Presented to the Coconino Plateau Water Advisory Council July 25, 2014
Charles Mosley, Director of Wastewater City of Sedona, Arizona The Past History and need for Plan WEDLU Committee & Recommendations Upgrade to A+ Construction of wetlands & injection well The Present Injection well WWTP Capacity Upgrade Optimization Plan Constituents of Emerging Concern (CEC’s) The Future Land Use Work Group Implementation Plan Plant capacity upgrade Wetlands recreation amenities
1992 -- Sedona WRP Contructed with 1.0 mgd capacity 2001 -- Flows exceed 800,000 gpd and Long- Term Effluent Master Plan prepared (irrigation based) 2005 –Point Source Discharge/Water Reuse Study (Presented to Council July 8, 2008)
July, 2008 – City Council forms Wastewater Effluent Disposal and Land Use Task Force (WEDLU). Consider options for effluent management (reuse and disposal) Consider alternative land uses once spray irrigation was replaced by another method of disposal May, 2010 – WEDLU reports findings and recommendations to City Council. Council favors On-Plant solution.
WEDLU recommends: Develop an Effluent Management Plan to determine optimum methods of effluent management Develop a test wetlands project Conduct testing for the feasibility of injection as a method of effluent management Ultra-violet disinfection upgrade to “A+” Disband WEDLU and wait to study land uses until Effluent Management Plan is completed WEDLU recommendations provided the City the roadmap for moving forward
1. Plant Water Quality 2. Wetlands 3. Test Injection 4. Optimization Design of wetlands, plant upgrade, and injection well research begins in September 2010 Citizen’s Expert Advisory Group formed (CEAG) Construction begins September 2011 for construction of 27 acre wetlands, and upgrade of plant to produce A+ effluent. Total contract cost: $2.7 million Spring 2012: WWTP begins producing A+ effluent Fall 2012: 27-acre Constructed Wetlands completed (soft opening) November 2012: Wetlands established as a public recreational amenity. Official name established as Sedona Wetlands Preserve Plant originally designed to process 2MGD 1.54MGD needed to serve current wastewater service area (connected & committed) Due to increase in strength of waste, capacity of treated A+ effluent only 1.4MGD Lower capacity due to water conservation. WWRP Treatment Capacity is Currently Limited by Secondary Processes
Unit Process Firm 4.0 Capacity
3.8 1.1 mgd current 3.6 flow 3.4 1.63 mgd Flow 3.2 Projection (2027) 3.0 2.8 2.6 Secondary Treatment 2.4 Annual 2.2 Average 2.0 Day Flow 1.8 Capacity 1.6 (mgd) 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 2012 connected and committed connections: 7,286 (1.54 MGD) 2027 projected connections: 7,721 (1.63 MGD) Improvements include: secondary clarifier basin, replacements of aeration blower system, digester Estimated costs: $2.1 -$3.9 million Upgrade design is completed These upgrades are critical to assure that the WWTP can continue to produce A+ effluent as the City grows
Background: Aquifer injection identified as a potentially feasible strategy to help manage reclaimed water Requires class A+ water quality Creates potential to accumulate future groundwater storage credits Schedule: Construction: March – October 2013 Test: Early October – Late November 2013 1. Capacity of Test Well 2. Constituents of Emerging Concern (CEC)
WWTP Site
Test Well
Wetlands Aquifer Injection Well targeted fractured bedrock aquifer below 600 ft
600 FT
Well screen
1,200 FT
Conclusions 0.36 MGD (250 GPM) sustainable injection rate (conservative estimate) Multiple wells could be installed on WWRP site for additional effluent management capacity Aquifer injection could provide critical effluent management capacity
Recommendations: Convert test well to permanent injection well Redundant well recommended to maintain injection capacity during maintenance/outage
Constituents of Emerging Concern: “CECs” CECs are not currently regulated Testing at WWTP occurred between Oct. & Nov. 2013 Studied pharmaceuticals, personal care products, hormones, food additives, etc Study monitored for 112 compounds not currently regulated by EPA/State of Arizona Ongoing research to identify levels representing human health risk National Water Research Institute (NWRI) established thresholds for selected CECs for “Potable Reuse” applications Conservative approach for this project. NWRI thresholds may end up being more stringent than EPA thresholds. Most CECs effectively reduced with biological and soil-aquifer treatment Artificial sweeteners not biologically amenable
Main Objective: Identify Impacts of injection to Aquifer Water Quality Determine background CEC levels in groundwater Evaluate CEC levels in A+ reclaimed water Measure CECs in groundwater after injection Compare levels to “guidance thresholds”
“No measured CEC concentrations in groundwater representing known human health risk”
CEC Detections Indicate Highly Effective Treatment at WWRP and in Aquifer
45% 40%
35% 30%
25%
Detected
20%
CECs 15%
% % 10% 5% 0% WW A+ POC Well POC Well Injection Potable Influent Reclaimed Pre-Inj Post-Inj. Test Well Well Water Pre-Inj. 99% reduction Very low levels of CECs found in groundwater Less than NWRI guidance thresholds for human health impacts WWTP reduced CEC levels by 99% (not including sucralose) No indication that injection of Class A+ reclaimed water adversely affects aquifer water quality from CEC perspective Perform groundwater travel time analysis & potentially continue to monitor for CEC tracers Approach Calculate seasonal Effluent Management Strategies (EMS) capacity Develop life-cycle cost of each strategy Develop evaluation criteria to assign a “value” to each EMS Develop “optimized” operational strategies accounting for seasonal changes in capacity Irrigation & Wetlands Capacity Varies by Season 6,000
5,000
4,000
3,000 Irrigation Wetlands
2,000 Capacity (gal/day/acre) Capacity 1,000
- Spring Summer Fall Winter Annual Avg Reservoir plays critical role to equalize flow 70
60
50
40
30
20 Reservoir Volume (MG) Volume Reservoir
10
0 Jan July Dec Irrigation Wetlands Injection Well
Unit Capital Cost $45k/ac $55k/ac $1.4M/ea
Unit Annual O&M $600/ac $1k/ac $49k/ea Cost
Unit Capacity 3,079 gal/day/ac 3,928 gal/day/ac 320,000 gal/day
Life-Cycle Cost* per 1,000 gal $2.38 $2.39 $0.80
* 20 year life cycle Importance Factor (1-5) 1=Low 5=High Criteria Definition Environmental- Cost-Based Based Evaluation Evaluation Cost- Cost of EMS per gallon of Effectiveness 5 3 ($/gal) effluent
Habitat restoration, water Environmental 3 quality 5
Economic Land use, tourism, revenue 4 3
Sustainability of groundwater Water Resource 5 5 supply, future credits Cost-Based Evaluation
Evaluation Importance EMS Ranking (1-3) Criteria Factor (1-5) 1=Lowest Benefit, 3=Highest Benefit 1=Low 5=High Irrigation Wetlands Aquifer Storage
Cost 5 1 1 3 Environmental 3 1 3 2 Economic 4 1 3 2 Water 5 Resource 1 2 3 Value N/A 17 36 44 Environmental-Based Evaluation
Evaluation Importance EMS Ranking (1-3) Criteria Factor (1-5) 1=Lowest Benefit, 3=Highest Benefit 1=Low 5=High Irrigation Wetlands Aquifer Storage
Cost 3 1 1 3 Environmental 5 1 3 2 Economic 3 1 3 2 Water 5 Resource 1 2 3 Value N/A 16 37 40 mgd 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 - Scenario Irrigation 0.1 1.0 0.9
Wetlands Scenario 0.3 1.7
Scenario Injection 0.1 1.9
Balanced Scenario 0.3 1.6 0.1 1
Balanced Scenario 0.1 1.3 0.6 2
Balanced Scenario 0.1 1.6 0.3 3
Wetlands Injection Irrigation
3
-
-
-
Focused Focused
Injection
Irrigation Focused
Wetlands
Balanced 1 Balanced 2 Balanced Balanced
Irrigation (acres) 304 0 0 40 192 100
Wetlands 27 721 27 66 27 27 (acres) Injection Wells 4 2 7 6 5 6 (#)* Freed-Up Land 0 -392 300 220 107 200 (acres)
* Includes one redundant well $45
$40 $39.3
$35
$30
$25 Capital Cost
$20
Capital Cost($M) 5 Yr CIP Budget $15 Recommended Scenario $10 $8.6
$5 $7.2 $5.5 Within current 5- Potential for modification year CIP budget of projected WW rate structure $- Irrigation-Focused Balanced 3 Injection Focused Wetlands-Focused
Max on-site Irrigation Reduce Irrigation Eliminate Irrigation Eliminate Irrigation Keep Existing Wetlands Keep Existing Wetlands Keep Existing Wetlands Max Wetlands Injection Wells (4) Injection Wells (6) Injection Wells (7) Injection Wells (2) 0 acres freed up ~200 acres freed up ~300 acres freed up ~400 off-site acres required Implement “Balanced 3” EMS Scenario Expand injection (6 wells) Maintain existing wetlands Reduce irrigation – free up land (200 acres) The actual number of required injection wells will depend on future land uses and potential use of A+ effluent Citizen’s Land Use Work Group Upgrade WWTP capacity from 1.4 MGD to 1.63 MGD Complete Effluent Implementation Plan Identify 200 acres for other purposes Identify locations at WWTP for future injection wells Groundwater travel time analysis Water credits Continue with developing recreational component of Wetlands Preserve Viewing platform for reservoir Other improvements as funding permits Questions? Options studied by WEDLU Effluent injection & upgrades Direct discharge to Verde River Constructed wetlands Algae farming Mechanical evaporators Recharge basins Sale of water credits
Wetlands amenities: Initial budget of $227,000 $177,000 in CIP for recreational amenities Funds parking lot, restrooms, bike racks, trash cans, waste stations Yavapai County Grant: $35,000 reimbursable grant pays for picnic tables, benches, and shade structures Road is improved: Wastewater budget pays for road improvements ($15,000) Formal dedication: Late September 2013 The Test Injection Well Constituents of Emerging Concern The Optimization Plan
CEC results reported in “parts per trillion” (PPT) 1 PPT = 1 drop of water in 20 Olympic-size swimming pools (13,200,000 gallons)
1 PPT = X 20