The invention relates to the technical field of municipal
sludge treatment, in particular to a method for recycling
nitrogen and
phosphorus elements from municipal
sludge. According to the method, the municipal
sludge is subjected to
hydrothermal carbonization treatment, the treated
solid-phase product is dried and ground to a specific particle size, the
solid-phase product is subjected to acid leaching under a specific condition to extract the
phosphorus element, and then heavy
metal and
metal elements such as Al and Fe in the acid leaching liquid are removed by adopting strong-acid
ion exchange resin and a chemical precipitant, so that the
phosphorus element is obtained. And finally, mixing the
struvite with a hydrolyzate which is subjected to
hydrothermal carbonization treatment and is rich in
ammonia nitrogen, and precipitating by adjusting the element proportion and the pH value to obtain a
solid-phase product
struvite crystal. According to the method, external
nitrogen-containing substances do not need to be added, the content of heavy
metal in the solid-phase product
struvite can be effectively reduced, the
recovery rate of phosphorus can reach 93% or above, the
recovery rate of
ammonia nitrogen can reach 63% or above, the
recovery rate of nitrogen and phosphorus is high,
energy consumption is low, and the treatment cost is low.