Impact of Urban Water Conservation on Receiving Water Body Nutrient - - PowerPoint PPT Presentation

Center for Comprehensive,

• ptimaL and Effective

Abatement of Nutrients (CLEAN)

Impact of Urban Water Conservation on Receiving Water Body Nutrient Quality

Sybil Sharvelle, Brock Hodgson, JoAnn Silverstien (CU)

May 4, 2017

EPA Centers for Water Research on National Priorities Related to a Systems View of Nutrient Management

• Established in 2013
• One of 4 national centers
• The only center with

irrigated agriculture components

The CLEAN Center

Mission of CLEAN Create knowledge Build capacity Forge collaboration To develop and demonstrate sustainable solutions for reduction of nutrient pollution

Water Demand Reduction

Indoor and Outdoor Conservation Graywater Reuse Stormwater Use Effluent Reuse

Water Conservation Impacts

No Conservation

Wastewater Nutrient Load

Conservation

Wastewater Nutrient Load Water Demand Water Demand Result is more concentrated wastewater

Boulder 75th St WWTF Case Study

• 75th St WWTF serves

Boulder, CO

• Permitted capacity

= 25 MGD

• Average operating flow =

15.2 MGD (Reg. 85 Data)

• Biological Nutrient Removal

– 4 Stage Bardenpho

2 4 6 8 10 12 14 16 18 20 EFF-TIN mg/L - N EFF-TN mg/L - N EFF-TP mg/L - P Concentration (mg/L)

Source: https://bouldercolorado.gov/water/wastewater-treatment Source: Regulation 85 Reported Data n = 12

Approach

Downstream Baseline Effluent Baseline Influent

• Reg. 85 Data

Baseline Removal Rate

• Reg. 85 Flow

Influent Concentration Effluent Strategy BioWin Modeling Impact on Removal IUWM Modeling Impact on Influent Upstream

• Reg. 85 Data

Modeling Approach

• BioWin modeling of WWTP’s for source control, reuse and

conservation scenarios – Indoor Conservation

• 15-54% flow reduction
• Constant contaminant loading

– Urine Separation

• 5%, 15%, 30%, 75% and 100% population adoption

– Flow change = 10 gallons/person/day

• Loading adjusted assuming 11 g N/person/day and 1 g P/person/day

– Graywater Reuse

• 5%, 15%, 30%, 75% and 100% population adoption

– Toilets: 12 gallons/person/day – Irrigation: 25 gallons/person/day

• Loading adjusted according to literature estimates

Impact of Practice to WW Influent Quality

2 4 6 8 10 12 14 16 5 10 15 20 25 30 35 40 45 50 Baseline Conservation - 23% Indoor Conservation Source Separation - 26% Population Adoption Graywater Toilet Reuse

• 26% Population

Adoption Graywater Irrigation Reuse - 26% Population Adoption Flow (MGD) Concentration (mg/L) TKN (mg/L - N) TP (mg/L - P) Flow (MGD)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0% 10% 20% 30% 40% 50% 60% Effluent TIN ratio (Conservation/Base) Indoor conservation: influent flow reduction

Effluent TIN normalized concentration ratio

Boulder Longmont Metro Regression

Approach

Downstream Baseline Effluent Baseline Influent

• Reg. 85 Data

Baseline Removal Rate

• Reg. 85 Flow

Influent Concentration Effluent Strategy BioWin Modeling Impact on Removal IUWM Modeling Impact on Influent Upstream

• Reg. 85 Data

Impact of Practices on Effluent Discharge

• Conservation practices result in

increase in nutrient discharge concentration

• Source separation decreases

effluent discharge

Conservation Source Separation Graywater Irrigation

50 100 150 200 250 5 10 15 20 25 30 0% 20% 40% 60% LEFF (lbpd -N or P) CEFF (mg/L-N or P) Percent Aditional Indoor Conservation (%) 50 100 150 200 250 2 4 6 8 10 12 14 16 0% 20% 40% 60% 80% 100% LEFF (lbpd -N or P) CEFF (mg/L-N or P) Percent Population Adopting Technology (%) Effluent TN Conc. Effluent TP Conc. Effluent TN Load Effluent TP Load 50 100 150 200 250 2 4 6 8 10 12 14 16 18 20 0% 20% 40% 60% 80% 100% LEFF (lbpd -N or P) CEFF (mg/L-N or P) Percent Population Adopting Technology (%)

Impact of Practices on Downstream Concentration

Conservation Source Separation Graywater Irrigation WWTP Effluent Reuse

500 1000 1500 2000 2500 3000 1 2 3 4 5 6 0% 20% 40% 60% LEFF (lbpd - N) CDS (mg/L - N) Percent Additional Indoor Conservation (%) Downstream TN Concentration Effluent TN Load 500 1000 1500 2000 2500 1 2 3 4 5 6 0% 20% 40% LEFF (lbpd - N) CDS (mg/L - N) Percent of Effluent Reused (%) Downstream TN Concentration Effluent TN Load 500 1000 1500 2000 2500 3000 1 2 3 4 5 6 0% 50% 100% LEFF (lbpd - N) CDS (mg/L - N) Percent Population Adopting Technology (%) Downstream TN Concentration Effluent TN Load 500 1000 1500 2000 2500 1 2 3 4 5 6 0% 50% 100% LEFF (lbpd - N) CDS (mg/L - N) Percent Population Adopting Technology (%) Downstream TN Concentration Effluent TN Load

Bars indicate min and max

Conservation Impact: P

• Effluent

concentration increases, but load does not substantially change

50 100 150 200 250 5 10 15 20 25 30 0% 20% 40% 60% LEFF (lbpd -N or P) CEFF (mg/L-N or P) Percent Aditional Indoor Conservation (%) Effluent TN Conc. Effluent TP Conc. Effluent TN Load Effluent TP Load 50 100 150 200 250 300 350 400 450 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 0% 20% 40% 60% LEFF (lbpd - P) CDS (mg/L - P) Percent Additional Indoor Conservation (%) Downstream TP Concentration Effluent TP Load 50 100 150 200 250 300 350 400 450 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 0% 20% 40% 60% LEFF (lbpd - P) CDS (mg/L - P) Percent Additional Indoor Conservation (%) Downstream TP Concentration Effluent TP Load

Conserved flow stays in stream Conserved flow removed from system

Summary

• Conservation can increase effluent discharge concentrations,

especially nitrogen species – Minimal impact to nutrient mass loads – Impact to downstream concentrations depends on surface water flow and mixing zone characteristics

• Municipalities encouraging conservation will need to consider

impacts to POTW performance/operations

• Potential Utility Costs:

– Energy costs of increasing SRT and aeration rate – Greater impact of sidestream (centrate) nutrients – Chemical addition for pH control – Labor and materials for increased sewer maintenance

Thank you.

To join stakeholder group:

Theresa.Connor@colostate.edu