Point of the Mountain Water Treatment Plant Final Design

Metropolitan Water District of Salt Lake and Sandy, 
Utah

Point of the Mountain Water Treatment Plant Final Design

Awards: 
2008 Grand Award for Water and Wastewater - American Council of Engineering Companies, Utah Chapter
Service Type: 
Project Highlights: 
  • Piloting, design, construction and startup of a new water treatment plant using pre- and intermediate ozonation and biologically active filtration with GAC media, followed by UV disinfection.
  • Bench and pilot testing of three treatment trains during a 10-month study.
  • 3-D modeling performed on select project components for key milestones to illustrate layouts.
  • Optimized UV system validation, dose monitoring, and control.
  • Biologically active carbon filtration proved an effective aid in removal of TOC and reduction of DBP formation.
POM interior
Carollo evaluated membrane filtration of raw feed water and pretreated feed water along with conventional treatment processes.

Carollo was the lead consultant for design and construction services for the new 70-mgd Point of the Mountain Water Treatment Plant (POMWTP) for the Metropolitan Water District of Salt Lake and Sandy, located near Salt Lake City, UT. The $100 million project incorporated enhanced conventional processes based on a 12-month pilot test program that was conducted by Carollo. The processes included flash mix; flocculation; sedimentation, including plate settlers and intermediate ozone; biologically active filters, ultraviolet light (UV), and chlorine disinfection. Other plant facilities included a 70 mgd finished water pump station, a 20 MG finished water reservoir, solids settling basins, solids handling facilities, a standby power generation facility and a 6 MW maintenance facility.

Disinfection facilities for the POMWTP included provisions for complementary use of ozone, chlorine, and UV technologies. Effective ozone contactor design was of particular concern to help control costs and provide effective disinfection. Due to the high complexity of diphasic (gas and liquid) contactors, Carollo used comprehensive CFD modeling to optimize design criteria and minimize ozone contactor costs. Ultimately, the ozone contactor was designed using a serpentine layout similar to typical chlorine contactor basin designs. Using this approach Carollo has achieved a 0.7 baffling correction factor for even the most complex contactor projects.

Carollo provided standard services during construction, which began in August 2004. We also completed O&M manuals well in advance of start-up throughout a series of workshops and submission of draft writeups in combination with review of the O&M data from equipment suppliers.
The 20 MG finished water reservoir was designed with specific inlet and outlet baffling to complement the ozone and UV facilities while minimizing DBP formation.

Construction Services

Carollo completed pilot testing, master planning, preliminary design, final design, and construction services for the 70-mgd Point of the Mountain Water Treatment Plant for Metropolitan Water District of Salt Lake & Sandy, Utah. This $90-million greenfield project included ozone, UV disinfection, biologically active filters, flocculation/sedimentation basins with plate settlers, and solids handling facilities.

The Metropolitan District of Salt Lake and Sandy retained a third party to provide contract administration services for the construction of the project. Carollo Engineers provided the following services related to construction:

  • Office engineering services
  • Field support for the following:
    • Construction/progress meetings.
    • Discipline site review.
    • Startup planning/assistance.
  • Record drawings.
  • Operations Manual.
  • Operators’ training.

Pilot Study

Carollo conducted pilot studies on three treatment trains to determine the most cost efficient arrangement of unit processes for the 70-mgd Sandy Point of the Mountain WTP. Carollo led the four major components of the study: a pilot advisory team to guide the project, raw water quality monitoring and bench-scale treatability studies, pilot-scale testing, and treatment train evaluation and costs estimation. The pilot advisory team selected three alternative treatment trains to be evaluated as follows:

Train No. 1 - Low-pressure membrane filtration with conventional pretreatment.
Train No. 2 - Low-pressure membrane filtration with presedimentation and post GAC adsorption.
Train No. 3 - Ozonation/Biologically active filtration with conventional pretreatment and UV disinfection.

POM pilot study

Carollo's custom-built remote data acquisition system allowed effective and convenient data collection from three alternative treatment trains comprised of nine pilot skids.

Carollo conducted a comprehensive, 18-month raw water quality-monitoring program on both sources of supply for the new plant. Carollo also performed bench-scale testing including an ozone evaluation, rapid small-scale column tests, and jar testing on batches of water collected from two raw water supplies: the Provo Reservoir Canal and the Jordan Aqueduct.

Carollo performed pilot-scale testing over a 10-month duration and on both sources of supply. Carollo constructed a building to house the pilot facilities near the future plant intake. Carollo also designed a 6-gpm pilot plant to conduct process testing of Train No. 3. Carollo pre-qualified four membrane equipment suppliers for testing of Trains No. 1 and 2, and those suppliers provided pilot plants to test membrane modules representative of those proposed for the full-scale plant.

Carollo also developed a custom treatment train evaluation and scoring procedure to evaluate the results of the pilot study and to facilitate consensus development on the final treatment train recommendation.

UV Disinfection

Carollo was the lead consultant for design and construction services for the new 70-mgd Point of the Mountain Water Treatment Plant (POMWTP) for the Metropolitan Water District of Salt Lake and Sandy, located near Salt Lake City, UT. The POMWTP incorporated enhanced conventional processes based on a 12-month pilot test program that was conducted by Carollo. The processes included flash mix; flocculation; sedimentation, including plate settlers and intermediate ozone; biologically active filters, ultraviolet light (UV), and chlorine disinfection. Other plant facilities included a 70-mgd finished water pump station, a 20-MG chlorinated reservoir, solids settling basins, solids handling facilities, a standby power generation facility and a maintenance facility.

Disinfection facilities for the POMWTP included provisions for complementary use of ozone, chlorine, and UV technologies, for a robust multiple barrier approach to public health protection. The UV system was designed to deliver a low pressure high output (LPHO) dose of  28 mJ/cm2 as per UVDGM Tier 1 requirements for 2.5-log Cryptosporidium and Giardia inactivation.

Biological Filtration

The POMWTP was designed and constructed with the capability to fully manage biological filtration.  Intermediate ozonation upstream of the filters enhances biological growth in the filters by increasing the assimilable organic carbon. The plant also has the ability to promote growth by operating the filters without chlorine and by backwashing with chlorine free water. It has the ability to control growth by adding chlorine on top of the filters, by backwashing with typical chlorinated potable water, and by backwashing with superchlorinated water.