Meeting SB1 Requirements and TP Removal Fundamentals June 5, 2017
Agenda SB1 requirements for P TP removal mechanisms Biological removal Chemical removal
SB No. 1 Requirements for Phosphorus ** WWTP / WRF facilities without a TP limit Requirement #1: Who: > 1.0 mgd capacity or major discharger Requirement #2: Who: > 1.0 mgd capacity or major discharger What: Monthly monitoring total and dissolved TP concentrations What: Technical and financial capability to reduced effluent TP to 1 mg/l When: Dec 1, 2016 When: Dec 1, 2017
Wastewater Characteristics for Phosphorus Ortho- Phosphate Biological P Removal Chemical P Removal Total Phosphorus Poly-phosphate Organically Bound Particulate Phosphorus Biodegradable Soluble Inert Soluble Solids Separation Chemical Coagulation Adsorption Cannot Remove
Phosphorus Removal Mechanisms Biological removal Enhanced Biological Phosphorus Removal (EBPR) Chemical removal Addition of metal salts to promote precipitation Physical removal Settling in a solids separation unit Filtration Also Recovery Intentional formation of a P product for reuse
Hierarchy of Nutrient Removal
Enhanced Biological Phosphorus Removal (EBPR) Carbon Conditions Capture Operational considerations EBPR case study
Ideal Influent Carbon for EBPR Carbon drives EBPR Chemical Oxygen Demand (COD) Biological Oxygen Demand (BOD) Volatile Fatty Acids (VFA) Characteristics Target Ratios COD:TP > 43 BOD:TP > 25 VFA:TP > 2 Constituents COD BOD VFA Typical Influent (TP = 7 mg/l) 300 mg/l 175 mg/l 14 mg/l
EBPR Process Configuration Unaerated (Anaerobic) Aerated (Aerobic) Influent Effluent Clarifier
EBPR Biological Process
Anaerobic Zone Release Anaerobic Zone Selects for PAOs HRT 1 3 hours Presence of anaerobic zone also results in improved settling Influent Effluent Clarifier
Aerobic Zone - Uptake PO4-P (mg/l) 12 10 8 6 4 2 0 INF ANA AER1 AER2 AER3 AER4 EFF RAS Sludge Blanket Depth Control Secondary Release Influent Effluent Clarifier Aeration Control Sufficient aerobic HRT for PO4-P uptake
Anaerobic Zone Integrity Aeration Control Prevent Over-Aeration (high DO) Influent Effluent Clarifier Size of Anaerobic Zone Effectively Reduced Low DO INFLUENT RAS High DO or NO 3 -N Anaerobic Zone Available Carbon for PAOs Reduced by OHOs RAS Control RAS to minimize high DO and NOX-N returns
Solids Handling Considerations Influent Effluent Clarifier Solids Handling Impact of Sidestreams Anaerobic environment releases-p High TP, Low BOD (ratio issue) Up to 50% P-load recycled
Clarifier Considerations Solids Removal Clarifier performance for low TP Tertiary filtration for limits < 0.5 mg/l Influent Effluent Clarifier Non-EBPR biomass is approximately 1.5% to 2% phosphorus EBPR biomass can be as high as 8%-12% phosphorus
EBPR Case Study Configuration 3 Pass Aerobic 1 st Pass Swing Zone Aerobic Digestion ~ 3 mg/l effluent TP
EBPR Case Study Configuration 1 st Pass Unaerated 2 nd & 3 rd Aerobic Maintain SVI
EBPR Performance Case Study
EBPR Performance Case Study
EBPR Performance Case Study
Chemical Trim for Phosphorus Removal Facilities with EBPR processes should include provisions for chemical addition To meet effluent limits below EBPR capabilities Reliability and redundancy Achievable effluent concentrations Typically 0.5 mgp/l (without tertiary filtration) Lower with optimized addition and solids separation
Chemical Phosphorus Removal Trimming Low effluent TP Chemical types Design considerations Pilot study
Chem-P Removal Advantages and Disadvantages Not biologically based performance Reduces sidestream impacts Particulate removal Low effluent TP Lower capital costs Advantages Disadvantages Higher solids production Impacts to digestion VSR Alkalinity consumption Potential overdosing Higher operational costs
Generic Chem-P Removal Mechanism 1. Dose chemical 2. Rapid mix to disperse chemical 3. Hydrous metal oxide (HMO) particles form 4. PO4 binds to HMO particles 5. HMO floc form 6. HMO floc trap additional PO4 7. PO4 surface adsorption to HMO floc 8. Solids settle in clarifier
Common Chem-P Removal Chemicals Typically, Al or Fe metals Aluminum Based Iron Based Aluminum sulfate Al 2 (SO 4 ) 3 14H 2 O Ferric chloride FeCl 3 Sodium aluminate Ferrous chloride Na 2 Al 2 O 4 FeCl 2 Poly-aluminum chloride (PACl,PAX) Al n Cl( 3n-m )(OH) m Ferrous sulfate Fe (SO 4 )
Typical Chemical Properties
Typical Chem-P Dosing Requirements +500% +50% +150%
Multi-Point Chemical Addition Multi-Point Addition Primary clarifiers (dose at Q) Secondary clarifiers (dose at Q + RAS) Filters (final polishing) Recycle streams (dose concentrated load)
2015 Full Scale Chemical P Removal Pilot Sodium aluminate effluent control study Feed locations: Raw Influent, Belt Press Filtrate
Chem-P Pilot Study No Chem Filtrate Only Filtrate + Influent
Chem-P Pilot Study No Chem Filtrate Only Filtrate + Influent
Chem-P Pilot Study No Chem Filtrate Only Filtrate + Influent
Chem-P Removal Design Considerations Criteria Materials of Construction Storage Crystallization Consideration Most are corrosive (low ph) FRP, plastic and lined steel Mixing G-value > 200 s -1 Pacing May require heated tanks, heat tracing or in building 35% ferric ~ -42 F 42% ferric ~ 20 F Alum ~ 32 F Flow pacing may overdose (I/I or variable P-conc) TP pacing at higher cost
Summary of Phosphorus Removal EBPR Biological process Influent characteristics Basin volume Secondary release Chem-P trimming Chem-P Chemical process Multi-point addition Mixing intensity More solids Over-dosing Both approaches can meet 1.0 mg/l TP effluent
Scott Phipps, PE 614-396-8745 sphipps@hazenandsawyer.com
Typical Chemical Dosing and Costs
Phosphorus Removal Potential 1.7 Soluble P Particulate P P Concentration (mg/l) 1.3 1.0 0.7 0.3 0.0 An Effluent TP limit of 1mg/L is typically achievable through EBPR and/or Chemical Removal Biological P Removal EBPR + Chemical Trim Filtration Chemical Trim + Filters 2 stage filtration/ membranes Two Stage Filtration/Membranes Reverse Osmosis R.O.