Methodology

LOWER MINIMUM QUANTITATIVE LEVELS - WHY?

Via memo's published by EPA Executives, Offices have been directed to integrate the use of lower MQL's for NPDES permitting. To reach the new mercury MQL, speical sampling and laboratory techniques are needed.

The Hanlon Memo

“… in the light of existing regulatory requirements for NPDES permitting, only the most sensitive methods such as Methods 1631E and 245.7 are appropriate in most instances for use in deciding whether to set a permit limitation for mercury and for sampling and analysis of mercury pursuant to the monitoring requirements within a permit.”

James A. Hanlon, Director,
EPA Office of Wastewater Management
August 23,2007

THE Hosch Memo

EPA Region 6 has “… revised the MQL’s (Minimum Quantification Levels) which we will be accepting for EPA issued permits. … Region 6 expects that you (delegated States) will revise your procedures to incorporate these revised MQL’s” into your permitting procedures.

Claudia V. Hosch, Chief
EPA Region 6
NPDES Permit and TMDL's Branch
February 8, 2008

While it's true that the costs of reaching these new lower MQLS are higher by requiring the use of EPA Method 1669 clean sampling procedures to collect contamination-free samples and by requiring the use of clean (low-detection limit) analytical methods, the goal of measuring accurate, reliable, and valid data can still be acheived at nominal costs if your sampling plan is implemented smartly and if Permitees take an active role in data QC and validation.

HOW IMPLEMENTING LOW LEVEL TESTING AND CLEAN SAMPLING PROCEDURES CAN HELP YOU

  • Does your WWTP have metals limits?

    • Then you need to ensure that you are accurately measuring metals at the levels at which you are being regulated. This is turn helps you know how close you are to violating.
  • Don't have WWTP metals limits and want to avoid them?

    • Accurately meaure your current metals levels before your next permit renewal to ensure that you avoid meeting your regulator's threshold for "report only". This designation is given when paramters are generally within 70% of the current receiving streams liits.
  • Would you like to know how well your WWTP is operating in terms of metals removal?

    • Accurate representations of background concentrations and removal efficiencies can help you INCREASE allowable local limits during technically based local limit reassesments. For cities and their economic development boards, this provides a valuable tool for attracting new industry and for decreasing the operating costs of manufacturers already present within their city.
  • Would you like to know how much your effluent is affecting receiving streams?

    • By collecting regular, accurate, and reliable data about your contributions to the receiving stream, you can ensure you and your city are not held accountable as a point source for increases found during reassessments of the waters of the State.

METHOD SELECTION

There are two EPA methods for reaching these new MQLS's:

EPA METHOD 1631E
  • "The" preferred low-level mercury testing method.
  • Purge & trap / Cold vapor atomic fluorescence.
  • Reporting limit (ML) 0.0005 ppb.
  • Approved for CWA use November 2002.
  • Driven by Great Lakes Initiative (WQC 1.3 pptr) and National Toxics Rule (WQC 12 pptr).
  • Rigorous and difficult EPA Method 1669 clean sampling technique to perform.
  • Ease of contamination at sub-pptr level is great.
  • Good results achievable using good equipment and guidance.
  • Requires robust QA/QC:
    • Acceptable field blanks for every sampling point and report to MDL.
    • Batch specific AND DISCHARGE (MATRIX) SPECIFIC matrix spikes/MS duplicates.
    • Equipment Blanks (bottles and sampler).
    • Field duplicates required.
    • Lab requires method blanks, reagent blanks, quality check samples, instrument calibration.
    • Optional lab QA/QC requirements include duplicates, blank spikes, certified reference materials.
EPA METHOD 245.7
  • “New" alternative low-level Hg method.
  • Cold Vapor Atomic Fluorescence Direct method - no gold traps.
  • MDL 1.8 pptr & ML 5 pptr (ng/L).
  • Validation study conducted 2001 Albion Environmental 1 of 7 labs submitting validation data plus referee laboratory (Total 8 labs) AMSA petitioned EPA to promulgate 245.7.
  • Lower costs associated with testing, but at risk of the tendency of method to underestimate true Hg concentration.
  • Method is more prone to interferences from air, 02, and organics not removed from Nafion (Perma-Pure) permeation dryer.
  • Low-level recovery is matrix dependent and varies on a sample by sample basis.
  • Have to perform MS/MSD on every sample matrix Validation Study: Several labs for low samples reported ND when true value was more than twice the MDL of 1.8 ng/L In many cases, the results reported were even less than the spike additions.
  • Very poor performance on elevated chloride (seawater) and industrial wastewaters.
  • Wide spread of data in Validation Study (4 of 7 labs outliers). Enhanced variability related to interferences varying from sample to sample.

It is of Alibion Environmentals opinion that EPA Method 245.7 is overall not cheaper than 1631e due to potential resampling liabilites and costs associated with higher usage of Nafion tubes - a high maintenance item. There is consensus within the scientific community that EPA Method 1631e is more robust and reliable. Most research labs and many State labs have STOPPED using EPA Method 245.7 in favor of automated, flow-injection EPA Method 1631e.

We know implementing EPA Methods 1631e and 1669 can be daunting. Albion Environmental can help. Contact us today and let us show you how.

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