Salt Management in Recycled Water at Irvine Ranch Water District

Transcription

1 Salt Management in Recycled Water at Irvine Ranch Water District Paul A. Weghorst Executive Director of Water Policy Irvine Ranch Water District February 2, 2017

2 Presentation Overview Introduction to Irvine Ranch Water District (IRWD) Overview of IRWD s recycled water system Need for salt management Sources of salt Development of Salt Management Model Important model findings Salt management objectives Future forecast of recycled water quality Ongoing activities Conclusions

3 Irvine Ranch Water District Service Area 6 Cities Irvine Lake Forest Tustin Newport Beach Orange Costa Mesa Unincorporated Orange County 20% of Orange County IRWD covers a large portion of central Orange County 181 square miles Size of District 3

4 IRWD Services Drinking Water 5 water treatment plants - Including 2 desalters 27 Wells and 36 reservoirs 1760 miles of water pipeline Sewage Collection 1070 miles of collection pipeline Recycled Water 2 recycled water plants Urban Runoff Treatment IRWD San Joaquin Marsh 27 wetland treatment sites 4

5 IRWD Water Supply Sources 1990 Population Served: 114,000 Total Water Provided: ~70,000 AF 2017 Total Water Demands: ~90,000 AF Population Served: 390,000 Total Water Provided: ~82,000 AF 11% 9% 14% 66% 28% 18% 15% 36% Imported Water Clear Groundwater Local Surface Water Recycled Water Imported Water Clear Groundwater Recycled Water Treated Groundwater 5

6 IRWD Recycled Water System One of the largest in the United States First deliveries in 1967 Two water recycling plants for a total of 33 mgd 28% 525 miles of pipeline 5,500 metered connections Up to 30,000 AF/year served 71 dual-plumbed buildings Offset to imported water Landscape Agriculture Office Buildings Industrial Processes 6

7 Recycled Water Use is Increasing Recycled Water Sales (AFY) Number of Recycled Water Customers Year 7

8 Recycled Water Uses are Sensitive to Water Quality 7 golf courses More than 50 parks More than 40 schools Numerous homeowners associations More than 620 Individual residences, front and back yards More than 40 Agricultural sites Composting, concrete production, carpet dyeing, cooling towers 71 dual plumbed commercial buildings 8

9 Need for a Salt Management Recycled Water Total Dissolved Solids (TDS) 12 month running average exceeded RWQCB limit of 720 mg/l Limit Effluent TDS Samples TDS (mg/l) 500 Regional Water Quality Control Board Limit = 720 mg/l for discharges to waters of the US 9

10 What are the Sources of Salt in IRWD sewers? IRWD hired engineers at HDR to: Determine what are the sources of salt in IRWD s recycled water system Develop a computer model of the system to predict historic and future changes in recycled water quality Average Salt Load 2008 to 2012 = 20,000 tons/year 10

11 TDS in IRWD Source Water Supplies 11

12 Residential Salt Contributions Fixture Types Percent Contribution to the Sewer System Toilets 26.4 % Clothes Washers 24.7 % Showers 15.8 % Faucets 15.5 % Baths 1.3 % Dishwashers 1.7 % 12

13 HDR Developed a Salt Management Model 13

14 Model Finding - Water Source is Important 720 Limit Recycled Water TDS Permit limit exceeded during period when imported water was used in-lieu of groundwater TDS (mg/l) 600 Effluent TDS Samples

15 Recycled Water Salt Management Objectives Maintain TDS < 720 mg/l Use Salt Management Model to evaluate: Extent of in-lieu program participation Impacts of new salt loads Impacts of new water supplies Changes in water quality of existing sources Costs of desalting recycled water 15

16 Future Forecast of TDS in Recycled Water Buffer mg/l below RWQCB limit Assumes no new water sources in the future Baseline A (solid line) Optimistic with no in-lieu program Baseline B (dashed line) Less Optimistic with in-lieu program 16

17 Ongoing Modeling Activities Hired Thomas Harder & Company and HDR to: Develop water quality model of Orange County Groundwater Basin TDS, Chlorides and Boron Establish links to recycled water Salt Management Model Evaluating potential effects of: Mid-basin injection of advanced treated recycled water Recharging desalinated seawater in the Basin 17

18 Conclusions IRWD has a TDS buffer of 50 to 60 mg/l in its recycled water IRWD must be vigilant in: Monitoring TDS of imported water Avoiding degradation of groundwater quality Avoiding new water supplies that offset existing high quality groundwater Managing its in-lieu program participation Evaluating new sewer discharges 18

19 IRWD Contact Information Paul Weghorst Executive Director of Water Policy (949)