BENEFICIAL REUSE OF EPA CLASS B BIOSOLIDS – LESSONS LEARNED

The regulation establishing standards for the Use or Disposal of Sewage Sludge (40 CFR Part 503) was published by the Environmental Protection Agency ten years ago. The preamble for the rule indicated that approximately one-third of the wastewater sludge (biosolids) produced in the United States are beneficially reused by land application. The remaining two thirds are disposed of in some other way (i.e. incineration, landfill, co-disposal, surface disposal, etc.) The goal of these regulations are to encourage and increase beneficial use of biosolids.A review was conducted of several New England communities with successful programs applying Class B biosolids to restricted sites. These communities are using various methods for pathogen reduction and vector attraction control. Four case studies are presented in the paper.Case 1 involves a Wastewater Treatment Facility (WWTF) which anaerobically digests primary and secondary sludges. The digested liquid sludge is stored in a reinforced concrete holding tank at the wastewater treatment facility. The biosolids are transported and applied to several nearby agricultural sites as a fertilizer during the spring and fall. The anaerobically digested liquid biosolids are injected below the surface of the land, by the WWTF staff.Case 2 involves a WWTF which lime stabilizes dewatered primary and secondary sludges. The dewatered sludges are mixed with calcium oxide to raise the pH above 12.0 for two hours (and above 11.5 for 24 hours). The lime stabilized biosolids are stockpiled at the land application site, and spread by the WWTF staff on most sites. The biosolids are applied by the landowner on a few of the permitted sites, and by the WWTF staff on some others.Case 3 involves a WWTF which uses plate and frame filter presses to dewater lime-stabilized primary and secondary sludges which have been raised to a pH of 12.0 for two hours (and above 11.5 for 24 hours). The lime stabilized biosolids are land applied on permitted sites by an independent contractor.Case 4 involves a WWTF which lime stabilizes dewatered primary and secondary sludges using high-magnesium (dolomitic) lime. The biosolids are stockpiled at the land application site. The biosolids are land applied by the property owner who receives a spreading fee from the WWTF.This paper will review the pros and cons of land application of Class B Biosolids, and some of the lessons learned after working with the EPA Part 503 regulations during the past ten years.