Following a recent installation at his facility, membranes have made a believer out of Bud Hart, water supply, treatment and quality manager at the 50 mgd Columbine (Colo.) Water Treatment Plant (CWTP).
In addition to being cost-effective, the membrane installation and subsequent treatment process provided the plant with an effective removal barrier for turbidity, Cryptosporidium and Giardia.
Recently, WWD discussed the membrane installation at the CWTP with Hart, who, incidentally, recommends that other water treatment providers give strong consideration to installing membranes at their facilities.
WWD: Please describe in detail the city of Thornton, Colo.’s CWTP in terms of what type of facility it is, where the facility draws its water and its capacity.
Bud Hart: Originally, the city of Thornton’s Columbine plant was a 30 mgd conventional water treatment plant. The main water supply for this facility is the South Platte River. The city of Thornton decided to upgrade the plant due to water quality concerns of its source water and the need to expand the capacity of the facility.
The new 50 mgd CWTP uses advanced water treatment processes including state-of-the-art ultrafiltration membranes to remove suspended solids in the source water down to .04 microns and ultraviolet disinfection technologies to provide pathogen-free high quality drinking water.
WWD: What led to the incorporation of membranes into the water treatment process at the CWTP?
HART: Working closely with the consultants, Burns & McDonnell Engineering, we found that membranes offered a lower cost option as part of a retrofit to the existing plant.
WWD: Has the installation of the membranes helped reduce the amount of turbidity, Cryptosporidium and Giardia in the water system?
HART: Yes, it has reduced the amount of turbidity in the water. The membranes have also helped provide a positive barrier against Cryptosporidium and Giardia.
WWD: Were any other membrane-related criteria such as lifecycle costs or reliability considered?
HART: We did extensive piloting on a number of membranes and developed criteria such as lifecycle costs and considered power, chemical, overall performance, particle analysis, turbidity removal, replacement costs and the retrofit costs within the existing plant, plus corporate principles of the membrane supplier.
WWD: What types of membranes were installed at the facility?
HART: The membranes that were installed in the facility were the ZeeWeed 500D manufactured by Zenon.
We have seven trains with a flux rate of 40 gal/ft2/day. We also have an eighth train, which provides for a secondary recovery of reject water of over 99% recovery.
WWD: Have there been any problems with the membranes, and if so, how were the problems resolved?
HART: We have not experienced any significant problems associated with the membrane installation. Accordingly, we are continuing to track all the significant parameters of their performance on a continuous basis utilizing the Zeno Trac system.
WWD: Where does the CWTP send the water rejected by the membranes?
HART: We currently have approximately 99% recovery of our reject water through the eighth train; the remaining reject is recycled through a lagoon system and returned to a raw water supply lake and then returned to the plant.
WWD: Have membranes been installed in other water treatment plants in the area, and if so, what has been the reaction to the membranes since the installation?
HART: There have been some smaller facilities and medium size facilities in our approximate area that are utilizing membrane technology. They are also experiencing favorable reactions to this membrane technology.
WWD: Are there any future plans to incorporate additional membrane-related technology into the CWTP?
HART: We may be adding the possibility of reverse osmosis to the Columbine Plant in the future and will be considering membrane technology for expansion of our Thornton Water Treatment Plant at sometime in the future.
WWD: Overall, would you say your experience since the installation of the membranes at the CWTP has been positive?
HART: I would say that it has been very positive, and this technology will enable the water treatment industry to meet many of the water quality challenges of the future. As regulation becomes more stringent and the number of regulated contaminants increases, membrane technology will provide a tool to help meet these demands. It is also more cost-effective than conventional treatment processes and provides a positive treatment removal barrier for turbidity, Cryptosporidium and Giardia.
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