Over the years, the quality of biosolids has greatly improved, thanks largely to the technologies that have been developed. But there was a time that the greatest concern on the use of biosolids was the amount of high concentrations of heavy metals and pathogens that could potentially be left in the land where the biosolids will be applied.
The industry, however, has already regulated the treatment of biosolids through pretreatment programs that will follow certain guidelines on discharging sewage waste into the system, treating wastewater sludge into biosolids, and applying biosolids on land.
The improved quality of biosolids did not deter the United States Environmental Protection Agency (USEPA) to classify it into four categories: Exceptional Quality, Pollutant Concentration, Cumulative Pollutant Loading Rate, and Annual Pollutant Loading Rate.
Exceptional Quality Biosolids
Biosolids that have been categorized as “Exceptional Quality” means that the pollutant concentration level is well below the limits (PCLs). It must also meet Class A pathogen reduction limit and a vector reduction that reduces the level of degradable compounds. Meeting the pathogen and vector requirements is generally difficult because of the need to be treated by alkaline stabilization, composting, or heat drying. EQ biosolids can be applied like any ordinary fertilizer or soil amendment to any type of land.
Pollutant Concentration Biosolids
Like EQ biosolids, PC biosolids met the pollutant concentration level needed. However, it has only been classified as Class B biosolids, and not Class A because of pathogen reduction requirements. This type of biosolids, though generally safe, must be injected or incorporated into the soil to prevent exposure of biosolids pathogens to humans and animals. It can be applied to many type of lands, except for lawns, home gardens, and other lands with a high potentiality for public exposure.
Cumulative Pollutant Loading Rate Biosolids
This kind of biosolids exceed at least one of the PCLs but it has no pollutants that exceed the Ceiling Concentration Limits (CCLs). It has to be applied to land in bulk form, and they cannot be bought or given away in bags or other containers. The cumulative levels of biosolids pollutants applied on the site must be monitored and cannot exceed any CPLR. Biosolids under this categorization must either be Class A or Class B.
Annual Pollutant Loading Rate Biosolids
These biosolids are Class A categorization that are sold or given away in bags or other containers. These are applied to land and have pollutant concentrations that exceed one or more PCLs. They, however, do not exceed any of the CCLs.