Evaluation of the Port Hueneme Demonstration Plant - An Analysis of 1 MGD Reverse Osmosis, Nanofiltration, and Electrodialysis Reversal Plants Run Under Essentially Identical Conditions

Bureau of Reclamation; Denver CO.
May 2001

Report #65 - Executive Summary -

The Port Hueneme Demonstration Plant was established to supply communities neighboring Port Hueneme with increased quantities of high quality water and to provide a comparison of three membrane processes operating as nearly as possible on the same water under identical conditions. The second objective is the subject of this paper. The raw feed water is typical of brackish water in southern California.

Three different desalination processes were used: RO, NF, and EDR. Each desalting process has the same production capacity to facilitate the comparative evaluation of performance and costs. Since the desalted product is of higher quality than the 370 mg/L quality required, some water could be bypassed around the plant to be blended with the desalted product. The Port Hueneme Water Agency has collected data on the chemical usage and power consumption, and has tracked the other operating and maintenance costs for each of the three membrane sections.

Data on plant operation were supplied to Reclamation by the Agency. Most of these data were accumulated by the plant automated data accumulation and storage system. This record that Reclamation received during the evaluation period had been reduced to one point for each parameter per day. Selected values were manually entered into a spreadsheet from which analysis proceeded.

For the purpose of this analysis, records that were much more detailed than usual were kept on how the labor was employed at the plant. This information itself may find wide utility for individuals tasked with estimating the number of staff hours required for operation of a desalting facility. Data were extracted from monthly labor reports and daily operator logs to assemble a spreadsheet itemizing staff hours and labor costs for each of the separate desalting section and for the plant. The last category covers operations that were common to all sections or that could not be separately allowed.

The evaluation period used ran from March 1999 to February 2000. Calculated water treatment costs are expressed as 1999 dollars per thousand U.S. gallons.

The procedure used ran as follows:
- determine the quality and concentration of water produced by each desalting section,
- determine the effective flow, i.e., product plus blend flow for each section,
- calculate the cost of energy and chemicals used in each section and in the plant,
- allocate the costs attributable to the plant evenly to the tree sections,
- calculate the cost of labor in the same fashion,
- determine the amortized cost of capital from the three sections, and
- sum the cost components to get an (almost) all-inclusive cost of desalting.

The costs of desalination determined in the manner were 72.6¢/kgal for NF, 74.7¢/kgal for RO, and 79.6¢/kgal for EDR. The unsatisfying part of this analysis is that membrane replacement is not included. A rough estimate of membrane replacement is about 10¢/kgal. However, they would probably not be the same for the three processes. It would be interesting to see what a similar comparison would show at a time when the membrane element replacement rate could reasonable be calculated.

Overall each process worked well, once the startup problems were resolved. This demonstration clearly showed that a low-TDS brackish water can be desalted for an all inclusive cost less than $0.90/1000gals.