Meeting SB1 Requirements and TP Removal Fundamentals

Transcription

1 Meeting SB1 Requirements and TP Removal Fundamentals June 5, 2017

2 Agenda SB1 requirements for P TP removal mechanisms Biological removal Chemical removal

3 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

4 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

5 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

6 Hierarchy of Nutrient Removal

7 Enhanced Biological Phosphorus Removal (EBPR) Carbon Conditions Capture Operational considerations EBPR case study

8 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

9 EBPR Process Configuration Unaerated (Anaerobic) Aerated (Aerobic) Influent Effluent Clarifier

10 EBPR Biological Process

11 Anaerobic Zone Release Anaerobic Zone Selects for PAOs HRT 1 3 hours Presence of anaerobic zone also results in improved settling Influent Effluent Clarifier

12 Aerobic Zone - Uptake PO4-P (mg/l) 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

13 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

14 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

15 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

16 EBPR Case Study Configuration 3 Pass Aerobic 1 st Pass Swing Zone Aerobic Digestion ~ 3 mg/l effluent TP

17 EBPR Case Study Configuration 1 st Pass Unaerated 2 nd & 3 rd Aerobic Maintain SVI

18 EBPR Performance Case Study

19 EBPR Performance Case Study

20 EBPR Performance Case Study

21 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

22 Chemical Phosphorus Removal Trimming Low effluent TP Chemical types Design considerations Pilot study

23 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

24 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

25 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 )

26 Typical Chemical Properties

27 Typical Chem-P Dosing Requirements +500% +50% +150%

28 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)

29 2015 Full Scale Chemical P Removal Pilot Sodium aluminate effluent control study Feed locations: Raw Influent, Belt Press Filtrate

30 Chem-P Pilot Study No Chem Filtrate Only Filtrate + Influent

31 Chem-P Pilot Study No Chem Filtrate Only Filtrate + Influent

32 Chem-P Pilot Study No Chem Filtrate Only Filtrate + Influent

33 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

34 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

35 Scott Phipps, PE

36 Typical Chemical Dosing and Costs

37 Phosphorus Removal Potential 1.7 Soluble P Particulate P P Concentration (mg/l) 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.