Study On The Transformation Characteristics Of Phosphorus During Thermochemistry Treatment Of Municipal Sludge

Sewage sludge is a by-product of wastewater treatment, and highly concentrated organicand inorganic pollutants, including phosphorus (P), existed in mechanical dewatered sludge.In addition, the role of P in the eutrophication of surface water has long been recognized.However phosphorus is an irreplaceable nutrient for all living organisms; The majority of theworld’s agricultural crops today rely on fertilisers derived from inorganic minerals, such asphosphate rock, a non-renewable resource that is used almost exclusively in agriculture. So,natural phosphorus ores are rapidly dissipating.This paper based on the three-step process of heat treatment to achieve the disposal ofsludge and the utilization of phosphorus, and based on the method of SMT to depthly studythe transformation rule and the phosphorus enrichment behavior interaction mechanism ofphosphorus form different temperature. Combined with NMR, SEM and X-ray diffractometer,after processing of the sample phosphorus structure were analyzed, and the phosphorusenrichment mechanism and occurrence in the ash formation distribution were also analyzed.Through this research, we can get the new knowledge of the thermal treatment process andcontrolled aspects of phosphorus transformation, and formate some new research methods,provide theoretical support for solid waste harmless and resource recovery.From the results obtained, the content of inorganic P clearly increased as the content oforganic P decreased at90℃. The31P NMR analysis results show the change in P fractions atdifferent temperatures. Inorganic phosphorus is the major fraction in sewage sludge, andnon-apatite phosphorus fraction and apatite phosphorus fraction were changing whiletemperature changed. The transformation non-apatite phosphorus fraction and apatitephosphorus fraction at240oC result from the conversion of the forms associated withphosphorus and aluminum oxy hydrates into other forms. The phosphorus in sewage sludgecan be concentrated as apatite with increasing the temperature. The results could serve asreference for P recovery from sewage sludge. In addition, this study investigated the influence of incineration temperature andadditives on P enrichment and transformation in sewage sludge to determine an effective Precovery method. The maximum P content of sewage sludge ash was67.21mg g-1at750°C.After adding MgO or CaO into the sewage sludge during incineration, the content ofphosphorus in ash was not significantly increase, but contributed to P fractions transformation.X-ray diffraction results suggest that the fraction of P bound as aluminum phosphate wasconverted into calcium phosphate (Ca-P) and magnesium phosphate (Mg-P) after adding theseadditives.