Southern California Salinity Coalition TDS Trends Study Update for - PowerPoint PPT Presentation

Southern California Salinity Coalition TDS Trends Study Update for the Basin Monitoring Program Task Force October 18, 2017 Daniel B. Stephens & Associates, Inc.

Problem Statement 1. Evaluate the long-term trends for salinity in wastewater and recycled water 2. Assess how periodic droughts and various conservation measures may influence these trends 3. Primary Research Questions: a. What portion of the increment from use (IFU) can be attributed to water conservation measures? b. If trends of conservation measures continue, what portion of the IFU can be attributed to water conservation measures Daniel B. Stephens & Associates, Inc.

Problem Statement Temecula Valley Sewershed • Increment from use (IFU) 1,000 typically ranges from 200 900 800 to 250 mg/L. TDS Concentration (Mg/L) 700 • IFU can drive effluent 600 TDS above the discharge 500 400 limit. 300 • How much of IFU is due Source 200 Effluent to conservation Influent 100 Temecula Valley Discharge Limit: 750 mg/L 0 measures? 2007 2008 2009 2011 2012 2013 2015 2016 2017 Daniel B. Stephens & Associates, Inc.

Increase in TDS from MSLs from Indoor Use 500 450 1980 Indoor Water Use 2016 Indoor Water Use (77 gcpd) (52 gcpd) 400 350 Increment from Use TDS (mg/L) 300 250 200 150 100 Salt Load = 0.17 pounds per capita per day 50 Salt Load = 0.15 pounds per capita per day 0 85 80 75 70 65 60 55 50 45 40 Indoor Water Use (gpcd) Daniel B. Stephens & Associates, Inc.

Regression Tree Analysis for Influent TDS • Indicates important explanatory variables: – Population (POP) – Source TDS (STDS) – Source Flow (SFLOW) Daniel B. Stephens & Associates, Inc.

Principal Component Analysis PCA indicates an initial EMWD multiple regression model: • ITDS ˜ POP + STDS + SFLOW + PMDI + IFLOW Backward stepping from the initial model resulted in removal of first SFLOW and second PMDI: • ITDS ˜ POP + STDS + IFLOW Daniel B. Stephens & Associates, Inc.

EMWD Multiple Regression Analysis 800 • Variables: – STDS: Source TDS 750 – IGPCD: Influent per 700 capita water use mg/L ITDS 650 • R -squared = 0.979 Model 600 • Relative Importance – STDS: 88.2 550 – IGPCD: 11.8 500 10/10/06 02/22/08 07/06/09 11/18/10 04/01/12 08/14/13 12/27/14 05/10/16 09/22/17 Daniel B. Stephens & Associates, Inc.

EMWD Multiple Regression Analysis 800 800 • Variables: – STDS: Source TDS 750 750 55 gpcd – IGPCD: Influent per 700 700 capita water use mg/L mg/L ITDS ITDS 650 650 66 gpcd Model • C_gpcd: Constant Model C_gpcd water use of 66 gpcd 600 600 (no conservation) 550 550 – IFU Difference: 500 500 ~18mg/L 10/10/06 10/10/06 02/22/08 02/22/08 07/06/09 07/06/09 11/18/10 11/18/10 04/01/12 04/01/12 08/14/13 08/14/13 12/27/14 12/27/14 05/10/16 05/10/16 09/22/17 09/22/17 Daniel B. Stephens & Associates, Inc.

IEUA Multiple Regression Analysis 560 800 • Variables: 540 – STDS: Source TDS 750 520 – IGPCD: Influent per 700 500 capita water use mg/L mg/L ITDS ITDS 480 650 • R -squared = 0.75 Model Model 460 600 • Relative Importance 440 – STDS: 67.2 550 420 – IGPCD: 32.8 400 500 07/24/98 10/10/06 02/22/08 04/19/01 07/06/09 01/14/04 11/18/10 10/10/06 04/01/12 07/06/09 08/14/13 04/01/12 12/27/14 12/27/14 05/10/16 09/22/17 09/22/17 Daniel B. Stephens & Associates, Inc.

IEUA Multiple Regression Analysis 560 560 800 • Variables: 540 540 – STDS: Source TDS 750 70 gpcd 520 520 – IGPCD: Influent per 700 500 500 capita water use mg/L ITDS mg/L mg/L ITDS ITDS 480 480 650 Model • C_gpcd: Constant Model Model C_pgcd 95 gpcd 460 460 water use of 95 gpcd 600 440 440 (no conservation) 550 420 420 – IFU Difference: 400 400 500 ~20mg/L 07/24/98 07/24/98 10/10/06 02/22/08 04/19/01 04/19/01 07/06/09 01/14/04 01/14/04 11/18/10 10/10/06 10/10/06 04/01/12 07/06/09 07/06/09 08/14/13 04/01/12 04/01/12 12/27/14 12/27/14 12/27/14 05/10/16 09/22/17 09/22/17 09/22/17 Daniel B. Stephens & Associates, Inc.

Source Flow Seasonal trends Drought Index Source TDS % SPW Allocation State Mandate Influent TDS Long term conservation trends Local Conservation = Indoor per Effluent TDS State Mandate capita water use Technology enhancements Daniel B. Stephens & Associates, Inc.

Summary • Unintended consequences from water conservation measures – lower water quality (higher TDS) – less quantity of recycled water – less revenue – infrastructure O&M • Observation data from groups of sewering agencies rather than individual WWTP is more reliable due to the following factors – Population (city boundaries, sewershed boundaries) – Operations can divert flows from plant to plant Daniel B. Stephens & Associates, Inc.

Summary • Drought impacts both source water quality and an agency’s source(s) of supply. • “...drought, and the conservation strategies that are often enacted in response to it, both likely limit the role reuse may play in improving local water supply reliability.” Daniel B. Stephens & Associates, Inc.