The San Patricio Municipal Water District in Ingleside, Texas, northeast of the port of Corpus Christi, recently began operation of a new, expandable membrane filtration plant.
The ability to expand the plant already has been put to the test. Although originally scheduled to be 5.2 mgd, before construction began the district decided to expand the plant to 7.8 mgd. The plant went online in January, and design work already is under way to expand the facility another 2 mgd.
The San Patricio water district is located in a growing area with an active industrial base. The district has three separate water treatment facilities on its campus, which is located within an industrial park, said Don Roach, the district?s assistant manager. The other two plants include a 9 mgd conventional treatment facility and a 6 mgd Trident Microfloc plant.
The district currently draws raw water from the Nueces River. Turbidities average 25 ntu but can range from 5 ntu to 200 ntu. Water temperature ranges from 8 degrees C to 30 degrees C, averaging 22 degrees C. Water hardness averages 230 mg/L as CaCO3 and ranges from 100 to 300 mg/L. Construction is under way to bring additional water supplies from Lake Texana by mid-year.
When planning its new facility, the district evaluated the feasibility of several alternatives and determined that conventional settling followed by membrane filtration would be the most effective method of achieving treatment goals. Research indicated that membrane flux could be maximized when preceded by settling, resulting in a process that was economically competitive to conventional treatment.
The district selected a Pall Microza™ Drinking Water Filtration System. Microza is a registered trademark of Asahi Chemical Industry Co. Ltd.
Upon completion of pilot testing, the equipment procurement phase of the project began. In order to simplify procurement and maintain a tight schedule, the membrane filtration system and auxiliary equipment were bid before the rest of the project. This sequence allowed the on-site facilities to be designed to match the microfiltration equipment and the construction to proceed while the membrane system was being fabricated.
Since the bid prices were lower than projected, the district used the remaining funds in the budget to increase the facility capacity to 7.8 mgd. Both the district and their engineer also commented on the advantages they saw as inherent to the Pall design.
?For this site, the results of the pilot study and bid evaluation indicated that the Pall microfiltration system was the most economical alternative,? said Senior Project Engineer Jim Vickers, P.E., of Malcolm Pirnie, consulting engineer to the Water District.
?We also believe that it is important to exceed current as well as proposed regulatory standards, and the use of microfiltration will allow the district to provide the highest level of filtration possible within the constraints of the project.?
The district?s microfiltration system consists of six racks each containing 50 membrane modules. The membranes have a pore size of only 0.1 micron, which serves as a barrier for all bacteria and some viruses.
A portion of the filtered water is diverted to a nearby industrial customer prior to chlorination. The rest is blended with water from the conventional treatment plant, chlorinated and sent to the distribution system.
With three filtration systems on the same site, the district is able to customize the kind of water provided to individual industrial customers, Roach said. ?We are able to produce whatever a customer needs,? he said. ?The district sells raw water to some customers, industrial treated water, potable water, etc. We are also designing a reuse system.?
One reason the district settled on the membrane system was the ease with which it can be expanded, Roach said. The facility is designed to accommodate an eventual expansion to 15 mgd.
?Once the basic infrastructure is laid in, the buildings, the piping, etc., it?s only a matter of adding pumps and membrane filter modules,? he said.
