AWWA WQTC69312

The use of membrane technology and, in particular, microfiltration (MF) is becoming more popular as a water treatment technology. The potential lifetime of MF can be reduced by natural organic matter (NOM) which is a known foulant to these membranes. The MIEX dissolved organic carbon (DOC) process was developed to remove NOM from raw water sources. It is anticipated that the reduction in NOM resulting from the MIEX DOC process would also improve the performance of MF systems. A pilot plant study was undertaken to directly measure the impact of MIEX pretreatment on MF performance. A single module continuous microfiltration - suspended (CMF-S) membrane pilot plant was provided on lease from Veolia Water. The unit incorporated a suspended S10V membrane module supplied by Memcor. The S10V module consists of 14,000 hollow fiber filaments made from PVDF polymer with a nominal pore size of 0.04µm. The module's fresh weight was 6.7kgs and it is capable of withstanding 200ppm of free chlorine. It was necessary to produce MF treated water from MIEX and raw source waters, using two modules in a staggered parallel mode. One membrane was stored in a refrigerator in chlorinated WTP treated water when not in use. During the change over, the membranes were rinsed with WTP treated water. Some programmable logic controller modification was required to allow the membrane to run in staggered parallel fashion. The rig was operated at 1000L/hr flow rate (39.5L/hr/m² flux rate) and was backwashed by air scour every 45 minutes. A weekly pressure decay test was performed to detect any broken membrane fibers. A clean-in-place (CIP) was conducted after 600 hours of operation of each module which involved a 3 hour recycling and soaking cycle at pH 2 with 4g of EDTA at 40ºC. Fouling of the membranes was determined using the resistance, a value calculated from the transmembrane pressure (TMP). Includes 5 references, figures.