Hemet Water Filtration Plant Design

Eastern Municipal Water District, 

Hemet Water Filtration Plant Design

2008 Water Project of the Year (Honorable Mention) - American Society of Civil Engineers, Region 9
2007 Outstanding Civil Engineering Project of the Year - American Society of Civil Engineers, Region 9, Los Angeles Section
Service Type: 
Project Highlights: 
  • Carollo's compac t layout will provide 40 mgd of state-of-the-art treatment on a five-acre site.
  • Plant design allows for fast and easy expansion.
  • Membrane filtration and PAC adsorption will allow EMWD to switch from groundwater supply to surface water supply without customer complaints.
  • The use of membrane filtrationand chloramination will prevent formation of carcinogenicdisinfection by-products.
Zebon submerged membrane system
The Eastern Municipal Water District's new Hemet Water Treatment Plant uses a Zenon submerged membrane system.

The Eastern Municipal Water District (EMWD) currently depends on imported surface water for approximately 75 percent of its water supply. The remainder is produced from local groundwater supplies and extensive use of reclaimed water (EMWD operates five reclamation plants with a combined capacity of 50 mgd). However, a severe six-year drought and the pressure of continued growth within the service area has stretched EMWD’s supplies to the limit, forcing it to rely increasingly on imported water, which must be treated.

In 2002, Carollo and others designed the Perris Water Treatment Plant with an initial capacity of 10 mgd. The Perris plant is currently being expanded, but the supply is being outstripped by relentless growth. Having no time to lose, EMWD realized it needed further filtration capacity and retained Carollo to develop a strategy for designing and constructing a 10-mgd membrane filtration plant expandable to 40 mgd, using State Project Water, in 32 months. State Project Water is a good quality, raw water. However, it is subject to taste and odor events and disinfection by-product formation.

To accommodate the relatively tight project schedule, Carollo awarded a subconsultant design contract to the membrane supplier. By doing that, Carollo protected the owner ’s interests (the engineer is responsible for the full design) and reduced construction time (the submittal review of the membrane system was performed during design). To ensure that the membranes are fabricated, tested, delivered, and ready for installation when construction progresses to the appropriate point, Carollo prepared a prepurchase contract which also incorporated strict performance and quality control requirements.

The plant will utilize 500 micron mechanical screens followed by a unique two -zone, single-tank membrane system with 98 percent recovery. The plant will combine membranes with chloramination to meet state and federal requirements for removal and inactivation of pathogens such as Giardia, Cryptosporidium, and viruses.

In order to achieve taste and odor control and provide further disinfection capability, the plant’s design accommodates the future addition of GAC contactors or dosing PAC within the flocculation basins and UV disinfection.

The Hemet Water Filtration Plant will greatly contribute to the supply of water to the fast growing area serviced by EMWD. The construction contract was awarded in November 2004.