Evaluation of Local Discharge Limits - King County Sanitary Sewer System

Transcription

1 Evaluation of Local Discharge Limits - King County Sanitary Sewer System 1

2 Changes to KC System and Need for Local Limits Evaluation Existing: South Treatment Plant (STP) & West Point Treatment Plant (WPTP) Future: Brightwater Treatment Plant (BWTP), STP & WPTP BWTP Service Area Removed from Service Areas of STP & WPTP 2

3 King County Sanitary Sewer System Northern Portion 3

4 How Are Local Limits Calculated? Determine the Relevant Environmental Criteria: Activated Sludge Inhibition, Biosolids Quality, NPDES Discharge Limits, Etc. Determine Removal Efficiency for a Given Parameter and Work Backwards From Environmental Criterion to Determine Allowable Headworks Loading (AHL) Find the Most Stringent AHL for a Given Parameter to Determine Maximum Allowable Headworks Loading (MAHL) Remove Loadings from Uncontrollable Sources (i.e., Residential and Commercial) Remaining Loading (Minus Safety Factor) is Allocated to Industrial Users Maximum Allowable Industrial Loading (MAIL) 4

5 Allowable Headworks Loading (AHL) Determination 5

6 BWTP Membrane Bioreactor Technology 6

7 Treatment Plant Removal Efficiencies 7

8 Evaluation of KC System Loadings 2009 KCIW Sampling in Future BWTP Service Area 6 Rounds of Weekly Sampling 2007 to 2009 Intensive Sampling Events at STP and WPTP 2007 to 2009 Data from Industrial Users That Are Monitored for Metals (For Comparison) Subtraction of Loadings From Swamp Creek/Kenmore and Flow Swap Area to Calculate Future Loadings at STP and WPTP Comparison of Treatment Plant Loadings to Maximum Allowable Headworks Loadings (MAHLs) 8

9 Comparison of Loadings Calculated Headworks Loading as a Percentage of Maximum Allow able Headw orks Loading (MAHL) (a) 100.0% 80.0% 60.0% 40.0% 20.0% BWTP STP-Existing STP-Future WPTP-Existing WPTP-Future 0.0% As Cd Cr Cu Pb Hg Mo Ni Se Ag Zn Industrial User Loading as a Percentage of Calculated Headw orks Loading 100.0% 80.0% 60.0% 40.0% 20.0% BWTP STP-Existing STP-Future WPTP-Existing WPTP-Future 0.0% As (b) Cd Cr Cu Pb Hg Mo Ni Se (b) Ag (b) Zn Notes: As (Arsenic), Cd (Cadmium), Cr (Chromium), Cu (Copper), Pb (lead), Hg (Mercury), Mo (Molybdenum), Ni (Nickel), Se (Selenium), Ag (Silver), Zn (Zinc) Loadings calculated by using 1/2 MDL for non-detect values (a) MAHL values include a 25% safety factor (b) Analyte detected less than 10% of the time in the industrial users sampled 9

10 BWTP Loadings as Percentage of MAHL 10

11 STP Loadings as Percentage of MAHL 11

12 WPTP Loadings as Percentage of MAHL 12

13 Loadings at Highest Percentage of MAHL 13

14 Industrial User Loading - Arsenic 14

15 Industrial User Loading - Copper 15

16 Industrial User Loading - Molybdenum 16

17 Industrial User Loading - Nickel 17

18 Industrial User Loading - Selenium 18

19 Industrial User Loading - Silver 19

20 Regarding Residential/Commercial Data Comparison to EPA Residential/Commercial Data Metal Concentrations, µg/l CTP Swamp Crk Trunk STP WPTP EPA - Average Chromium, Total Copper, Total Lead, Total Mercury, Total Nickel, Total Zinc, Total

21 Conclusions The Metals at the Highest Percentage of the Maximum Allowable Headworks Loading (MAHL) Were Associated with Loadings Attributed Primarily to Non-Industrial Sources (e.g., Copper, Lead, and Zinc from Household Plumbing) Continuing Monitoring of Industrial Dischargers for Industrial Metals (e.g, Cadmium, Chromium, Nickel) Needs to be Maintained. After Removal of the BWTP Service Area, Biosolids Metals Concentrations Will Likely Increase at STP & WPTP. Based on the MAHL Analyses, No Revision of Local Limits Needed Prior to Startup of BWTP; However, BWTP Local Limits to be Evaluated Using Full-Scale Operational Data Prior to End of Permit Cycle (2016) Recommendation to Pretreatment Programs: Use Sensitive Metals Analysis (ICP/MS) to Determine Residential/Commercial Loadings When Developing Local Limits 21

22 Thank You! Bruce Tiffany King County Industrial Waste Program T: E: 22