Cradle to Gate
Identity ID
987b09f3-680c-48ce-a3b0-b57bc495d625
Waste treatment
Associated ID
8759926a-78bf-4194-998f-61c61e859d20
Included activities starts
Included activities ends
Description
Raw sludge (95% moisture content) is first thickened and then centrifugally dewatered with the addition of polyacrylamide (PAM), reducing its moisture content to 75%. The removed water is treated with a certain amount of FeCl₃ and discharged after meeting regulatory standards. The dewatered sludge is mixed with a certain amount of rice straw for aerobic composting, promoting the decomposition of organic matter in the sludge and producing a nutrient-rich compost product. This compost can be used as a soil amendment in land application, replacing phosphate and nitrogen fertilizers to provide nutrients to the soil. However, it may also generate greenhouse gases and release nitrogen, phosphorus, and heavy metal elements, causing environmental pollution. Each ton of dry sludge can substitute 32 tons of triple superphosphate (TSP). 385 kg, ammonium nitrate 40.18392 kg.
Activity Description
During the treatment process, sludge first undergoes a thickening stage to reduce its volume and increase its solids content. The thickened sludge then proceeds to dewatering, where, with the aid of flocculants, its moisture content is further reduced. The separated water is treated with flocculants and discharged after meeting regulatory standards. The dewatered sludge is mixed with other auxiliary materials and undergoes aerobic composting, where microbial metabolic activity promotes the decomposition of organic matter, generating stable humus and producing a nutrient-rich compost product. Compost products can be applied to land as soil amendments or fertilizers to improve soil structure and provide nutrients. However, pollutants in the compost may also enter the environment; therefore, pollutant concentrations possibly present in the sludge must be strictly controlled to ensure they remain within safe limits.
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 solid content of the sludge through gravity thickeners. Commonly used equipment in the dewatering stage includes centrifugal dewatering machines, belt filter presses, and plate-and-frame filter presses. Aerobic composting is a biological treatment technology that converts organic waste into stable, humus-rich organic fertilizer through microbial metabolic activities in an aerobic environment. This process requires control of appropriate carbon-to-nitrogen ratio, moisture, pH, and aeration conditions to promote microbial activity and accelerate the decomposition of organic matter. Land application techniques involve the use of appropriately treated sludge or compost as fertilizer or soil amendment to enhance soil fertility and improve its physical properties. Common implementation methods include surface application directly onto the soil, mixing into the soil to improve soil structure, band application to provide nutrients directly to crops, mulching to reduce water evaporation and suppress weeds, and deep plowing to accelerate organic matter decomposition. These methods aim to ensure the safe and efficient utilization of sludge or compost while promoting sustainable agricultural development.