MassDEP: New Standard for Mo in Biosolids
Public comment period closes July 13th
Public hearing in Boston June 27th

A revised standard for molybdenum in biosolids applied to soils in Massachusetts (MA) will likely take effect later this year.  On June 3rd, the MA Department of Environmental Protection (MassDEP) announced the proposed change to the "sludge and septage" regulations (310 CMR 32.00).  Last fall, MassDEP Commissioner Martin Suuberg and others had indicated the Department's plan to make the change after Mark Smith and others of the Research and Standards division had completed a technical review and risk assessment. The existing Mo standard dates back to the 1980s.

Last June, NEBRA helped arrange a workshop at which expert research scientists George O'Connor (University of Florida), Rufus Chaney (U. S. Dept. of Agriculture), and Gary van Riper presented the results of their extensive risk assessment on Mo in biosolids applied to soils.  MassDEP staff were involved in the workshop, as were staff of the MA Water Resources Authority (MWRA), who have for several years urged MassDEP to adjust the Mo standard based on current science.  The existing standard resulted in unnecessary restriction on the use of MWRA biosolids fertilizer in the state.

The proposed changes to the MA "sludge" rules specifically include changing the Mo numerical standard for Type I and Type II biosolids from 25 mg/kg (biosolids not applied to forage crops) and 10 mg/kg (biosolids applied to forage crops) to one number: 40 mg/kg for all biosolids applied to soils. New York state has the same standard, and the U. S. EPA has indicated that, if they were to add a low-metals (Table 3) standard for Mo to the Part 503 regulations, it would be 40 mg/kg.

In addition to the numerical standard change, MassDEP is proposing that: 

  1. the soil testing required for land application of Type II or Type III sludge or septage must now include Mo as one of the analytes; and
  2. "Sludge containing molybdenum shall be accompanied by a written label or bill of lading that states the following:  'This product contains molybdenum. While the regulatory standard is generally protective, under certain site conditions, if used on soils growing crops that will be used to feed ruminant animals (e.g., cattle, sheep and goats) there is a small risk that molybdenosis could occur. This risk is greater for alkaline stabilized biosolids. Animal managers are advised to refer to additional information on the site conditions of concern and management options at (input link to more detailed information).' A statement indicating whether the biosolids have been alkaline stabilized shall also be included."

A public hearing on this and other MassDEP regulatory changes proposed under Governor Charlie Baker's regulatory reform initiative (Executive Order 562) will be held Monday, June 27th, 10 am - Noon, at the MassDEP offices in Boston.  Comments are due by July 13, 2016.


MassDEP rulemaking page (includes redline and clean copies of proposed regulation changes)