Systems analysis of metropolitan-scale reuse with effects on water supply resilience and water quality

Figures & data

Figure 1 . Major sources of imported water supply to Los Angeles County.

Figure 2 . Within Los Angeles, a complex system of water management includes (a) Water supply agencies, (b) Major watersheds associated with rivers, (c) Groundwater basin management areas, (d) Stormwater capture facilities.

Figure 3 . Wastewater treatment facilities in metropolitan Los Angeles.

Table 1 . Operational treatment capacity parameters for current wastewater treatment and water reuse facilities, based on data from available sources. The parameters were used as constraints in the modeling (WRP = water reclamation plant).

Name	Design Capacity (MCM/day)		Total Annual Capacity (ac–ft)	Existing Reuse Capacity (mgd)
	Dry Weather	Wet Weather
Burbank WRP	0.04	0.04	17.02	0.03
LA-Glendale WRP	0.06	0.09	34.03	0.06
Hyperion WRP	1.35	2.55	885.48	0*
LA County Joint Pollution Control Plant (JWPCP)	1.2	1.2	544.91	0
La Canada WRP	0	0	0.27	0
Long Beach WRP	0.08	0.08	34.06	0.03
Los Coyotes WRP	0.11	0.13	55.51	0.03
Edward Little WRP (Total Reuse)	0.14	0.14	63.76	0.14
Edward Little WRP (Title 22)	0.19	0.19	84.87	0.11
Malibu Mesa WRP	0	0	0.27	0
Pomona WRP	0.05	0.05	20.43	0.04
San Jose Creek WRP	0.3	0.3	136.22	0.3
Santa Monica Urban Runoff Recycling Facility (SMURF)	0.002	0.002	0.68	0.3
Tapia WRP	0.05	0.05	22.47	0.05
Terminal Island WRP	0.09	0.09	40.87	0.02
Donald Tillman WRP	0.24	0.3	122.61	0.1
Whittier Narrows WRP	0.05	0.05	20.43	0.05

*Hyperion WRP sends effluent to the Donald Tillman WRP for advanced water treatment and may have new water reuse capacity in future years.

Table 2 . Proposed new water reuse operations and associated costs added to the model for this analysis. Many operations are being flexibly designed to provide either indirect or direct potable supplies as existing and emerging regulations allow (MCM/Day = millions of cubic meters per day).

Facility	Proposed Design Capacity (MCM/Day)	Destination	Source
Hyperion Wastewater Treatment Plant: New Reuse	0.51	Edward C. Little Reclamation Plant Central/West Coast Basin Groundwater Replenishment (modeled as recharge through Rio Hondo Spreading Grounds)	Los Angeles Department of Water and Power (2019)
Los Coyotes WRP: newly included connections	0.03	Montebello Mutual Water Company Golden State Water City of Lynwood City of South Gate City of Pico Rivera City of Monterey Park	LA County Department of Sanitation (2015)
Whittier Narrows WRP: Newly included connections	0.05	City of Arcadia City of El Monte	LA County Department of Sanitation (2015)
Joint Water Pollution Control Plant: New Reuse Capacity (LA County and MWD)	0.45	Whittier Narrows Dam (Rio Hondo) for groundwater replenishment Long Beach Coastal Injection Wells (proposed) Santa Fe Spreading Grounds Eaton Wash Spreading Grounds Garvey Reservoir (MWD) Injection into MWD’s water treatment plant for distribution	MWD (2016)

Figure 4 . Schematic depicting architecture and data flows of the Artes model

Figure 5 . Supply portfolios from the hydroeconomic modeling framework. The two scenarios modeled responses to an imposed reduction of 50% of historic imported water supplies with and without new large-scale reuse project capacity (MCM = Millions of Cubic Meters). The percentages represent the percent of total supply in the scenario from a source.

Figure 6 . Water reuse as a percentage of supply for water retailers throughout LA County in the modeled scenario with an imposed 50% reduction in available imported water.

Figure 7 . Historic and modeled influent flows to the two largest wastewater treatment facilities in LA. The modeled flows are from a scenario with 30% available imported water, which represents extended water scarcity from drought.

Figure 8 . Daily influent monitoring data for contaminant concentration and percent removal of Biochemical Oxygen Demand (BOD) and Total Suspended Solids (TSS) for Hyperion WRP (2011–2019). Source: Based on data from the California Integrated Water Quality System and published by Keene, Babchanik, and Porse (2022).

Table 3 . Results from multiple regression modeling with a semi-log formulation.

Explanatory Variables	Coefficient	Standard Error	t-value
Response Variable: Percent Removal of TSS (R^2=  0.44)
Intercept*	0.77	0.03	37.7
log(Influent Flow)*	0.027	0.004	−8.3
log(Influent TSS Concentration)*	0.56	0.002	33.8
Response Variable: Percent Removal of BOD (R^2=  0.29)
Intercept*	0.80	0.02	28.0
log(Influent Flow)*	−0.027	0.003	−7.2
log(Influent BOD Concentration)*	0.51	0.001	22.4

*Indicates statistically significant variables with p < 0.001

Table 4 . Modeled scenarios of imported water availability with available reuse capacity, including both existing indirect potable reuse and newly proposed advanced water treatment.

Scenario: Imported Water Available	Modeled % from Supply Sources^b			Average total water supply from all sources (MCM)	Average annual net electricity use (GWh/MCM)	Per capita water use (lpd^c)
	% Imported	% Groundwater	% Recycled Water
100%	65%	27%	7%	1,530	2.6	438
70%	50%	42%	8%	1,431	2.1	408
50%	43%	46%	9%	1,351	1.6	386
30%	31%	51%	18%	1,332	1.8	382
0%^a	17%	56%	27%	1,252	1.8	359

^a % imported water used in this scenario is from initial available storage.

^b Does not report surface water use, which is approximately 1%.

^c lpd = liters per capita per day.

Table 5 . Average value of electricity intensity during drought, non-drought, and all years for the modeled scenario of 50% of historic imported water availability (kWh = Kilowatt-Hours). Drought and non-drought years are identified as years with greater or less than the 50th percentile of annual precipitation during the time period from 1986 to 2010.

Model Result Parameter	Non-Drought (n = 8)	Drought (n = 7)	All Years
Average % Supply from Groundwater	43%	45%	45%
Average % Supply from Imported Water	50%	41%	44%
Average % Supply from Non-Potable/Indirect Reuse	7%	12%	9%
Average % Supply from Direct Potable Reuse	0%	1%	0%
System-wide Electricity Intensity (kWh per MCM)	1.5	1.5	1.5

LADWP. 2019. Hyperion Water Reuse and Resiliency Program. Los Angeles, CA: Los Angeles Department of Water and Power. https://s3-us-west-2.amazonaws.com/ladwp-jtti/wp-content/uploads/sites/3/2019/09/19144819/Hyperion-reuse-5.pdf.

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LACSD. 2015. Twenty-Sixth Annual Status Report on Recycled Water use. Doc No 3392791. Los Angeles, CA: Sanitation Districs of Los Angeles County.

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MWD. 2016. Potential Regional Recycled Water Program Feasibility Study. 1530. Los Angeles, CA: Metropolitan Water District of Southern California.

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Keene, Dakota, David Babchanik, and Erik Porse. 2022. “Influent Parameter Concentrations, Mass Loading Values, and Influent Flow Values for Evaluating Operations During Dry Weather Flows at California Wastewater Treatment Facilities.” Office of Water Programs, Sacramento State University, https://doi.org/10.4211/hs.e02c71690d3d4df9abfaf8ec33f7f9c7.

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Data availability

Model documentation, data, and software are openly available (Porse 2022). Supporting data for the analysis is available as a supplementary file. Wastewater treatment facility data used to evaluate potential water quality and treatment effects is available through a Hydroshare repository (Keene, Babchanik, and Porse 2022).