Thermochemical treatment of sewage sludge ashes for phosphorus recovery.
Phosphorus (P) is an essential element for all living organisms and cannot be replaced. Municipal sewage sludge is a carrier of phosphorus, but also contains organic pollutants and heavy metals. A two-step thermal treatment is suggested, including mono-incineration of sewage sludge and subsequent thermochemical treatment of the ashes. Organic pollutants are completely destroyed by mono-incineration. The resulting sewage sludge ashes contain P, but also heavy metals. P in the ashes exhibits low bioavailability, a disadvantage in farming. Therefore, in a second thermochemical step, P is transferred into mineral phases available for plants, and heavy metals are removed as well. The thermochemical treatment was investigated in a laboratory-scale rotary furnace by treating seven different sewage sludge ashes under systematic variation of operational parameters. Heavy metal removal and the increase of the P-bioavailability were the focus of the investigation. The present experimental study shows that these objectives have been achieved with the proposed process. The P-bioavailability was significantly increased due to the formation of new mineral phases such as chlorapatite, farringtonite and stanfieldite during thermochemical treatment.
Adam
C
C
Federal Institute for Materials Research and Testing (BAM), Division IV.3 Waste Treatment and Remedial Engineering, Unter den Eichen 87, 12205 Berlin, Deutschland, Germany. christian.adam@bam.de <christian.adam@bam.de>
Peplinski
B
B
Michaelis
M
M
Kley
G
G
Simon
F-G
FG
D001031:Apatites; D001682:Biological Availability; D002244:Carbon / Q000032:analysis* / Q000737:chemistry; D002947:Cities; D060729:Coal Ash; D003247:Conservation of Natural Resources; D005858:Germany; D017745:Incineration; D019216:Metals, Heavy / Q000032:analysis / Q000737:chemistry; D008903:Minerals / Q000032:analysis / Q000737:chemistry; D052638:Particulate Matter / Q000032:analysis* / Q000737:chemistry; D010758:Phosphorus / Q000737:chemistry / Q000302:isolation & purification*; D012722:Sewage / Q000737:chemistry*; D013696:Temperature; D014865:Waste Disposal, Fluid / Q000295:instrumentation / Q000379:methods*
D001031:Apatites; D060729:Coal Ash; D019216:Metals, Heavy; D008903:Minerals; D052638:Particulate Matter; D012722:Sewage; C051449:chlorapatite; D010758:Phosphorus; D002244:Carbon