New phosphate fertilizer preparation process from sewage sludge ashes

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Sewage sludge ashes will soon be produced in Geneva. The recycling of contained phosphorous will be compulsory from 2026. We intend to test the possible production of agricultural fertilizer from sewage sludge ashes with innovative cleaning, without chemical separation of phosphates, using pelletization techniques and additives. The role of coagulants used (Fe or Al-based) in waste water treatment plant (WWTP) on phosphorus accessibility in the final fertilizer will be assesed in HEPIA (Institut inTNE). Sewage sludge ashes are present as powder and still contain some pollutant at a relatively low level (Cu, Zn, Cd, Ni, As). Although these elements are below the legal limits for fertilizers, a new leaching/rinse process using alcaline solutions has been tested sucessfully in July 2022 during preliminary testworks in HEPIA.The treated ashes still remain in powder and it needs to be prepared in pellets for direct agriculture use. Such P-rich pellets may be directly suitable to commercialisation.Another aspect that need to be tested is the role of the phosphorous coagulation in waste waters (using either ferric chloride or aluminium salts). The phosphate precicipation followed by incineration forms Fe-P or Al-P binding and this may affect the efficiency of phosphate availability to plants.Primary digested sludge and ashes will be directly supplied by Services Industriels des Genève (SIG) - Eaux Usées and then prepared in HEPIA for leaching and pelletization. Final fertilizers will be assesed in a second time in HEPIA in Lulier (Institut inTNE).

Project Idea Metadata

• Project Idea Name: New phosphate fertilizer preparation process from sewage sludge ashes
• Date: 9/2/2022 10:07:06 AM
• Administrators:

Project Idea Description

Sewage sludge ashes are present as powder and still contain some pollutant at a relatively low level (Cu, Zn, Cd, Ni, As). Although these elements are below the legal limits for fertilizers, a new leaching/rinse process using alcaline solutions has been tested sucessfully in July 2022 during preliminary testworks in HEPIA.

The treated ashes still remain in powder and it needs to be prepared in pellets for direct agriculture use. Such P-rich pellets may be directly suitable to commercialisation.

Another aspect that need to be tested is the role of the phosphorous coagulation in waste waters (using either ferric chloride or aluminium salts). The phosphate precicipation followed by incineration forms Fe-P or Al-P binding and this may affect the efficiency of phosphate availability to plants.

Primary digested sludge and ashes will be directly supplied by Services Industriels des Genève (SIG) - Eaux Usées and then prepared in HEPIA for leaching and pelletization. Final fertilizers will be assesed in a second time in HEPIA in Lulier (Institut inTNE).

Sewage sludge ashes will soon be produced in Geneva. The recycling of contained phosphorous will be compulsory from 2026. We intend to test the possible production of agricultural fertilizer from sewage sludge ashes with innovative cleaning, without chemical separation of phosphates, using pelletization techniques and additives. The role of coagulants used (Fe or Al-based) in waste water treatment plant (WWTP) on phosphorus accessibility in the final fertilizer will be assesed in HEPIA (Institut inTNE).