Download - Water Residuals Management - WEAT
Water Residuals Management
May 8, 2014
Presented by;
Michael Graves, P.E.
• Comparison of Wastewater & Water Residuals
• Residuals Management Basics
• Hefner WTP Evaluation
– Develop Your Goals
– Know Your Residuals
– Review Your Process
– Consider Operating Options
Discussion Topics
History of Residuals Management
Increasing Complexity over Time
Water Treatment Residuals Wastewater Sludge
1980s 2014
Time
Op
eratio
na
l C
om
plex
ity
1980s 2014
Time
Op
eratio
na
l C
om
plex
ity
Sources of Residuals
Identified Sources
Water Treatment Residuals Wastewater Sludge
• Bulk Screenings
• Inorganic Particulate (Grit )
• Primary Sludge
• WAS Activated Sludge
• Combined Primary & WAS
• Bulk Screenings
• Pre-Sed Sediment
• Chemical Sludge
• Filter Backwash
Municipal WTP
Municipal WWTP
Characteristics of Residuals
Characteristics
Water Treatment Residuals Wastewater Sludge
• Bulk Screenings / (Grit)
•Inorganic Solids
• Primary Sludge
•Inorganic / Organic Solids
• WAS Activated Sludge
•Organic / Volatile Solids
• Pre-Sed Sediment
• Inorganic Particulates
• Chemical Sludge
• Coagulated Colloids
• Filter Backwash
• Sheared Chemical Flocs
Municipal WTP
Municipal WWTP
Fate of Residuals
Typical Disposal Options
Water Treatment Residuals Wastewater Sludge
• Bulk Screenings / (Grit);
• Typically Landfilled
• Primary Sludge;
• Inorganic / Organic Solids
• Further Stabilization
• Landfilled
• Energy Recovery
• WAS Activated Sludge;
• Further Stabilized
• Landfilled
• Beneficially Reused
• Energy Recovery
• Incinerated
• Pre-Sed. Sediment;
• Landfilled
• Land Application
• Chemical Sludge;
• Landfilled
• Land Application
• Building Materials
• AgLime
• Filter Backwash;
• Recovered Water Ponds
• Land Fill Solids
• Land Application
Residual Management Operations
Typical Disposal Options
Water Treatment Residuals Wastewater Sludge
• Thickening;
• Gravity Thickening
• Mechanical Thickening
• Sludge Stabilization;
• Aerated Digestion
• Anaerobic Digestion
• Dewatering
• Evaporation
• Mechanical Dewatering
• Disposal
• Thickening;
• Gravity Thickening
• Mechanical Thickening
• Dewatering;
• Gravity / Evaporation
• Mechanical Dewatering
• Disposal
• Thickening;
– Gravity Thickening
– Mechanical Thickening
• Dewatering;
– Gravity & Evaporation
– Mechanical Dewatering
Water vs. Wastewater Residuals
• Stabilization;
– Digestion
– Energy Recovery
• Disposal;
– Regulated Landfilling
– Regulated Land Application
– Incineration
• Regulatory Constraints
Difference in Residuals Properties
Differences in Residuals
Water Treatment Residuals Wastewater Sludge
• Primary Sludge;
• Water held within floc
•Biological Sludge;
•Water Held Inside Floc
•Water held inside Cells
•Harder to remove water
• Sediment;
• Water drains by gravity
• Chemical Sludge;
• Water Held within floc
• Gravity Thickening;
– Thickening in Sedimentation Basin
– Gravity Thickeners
Thickening Water Treatment Residuals
• Mechanical Thickening
– Gravity Belt Thickeners
– Rotary Drum Thickeners
Sedimentation Basin
Gravity Thickener
• Belt Filter Presses
• Centrifuges
Mechanical Dewatering
Hefner WTP Residuals Study
• 100% mechanical dewatering during all treatment
conditions up to 200 MGD
• High level of redundancy
• Recovery Pump Station: 15-20% recycle at 150 MGD
• Sludge Pump Station: Dry pit to reduce maintenance
Design Goals
Mass Balance – Lime Usage
Mass Balance – Hardness Removal
Mass Balance – Solids Production
Raw/recovery water solids: 24,236 lb/d (5.6%)
Ferric precipitates: 7,074 lb/d (1.6%)
Lime precipitates: 400,628 lb/d (92.8%) Predominated
Total solids: 431,938 lb/d
Review Process Changes
• Based on Historical Chemical Usage
• Impact of Polymer
Parameter Unit Capacity
75 mgd 100 mgd 150 mgd 200 mgd
Solids Handling Capacity
(Optimized Lime Dose)
lb/d dry
solids 140,000 190,000 280,000 370,000
Wet Solids Volume (4% Solids Content)
Solids Handling mgd 0.4 0.6 0.8 1.1
Parameter Unit Capacity
75 mgd 100 mgd 150 mgd 200 mgd
Solids Handling Capacity
(Historical Lime Dose)
lb/d dry
solids 215,000 287,000 430,000 575,000
Wet Solids Volume (1% Solids Content)
Solids Handling mgd 2.5 3.5 5 7
Consider Constructibility
Solids Pump
Station Force Main
Solids
Handling
Facility Site
Proposed Process
Clarifiers Flow / Solids Meters Solids Pump Station
Thickeners Balancing
Tanks Mechanical Dewatering
Solids Storage Hauling and Disposal
Consider How You Want to Load the Trucks
Direct Loading Advantages Stacking Pad Advantages
Minimize stacking of product. Allows for Operational Flexibility. More storage available.
Reduces storage of the product on-site. Single story building.
Eliminates handling the product multiple times.
Less dependent on truck hauling schedules.
Small Footprint
Belt Filter Press 24/7 with Stacking Pad
Centrifuge 24/7 with Direct Loading
1. Base Scenario
2. High Lime - Historical Lime Dosages
– 190 mg/L of Lime
– Mechanical Dewatering to 200 MGD
3. Low Lime – Considers Polymer Usage
– 110 mg/L of Lime
– Mechanical Dewatering to 200 MGD
4. Hybrid – Partial Use of Lagoons to Save Capital
– 110 mg/L of Lime
– Partial Mechanical Dewatering to 80 MGD.
– Over 80 MGD, solids flow to lagoons.
Scenarios
Base Scenario
Item Operation with Polymer
(Lime Dosage = 110 mg/L)
Operation without Polymer
(Lime Dosage = 190 mg/L)
Capital Cost $14,570,000 $14,570,000
Annual Dewatering,
Hauling, and
Disposal
$2,920,000 $136,480,000
Total 30-Year
Cumulative Value $132,660,000 $151,050,000
30-Year Net Present
Value $72,900,000 $82,200,000
Base Scenario Costs
Mechanical Dewatering Scenarios
Item Scenario 1 - High Lime Scenario 2 – Low Lime
Capital Cost $27,670,000 $23,390,000
Maintenance Costs $5,020,000 $4,280,000
Operations Cost $52,820,000 $49,320,000
Hauling, and Disposal $30,330,000 $26,250,000
Total 30-Year Cumulative Value $115,840,000 $103,240,000
30-Year Net Present Value $70,000,000 $61,800,000
Item Hybrid – Partial
Mechanical Dewatering
Capital Cost $12,030,000
Maintenance Costs $5,320,000
Operations Cost $47,900,000
Hauling, and Disposal $36,700,000
Total 30-Year Cumulative Value $101,950,000
30-Year Net Present Value $56,400,000
• Dewatering water and wastewater solids is similar
but different
• Consider the entire process in making changes
• Design Goals - The cheapest solution may not be the
best for a utility
Take Aways
Questions & Answers