the standard blocking model a nd cake filtration model were verified. From the study conducted in the Kaolin clay and colloids suspension, it was found that no single mechanism was sufficient to describe clogging. The pretreatment of flocculation by alum for prior particle size enlargement was found to improve microfiltration performance significantly. The suitability of crossflow microfiltration with backflush technique for the treatment of natural water and filter back wash wastewater were also studied. The periodic backflush technique applied once in 1 min. for 5 sec. duration was found to be optimum. the flux increase was 250% and 148% for natural water and filter back wash wastewater, respective l y , with backflush technique compared to those without backflush technique.