Sewage Sludge Drying

Sewage sludge drying

Wastewater treatment and sewage sludge treatment are key technical, economic and environmental issues for municipalities. Sewage sludge disposal has undergone major changes in recent years. Spreading restrictions and stricter limits are making it increasingly difficult to find buyers for sewage sludge. As a result, more and more sewage sludge is being incinerated.

SLUDGE TREATMENT

For the reasons mentioned above, sludge treatment is becoming increasingly important throughout Germany. Sludge treatment refers to all processes that improve the usability or the transportability and storability of sewage sludge. Sludge treatment processes include thickening, hygienisation, stabilisation, dewatering, drying and incineration.

Wet sludge that comes directly from the sewage treatment process is usually pre-dewatered. Mechanical dewatering of the sewage sludge in decanters, centrifuges and presses achieves a solids content, measured as dry residue (TR), of between 20 and 45 %.

ADVANTAGES OF SLUDGE DRYING

In a second step, the dry residue in the sewage sludge can be increased to more than 50 % using different drying processes. During drying, a distinction is made between partial drying of e.g. 50 to 55 % DR and full drying with more than 90 % DR.

Dry sewage sludge has the following advantages over wet sludge:

Sewage sludge as a substitute fuel

Depending on the intended sewage sludge disposal route, the achievable calorific value or dry matter content is an important target value. For thermal treatment in sewage sludge mono-incineration plants, partial drying is usually advantageous. Co-incineration in cement works, on the other hand, requires full drying.

DRYING PROCESS

Various drying techniques are used to fully dry the sewage sludge. Of all dryer types, belt dryers have the widest capacity range with 140 - 25,000 tonnes dry matter per year and are therefore being used more and more frequently. Larger plants are operated with hot air.

These low-temperature belt dryers have been developed to dry a wide variety of sludges reliably, with low energy consumption and low dust levels. Industrial/commercial waste heat or heat from combined heat and power plants (e.g. biogas CHP, wood gasifiers, etc.) is particularly suitable for cost-effective heat generation.

Which concept could be of interest to you?

We have been planning and realising sewage sludge drying projects since 2007. Based on our many years of experience in this field, we support you from the initial project idea through all planning phases (preliminary planning, approval, tendering, construction, etc.) to successful commissioning.