If the biosolids land applied are liquid, they generally contain a substantial amount of water. Tanker trucks are used to transport the biosolids from the WWTP to the location of land application. Usually liquid biosolids are generally 2-10% solid, meaning that up to 98% of what is being applied is water content. To deliver the nutrients required to the field, it may take numerous trips to deliver the biosolids.
Additionally, biosolids must be land applied at an agronomic rate that cannot exceed the recommended nitrogen, phosphorus, potassium (NPK) value for the crops grown at a specific biosolids site. Biosolids sites must have a soil analysis no less than two years old on file that provides these recommendations. If the biosolids are not being applied above agronomic rate, it is unlikely that too much is being applied.