APPLICATION OF IMMERSED ULTRAFILTRATION MEMBRANESFOR LARGE SCALE DRINKING WATER TREATMENT PLANTS

摘要

Application of microfiltration (MF) and ultrafiltration (UF) membrane systems for municipalpotable water treatment is becoming increasingly common. Total installed capacity for MF andUF membrane systems combined in North America currently exceeds 225 MGD (CH2MHILL,1999), with in excess of two hundred operating facilities. Typically, the capacity of these plantsis less than 10 MGD. However, several large capacity UF plants are in design or underconstruction utilizing immersed membranes. For example, the Olivenhain Municipal DrinkingWater Treatment facility near San Diego, scheduled for completion in September, 2001, will havean initial and ultimate rated capacity of 25 MGD and 30 MGD, respectively.In addition to being a positive barrier to parasites, immersed membranes were selected for thisfacility because they are ideally suited for large scale treatment facilities up to and exceeding 100MGD in capacity. Unlike conventional canisterized membranes, they can be installed directly innew or existing open tankage without an enclosure. This also allows the convenient retrofit ofexisting sedimentation basins or filters with UF membranes to meet increasingly stringentmicrobial and turbidity regulations. New infrastructure including buildings and tankage istypically not required for retrofit applications and is minimized for new plants.The use of large process trains with the immersed membrane system also requires fewer permeatepumps, blowers, and valves. In lieu of feed piping, channels can be used to convey water into theprocess tanks; thereby reducing system headloss and allowing flow through the plant by gravity.Common backpulse equipment can also be used for multiple trains. These reductions inequipment translate into a smaller building footprint, reduced system complexity, and lowercapital and operating costs.Additionally, a very large (>5 MGD), immersed membrane process train has recently beenintroduced for extremely large treatment facilities (>50 MGD). This design utilizes membranecassettes oriented both longitudinally and transversely within a train; resulting in operationalimprovements and increased productivity.