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PCBs in San Francisco Bay Area Municipal Wastewater Effluents

Investigating PCB levels in SF Bay Area wastewater effluents to evaluate potential impacts, water quality criteria, and estimate loads to the environment. Analyzing sampling methods, lab comparisons, and analytical variability for effective monitoring.

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PCBs in San Francisco Bay Area Municipal Wastewater Effluents

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  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. 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 SB/FS Sampling CB Sampling

  5. 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 SPE Sampling (SB/FS) FB Sampling (CB)

  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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