Survival, Growth, and Regrowth of Enteric Indicator and Pathogenic Bacteria in Biosolids, Compost, Soil, and Land Applied Biosolids

MILLIONS of dry tons of biosolids are produced every year. Recycling of them and the safety of disposal is an issue at the center of a national debate. Due to the nutrient content of biosolids, they can be reused beneficially as a soil amendment on numerous areas, such as parks, forests, and agricultural land [41]. Biosolids can also be sold in bulk to consumers for use on home gardens or lawns, as in the case of Milorganite“. One of the reasons for the continuing debate regarding land application is that even though biosolids treatment is required, metals, harmful toxins, and pathogens may still be present following treatment. Microorganisms present in biosolids may include, viruses, bacteria, helminthes, and protozoa [11,12,30]. Many concerns and allegations exist regarding the effect of land applied biosolids on the health of the general population and personnel in the wastewater industry [6,18,20,24]. However, there has never been an established link between land application and illness. Although the United States Environmental Protection Agency supports and regulates the land application of biosolids, the concerns of pathogens affecting humans and animals through direct contact, transfer to groundwater, run-off into surface water, transfer to food crops grown on land applied field, or even through aerosols remain [40,42]. Although it is known that bacteria in biosolids normally decrease to low or non-detectable levels following treatment, a major concern is that regrowth of pathogens may occur. Specifically the question arises: “Does regrowth occur following reintroduction or recolonization of pathogens after land application or during storage under favorable conditions.”