Created By Jenny Yu and Jonathan Damora
One of the most economical approaches to limit future water shortages is to recycle the water we already have. There are two approaches to recycling water, Indirect Potable Reuse and Direct Potable Reuse. Indirect potable reuse is currently being implemented in many places, such as The Ground Water Replenishment System in Orange County. At the Orange County plant, treated wastewater is sent to an advanced treatment plant where it undergoes microfiltration, reverse osmosis, and then advanced oxidation in order to clean it to the point where it is safe for human consumption. Then it is sent to various sites within Orange County where it is injected into the ground in order to replenish groundwater supply as well as used as a barrier to prevent seawater intrusion into the water table.
2. GWRS - Overview
● Current production capacity
of 70 mgd, enough water
for 600,000 people
● Purifies already highly
treated wastewater to
near-distilled quality
● Provides additional peak
wastewater flow disposal
relief
3. Major Benefits
● Reduces economic and environmental
impact of droughts, $478/AF with subsidies
● Provides all necessary low-turbidity water
for the Talbert Seawater Barrier
4. History
● Operational since January 2008
● Jointly funded by the Orange
County Water District and the
Orange County Sanitation
District
● Largest issues were the lack of
planning for diurnal flow and
optimizing the decarbonation
and lime stabilization process.
7. Pre-Purification
● first treated at the Orange County
Sanitation District (OCSD)
● 200 million gallons of wastewater per day
● bar screens, grit chambers, trickling
filters, activated sludge, clarifiers and
disinfection processes
9. Step 2
reverse osmosis
RO process
● disinfects and destroys
any trace organic
compounds
● NDMA, 1-4 Dioxane
Step 3
UV & H202
10. distribution
35 million gallons → injected into seawater intrusion barrier
● Water Factory 21 (WF-21)
● 23 wells along the coast
35 million gallons → pumped into Anaheim groundwater
recharge basins
● 13 mile pipeline to Kraemer and Miller
12. References
• R. Herndon and M. Markus, Orange County Water District, 18700 Ward Street, Fountain Valley, California 92708, Large‐Scale Aquifer
Replenishment and Seawater Intrusion Control Using Recycled Water in Southern California.
• William Dunivin, Mehul Patel, and James H. Clark, Orange County Water District Black &
Veatch Corresponding author e-mail: BDunivin@ocwd.com, Building on Lesson Learned for
Expanding the Next Phase of the Groundwater Replenishment System
• GWRS Technical Brochure,
http://www.gwrsystem.com/images/stories/AboutGWRS/GWRS%20Technical%20Brochure.pdf
Notes de l'éditeur
With a capacity of 187m3/min (70 mgd), the GWR System provides all of the low‐turbidity water that the barrier requires, with the remainder conveyed to OCWD’s infiltration basins in the city of Anaheim
Uses less than half the energy to pump imported water from Northern CA
Uses less than ⅓ the energy to desalinate ocean water
Water from northern California costs $600-$800/ ac-ft
Desal water costs $1200+/ac-ft
** groundwater costs 250
OCWD’s Talbert Seawater Barrier has been in operation since 1976 and was originally supplied with a blend of imported water and recycled water from Water Factory 21
OCSD clarified secondary effluent, normally disposed to the ocean, first goes through a
screening process prior to MF membrane treatment
MF reject streams are returned to OCSD’s Plant No. 1 for treatment
The RO concentrate or brine is discharged into the
ocean via the existing OCSD ocean outfall. Based on a design recovery of approximately 85
percent, the production rate of RO is 265 MLD (70 mgd).
Following RO, the RO permeate undergoes UV treatment. UV treatment involves the use of UV
light to penetrate cell walls of microorganisms
Target a lower pH (7.8-8.0) and higher alkalinity (40-50 mg/L) in the final product water
to increase buffering capacity and to decrease variability in the water quality while still
meeting targets to avoid scaling.
Install flow meters and flow control valves at the decarbonation towers to achieve
reliable flow distribution to the decarbonation towers, and allow automated adjustment of
by-pass based on feed pH.
Increase the by-pass capacity around the decarbonation towers to support a higher
alkalinity target by maintaining higher levels of carbon dioxide for conversion to
bicarbonate alkalinity with lime addition.
Modify the existing decarbonation tower effluent configuration to provide individual lime
feed for decarbonated water and by-pass water with the objective of improved pH feed
back control for lime feed and thus a more accurate lime dose for improved process
control.
Replace lime slurry make-up system based on findings from a pilot testing program
which support replacement with the RDP Lime Slaking system to increase delivery
accuracy to the lime saturators.
Install an additional lime saturator to support higher plant flow rates and higher lime
dosages without increasing turbidity.
