Treatment method and application of kitchen waste three-phase centrifugal waste liquid

Abstract

The invention provides a kitchen waste three-phase centrifugal waste liquid treatment method and application, and the kitchen waste three-phase centrifugal waste liquid treatment method comprises the following steps: S1, under a stirring condition, adding an alkaline substance, and adjusting the pH value of the three-phase centrifugal waste liquid to be alkaline; s2, under a stirring condition, adding a coagulant into the three-phase centrifugal waste liquid obtained in the step S1, and carrying out a coagulation reaction; s3, under a stirring condition, adding a flocculating agent into the three-phase centrifugal waste liquid obtained in the step S2, and carrying out a flocculation reaction; s4, performing solid-liquid separation on the three-phase centrifugal waste liquid obtained in the step S3 to obtain residues and waste liquid, recycling the residues, and discharging the waste liquid into a sewage biochemical treatment system for purification; wherein the steps S1, S2 and S3 are carried out in the same reactor; the method has the advantages that the oil and phosphorus removal operation process of the three-phase centrifugal waste liquid is simplified, the oil removal rate and the phosphorus removal rate are increased, and the follow-up sewage treatment operation load is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of kitchen waste treatment, and in particular to a method for treating kitchen waste three-phase centrifugal waste liquid and its application. Background Art

[0002] With economic growth and the improvement of people's living standards, people's consumption in catering is increasing day by day, and the rapid development of the catering industry has also led to a sharp increase in the amount of corresponding restaurant kitchen waste. The disposal process of restaurant kitchen waste (including waste cooking oil) is three-phase centrifugation after impurity removal, pulping, and oil extraction, and waste residue, waste liquid and grease are separated. For most of the restaurant kitchen waste treatment plants and restaurant kitchen waste treatment equipment that have been put into operation for many years, the oil content and phosphorus content of the waste liquid after three-phase centrifugation are still too high, and it cannot directly enter the sewage biochemical treatment system, and can only be hydrolyzed and fermented together with the waste residue. Among them, each ton of restaurant kitchen waste produces about 0.9 tons of three-phase centrifugal waste liquid, and each ton of waste cooking oil produces about 0.6 tons of three-phase centrifugal waste liquid. The oil content in the three-phase centrifugal waste liquid is relatively high, which affects the activity of subsequent anaerobic hydrolysis and biogas-producing bacteria, and also affects the operating load and treatment capacity of the restaurant kitchen anaerobic system and the sewage biochemical treatment system.

[0003] In the related art, the restaurant kitchen wastewater recycling system is equipped with an oil removal tank, a regulating tank, a coagulation tank, and a biochemical tank in the oil and phosphorus removal process; the key step is to add PAC (polyaluminium chloride) into the coagulation tank for coagulation treatment.

[0004] With regard to the above-mentioned related technologies, the three-phase centrifugal waste liquid needs to pass through multiple functional pools, the treatment process is cumbersome, and the oil removal rate and phosphorus removal rate are not high enough. In addition, the use of PAC for coagulation requires a large amount of reagents, which increases the disposal water volume and operating load of the subsequent anaerobic system for food and sewage biochemical treatment system. Therefore, there are defects such as the complex operation process of three-phase centrifugal waste liquid oil and phosphorus removal, the low oil removal rate and phosphorus removal rate, and the large subsequent sewage treatment operating load. Summary of the invention

[0005] The purpose of the present invention is to provide a method for treating three-phase centrifugal waste liquid of kitchen waste and its application, so as to solve the problems of complex oil and phosphorus removal operation process of three-phase centrifugal waste liquid, insufficient oil and phosphorus removal rate, and large operation load of subsequent sewage treatment.

[0006] In order to achieve the above-mentioned object, in a first aspect, the present invention provides a method for treating three-phase centrifugal waste liquid of kitchen waste, which adopts the following technical scheme:

[0007] A method for treating three-phase centrifugal waste liquid from kitchen waste comprises the following steps:

[0008] S1. Under stirring conditions, adding an alkaline substance to adjust the pH of the three-phase centrifugal waste liquid to alkaline;

[0009] S2. Under stirring conditions, adding a coagulant to the three-phase centrifuged waste liquid obtained after step S1 to perform a coagulation reaction;

[0010] S3. Under stirring conditions, adding a flocculant to the three-phase centrifuged waste liquid obtained after step S2 to perform a flocculation reaction;

[0011] S4. The three-phase centrifugal waste liquid obtained after step S3 is subjected to solid-liquid separation to obtain a residue and a waste liquid, the residue is recycled, and the waste liquid is discharged into a sewage biochemical treatment system for purification;

[0012] Among them, steps S1, S2 and S3 are all carried out in the same reactor; and step S4 is carried out in a solid-liquid separation device.

[0013] Preferably, in step S1, the pH of the three-phase centrifugal waste liquid is adjusted to 8-11.

[0014] Preferably, the alkaline substance includes at least one of slaked lime, liquid caustic soda and flake caustic soda.

[0015] Preferably, the coagulant comprises at least one of an FeCl3 aqueous solution and a demulsifier, wherein the mass concentration of the FeCl3 aqueous solution is 10% to 20%, and the mass concentration of the demulsifier is 1% to 10%.

[0016] Preferably, in step S2, the volume dosage of the coagulant is 0-2% of the volume of the three-phase centrifugal waste liquid.

[0017] Preferably, the flocculant is a PAM aqueous solution with a mass concentration of 0.1% to 1.5%.

[0018] Preferably, in step S3, the volume dosage of the flocculant is 0.5-5% of the volume of the three-phase centrifugal waste liquid.

[0019] Preferably, in step S4, the solid-liquid separation equipment includes at least one of a screw stacking equipment, a centrifugal equipment, a filter press equipment, and an air flotation equipment.

[0020] Preferably, in step S2, the stirring speed is 100-200 rpm; in step S3, the stirring speed is 40-70 rpm.

[0021] In a second aspect, the present invention provides a method for treating three-phase centrifugal waste liquid of food waste as described in any one of the above items, and its use in treating food waste species.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The method for treating three-phase centrifugal waste liquid of food waste provided by the present invention can effectively remove oil and phosphorus from the three-phase centrifugal waste liquid, and has a simple process and low equipment investment. There is no need to replace a new oil extraction system or centrifugal equipment at the front end, and there is no need to add an oil removal tank, a regulating tank, a coagulation tank, etc. at the back end, and it does not occupy a large amount of plant area.

[0024] (2) By selecting PAM (polyacrylamide) aqueous solution as flocculant and adjusting the dosage of coagulant and flocculant, the dosage of flocculant can be reduced, the operating load of the anaerobic system and sewage treatment system can be reduced, and the processing capacity of food waste can be increased, further reducing costs and increasing profits.

[0025] (3) The residue obtained after solid-liquid separation in the treatment method of the present invention can be sent to a waste incinerator for direct incineration or used as a raw material for organic residues in black soldier fly breeding for recycling, and the waste liquid can be directly sent to a sewage biochemical treatment system for purification. DETAILED DESCRIPTION

[0026] To make the technical solutions and advantages of the present invention more clear, the present invention and its beneficial effects will be further described in detail below in conjunction with specific implementation methods, but the implementation methods of the present invention are not limited thereto.

[0027] Kitchen waste includes kitchen garbage and waste grease (gutter oil). After the processes of impurity removal, crushing, pulping, oil extraction, etc., kitchen waste is generally separated into waste liquid, waste residue and grease. Among them, the three-phase centrifugal waste liquid is yellow-brown and viscous. The three-phase centrifugal waste liquid needs to be deoiled and dephosphorized first to meet the sewage discharge standards before it can be discharged into the sewage biochemical treatment system for purification.

[0028] In a first aspect, the present application provides a method for treating three-phase centrifugal waste liquid of kitchen waste, which adopts the following technical scheme:

[0029] S1. Under stirring conditions, an alkaline substance is added to the three-phase centrifugal waste liquid, wherein the alkaline substance is selected from at least one of slaked lime, liquid caustic soda, and caustic soda flakes, and the pH of the three-phase centrifugal waste liquid is adjusted to 8 to 11, so that the three-phase centrifugal waste liquid is alkaline;

[0030] S2. Under stirring conditions of a stirring speed of 100 to 200 rpm and a stirring time of 5 min, a coagulant is added to the three-phase centrifuged waste liquid obtained after step S1 to perform a coagulant reaction; wherein the coagulant is selected from a FeCl3 aqueous solution having a mass concentration of 10% to 20% and a FeCl3 aqueous solution having a mass concentration of 1% to 10%, and the volume amount of the coagulant is 0 to 2% of the volume of the three-phase centrifuged waste liquid;

[0031] S3. Under stirring conditions of a stirring speed of 100 to 200 rpm and a stirring time of 10 min, a flocculant is added to the three-phase centrifuged waste liquid obtained after step S2 to carry out a flocculation reaction; wherein the flocculant is a PAM (polyacrylamide) aqueous solution having a mass concentration of 0.1% to 1.5%, and the volume amount of the flocculant is 0.5 to 5% of the volume of the three-phase centrifuged waste liquid;

[0032] S4. The three-phase centrifuged waste liquid obtained after step S3 is subjected to solid-liquid separation to separate the residue and the waste liquid, the separated residue is sent to a waste incinerator for incineration or recycled as an organic residue raw material for black soldier fly breeding, and the wastewater is discharged into a sewage biochemical treatment system for purification;

[0033] Among them, steps S1, S2, and S3 are all carried out in the same reactor; step S4 is carried out in a solid-liquid separation device, and the solid-liquid separation device is selected from at least one of a spiral stacking device, a centrifugal device, a filter press device, and a flotation device.

[0034] The experimental principle of this treatment method is as follows: first, the three-phase centrifugal waste liquid is adjusted to alkaline, which is conducive to the hydrolysis and saponification reaction of the oil in the three-phase centrifugal waste liquid, converting the oil into suspended particles, and facilitating the reduction of the oil content in the waste liquid. Then, a coagulant is added to the three-phase centrifugal waste liquid to make the colloid in the water lose stability, and the colloidal particles condense into small particles, resulting in the formation of numerous "small alum flowers", which increases the speed of filtration or precipitation and helps to improve the efficiency of water treatment. Then, a flocculant is added to the three-phase centrifugal waste liquid, and a colloid with a strong adsorption effect is formed in the water by a polymer compound, which adsorbs the suspended particles in the water and aggregates them to form the final precipitate, while removing the suspended matter, chromaticity, organic matter and heavy metals in the water, which can improve the clarity of the water and the treatment efficiency. Finally, the residue and wastewater in the treated three-phase centrifugal waste liquid are separated by a solid-liquid separation device, and the residue is recycled for fuel or aquaculture feed to improve economic benefits. The wastewater meets the sewage discharge standard and enters the sewage biochemical treatment system for purification.

[0035] It is worth noting that the coagulant in this method can be omitted, or the dosage of the coagulant added can be controlled within the range of 0-2% of the volume of the three-phase centrifugal waste liquid, which can not only accelerate the sedimentation efficiency of suspended particles, but also avoid the coagulant from causing a large operating load on the sewage biochemical treatment system. In addition, in the prior art, PAC (polyaluminum chloride) is selected as the flocculant. The use of PAC requires the preparation of a large amount of aqueous solution, and the subsequent wastewater treatment has a large amount of water and a large load. However, this application selects PAM (polyacrylamide) as a flocculant, which can avoid excessive water volume in the subsequent wastewater treatment, thereby reducing the load, increasing production capacity, further reducing costs, and increasing profits.

[0036] The following examples and comparative examples further illustrate the technical scheme of the present invention in detail.

[0037] The three-phase centrifugal waste liquid used is the three-phase centrifugal waste liquid generated by the treatment of the same batch of kitchen waste, with a pH of 4.52, an oil content of 28000 mg / L, and a phosphorus content of 96.7 mg / L. The alkaline substance for adjusting the pH is soda lime, the coagulant is a FeCl3 aqueous solution with a mass concentration of 15% or a demulsifier with a mass concentration of 7%, the flocculant is a PAM aqueous solution with a mass concentration of 0.3, the reactor is a reactor, and the solid-liquid separation equipment is a spiral stacking equipment. The above reagents and equipment can be ordered directly from the market.

[0038] Example 1

[0039] This embodiment provides a method for treating three-phase centrifugal waste liquid from kitchen waste, comprising the following steps:

[0040] S1. Take 400 mL of the three-phase centrifugal waste liquid, add slaked lime, adjust the pH to 9-10, and stir continuously during addition;

[0041] S2. After adjusting the pH, a total of 4 mL of FeCl3 aqueous solution was added, the dosage was 1% (volume percentage) of the three-phase centrifugal waste liquid, and stirring was continued during addition, the stirring speed was 150 rpm, and the stirring time was 5 min;

[0042] S3. Add 8 mL of PAM aqueous solution of flocculant, the dosage is 2% (volume percentage) of the three-phase centrifuged waste liquid, the stirring speed is 60 rpm, and the stirring time is 10 min;

[0043] S4. After flocculation, the solid-liquid separation is carried out through the spiral stacking equipment to separate the liquid and the residue.

[0044] Wherein, the processes of steps S1, S2 and S3 are carried out in the same reactor;

[0045] The residue separated in step S4 is sent to a waste incinerator for incineration or used as raw material for organic residues for black soldier fly breeding.

[0046] The liquid obtained in step S4 has a pH of 9.67, an oil content of 949.2 mg / L, an oil removal rate of 96.61%, a phosphorus content of 16 mg / L, and a phosphorus removal rate of 83.45%.

[0047] After cost calculation, it was found that the cost of the direct treatment agent in this embodiment is 12.24 yuan / ton.

[0048] Example 2

[0049] This embodiment provides a method for treating three-phase centrifugal waste liquid from kitchen waste, comprising the following steps:

[0050] S1. Take 400 mL of the three-phase centrifugal waste liquid, add slaked lime, adjust the pH to 8-9, and stir continuously during addition;

[0051] S2. After adjusting the pH, a total of 4 mL of FeCl3 aqueous solution was added, the dosage was 1% (volume percentage) of the three-phase centrifugal waste liquid, and stirring was continued during addition, the stirring speed was 150 rpm, and the stirring time was 5 min;

[0052] S3. Add 8 mL of PAM aqueous solution of flocculant, the dosage is 2% (volume percentage) of the three-phase centrifuged waste liquid, the stirring speed is 60 rpm, and the stirring time is 10 min;

[0053] S4. After flocculation, the solid-liquid separation is carried out through the spiral stacking equipment to separate the liquid and the residue.

[0054] Wherein, the processes of steps S1, S2 and S3 are carried out in the same reactor;

[0055] The residue separated in step S4 is sent to a waste incinerator for incineration or used as raw material for organic residues for black soldier fly breeding.

[0056] The liquid obtained in step S4 has a pH of 8.49, an oil content of 1302 mg / L, an oil removal rate of 95.35%, a phosphorus content of 12.92 mg / L, and a phosphorus removal rate of 86.63%.

[0057] After cost calculation, it was found that the cost of the direct treatment agent in this embodiment is 12.2 yuan / ton.

[0058] Example 3

[0059] This embodiment provides a method for treating three-phase centrifugal waste liquid from kitchen waste, comprising the following steps:

[0060] S1. Take 400 mL of the three-phase centrifugal waste liquid, add slaked lime, adjust the pH to 10-11, and stir continuously during addition;

[0061] S2. After adjusting the pH, a total of 4 mL of FeCl3 aqueous solution was added, the dosage was 1% (volume percentage) of the three-phase centrifugal waste liquid, and stirring was continued during addition, the stirring speed was 150 rpm, and the stirring time was 5 min;

[0062] S3. Add 8 mL of PAM aqueous solution of flocculant, the dosage is 2% (volume percentage) of the three-phase centrifuged waste liquid, the stirring speed is 60 rpm, and the stirring time is 10 min;

[0063] S4. After flocculation, the solid-liquid separation is carried out through the spiral stacking equipment to separate the liquid and the residue.

[0064] Wherein, the processes of steps S1, S2 and S3 are carried out in the same reactor;

[0065] The residue separated in step S4 is sent to a waste incinerator for incineration or used as raw material for organic residues for black soldier fly breeding.

[0066] The liquid obtained in step S4 has a pH of 10.52, an oil content of 582.4 mg / L, an oil removal rate of 97.39%, a phosphorus content of 19.39 mg / L, and a phosphorus removal rate of 79.94%.

[0067] After cost calculation, it was found that the cost of the direct treatment agent in this embodiment is 12.32 yuan / ton.

[0068] Example 4

[0069] This embodiment provides a method for treating three-phase centrifugal waste liquid from kitchen waste, comprising the following steps:

[0070] S1. Take 400 mL of the three-phase centrifugal waste liquid, add slaked lime, adjust the pH to 9-10, and stir continuously during addition;

[0071] S2. After adjusting the pH, a total of 2 mL of FeCl3 aqueous solution was added, the dosage was 0.5% (volume percentage) of the three-phase centrifugal waste liquid, and stirring was continued during addition, the stirring speed was 150 rpm, and the stirring time was 5 min;

[0072] S3. Add 8 mL of PAM aqueous solution of flocculant, the dosage is 2% (volume percentage) of the three-phase centrifuged waste liquid, the stirring speed is 60 rpm, and the stirring time is 10 min;

[0073] S4. After flocculation, the solid-liquid separation is carried out through the spiral stacking equipment to separate the liquid and the residue.

[0074] Wherein, the processes of steps S1, S2 and S3 are carried out in the same reactor;

[0075] The residue separated in step S4 is sent to a waste incinerator for incineration or used as raw material for organic residues for black soldier fly breeding.

[0076] The liquid obtained in step S4 has a pH of 9.61, an oil content of 1178.8 mg / L, an oil removal rate of 95.79%, a phosphorus content of 16.48 mg / L, and a phosphorus removal rate of 82.95%.

[0077] After cost calculation, it was found that the cost of the direct treatment agent in this embodiment is 10.86 yuan / ton.

[0078] Example 5

[0079] This embodiment provides a method for treating three-phase centrifugal waste liquid from kitchen waste, comprising the following steps:

[0080] S1. Take 400 mL of the three-phase centrifugal waste liquid, add slaked lime, adjust the pH to 9-10, and stir continuously during addition;

[0081] S2. After adjusting the pH, a total of 8 mL of FeCl3 aqueous solution was added, the dosage was 2% (volume percentage) of the three-phase centrifugal waste liquid, and stirring was continued during addition, the stirring speed was 150 rpm, and the stirring time was 5 min;

[0082] S3. Add 8 mL of PAM aqueous solution of flocculant, the dosage is 2% (volume percentage) of the three-phase centrifuged waste liquid, the stirring speed is 60 rpm, and the stirring time is 10 min;

[0083] S4. After flocculation, the solid-liquid separation is carried out through the spiral stacking equipment to separate the liquid and the residue.

[0084] Wherein, the processes of steps S1, S2 and S3 are carried out in the same reactor;

[0085] The residue separated in step S4 is sent to a waste incinerator for incineration or used as raw material for organic residues for black soldier fly breeding.

[0086] The liquid obtained in step S4 has a pH of 9.73, an oil content of 772.8 mg / L, an oil removal rate of 97.24%, a phosphorus content of 15.79 mg / L, and a phosphorus removal rate of 83.67%.

[0087] After cost calculation, it was found that the cost of the direct treatment agent in this embodiment is 14.62 yuan / ton.

[0088] Example 6

[0089] This embodiment provides a method for treating three-phase centrifugal waste liquid from kitchen waste, comprising the following steps:

[0090] S1. Take 400 mL of the three-phase centrifugal waste liquid, add slaked lime, adjust the pH to 9-10, and stir continuously during addition;

[0091] S2. After adjusting the pH, add a total of 4 mL of demulsifier aqueous solution, the addition amount is 1% (volume percentage) of the three-phase centrifugal waste liquid, and stir continuously during addition, the stirring speed is 150 rpm, and the stirring time is 5 min;

[0092] S3. Add 8 mL of PAM aqueous solution of flocculant, the dosage is 2% (volume percentage) of the three-phase centrifuged waste liquid, the stirring speed is 60 rpm, and the stirring time is 10 min;

[0093] S4. After flocculation, the solid-liquid separation is carried out through the spiral stacking equipment to separate the liquid and the residue.

[0094] Wherein, the processes of steps S1, S2 and S3 are carried out in the same reactor;

[0095] The residue separated in step S4 is sent to a waste incinerator for incineration or used as raw material for organic residues for black soldier fly breeding.

[0096] The liquid obtained in step S4 has a pH of 9.17, an oil content of 1556.8 mg / L, an oil removal rate of 94.44%, a phosphorus content of 17.59 mg / L, and a phosphorus removal rate of 81.8%.

[0097] After cost calculation, it was found that the cost of the direct treatment agent in this embodiment is 41.04 yuan / ton.

[0098] Example 7

[0099] This embodiment provides a method for treating three-phase centrifugal waste liquid from kitchen waste, comprising the following steps:

[0100] S1. Take 400 mL of the three-phase centrifugal waste liquid, add slaked lime, adjust the pH to 9-10, and stir continuously during addition;

[0101] S2. After adjusting the pH, a total of 4 mL of FeCl3 aqueous solution was added, the dosage was 1% (volume percentage) of the three-phase centrifugal waste liquid, and stirring was continued during addition, the stirring speed was 150 rpm, and the stirring time was 5 min;

[0102] S3. Add 2 mL of PAM aqueous solution of flocculant, the dosage is 0.5% (volume percentage) of the three-phase centrifuged waste liquid, the stirring speed is 60 rpm, and the stirring time is 10 min;

[0103] S4. After flocculation, the solid-liquid separation is carried out through the spiral stacking equipment to separate the liquid and the residue.

[0104] Wherein, the processes of steps S1, S2 and S3 are carried out in the same reactor;

[0105] The residue separated in step S4 is sent to a waste incinerator for incineration or used as raw material for organic residues for black soldier fly breeding.

[0106] The liquid obtained in step S4 has a pH of 9.89, an oil content of 1209.6 mg / L, an oil removal rate of 95.68%, a phosphorus content of 16.54 mg / L, and a phosphorus removal rate of 82.89%.

[0107] After cost calculation, it was found that the cost of the direct treatment agent in this embodiment is 10.32 yuan / ton.

[0108] Example 8

[0109] This embodiment provides a method for treating three-phase centrifugal waste liquid from kitchen waste, comprising the following steps:

[0110] S1. Take 400 mL of the three-phase centrifugal waste liquid, add slaked lime, adjust the pH to 9-10, and stir continuously during addition;

[0111] S2. After adjusting the pH, a total of 4 mL of FeCl3 aqueous solution was added, the dosage was 1% (volume percentage) of the three-phase centrifugal waste liquid, and stirring was continued during addition, the stirring speed was 150 rpm, and the stirring time was 5 min;

[0112] S3. Add 20 mL of PAM aqueous solution of flocculant, the dosage is 5% (volume percentage) of the three-phase centrifugal waste liquid, the stirring speed is 60 rpm, and the stirring time is 10 min;

[0113] S4. After flocculation, the solid-liquid separation is carried out through the spiral stacking equipment to separate the liquid and the residue.

[0114] Wherein, the processes of steps S1, S2 and S3 are carried out in the same reactor;

[0115] The residue separated in step S4 is sent to a waste incinerator for incineration or used as raw material for organic residues for black soldier fly breeding.

[0116] The liquid obtained in step S4 has a pH of 10.23, an oil content of 120.4 mg / L, an oil removal rate of 99.57%, a phosphorus content of 9.17 mg / L, and a phosphorus removal rate of 90.51%.

[0117] After cost calculation, it was found that the cost of the direct treatment agent in this embodiment is 14.24 yuan / ton.

[0118] Comparative Example 1

[0119] This embodiment provides a method for treating three-phase centrifugal waste liquid from kitchen waste, comprising the following steps:

[0120] S1. Take 400 mL of the three-phase centrifugal waste liquid, add slaked lime, adjust the pH to 9-10, and stir continuously during addition;

[0121] S2. After adjusting the pH, no coagulant is added;

[0122] S3. Add 8 mL of PAM aqueous solution of flocculant, the dosage is 2% (volume percentage) of the three-phase centrifuged waste liquid, the stirring speed is 60 rpm, and the stirring time is 10 min;

[0123] S4. After flocculation, the solid-liquid separation is carried out through the spiral stacking equipment to separate the liquid and the residue.

[0124] Wherein, the processes of steps S1, S2 and S3 are carried out in the same reactor;

[0125] The residue separated in step S4 is sent to a waste incinerator for incineration or used as raw material for organic residues for black soldier fly breeding.

[0126] The liquid obtained in step S4 has a pH of 9.6, an oil content of 2464 mg / L, an oil removal rate of 91.2%, a phosphorus content of 17.45 mg / L, and a phosphorus removal rate of 81.95%.

[0127] After cost calculation, it was found that the cost of the direct treatment agent in this embodiment was 7.22 yuan / ton.

[0128] Comparative Example 2

[0129] This embodiment provides a method for treating three-phase centrifugal waste liquid from kitchen waste, comprising the following steps:

[0130] S1. Take 400 mL of the three-phase centrifugal waste liquid without adjusting the pH;

[0131] S2. After adjusting the pH, a total of 4 mL of FeCl3 aqueous solution was added, the dosage was 1% (volume percentage) of the three-phase centrifugal waste liquid, and stirring was continued during addition, the stirring speed was 150 rpm, and the stirring time was 5 min;

[0132] S3. Add 2 mL of PAM aqueous solution of flocculant, the dosage is 0.5% (volume percentage) of the three-phase centrifuged waste liquid, the stirring speed is 60 rpm, and the stirring time is 10 min;

[0133] S4. After flocculation, the solid-liquid separation is carried out through the spiral stacking equipment to separate the liquid and the residue.

[0134] Wherein, the processes of steps S1, S2 and S3 are carried out in the same reactor;

[0135] The residue separated in step S4 is sent to a waste incinerator for incineration or used as raw material for organic residues for black soldier fly breeding.

[0136] The liquid obtained in step S4 has a pH of 4.49, an oil content of 28000 mg / L, an oil removal rate of 0%, a phosphorus content of 47.19 mg / L, and a phosphorus removal rate of 51.19%.

[0137] The oil and phosphorus contents did not meet the emission standards and the costs were not calculated.

[0138] Comparative Example 3

[0139] This embodiment provides a method for treating three-phase centrifugal waste liquid from kitchen waste, comprising the following steps:

[0140] S1. Take 400 mL of the three-phase centrifugal waste liquid, add a small amount of slaked lime, and adjust the pH value to 6-7;

[0141] S2. After adjusting the pH, a total of 4 mL of FeCl3 aqueous solution was added, the dosage was 1% (volume percentage) of the three-phase centrifugal waste liquid, and stirring was continued during addition, the stirring speed was 150 rpm, and the stirring time was 5 min;

[0142] S3. Add 2 mL of PAM aqueous solution of flocculant, the dosage is 0.5% (volume percentage) of the three-phase centrifuged waste liquid, the stirring speed is 60 rpm, and the stirring time is 10 min;

[0143] S4. After flocculation, the solid-liquid separation is carried out through the spiral stacking equipment to separate the liquid and the residue.

[0144] Wherein, the processes of steps S1, S2 and S3 are carried out in the same reactor;

[0145] The residue separated in step S4 is sent to a waste incinerator for incineration or used as raw material for organic residues for black soldier fly breeding.

[0146] The liquid obtained in step S4 has a pH of 6.51, an oil content of 15500.8 mg / L, an oil removal rate of 44.64%, a phosphorus content of 20.89 mg / L, and a phosphorus removal rate of 78.39%.

[0147] If the oil content does not meet the emission standards, the cost will not be calculated.

[0148] Comparative Example 4

[0149] This embodiment provides a method for treating three-phase centrifugal waste liquid from kitchen waste, comprising the following steps:

[0150] S1. Take 400 mL of the three-phase centrifugal waste liquid, add slaked lime, adjust the pH to 9-10, and stir continuously during addition;

[0151] S2. After adjusting the pH, a total of 4 mL of FeCl3 aqueous solution was added, the dosage was 1% (volume percentage) of the three-phase centrifugal waste liquid, and stirring was continued during addition, the stirring speed was 150 rpm, and the stirring time was 5 min;

[0152] S3. No flocculant is added;

[0153] S4. After flocculation, the solid-liquid separation is carried out through the spiral stacking equipment to separate the liquid and the residue.

[0154] Wherein, the processes of steps S1, S2 and S3 are carried out in the same reactor;

[0155] The residue separated in step S4 is sent to a waste incinerator for incineration or used as raw material for organic residues for black soldier fly breeding.

[0156] The liquid obtained in step S4 has a pH of 8.76, an oil content of 23399.6 mg / L, an oil removal rate of 16.43%, a phosphorus content of 54.59 mg / L, and a phosphorus removal rate of 43.23%.

[0157] The oil and phosphorus contents did not meet the emission standards and the costs were not calculated.

[0158] Comparing the above embodiments and comparative examples, it can be seen that:

[0159] In Examples 1 to 3, the effects of different pH values ​​on the oil removal and phosphorus removal of three-phase centrifugal waste liquid were compared. The detection indicators showed that adjusting the pH value to 8 to 11 in step S1 can make the oil removal rate of the method above 95% and the phosphorus removal rate above 75%. Within the corresponding range, the higher the pH value, the higher the oil removal rate, the lower the phosphorus removal rate, and the higher the reagent cost.

[0160] In Examples 1, 4 and 5, the effects of different volume amounts of coagulants on the oil and phosphorus removal of three-phase centrifugal waste liquid were compared. The test indicators show that the volume amount of coagulant in step S2 is in the range of 0.5-2%, which can make the oil removal rate of the method above 90% and the phosphorus removal rate above 80%. Further, in combination with Comparative Example 3, no coagulant may be added in step S2. The test indicators show that the oil removal rate is above 95% and the phosphorus removal rate is above 80%, but the oil removal rate and phosphorus removal rate are lower than those of Examples 1, 4 and 5. Based on the above analysis, the volume amount of coagulant in step S2 is in the range of 0.5-2%. The larger the volume amount of coagulant, the higher the oil removal rate, the higher the phosphorus removal rate, and the higher the cost of the agent.

[0161] Furthermore, in Example 1 and Example 6, the effects of different types of coagulants on the oil and phosphorus removal of three-phase centrifugal waste liquid were compared. The use of a demulsifier as a coagulant can make the oil removal rate of the method above 90% and the phosphorus removal rate above 80%, but the cost of the agent is much greater than that of the FeCl3 aqueous solution.

[0162] In Examples 1, 7 and 8, the effects of different volumetric dosages of flocculants on the oil and phosphorus removal of three-phase centrifugal waste liquid were compared. The detection indicators showed that when the volumetric dosage of the flocculant in step S3 was in the range of 0.5 to 5%, the oil removal rate of the method could be above 95%, and the phosphorus removal rate could be above 80%. Within the corresponding range, the larger the volumetric dosage of the flocculant, the higher the oil removal rate, the higher the phosphorus removal rate, and the higher the reagent cost.

[0163] In Comparative Examples 2 and 3, the effects of not adjusting the pH or adjusting the pH while keeping it acidic on the oil and phosphorus removal of the three-phase centrifugal waste liquid were tested. The test indicators showed that the oil removal rate and phosphorus removal rate were both low and did not meet the sewage discharge standards.

[0164] In Comparative Example 4, the effect of not adding flocculants on the oil and phosphorus removal of three-phase centrifugal waste liquid was tested. The test indicators showed that the oil removal rate and phosphorus removal rate were both low and did not meet the sewage discharge standard.

[0165] In summary, the treatment method provided by the present invention can effectively achieve the oil removal and phosphorus removal of three-phase centrifugal waste liquid, with an oil removal rate of more than 90%, which can reach 99%, and a phosphorus removal rate of more than 75%. The treatment method of the present invention has a simple process and low equipment investment. There is no need to replace a new oil extraction system or centrifugal equipment at the front end, and there is no need to add an oil removal tank, a regulating tank, a coagulation tank, etc. at the back end, and it does not occupy a large amount of plant area. By selecting a flocculant and adjusting the dosage of the coagulant and the flocculant, the operating load of the anaerobic system and the sewage treatment system can also be reduced, and the processing capacity of food waste can be increased.

[0166] In a second aspect, the present application provides a method for treating three-phase centrifugal waste liquid from kitchen waste and its application in kitchen waste, including any one of the above-mentioned treatment methods.

[0167] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for treating three-phase centrifugal waste liquid from kitchen waste, characterized in that: The steps include: S1. Under stirring conditions, adding an alkaline substance to adjust the pH of the three-phase centrifugal waste liquid to alkaline; S2. Under stirring conditions, adding a coagulant to the three-phase centrifuged waste liquid obtained after step S1 to perform a coagulation reaction; S3. Under stirring conditions, adding a flocculant to the three-phase centrifuged waste liquid obtained after step S2 to perform a flocculation reaction; S4. The three-phase centrifugal waste liquid obtained after step S3 is subjected to solid-liquid separation to obtain a residue and a waste liquid, the residue is recycled, and the waste liquid is discharged into a sewage biochemical treatment system for purification; Among them, steps S1, S2 and S3 are all carried out in the same reactor; and step S4 is carried out in a solid-liquid separation device.

2. The method for treating three-phase centrifugal waste liquid of kitchen waste according to claim 1, characterized in that: In step S1, the pH of the three-phase centrifugal waste liquid is adjusted to 8-11.

3. The method for treating three-phase centrifugal waste liquid of kitchen waste according to claim 2, characterized in that: The alkaline substance includes at least one of slaked lime, liquid caustic soda and flake caustic soda.

4. The method for treating three-phase centrifugal waste liquid of kitchen waste and its application according to claim 1, characterized in that: The coagulant comprises at least one of an FeCl3 aqueous solution and a demulsifier, wherein the mass concentration of the FeCl3 aqueous solution is 10% to 20%, and the mass concentration of the demulsifier is 1% to 10%.

5. The method and application of treating three-phase centrifugal waste liquid of kitchen waste according to claim 4, characterized in that: In step S2, the volume dosage of the coagulant is 0-2% of the volume of the three-phase centrifugal waste liquid.

6. The method for treating three-phase centrifugal waste liquid of kitchen waste and its application according to claim 1, characterized in that: The flocculant is a PAM aqueous solution with a mass concentration of 0.1% to 1.5%.

7. The method for treating three-phase centrifugal waste liquid of kitchen waste and its application according to claim 6, characterized in that: In step S3, the volume dosage of the flocculant is 0.5-5% of the volume of the three-phase centrifugal waste liquid.

8. The method for treating three-phase centrifugal waste liquid of kitchen waste and its application according to claim 1, characterized in that: In step S4, the solid-liquid separation equipment includes at least one of a screw stacking equipment, a centrifugal equipment, a filter press equipment, and an air flotation equipment.

9. The method for treating three-phase centrifugal waste liquid of kitchen waste and its application according to claim 1, characterized in that: In step S2, the stirring speed is 100-200 rpm; in step S3, the stirring speed is 40-70 rpm.

10. Use of the method for treating three-phase centrifuged waste liquid of kitchen waste as claimed in any one of claims 1 to 9 in treating kitchen waste species.