Ion exchange (IX) is a physical/chemical process where an ion on the surface of the IX media is exchanged with a contaminant ion in the feed water. The media is typically selected to preferentially adsorb the target contaminant. IX efficiency is influenced by the feed water concentration of the target contaminant, the selectivity of the resin for the contaminant and the presence of competing ions. A pre-filter is needed to protect ion exchange resins from suspended solids. Therefore, Staff is requesting a routine maintenance program that will require pre-filter replacements needed approximately every 3-4 months. There are a total of approximately 12,000 pre-filters and 50 door seals. The pre-filter unit cost is $13.01 and the average door seal unit cost is $490, depending on the size. The total cost for all five well sites is estimated to be  $225,000 annually for a period of five years that will cover the unit cost, sales tax and varying shipping costs. OCWD will reimburse the City for up to $75 per acre-foot of treated water. Sole source letters from the manufacturer have been submitted to the City to allow forgoing the competitive bid process as provided for by Section 2.050.060 of the Municipal Code for the purchase of these parts.

There is no impact to the General Fund. The total cost for all five well sites is estimated to be $225,000 annually for a period of five years. The cost of these pre-filters are included in the City’s adopted FY 2021-22 water budgets. OCWD will reimburse the City for up to $75 per acre-foot of treated water. 

• Authorize the Finance Director to issue a five year blanket purchase order with Towner Filtration allocating $225,000 annually for the purchase of water pre-filters at the new ion exchange treatment well sites.

By: Samuel Kim, P.E., Water Services Manager