Process for treating sludge from wastewater treatment plants

The method addresses the energy balance and odor control issues in sludge treatment by using solar drying and thermal treatment, with air recycling and humidity reduction strategies, achieving efficient and cost-effective sludge processing.

FR3150514B1Active Publication Date: 2025-06-20SUEZ INTERNATIONAL
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Patent Information

Application Number
FR2023006797
Authority / Receiving Office
FR · FR
Patent Type
Patents
Current Assignee / Owner
Filing Date
2023-06-28
Publication Date
2025-06-20
Estimated Expiration
2043-06-28

AI Technical Summary

Technical Problem

Existing methods for treating sludge from treatment plants face challenges in optimizing energy balance and controlling odor emissions during solar pre-drying, leading to inefficiencies and additional costs.

Method used

A method involving solar drying of sludge followed by thermal treatment, where extracted air is divided into two fractions: one sent to the thermal treatment unit to ensure self-thermality and the other fraction reduced in humidity and reheated to recycle back into the solar drying unit, thereby controlling odor accumulation and optimizing energy use.

Benefits of technology

This approach ensures self-thermality of the thermal treatment reactor using renewable solar energy, reduces odor emissions by processing bad odor-laden air within the thermal treatment unit, and recycles energy to maintain efficient sludge drying, thereby reducing operational costs and environmental impact.

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Abstract

The invention relates to a method for treating sewage sludge, comprising at least the following steps: - solar drying (10) in a solar sewage sludge drying unit, the solar drying unit comprising air regulated at a predetermined sludge drying temperature; - thermal treatment for decomposition of the organic matter (20) of said dried sewage sludge in a thermal treatment unit for decomposition of the organic matter, - extraction (70) of the air from the solar drying unit following the drying.The invention consists in that the extracted air is divided (80) into two fractions, one fraction of this air being conducted and introduced into the thermal treatment unit for decomposing the organic matter while the other fraction of this extracted air is subjected to a step of reducing the humidity level (30) of said fraction in a range of 10 to 50%, preferably to a level lower than 30%, said air fraction then being subjected to a heating step (80) to a predetermined temperature for drying the sludge and reintroduced into the solar drying unit as a drying medium, i.e. steam carrier. Figure 1.
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