British Columbia Water and Waste Association
The ‘Other’ Product of Water
Treatment:
Water Treatment Residuals
What They Are, Where They’re Going, and How They Get There
Denise Vieira, SYLVIS
Shawn Northwood, SYLVIS
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
May 4, 2010
British Columbia Water and Waste Association
Outline
1.
2.
3.
4.
5.
Objectives
Definition of water treatment residuals (WTR)
Production, types and characteristics of WTRs
British Columbia regulations
Opportunities for use and how WTRs are used in other jurisdictions
6. Summary & questions
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Objectives
By the end of this workshop, you will:
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•
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
Understand how water treatment residuals are generated
Understand the characteristics of the different residuals
Be aware of the enabling regulations pertaining to the material
Be aware of opportunities for use of the residuals British Columbia Water and Waste Association
What are residuals?
Merriam Webster dictionary defines residuals as: “something that remains after a part is taken, separated, or designated or after the completion of a process”
Water Treatment Residuals are generated through the process of industrial or municipal water treatment.
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
Focus on drinking water treatment residuals.
British Columbia Water and Waste Association
Characteristics
Dictated by water source and treatment type
• Surface water
‐ variable due to raw water quality ‐ colloidal matter
‐ chemical floc
• Groundwater
‐ mineral based
‐ minimal organics
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
The “Other” Product of Water Treatment
Generation
• Derived from sedimentation and filtration of chemically conditioned water
‐ settling
‐ chemical precipitation
‐ membrane and sand filtration
‐ dissolved air flotation (DAF)
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Production
Typical surface water treatment method
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•
•
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•
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
Turbid river for example
Pre‐sedimentation (↓ settleable solids) – WTR (silt, detritus)
Lime softening ‐ chemical quality Al coagulation – WTR, chemical quality
Filtration to remove colloids ‐maintenance of treatment systems (backwashing for example) – WTR (colloid floc and unspent colloid hydroxides)
British Columbia Water and Waste Association
Production
Rate
• Governed by installation design, type of processing and operations management • Continuous or batch
‐ DAF systems
‐ back‐flushing • Typically a holding or storage system
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Types
Aluminum‐based residuals
• Aluminum used in treatment for colloid stabilization, flocculation, and water clarification
• Gelatinous due to aluminum hydroxides • Granular material after complete freezing or drying – does not revert to gelatinous form • Propensity to bind P
• Typically low in all nutrients (except P) • High in Al
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Types
Iron‐based residuals
• Typically ferric chloride
• High in iron
• Ferric hydroxide strong adsorbent of arsenic (V), provided the pH is low enough
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Types
Coagulation & lime / soda ash softening residuals
• Result from processing hard, turbid surface water (coagulation) or groundwater treatment
• Surface water – consists of organic matter, and suspended solids
• Contains Ca, magnesium hydroxide and other minerals (oxides of Fe and Mn) • Typically basic (due to CaCO3 )
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Dewatering
Options
• Typically < 2% solids unless dewatered
• Mechanical dewatering
• Air drying
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Mechanical Dewatering
Centrifugation
• Operational flexibility (moisture)
• Solids depend on type of residual and polymer dosage
Pressure filtration
• Aluminum residual if desire high solids content
• Filter is pre‐coated with diatomaceous earth or fly ash
• Solid blocks rather than paste
Vacuum filtration
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
• Not generally for alum residuals
• Primarily for dewatering softening residuals from groundwater treatment
British Columbia Water and Waste Association
Air Drying
Lagoons or Sand Beds
• Success dependant on climate, design features (under‐drains), and sludge characteristics and method of operation
• Freezing aids in dewatering alum residuals – decreases gelatinous nature
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Land Drying – BC Example
Operational trial
• Requirement for dewatering
• Parameters for land drying
‐ optimal depth, time
• Local partners supportive
• Technical advisory committee
• Investigate opportunities for use
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Land Drying – BC Example
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Land Drying – BC Example
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Land Drying – BC Example
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Enabling Regulation
Code of Practice for Soil Amendments ‐ Background
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
• Enacted in 2007
• Requirements similar to the OMRR
• Applies to residuals not covered by the OMRR
‐ wood waste
‐ ash ‐ primary and secondary pulp and paper residuals ‐ lime and lime mud
‐ water treatment residuals
• Beneficial application of WTR to land for the purpose of soil conditioning – Not disposal!
British Columbia Water and Waste Association
Quality Criteria Code of Practice for Soil Amendments (CoPSA)
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
• Required monitoring
‐ Trace elements
‐ Foreign matter
‐ prohibited from causing a “contaminated site”
• Land application requirements
‐ Land Application Plan (LAP) required for > 5 m3/site/year
‐ additional monitoring required for an LAP
• Supported by Best Management Guidelines
• http://www.env.gov.bc.ca/epd/industrial/regs/codes/soil_amend/pdf
/land‐app‐guide‐soil‐amend.pdf
British Columbia Water and Waste Association
Quality Example (ppm, dry wt)
Trace Element
WTR
CoPSA
Arsenic
10
75
Cadmium
0.5
20
Chromium
5
1,060
Cobalt
1
150
Copper
9
2,200
Lead
5
500
0.09
5
Molybdenum
10
20
Nickel
3
180
Selenium
10
14
Zinc
21
1,850
Mercury
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Why Use WTR?
Benefits
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•
•
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
Increased organic carbon (depending on WTR type)
Improved soil structure Increased water holding capacity (depending on type)
pH adjustment British Columbia Water and Waste Association
Opportunities for Use
Remediation of High Phosphorus Concentrations
Liming Agent
Cement Manufacture
Synergies with other Residuals – Co‐application
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Remediation of High P Concentrations
Al‐based WTR for removal of P species
• Razali et al., Separation and Purification Technology (2007)
• Al and Fe ions enhance adsorption and chemical precipitation
• Column study ‐ removal of P species at wastewater concentrations
‐ Orthophosphate, polyphosphate and organic phosphate
‐ Effect of pH tested (pH 4,5.5,7,9)
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Remediation of High P Concentrations
Results
• Degree of adsorption dependant on P species and pH • Greatest adsorption at acidic pH
• Orthophosphate highest adsorption capacity for all pH values tested
Orthophosphate > polyphosphate > organic phosphate
• Al‐based DWTR can adsorb a range of P species therefore applications to wastewater treatment – constructed wetland
• Considerations: WTR compaction may lead to ↓ pore volume & clogging (beyond scope of work) Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Liming Agent
Calcium Containing WTR
• Typically low concentration of all nutrients including P • pH 8‐9
• Applied to land to increase the soil pH
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Cement Manufacture
Addition to concrete products
• WTR use in cement manufacture ‐ moisture
• Studies in Thailand, Kaosol et al., Energy Research Journal (2010)
‐ addition of WTR reduces costs of concrete block manufacture
‐ Ratios of 10, 20, 30, 40 and 50 % WTR pass Thai Industrial Standards for non‐load bearing blocks
‐ Ratios of 10 and 20 % WTR pass Thai Industrial Standards for load bearing blocks
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Co‐application with other residuals
WTR and Biosolids
• Biosolids are a source of N and P
• Biosolids application rates typically based on agronomic N application – P? • WTR provide opportunity to adsorb excess P
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Co‐application with other residuals
WTR and Biosolids
• Bayley et al., Soil Science Society of America (2007)
‐ researched long‐term P adsorption by land applied WTR
‐ found that WTR were able to adsorb P in the short and long term
• Potential for use in mitigating P run‐off Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Outside the Box
Researching opportunities for WTR:
• Lime and Fe WTR in constructed wetlands – treatment of dairy and municipal wastewater
• Al‐based WTR as substrate for reed‐bed system of wastewater treatment
• Al‐based WTR for dye removal in textile industry effluent
• WTR for treatment of wastewater from a vegetable oil refinery
• Alum WTR for primary wastewater treatment
• WTR as a sorbent for perchlorate and arsenic removal
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Considerations
And Points to Ponder
• Reduction in plant available P
• Soil pH and EC
• Aluminum toxicity to plants Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment
British Columbia Water and Waste Association
Any Questions
Denise Vieira, SYLVIS
Email: [email protected]
Telephone: 604.777.9788
Water
Treatment
Residuals:
The ‘Other’
Product of Water
Treatment