What are the beneficial byproducts of wastewater treatment?

(FEBRUARY 3, 2023) The Columbia Boulevard Wastewater Treatment Plant in North Portland processes wastewater from homes, schools, and businesses in the metropolitan area. It filters and treats the water so that it is safe to return to the natural water cycle. The process has two interesting byproducts: biogas and biosolids.

The biogas comes from microorganisms that eat particles in the wastewater and solid waste. The gas they emit is a renewable natural gas (mostly methane and carbon dioxide). It has been used to generate heat and electricity. Now it is being "refined" or cleaned by removing other gasses, such as hydrogen sulfide, siloxane, and water vapor. The city says the final product can be used as a fuel to replace diesel in commercial vehicles, such as city trucks. The project hopes to:

• • • cut greenhouse gas emissions by 21,000 tons annually

    • generate upwards of $3 million in revenue a year for the city

    • replace 1.34 million gallons of diesel truck fuel

The biosolids are another valuable byproduct from wastewater treatment. After the wastewater is filtered, the solids that sink or float are collected and sent to another area called a "digester". The solids are heated to at least 95 degrees Fahrenheit. That allows microorganisms to break down the solids. This destroys pathogens and reduces orders. After about a month, the solids are dried and transported to places such as farms in Eastern Oregon. The biosolids add valuable organic matter to soil to help improve farming. For example, biosolids contain nitrogen, phosphorus, sulfur, and potassium. They also contain more rare minerals such as magnesium, manganese, iron, zinc, and calcium. The solid decompose slowly, so they benefit the farms for several years.