Useful Sludge: 3 Ways to Reuse Biosolids from Municipal Wastewater Treatment Plants

Sewage Sludge: from Refuse to Resource

The UK alone produces a hefty 53 million tonnes of sewage sludge each year, according to BAS. Historically, solids leftover from wastewater treatment were considered unusable and incinerated or disposed of in a landfill to the detriment of our environment and climate. Today, new treatment methods are making it possible for sludge to have a useful life after the wastewater treatment plant. In fact, sewage sludge has earned a new name – biosolids – and a new reputation as a valuable, renewable resource.

SurfCleaner Skimmer Separator Hybrid SCW 6000 removes floating sludge from municipal wastewater. While floating sludge makes up only about 5-10% of all municipal sludge, it has a lot of potential for reuse. The floating sludge that is collected by the Skimmer  Separator Hybrids can often be combined with primary and secondary sludge to make helpful products. This article outlines three beneficial uses for recycled biosolids.

Reusing Sludge As Fertilizer

Agricultural fertilizers are the most common use for the biosolids that come from wastewater treatment plants. Sewage sludge is a naturally rich source of the nutrients plants love – like nitrogen, phosphorus, magnesium and potassium. After being properly treated and carefully assessed for safety from pollutants, sewage sludge can be effectively used to add nutrients to soil.

In the US, 29% of the biosolids produced are applied to  agricultural land. 19% of the sewage produced in the EU is used for agricultural fertilizers. In some countries, there is work to be done for proper regulation and adequate testing to ensure that biosolids which are applied to land are safe and free from toxins or other pollutants. In municipal wastewater treatment, floating sludge may include oil, grease, wood and vegetable matter. The floating organic material recovered by SurfCleaner devices, after proper treatment, can become an excellent source of fertilizer with huge environmental and economic benefits.

Creating Energy from Sludge

Biogas is an exciting renewable energy option which is only just beginning to enjoy mainstream visibility. In many wastewater treatment plants, after the skimmed and screened solids are separated from water, they undergo anaerobic digestion to reduce the mass of the organic matter and inactivate pathogens. The byproduct of this process is biogas, which is an environmentally-friendly fuel. According to researchers Makisha and Semenova, “Large wastewater treatment plants can cover up to 100% of their energy requirements through internal generation of electricity.”  As of 2017, 33% of the potential biogas systems in the US wastewater treatment sector were operational, leaving significant room for sustainability improvements and cost efficiencies. In the EU, biogas is a fast-growing energy source, with anaerobic digestion plants and wastewater treatment facilities contributing significantly to the growth in supply.

Biosolids as Building Materials

Studies are currently taking place to evaluate the potential for sewage solids to be used in the manufacture of construction materials. Germany and Switzerland have begun successfully using cement made from sludge ash. Another RMIT study evaluated the performance of bricks made of biosolids. These new manufacturing processes look favorable as a way to transition to more sustainable building and construction materials.

Harvesting Sludge with SurfCleaner SCW 6000

In order to activate the latent value which is hiding in sewage sludge, the sludge must first be “harvested,” or separated from the wastewater. SurfCleaner Skimmer Separator Hybrid technology is used to separate floating solids and grease from water. Removing this floating material is beneficial for smooth wastewater treatment processing, while recapturing the floating sludge adds value and volume to biosolid material which can be reused to produce helpful products.

Two of Sweden’s largest wastewater treatment plants are currently testing SurfCleaner SCW 6000; the device will soon be available on the market for use in municipal wastewater treatment facilities worldwide.