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PCBs in San Francisco Bay Area Municipal Wastewater Effluents Donald Yee*, Jon Leatherbarrow, Jay Davis.

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Presentation on theme: "PCBs in San Francisco Bay Area Municipal Wastewater Effluents Donald Yee*, Jon Leatherbarrow, Jay Davis."— Presentation transcript:

1 PCBs in San Francisco Bay Area Municipal Wastewater Effluents Donald Yee*, Jon Leatherbarrow, Jay Davis

2 Study Participants Fairfield Suisun*, Palo Alto, San Jose, Sunnyvale - (SB/FS) (~200 MGD)November 1999 – July 2000 CCCSD, CCSF, EBDA, EBMUD, Millbrae* - (CB) (~300 MGD)December 2000 – February 2001 Total SF Bay Area Municipal Effluents ~600 MGD * did not sample for all events

3 Why measure PCBs in effluent? Evaluate potential for impacts ° Water quality (fish tissue) criterion (170 pg/L total PCBs) ° Ambient water concentrations Estimate loads to SF Estuary ° Effluent potentially controllable pathway ° Evaluate in context of other loads Limited number of previous measurements ° Restricted use since 1979, expect decline

4 SB/FS Sampling CB Sampling PCBs only 2 sampling events 1 Lab FB system ° 4 L filled bottle (amber narrow neck solvent bottle) ° Second bottle taken as backup/ blind duplicate PAHs, PCBs, pesticides, dioxins 4 sampling events Intercomparison of ° 2 labs collecting (first event) ° 3 labs analyzing (all 4 events) Infiltrex (SPE) system ° 400 L solid phase extraction ° Glass fiber filter in series w/ ° 250 g or 2x70 g XAD2 columns

5 SPE Sampling (SB/FS)FB Sampling (CB) Advantages/disadvantages + Ease of collection (=4kg) ± Quick grab sample – Higher detection limits Advantages/disadvantages + Ease of sample handling (400 L = 400 kg = hernia) + Lower detection limits ± Slow composite sample – Potential incomplete recovery

6 PCBs in Effluent (First Event)(SB/FS) Sampling differences Lab A – one 250 g column Lab B – two 70 g columns (140 g total XAD2) Lab A recovery average 25% higher than Lab B Analytical differences Lab C no prior experience in SPE water matrix

7 Sampling Issues & Remedies(SB/FS) Issue: Collection differences? Different column sizes: larger column = greater retention Remedies Columns to collect breakthrough (in series) – Recovery improved but still incomplete (1/2 + 1/4 + 1/8…) Whole effluent/water analysis – To be used for select 2002 RMP water samples – Limited number of analytes (e.g. PCBs only)

8 PCBs in Effluent (All Events)(SB/FS) Lab B collected samples Sum of PCBs 120-320 pg/L (RMP average 600 pg/L) Event differences generally insignificant and < 2x Plant differences generally insignificant Annual loads < 0.1 kg/yr – (mean flow x concentration]

9 Analytical Variability(SB/FS) Intra-lab replicate analyses of XAD2 extracts or blank spikes RSD < 20% Inter-lab splits of XAD2 extracts RSD 20-80% (max:min = 1.5-9x) Average RSD = 51% with Lab C, 33% without Lab C

10 Analytical Issues and Remedies(SB/FS) Issues Inter-lab variability >> intra-lab – Surrogate recovery handling (ECD vs MS) – Interferences, peak shifts Remedies Intercalibration exercises – NIST (sediment, tissue) acceptable Z-scores ± 50% – ERA WP-83 (water) limits 30-150% (Aroclor 1242 @ 11 µg/L)

11 PCBs in Effluent(CB) SFEI/POTW staff collected 4 L grabs No sample splits Replicate sample

12 Sampling & Analytical Variability (CB) Samples from each event – ~2 month separation – Event flow differences up to ~2x – Sum PCBs RSD ~ 25% or less at a site Blind replicate sample – ~10 minutes separation – Sum PCBs RSD < 5%

13 Summary Measurable PCBs in effluents – Sum PCBs 100-7900 pg/L Municipal wastewater loads ~2 kg/yr – Small inter-season/event differences Inter-lab >> intra-lab variability – Familiarity with particular matrix important – Need reliable lab and/or additional QA/QC

14 What Next? Filling in PCB budget PCBs in refinery effluent (underway) – Preliminary results - also small component of loads Local tributary loads – (including stormwater) Delta loads – Even more sensitive to accuracy/precision issues

15 Next Refined RMP sampling – Representative site selection – Improved measurement accuracy Organics QA/QC workshop – Further the state of the art – @SFEI March 29, 2002 10am-3pm

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