Water Reuse in California and the West

• Mark Gold, D.Env.
• Director of Water Scarcity Solutions
• UCLA IoES Adjunct Professor

Presentation to UC Berkeley Law School Water Symposium – 2/15/25

Recommendations

• More Federal, State and Local funding for water reuse projects. States, Cities and Counties should work together to advocate for more Federal funding.
• Each state should set water reuse targets of at least 40% by 2040. Up to 1 MAFY of new water supply.
• Federal, State, and Local agency leaders should develop consensus guidance document on definitions of water reuse, Indirect Potable Reuse, and Direct Potable Reuse.
• Federal and States must develop standardized data submission and management approach that includes influent, effluent, reuse, and residuals volumes and how water is reused.

California Recycled Water Regulations

Increasing requirements for public health protection

Non-Potable

Reuse

Indirect Potable Reuse

Groundwater Replenishment

Indirect Potable Reuse

Reservoir Water Augmentation

2000

2014 2018

Direct Potable Reuse

Raw and Treated

Water

Augmentation

2023

Irrigation Industrial Uses

Water Recycling

• Tertiary Treatment (filtration and disinfection – Title 22 – bacteria 2.2 total coliforms cfu per 100 ml and turbidity not to exceed 10 NTU (nephlometric turbidity units))
• Advanced treatment – MF-RO, nitrification/denitrification (NDN), UV-peroxide –

NDMA removal

• Non-potable uses – irrigation and industry
• Indirect Potable Reuse – mixing – groundwater or reservoirs – purple pipe - for Groundwater – 12 log reduction for viruses, and 10 log reduction for Giardia and Cryptosporidium. Must use RO and advanced oxidation. For surface water augmentation – 8 log reduction for viruses and 7 log for both Giardia and Cryptosporidium based on dilution.
• Direct Potable Reuse – use existing infrastructure. California – regulations in place 10-1-24. 20 log virus reduction. 14-log for Giardia and 15 log reduction for Cryptosporidium. Must use membrane separation, advanced oxidation and ozone and biologically activated carbon (BAC).
• Current water reuse in California is 749K AFY. Modest gains in the last dozen years. State Recycled Water Policy is 1.5M AFY by 2020 and 2.5 MAFY by 2030. Recently weakened in California Water Strategy to only 800K AFY by 2030 and

1.8M AFY by 2040.. Lack of major state and federal investments.

• San Diego, LACSD/MWD and LA projects could be over 450K AFY alone!!! State sewage treatment plants receive over 3.4M AFY of wastewater so enormous potential for improvement.

Pure Water Southern California Facilities

MWD and LA County Sanitation Districts

Pure Water LA and Pure Water San Diego are similar.

Full buildout of the three facilities could be 450K AFY!

Recharge Facilities

A.K. Warren Water Resource Facility

Membrane Bioreactor

Conveyance Pipelines

Reverse Osmosis

UV/AOP

Program Overview – Phases 1 & 2

Phase 1 Total: 115 MGD

Phase 2 Total: 150 MGD

90 MGD

for IPR

Phase 1: 25 MGD for DPR using existing Azusa Pipeline

Phase 2: 60 MGD for DPR through

new pipeline

Nutrient Discharged Linked to Habitat Compression

Ho et al. (2023) used the ROMS-BEC ocean model to determine the effect of nitrogen reduction and water recycling on habitat availability. Increasing percent nitrogen reductions resulted in a significant increase in habitat space, pH, and dissolved oxygen availability, showing that effective nutrient management has great potential to protect California ecosystems from the harmful effects of OAH.