Cradle to Gate
Identity ID
37d788db-29e4-4275-a9b7-a0855f2b4ce5
Waste treatment
Associated ID
dad09057-afda-42f6-8727-1fb236f7dae9
Included activities starts
Included activities ends
Description
The initial sludge (97.5% moisture content) is first concentrated and dewatered to reduce its moisture content to 80%. Dewatered sludge is mixed with an appropriate proportion of quicklime (CaO), then stabilized, dried, and stored for a certain period, reducing the moisture content to 30%, after which it is transported to a cement plant. Sludge with 30% moisture content can be directly used for cement production without further drying, thus eliminating coal consumption. Lime-stabilized sludge can substitute part of the sandstone in concrete production, with every kg of initial sludge replacing 0.0015 kg of sandstone production.
Activity Description
In the treatment process, sludge first undergoes a thickening stage to reduce its volume and increase its solid content. The thickened sludge is then dewatered, further reducing its moisture content with the aid of flocculants. Lime can be used as a weighting agent, forming complexation reactions with ions in the sludge such as sulfate, phosphate, and sulfamate groups that can bind with metals, thereby increasing the sludge's weight. This aids coagulation and helps remove certain contaminants. Dehydrated sludge is mixed with an appropriate proportion of quicklime (CaO). After stabilization, drying, and a certain period of piling, the moisture content is reduced to 30%, meeting the requirements for use in concrete production. It can be directly used in the concrete preparation process without further drying treatment. This process reduces the extraction of raw materials for cement production and should also be considered in the calculations.
Process Description
"Sewage sludge" is a byproduct generated during the urban wastewater treatment process. 100% sewage sludge, with a moisture content of 97%. 5%, "sludge" consists of the following components: microorganisms, animal and plant residues, inorganic minerals, potential heavy metals, micropollutants, and pathogens. Treatment methods for this by-product include sanitary landfilling, municipal incineration, and use as a raw material for clinker production. Additionally, sludge can be converted into bioenergy through anaerobic digestion or applied to land following stabilization. In the HiQ database, treatment methods for this by-product include incineration, landfilling, aerobic composting, anaerobic digestion, wet oxidation, pyrolysis/hydrothermal carbonization, and land application. Furthermore, this by-product is utilized in the following processes: clinker production, among others.
Time period
2022
2026
Geography
China
Geography comment
National statistics, literature research
Macroeconomic value
Business-as-Usual
Data validation
Yes
Technology
Current Technology
Technology comment
In China's sludge treatment processes, the thickening stage primarily increases the solids concentration of the sludge using gravity thickeners. Commonly used equipment in the dewatering process includes centrifugal dewatering machines, belt presses, and plate-and-frame filter presses. Dewatered sludge mixed with an appropriate proportion of quicklime (CaO), after undergoing stabilization, drying, and a certain period of stockpiling, can be directly used in cement production. This process reduces the consumption of sandstone and realizes the value of waste recycling and reuse.