Water Pollution Control Biosolids Hauling

Each fall, after field crops are harvested and well into the winter, Utilities Department Water Pollution Control staff "land apply" biosolids to local farm grounds. Biosolids are primarily the organic solid product of wastewater treatment, which are nutrient-rich and can be beneficially used as fertilizer and soil amendment. When fall and winter weather cooperates, WPC staff can haul approximately 18,000 to 21,000 gallons of liquid biosolids daily. Road and field conditions, temperatures, wind, precipitation, and equipment maintenance are all variable factors that impact biosolids hauling. Each year, WPC staff will haul approximately 600,000 gallons of liquid biosolids.

Title 40, Code of Federal Regulations, Part 503 Rule, and technical support documents are the foundation for regulatory compliance when applying biosolids. This rule and guidance define acceptable risk-based chemical characteristics focusing on metal pollutant limits. Part 503 and state rules dictate sampling frequencies, parameters, and methodology. Testing includes:

• Part 503 metals (arsenic, cadmium, copper, lead, mercury, molybdenum, nickel, selenium, zinc).
• Nutrients (total Kjeldahl nitrogen, ammonium-nitrogen, nitrate-nitrogen, and phosphorus).
• Percent-total and percent-volatile solids.

Pathogen reduction and stabilization (vector attraction reduction) standards are also defined. Depending on process technology, pathogen reduction will be according to Class A or B standards. Class B product reuse has management practice limits to protect the operator and public health. Stabilization standards include:

• A minimum 38% reduction in volatile solids through digestion.
• Minimizing odors during product hauling and reuse.
• Helping reduce complaints.

WPC management must also prepare an annual report to the U.S. Environmental Protection Agency (EPA) for the previous year by February 19. The preparer must certify that all regulatory requirements have been met.