What Are Biosolids?

The wastewater industry has embarked on a significant new mission. It intends to make common the usage of a brand-new word in the English language--BIOSOLIDS. The word "biosolids" is intended to replace the term "sewage sludge" to denote the organic and nutrient rich by-product of the wastewater treatment process, a by-product which can be recycled as a fertilizer or soil conditioner.

Biosolids is a good material for soil improvement. The organic matter and nutrients replenish the soil, which is a benefit to the environment. Scientists have investigated biosolids recycling and have determined that biosolids recycling is a sound program. The potential for adverse effects from biosolids recycling is negligible. What is more, the quality of the biosolids applied to lands has greatly improved over the past decade. Today, PWD and most wastewater facilities are committed to making a biosolids product which is of far better quality than federal standards. And this is because of the wastewater industry's commitment to effective control of industrial discharges and to a high level of processing.

The Philadelphia Water Department's "Biosolids Management Program" is responsible for arranging the disposition of all of the collected biosolids from a regional wastewater system serving 2.3 million people. Philadelphia today enjoys a wastewater industry reputation for having one of the most successful, large-city biosolids recycling programs.

Biosolids are classified in the Pennsylvania's Solid Waste Management Act and implementing regulations as a municipal solid waste. Despite not enjoying the favorable designation as a "recyclable" municipal waste, biosolids produced in Philadelphia have nevertheless achieved a very high recycling rate (65%). The fertility of thousands of acres of lands in the Philadelphia metropolitan area and westward has been improved with biosolids. These lands include stripmines in western Pennsylvania, farms in Pennsylvania,  Maryland, and Virginia, hundreds of residential and commercial properties in the suburbs, and dozens of play fields in the City.

The Water Department has been extremely successful at practicing "source reduction." New processing equipment and more efficient plant operations has enabled the Water Department to reduce the total quantity of biosolids requiring disposition (by approximately 40% since 1992), while simultaneously improving effluent quality at the three wastewater plants.

The "showcase" biosolids product is traded as Earthmate, a fine-textured, nutrient-rich, dark compost especially well suited for the establishment of turf in disturbed soils common to construction sites.

The Earthmate product is no longer available at the PWD's facilities.