Method for recovering phosphorus from phosphorus-containing wastewater in steps

Abstract

The invention discloses a method for recovering phosphorus from phosphorus-containing wastewater in steps and belongs to technical field of wastewater treatment. The method comprises the following steps: (1) magnesium salt settlement treatment: adding ammonium salt and magnesium salt into the phosphorus-containing wastewater, wherein the mole ratio of phosphorus to nitrogen to magnesium in the wastewater after completely adding is ensured to be P:N:Mg=1:(0.95-1.02):(0.96-1.05); and regulating pH value of the wastewater to 7-11, stirring, standing, layering and then filtering, thereby acquiring a settling solid 1 and an upper filtrate 1; and (2) calcium salt settlement treatment: adding a calcium-containing reagent into the upper filtrate 1 acquired in the step (1), wherein the mole ratio of phosphorus to calcium in the wastewater after completely adding is ensured to be P: Ca=3:(3-6.2); and regulating pH value of the upper filtrate 1 to 7-11, settling and then filtering, thereby acquiring a settling solid 2 and an upper filtrate 2. According to the invention, the magnesium-process phosphorus removal and the calcium-process phosphorus removal are combined with each other, the defects of the two in the processing technology are overcome and the incomplete phosphorus removal problem of a single magnesium settlement process and the low benefit problem of a single calcium settlement process are primarily solved.

Description

technical field [0001] The invention relates to the technical field of wastewater treatment, in particular to a method for recovering phosphorus step by step from phosphorus-containing wastewater. Background technique [0002] Phosphorus is one of the important factors causing eutrophication of water bodies. When the total phosphorus concentration in the environmental water reaches 0.02mg / L, the ecological balance of the water body will be destroyed. The eutrophication pollution of water bodies in my country is already very serious: Among the 27 key lakes and reservoirs monitored in my country in 2004, 22.2% had Grade V water quality, and 37.0% had water quality inferior to Grade V. The eutrophic area of ​​Taihu Lake, Chaohu Lake and Dianchi Lake accounted for 77%. The nutritional status of 238 reservoirs was evaluated, and 2 / 3 of the reservoirs were in the mesotrophic state, and 1 / 3 of the reservoirs were in the eutrophic state. Therefore, it is urgent to strictly control...

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