Stabilization As A Type of Biosolids Treatment Process

Most biosolids undergo some form of treatment on site before they are used or disposed. They must meet regulatory requirements to protect public health and the environment. Every step of the biosolids treatment processes is regulated to ensure that the facilitation, the handling, and the disposal will be safe for the environment and the community. Yes, that’s right, even the disposal of the biosolids must follow certain guidelines for a municipality to choose it for the community.

Basically, there are two most common types of biosolids treatment. The first one is stabilization and the second one is dewatering. Stabilization refers to a number of processes that can reduce pathogen levels, odor, and volatile solid content.

Before being applied on land, disposed, or used in some other way, biosolids must first be stabilized. Methods used for the stabilization processes are alkali stabilization, anaerobic digestion, aerobic digestion, composting, and heat drying.

Alkaline Stabilization

The structural characteristics of biosolids reduce pathogen levels and odors. They are also easier to handle and is a provider of lime that helps neutralize acid soils. While lime is the often go-to material for alkaline stabilization, others are used, too, such as cement kiln dust, lime kiln dust, Portland cement, and fly ash.

Historically, quicklime or hydrated lime is added to either liquid biosolids before dewatering or dewatered biosolids in a contained mechanical mixer. But in recent years, this practice has been developed to add other chemicals and supplemental drying.

Anaerobic Digestion

To reduce the organic content, mass, odor, and pathogen content anaerobic digestion biologically stabilizes the biosolids in a closed tank. In this process, microorganisms consume a part of the organic portion of the biosolids and anaerobic bacteria that thrive in the oxygen-free environment convert organic solids to carbon dioxide, methane, and ammonia. This is the most common type of stabilization process used especially in large treatment works.

Aerobic Digestion

This is the biological stabilization of biosolids in an open or closed vessel with the use of aerobic bacteria to convert the organic solids content to carbon dioxide, water, and nitrogen. In the process, pathogens and odors are reduced. This process is used by smaller public-owned treatment plants.


Composting is a common method of treating waste even for households. It is the decomposition of organic matter by microorganisms in an environment that can facilitate the increase in temperature. This, therefore, could destroy most pathogens and odor. The output is a humus-like material that is excellent for growing healthy plants and reducing the mobility of metals.

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