METHOD FOR RECOVERING PHOSPHORUS FROM SLUDGE RICH IN CHEMICAL PHOSPHORUS PRECIPITATES USING HIGH-PROTEIN BIOMASS WASTE

Abstract

Disclosed is a method for recovering phosphorus from sludge rich in chemical phosphorus precipitates using a high-protein biomass waste, comprising introducing the sludge rich in chemical phosphorus precipitates into an anaerobic fermenter, adding a certain amount of a high-protein biomass by-product, sealing the fermenter and fermenting for 4-7 days. The method can effectively increase the phosphorus release efficiency from the sludge, and also generate volatile short-chain fatty acids and ammonia nitrogen in high concentrations. After dewatering, phosphorus and part of ammonia nitrogen can be recovered in a form of high-purity struvite crystals only by addition of a magnesium salt and adjustment of pH to 7.5-9.0. The volatile short-chain fatty acids can be used as an economical carbon source. The method allows simultaneous utilization of two solid wastes to recover carbon, nitrogen and phosphorus resources, and can reduce the usage of chemical reagents, saving the treatment cost.

Claims

1. A method for recovering phosphorus from sludge rich in chemical phosphorus precipitates using a high-protein biomass waste, comprising steps of: (1) introducing the sludge rich in chemical phosphorus precipitates into an anaerobic fermenter, adding a high-protein biomass by-product in proportion according to a total chemical oxygen demand of the sludge, removing oxygen to form an anaerobic environment, sealing the fermenter, and co-fermenting the sludge and the high-protein biomass by-product at 25-35° C. for 4-7 days, to effectively release phosphorus from the sludge rich in chemical phosphorus precipitates; (2) dewatering the sludge after being co-fermented in the step (1) to obtain a dewatered sludge liquor; and (3) adding an appropriate amount of a magnesium salt to the dewatered sludge liquor obtained in the step (2), adjusting pH to 7.5-9.0, stirring for 30 minutes and then standing for precipitation to obtain struvite crystals, and recovering the phosphorus in a form of the struvite crystals from the sludge.

2. The method for recovering phosphorus from sludge rich in chemical phosphorus precipitates using a high-protein biomass waste according to claim 1, wherein the sludge rich in chemical phosphorus precipitates in the step (1) is excess sludge produced from a sewage treatment plant after chemical phosphorus removal by adding an iron salt or an aluminum salt, wherein the iron salt includes a divalent iron salt and a trivalent iron salt.

3. The method for recovering phosphorus from sludge rich in chemical phosphorus precipitates using a high-protein biomass waste according to claim 1, wherein the high-protein biomass by-product in the step (1) is an inefficiently utilized high-protein biomass waste that is generated during product processing.

4. The method for recovering phosphorus from sludge rich in chemical phosphorus precipitates using a high-protein biomass waste according to claim 1, wherein the high-protein biomass by-product in the step (1) is added, according to the total chemical oxygen demand of the sludge, in an amount of 0.5-1.0 g of a total chemical oxygen demand of the high-protein biomass by-product per gram of the total chemical oxygen demand of the sludge.

5. The method for recovering phosphorus from sludge rich in chemical phosphorus precipitates using a high-protein biomass waste according to claim 1, wherein the dewatering of the sludge in the step (2) is performed by means of mechanical dewatering, including pressure filtration or centrifugation.

6. The method for recovering phosphorus from sludge rich in chemical phosphorus precipitates using a high-protein biomass waste according to claim 1, wherein magnesium chloride or magnesium oxide is added into the dewatered sludge liquor in the step (3) as the magnesium salt, in an appropriate amount controlled such that the molar ratio of PO.sub.4.sup.3−/Mg.sup.2+ is 1:1-1:2.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0021] Hereinafter, the present disclosure will be described in more detail on the basis of examples and with reference to the accompanying drawings, in which:

[0022] FIG. 1 is a process schematic diagram of the method for recovering phosphorus from sludge rich in chemical phosphorus precipitates of the present disclosure.

[0023] FIG. 2 is a diagram of the change in phosphorus release amount during the anaerobic co-fermentation of silkworm chrysalis powder and a simulated iron phosphate-containing sludge in Example 1 of the present disclosure.

[0024] FIG. 3 is a diagram of the concentration change in volatile short-chain fatty acids during the anaerobic co-fermentation of silkworm chrysalis powder and a simulated iron phosphate-containing sludge in Example 1 of the present disclosure.

[0025] FIG. 4 is a diagram of the concentration change in ammonia nitrogen during the anaerobic co-fermentation of silkworm chrysalis powder and a simulated iron phosphate-containing sludge in Example 1 of the present disclosure.

[0026] FIG. 5 is a diagram of the change in phosphorus release amount during the anaerobic co-fermentation of silkworm chrysalis powder and an iron phosphate-containing sludge from a sewage treatment plant in Example 2 of the present disclosure.

[0027] FIG. 6 is a diagram of the concentration change in volatile short-chain fatty acids during the anaerobic co-fermentation of silkworm chrysalis powder and an iron phosphate-containing sludge from a sewage treatment plant in Example 2 of the present disclosure.

[0028] FIG. 7 is a diagram of the concentration change in ammonia nitrogen during the anaerobic co-fermentation of silkworm chrysalis powder and an iron phosphate-containing sludge from a sewage treatment plant in Example 2 of the present disclosure.

DETAILED DESCRIPTION

[0029] Technical solutions in the examples of the present disclosure will be clearly and completely described hereinafter in conjunction with the accompanying drawings in the examples of the present disclosure. Obviously, the described examples are only a part of the examples of the present disclosure, rather than all of them. All the other examples, which are based on the examples in the present disclosure, obtained by those of ordinary skill in the art without creative labor, should fall within the protection scope of the present disclosure.

Example 1

[0030] 450 mL of pure biological sludge was introduced into an anaerobic fermenter, and 0.65 g of iron phosphate was added thereto to simulate the sludge rich in chemical phosphorus precipitates. 2.44 g of silkworm chrysalis powder was added to the sludge (i.e., 0.81 g of a total chemical oxygen demand of silkworm chrysalis powder per gram of a total chemical oxygen demand of the sludge was added). Oxygen was removed to form an anaerobic environment, and the fermenter was sealed. Thereafter, it was subjected to anaerobic co-fermentation at 35° C. for 7 days. Meanwhile, iron phosphate-containing sludge without adding the silkworm chrysalis powder was used as a control.

[0031] Referring to FIGS. 2-4, the concentration of soluble orthophosphorus after the co-fermentation of the silkworm chrysalis powder and the iron phosphate-containing sludge for 7 days was increased by 88% compared with that of the iron phosphate-containing sludge without adding the silkworm chrysalis powder. The concentration of total volatile short-chain fatty acids after the co-fermentation of the silkworm chrysalis powder and the iron phosphate-containing sludge for 7 days was increased by 531% compared with that of the iron phosphate-containing sludge without adding the silkworm chrysalis powder.

[0032] The sludge obtained after the anaerobic co-fermentation for 7 days was dewatered by means of centrifugation, and magnesium chloride was added to the resulting dewatered liquor in an appropriate amount to control the molar ratio of PO.sub.4.sup.3−/Mg.sup.2+ to be 1:1.1, and the pH was adjusted to 8.5. Thereafter, it was stirred for 30 minutes and left for precipitation to obtain struvite crystals, and phosphorus was recovered in a form of the struvite crystals from the sludge.

Example 2

[0033] 450 mL of excess activated sludge rich in iron phosphate from a sewage treatment plant was introduced into an anaerobic fermenter, and 5.67 g of silkworm chrysalis powder was added to the sludge (i.e., 0.81 g of a total chemical oxygen demand of silkworm chrysalis powder per gram of a total chemical oxygen demand of the sludge was added). Oxygen was removed to form an anaerobic environment, and the fermenter was sealed. Thereafter, it was subjected to anaerobic co-fermentation at 35° C. for 7 days. Meanwhile, iron phosphate-containing sludge without adding the silkworm chrysalis powder was used as a control.

[0034] Referring to FIGS. 5-7, the concentration of soluble orthophosphorus after the co-fermentation of the silkworm chrysalis powder and the iron phosphate-containing sludge for 7 days was increased by 954% compared with that of the iron phosphate-containing sludge without adding the silkworm chrysalis powder. The concentration of total volatile short-chain fatty acids after the co-fermentation of the silkworm chrysalis powder and the iron phosphate-containing sludge for 7 days was increased by 391% compared with that of the iron phosphate-containing sludge without adding the silkworm chrysalis powder.

[0035] The sludge obtained after the anaerobic co-fermentation for 7 days was dewatered by means of centrifugation, and magnesium chloride was added to the resulting dewatered liquor in an appropriate amount to control the molar ratio of PO.sub.4.sup.3−/Mg.sup.2+ to be 1:1.1, and the pH was adjusted to 8.5. Thereafter, it was stirred for 30 minutes and left for precipitation to obtain struvite crystals, and phosphorus was recovered in a form of the struvite crystals from the sludge.

[0036] The above examples are only intended to explain the technical solutions of the present disclosure, but not to limit the present disclosure. Although the present disclosure has been described in detail with reference to the above examples, those of ordinary skill in the art should understand that modifications can be made to the technical solutions recited in the above examples or equivalent replacements can be made to some or all of the technical features thereof, which modifications and equivalent replacements will not make the corresponding technical solutions deviate from the scope of the technical solutions in the examples of the present disclosure.

[0037] In addition, those skilled in the art shall understand that although some examples herein include some features rather than other features included in other examples, and that combinations of features in different examples are intended to fall within the scope of the present disclosure and constitutes different examples. For example, in the appended claims, any one of the claimed examples can be used in any combination. The information disclosed in the Background section is only intended to enhance the understanding of the general background of the present disclosure, and should not be taken as an acknowledgement or any form of suggestion that the information constitutes the prior art already well known to those skilled in the art.