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CE 421/521- Environmental Biotechnology

Pathogen Survival Rates After Pretreatment and Land Application of Biosolids 

Angela Kolz

 ABSTRACT

 Land application of municipal biosolids provides agricultural benefits and presents a cost-effective method of  sludge disposal following wastewater treatment.  However, reuse of municipal sludge presents health concerns that must be addressed and satisfied before land application is an accepted practice.  Health concerns include pathogen transmission to food or agricultural workers, contamination of ground water or surface water with fecal material from field run-off, and build-up of heavy metals or organic contaminants.  A review of US EPA pathogen reduction requirements and accepted techniques for meeting requirements for land-application is provided.  Factors affecting pathogen survival in biosolids-amended soil after land application are presented, however, variation in environmental conditions show that it is of great importance to have confidence in the sterility of biosolids before land application to prevent disease transmission and ensure public health. 

 KEYWORDS

 Pathogen inactivation, pathogen survival rates, biosolids land application, composting, digestion, stabilization

 INTRODUCTION

 Health concerns over disease transmittal cause by land-applied biosolids have been made prominent by news media in recent years.   Biosolids facilities have been blamed for maladies ranging from headaches and nosebleeds to several deaths (Chrostowski and O’Dette, 2002).  A lawsuit filed in New Hampshire in 2000 over the 1995 death of twenty-six year-old Shayne Connor blamed biosolids land application for causing a respiratory infection and the man’s subsequent death  (Renner, 2000 and O’Dette, 2002).  The deaths of two men in Pennsylvania in 1994 and 1995 have created additional public concern.  A July, 2000 USAToday article reported complaints from workers at a sludge composting facility, prompting the National Institute of Occupational Safety and Health (NIOSH) to investigate conditions at the facility.  US EPA requires classification of bioslids into Class A and Class B and sets forth standards of application to ensure appropriate treatment and ensure public health.  However, health concerns from biosolids-related cases have caused continued debate over the current federal regulations.  The United States Environmental Protection Agency (US EPA) has been asked to testify in congressional hearings whether it ignored health concerns in publishing its land-application requirements  (Renner, 2000). 

 To evaluate the validity of these concerns it is necessary to understand the capacity of land-applied biosolids to transmit disease.  This paper will summarize common sludge-treatment methods and pathogen-removal data.  Published data on pathogen survival rates following land application of biosolids is scarce due to the high variability of field conditions.  However, factors controlling survival of pathogens in the environment following land application are discussed.

 QUANTITY OF BIOSOLIDS

Estimations of twenty-five to forty kilograms (Kg) of waste per capita per year result in approximately 5.3 x 10⁶ mega-grams (Mg) dry waste per year in the United States that must be discarded.  Of this waste, approximately 16% is incinerated, 38% is landfilled, 36% land-applied and 10% disposed in other ways (Dumontet et al., 2001).