Biosolids 101

What Are Biosolids?

Biosolids are nutrient-rich materials that are a byproduct of the wastewater treatment process. After separating and treating the solid components to remove pathogens, the result is a safe, reusable product that benefits the environment.

Why Biosolids Matter

Biosolids are packed with essential nutrients like carbon, nitrogen, and phosphorus, making them valuable for:

  • Fertilizing farms and gardens

  • Landscaping and composting

  • Erosion control

Benefits of Recycling Biosolids

  • Renewable energy generation

  • Land reclamation after construction or mining activities

Types of Solids in PVSC Wastewater Treatment

Primary Solids
Settle during initial treatment (e.g., human and food waste)

Trucked Solids
Imported solids from other facilities

Waste Activated Solids (WAS)
Bacteria from secondary treatment

Barged Solids
Solids from other municipalities

Typical Solids Treatment Process

Biosolids Classifications

Biosolids are categorized by treatment level and public health safety (EPA Part 503 Rule). The highest quality of biosolids is Class A EQ (Exceptional Quality).

PVSC’s Solids Treatment Process

PVSC’s solids treatment process currently produces Class A EQ biosolids. However, due to the type of stabilization process used at PVSC (Zimpro Wet Air Oxidation), the biosolids have low nutrient value and are not suitable for use as fertilizer. As a result, the only available use for the biosolids produced at PVSC is as a daily cover for landfills. While alternative daily cover is a beneficial use – offsetting the needs to use soil or other products, landfills remain the only potential use for PVSC’s current biosolids.

PVSC’s Current Solids Treatment Process

As part of the Master Plan, PVSC is evaluating whether to keep the existing Zimpro stabilization process or replace it with a new treatment technology. Regardless of a long-term alternative, Zimpro will continue to be needed for some time and PVSC will continue to make appropriate investments to maintain operation of its plant. Some of the technologies being evaluated are listed below.

Treatment Technologies

The following table presents treatment technologies and improvements currently under consideration by PVSC as part of its long-term biosolids management.