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Lime Stabilization of Municipal Sludge

Burch Hydro provides sludge stabilization services for many of its customers and has a variety of methods available for use to ensure adequate lime dosage and thorough mixing.


Biosolids Stabilization

Purpose for Alkaline (Lime) Stabilization of Sludge

In order to be land applied, municipal biosolids must meet certain EPA-defined criteria in regards to pathogen content reduction and vector attraction reduction. There are several options available to wastewater treatment plants for meeting these criteria. Alkaline stabilization, achieved by the mixing of lime or other alkaline products with municipal sludge, is an option for meeting both pathogen reduction as well as vector attraction reduction.

Alkaline (Lime) Stabilization Facts

Creates an Inhospitable Environment

Alkaline stabilization of sludge solids works because the drastic increase in pH creates an environment unsuitable for pathogens and bacteria to thrive.

Required pH Level

For proper stabilization to take place, the pH of the sludge must be raised to 12 or above and must remain above certain defined levels for an extended period of time.

Required Dosages Vary

The amount of lime, or other alkaline material, necessary for adequate pH adjustment can vary based upon certain sludge characteristics and the make-up of the lime product being added.

Produces Lower Nitrogen Biosolids

Biosolids that have been lime stabilized are often lower in Nitrogen. This is because the addition of lime causes the Nitrogen to convert to ammonia.

Reliable Pathogen Reduction

According to the EPA, testing has been done on Class B lime stabilized biosolids that indicates that total coliforms, fecal coliforms and fecal streptococci bacteria are reduced by more than 99.9%.

Ideal for Stored Liquid Sludge

Proper mixing is key to adequate stabilization of the sludge solids. This is most easily achieved with stored sludge in liquid form where an appropriate quantity of lime (or other alkaline material) can be added all at once and thoroughly mixed with pumps and/or mixers.

Not Suited for all Situations

Certain types of sludges and certain plants may be less suited for lime stabilization. The addition of lime affects the activation of polymer used for dewatering, so it is often suggested that lime stabilization occur after dewatering, which can be more difficult. Lime addition can also cause potential odor issues due to the ammonia produced and is, therefore, not ideal in areas sensitive to odors.

Benefits of Alkaline (Lime) Stabilization

Ideal for Smaller Plants

Lime stabilization can often be the most cost-effective means for smaller wastewater plants to produce biosolids meeting land application criteria.

Effective Alternative for Meeting VAR

Many plants occasionally have disturbances in their ability to meet Vector Attraction Reduction. In this case, lime stabilization may be the best alternative for temporarily meeting VAR and maintaining Class B.

Ideal for Farmers in Acidic Soil Areas

For farmers located in areas with soils naturally higher in acidity, the application of lime stabilized biosolids can be a huge value. Not only is the soil enriched with the nutrients present in the biosolids, but it also benefits from a necessary pH adjustment attributed to the lime.

If you’re searching for an organization to provide sludge stabilization, Burch Hydro can help. Click the button below, complete the form and submit it. Or, just give us a call.

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