In the future, land application rules may change due to contaminants of emerging concern, but more research needs to be done
The federal biosolids rule is contained in 40 CFR Part 503 and is a major focus of the Resource Conservation and Recovery Act. It contains the regulations and quality standards for biosolids land application. It clearly divides biosolids into a number of categories, septage being one of them. The number and type of requirements associated with the land application of septage are affected not only by quality (pollutant levels, level of pathogen reduction, and attractiveness to vectors), but also by the method of distribution.
Contaminants of Emerging Concern, including hormones, pharmaceuticals and personal care products, are a diverse group of common household substances used for health, beauty and cleaning purposes. These also include disinfectants, fragrances, insect repellents, preservatives, etc. Some of them are considered chemicals of emerging concern due to their presence and negative impact on aquatic ecosystems, especially related to endocrine disruption and reproductive disorders. Biosolids, septage and manure contain various natural and synthetic chemicals. There is the potential for a large variety of synthetic chemicals, such as pharmaceuticals and personal care product chemicals, to be present.
There is limited published research on CECs in municipal biosolids, but even less relating to septage from septic systems. In general, septage is less concentrated than biosolids. In a thesis by Puddephat (2013), the traces of biosolids-borne chemicals on soil biota, plants, crops, animals and food were found to not have significant impacts under real-world field conditions. In a soon-to-be-published study by the Minnesota Pollution Control Agency, soils and groundwater were tested for personal care products in the soil and downstream from a land application site. As part of the study, the land application site, along with large septic systems and rapid infiltration basins, were evaluated for hormones, pharmaceuticals, antibiotics and hazardous waste compounds. The only category of contaminant found was steroids in the groundwater near the land application site. When the soil itself was analyzed at the land application site, pharmaceuticals (seven), steroids (nine), fragrances (five), polycyclic aromatic hydrocarbons (four), pesticides (two), alkyl phenols (two), plasticizers (two) and flame-retardants (one) were found.
An outdoor mesocosm study was conducted in Baltimore, Maryland, to explore the fate of 72 pharmaceuticals and personal care products (PPCPs) over the course of three years, during which they were placed in plastic containers made from polyvinylchloride and kept exposed to ambient outdoor conditions. Of the 72 PPCPs, 15 were initially detected in the soil/biosolids mixtures at concentrations ranging from low parts-per-billion to parts-per-million levels. Many PPCPs degraded over time, but some compounds persist in the soil years after the application of the biosolids containing them.
Also requiring further research is the potential for plants and crops to take up microcontaminants from biosolids-amended soils. For example, it has been documented that certain antibiotics, specifically tetracyclines and fluoroquinolones, can be taken up by crop plants, but have been found at very low levels.
There are currently no plans to change the Federal 503 rules to deal with CECs. With the lack of research focusing on septage, it is best for industry professionals to stay tuned as new studies are published, and to request that more research is funded in this area at both the state and federal level.
About the author
Sara Heger, Ph.D., is an engineer, researcher and instructor in the Onsite Sewage Treatment Program in the Water Resources Center at the University of Minnesota. She presents at many local and national training events regarding the design, installation and management of septic systems and related research. Heger is education chair of the Minnesota Onsite Wastewater Association (MOWA) and the National Onsite Wastewater Recycling Association (NOWRA), and serves on the NSF International Committee on Wastewater Treatment Systems. Send her questions about septic system maintenance and operation by email to email@example.com.