Reducing costs for large-scale desalting plants using large-diameter,reverse osmosis membranes

摘要

The Metropolitan Water District of Southern California (Metropolitan),in conjunction with Koch Membrane Systems (KMS),evaluated three generations of a 16"-diameter by 60"-long reverse osmosis (RO) element in parallel with a commercially available 8"-diameter element.Design inefficiencies in the first-generation 16" element resulted in a 20% lower specific flux when compared to an 8" element.After making improvements in element design,the overall specific flux for the last-generation 16" element was shown to be comparable to that of the 8" element.However,a slightly higher fouling rate was observed for the 16" element.An economic evaluation comparing costs using both 16" and 8" diameter elements for a 185-million gallon per day (mgd) [700 million l/d (ML/d]] RO plant showed that a design using 16" elements may save as much as 12.4% (4.2 million per year) in combined capital and operations and maintenance costs.The present value of capital-cost savings alone was estimated at 44.3 million - a 27% reduction.The majority of these cost savings were attributed to reductions in train piping,support frame,miscellaneous train equipment (i.e.,instrumentation,cleaning skid,and prefilters),and footprint.