A treatment process for surimi processing wastewater

Abstract

The present invention discloses a process for treating surimi processing wastewater. The process includes the following steps: flocculation of the surimi processing wastewater; initial dehydration of the flocs to form activated sludge; hydrolysis of the activated sludge; reconcentration of the hydrolyzate; and sterilization and packaging of the product. This process not only effectively reduces the COD and ammonia nitrogen contents in the surimi processing wastewater, meeting the discharge requirements of urban pipe networks, but also effectively collects and efficiently utilizes organic matter such as protein in the surimi wastewater, transforming waste into valuable resources and achieving sustainable economic and environmental development.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a treatment process for wastewater from surimi processing. Background Art

[0002] In recent years, the primary method for treating organic wastewater has been flocculation, which produces activated sludge and then processes it. This method primarily uses flocculants such as polyferric chloride, polyaluminum chloride, and polyacrylamide. The activated sludge treated with these flocculants is difficult to dispose of and must be landfilled, resulting in very high disposal costs.

[0003] Surimi processing consumes a significant amount of water, requiring 10-20 tons of tap water to process one ton of surimi. The resulting wastewater contains significant amounts of organic matter, such as protein and fat, and direct discharge poses significant environmental risks. However, unlike municipal sewage treatment plant wastewater, this wastewater comes from a single source and is free of toxic and hazardous pollutants. Protein and organic matter can be effectively recovered through flocculation. Activated sludge recovered through flocculation with polyaluminum chloride and polyferric chloride is difficult to use in feed, as it can easily lead to excessive aluminum levels, which can be transmitted to humans through the food chain. Sludge containing polyaluminum chloride, polyferric chloride, and polyacrylamide can easily cause soil contamination and compaction when used in organic fertilizers.

[0004] Modified starch is used as a novel flocculant in the treatment of surimi wastewater, eliminating the need for external pollutants and promoting environmental protection. However, the activated sludge produced using activated starch has a high water content and good water retention, making it difficult to reduce the sludge's moisture content, hindering subsequent processing. The present invention combines enzymatic hydrolysis with surimi wastewater treatment to effectively reduce moisture, efficiently utilize protein in the wastewater, and effectively utilize the activated sludge. This eliminates the need for enterprises to incur the cost of activated sludge treatment while also achieving certain economic benefits. Summary of the Invention

[0005] To address existing technical issues, the present invention provides a process for treating surimi processing wastewater. This process not only effectively reduces the COD and ammonia nitrogen contents in surimi processing wastewater, meeting the discharge requirements of urban pipe networks, but also effectively collects and efficiently utilizes organic matter such as protein in the surimi wastewater, transforming waste into valuable resources and achieving sustainable economic and environmental development.

[0006] The technical solution adopted in the present invention is:

[0007] A process for treating surimi processing wastewater comprises the following steps:

[0008] (1) Flocculation of surimi processing wastewater;

[0009] (2) Initial dewatering of flocs into activated sludge;

[0010] (3) Hydrolysis of activated sludge;

[0011] (4) reconcentration of the hydrolyzate;

[0012] (5) Product sterilization and packaging.

[0013] Furthermore, the step (1) is specifically as follows: adding a branched modified starch solution to the surimi processing wastewater and stirring the mixture evenly, and then allowing the mixture to stand to obtain floccules.

[0014] Preferably, the solid content of the surimi processing wastewater is 1-2% by mass, the added starch solution is 1-5% of the wastewater by mass, and the mass concentration of the starch solution is 0.1-0.2%.

[0015] Preferably, the stirring speed is 30-50 r / min and the stirring time is 2-3 min.

[0016] Furthermore, the step (2) is specifically as follows: the flocculent is subjected to flotation to initially separate the flocculent residue and water, the flocculent residue enters a screw press sludge machine for further dehydration to obtain activated sludge, and at the same time, the activated sludge is sprayed with amylase at the outlet of the screw press sludge machine to obtain activated sludge containing amylase.

[0017] Preferably, the water content of the activated sludge after dehydration is 80-85 wt%.

[0018] Preferably, the weight of amylase is 0.1% of the weight of the activated sludge.

[0019] Furthermore, the step (3) is specifically as follows: the activated sludge containing amylase is hydrolyzed for the first time, the first hydrolysis temperature is 50-55°C, and the time is 30-50min; then alkaline protease is added and stirred for a second hydrolysis, the second hydrolysis temperature is 50-55°C, and the time is 5-8h; finally, it is heated to 90°C and kept warm for 30min to inactivate the enzyme and sterilize.

[0020] Activated sludge after flocculation has strong water retention, making it difficult to dry to less than 8% moisture for use as fish meal, and difficult to meet fluidity requirements for use as liquid feed or fertilizer. The present invention utilizes amylase to rapidly decompose modified starch into polysaccharides, eliminating the flocculation effect of the modified starch. The flocculated water-soluble proteins and some ground meat can then be restored to their original fluid state by adding protease, further hydrolyzing the proteins into peptides, facilitating their use in specialty feeds and fertilizers.

[0021] Preferably, the amount of alkaline protease added is 0.1-0.3% of the weight of the activated sludge.

[0022] Preferably, the stirring speed is 45-50 r / min, and most preferably, the stirring speed is 47 r / min.

[0023] Furthermore, the step (4) is specifically as follows: the hydrolyzate obtained in step (3) is filtered through a vibrating screen to remove some sand and gravel, and then vacuum concentrated through a three-effect rising membrane concentration device to a solid content of more than 60%.

[0024] Optionally, NaOH is added to adjust the pH value of the hydrolyzate obtained in step (3) to greater than 10.0. The concentration of the hydrolyzed peptide needs to determine whether NaOH needs to be added to adjust the pH according to the application direction of the product. When the application direction is feed, it is necessary to adjust the pH>10. At this pH value, the alkaline gas in the liquid is easily volatilized during concentration, and the volatile basic nitrogen of the final product is <120 mg / 100 g, which meets the feed requirements. When the application direction is special agricultural fertilizer, there is no need to adjust the pH value of the hydrolyzate.

[0025] Preferably, the evaporation chamber of the three-effect rising film concentration equipment needs to be raised by 1 meter to prevent the material from flowing out in the form of foam together with the evaporated condensed water.

[0026] Furthermore, the step (5) is specifically as follows: the vacuum concentrated material is heated to 90° C., hot-filled into a plastic ton barrel, and then the barrel cover is quickly tightened and stored in a cool place.

[0027] Beneficial effects of the present invention:

[0028] (1) The present invention uses modified starch as a flocculant to enrich organic matter such as protein and fat in fish paste wastewater. Compared with flocculants such as polyaluminum chloride, polyferric chloride, and polyacrylamide, it does not produce secondary pollution and significantly reduces the cost of fish paste wastewater treatment process compared to direct heating concentration method.

[0029] (2) The present invention utilizes amylase and protease to hydrolyze the activated sludge after flocculation, thereby expanding its application in special feeds and special fertilizers and having good economic value.

[0030] (3) The present invention can effectively reduce the COD and ammonia nitrogen contents in the surimi processing wastewater to meet the discharge requirements of the urban pipe network. In addition, the present invention can effectively treat the surimi wastewater while extracting the nutrients in the wastewater, turning waste into treasure and achieving a win-win situation of economic benefits and environmental protection. DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to these specific embodiments. On the contrary, the purpose of providing these embodiments is to make the disclosure of this application more thorough and comprehensive.

[0032] Example 1

[0033] Three tons of surimi wastewater were tested for COD and ammonia nitrogen. Sixty kilograms of a 0.2% modified starch aqueous solution were slowly added, with the stirring speed adjusted to 47 rpm. After the modified starch was added, stirring was continued for two minutes. The mixture was then stopped to observe the rapid separation of the flocs and water, resulting in a clear water. The supernatant was tested, and COD levels dropped from 7800 to 460 mg / L, and ammonia nitrogen levels dropped from 120 to 31 mg / L.

[0034] The flocs were separated and transferred to a spiral sludge press for dewatering, yielding 180 kg of activated sludge with a moisture content of 83%. The sludge was then quickly mixed with 180 g of amylase and transferred to a 200 L enzymatic hydrolysis tank. Enzymatic hydrolysis was maintained at 53°C for 40 minutes, at which point the modified starch was substantially hydrolyzed, transforming the semi-solid material into a liquid. 180 g of alkaline protease was then added for further enzymatic hydrolysis. The temperature was maintained at 53°C for 5 hours, and after completion, the temperature was rapidly raised to 90°C. Stirring was continued, and a 6 mol / L NaOH solution was added to the material to a pH of 10.5. The material was then pumped into a triple-effect rising membrane concentrator for vacuum concentration. After one hour of concentration, 48 kg of material was obtained, with a measured concentration of 61%. The vacuum was removed, the temperature was raised to 90°C, and hot-filled into ton drums. A sample of the finished product was determined to contain 85 mg / 100 g of volatile basic nitrogen.

[0035] The final product obtained can be used in fish feed concentrate.

[0036] Example 2

[0037] Three tons of surimi wastewater were tested for COD and ammonia nitrogen. Sixty kilograms of a 0.2% modified starch solution were slowly added, with the stirring speed adjusted to 47 rpm. After the modified starch was added, stirring was continued for two minutes. The mixture was then stopped to observe the rapid separation of the flocs and water, resulting in a clear water. The supernatant was tested, and COD levels dropped from 7600 to 480 mg / L, and ammonia nitrogen levels dropped from 130 to 32 mg / L.

[0038] The flocculent material is separated and transferred to a spiral sludge press for dehydration, yielding 190 kg of activated sludge with a moisture content of 84%. This is then quickly mixed with 190 g of amylase and transferred to a 200 L enzymatic hydrolysis tank. The system is maintained at 55°C for 45 minutes, at which point the modified starch is essentially hydrolyzed, transforming the semi-solid material into a liquid. 180 g of alkaline protease is then added for further enzymatic hydrolysis. The temperature is maintained at 55°C for 5 hours, and upon completion, the temperature is rapidly raised to 90°C. The material is then pumped into a triple-effect rising membrane concentrator for vacuum concentration. After one hour of concentration, 49 kg of the material is obtained, with a measured concentration of 62%. The vacuum is removed, the temperature is raised to 90°C, and then hot-filled into ton barrels.

[0039] The final product can be used as agricultural organic fertilizer.

[0040] The above specific embodiments are used to illustrate the present invention rather than to limit the present invention. Any modifications and changes made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A process for treating surimi processing wastewater, characterized in that: The steps include: (1) Flocculation of surimi wastewater, specifically: adding a branched modified starch solution to the surimi wastewater, stirring evenly, and then allowing it to stand to obtain floccules; (2) Preliminary dehydration of the flocs into activated sludge, specifically: the flocs are subjected to air flotation to obtain a preliminary separation of flocculent residue and water, the flocculent residue is further dehydrated in a screw press sludge press to obtain activated sludge, and the activated sludge is simultaneously sprayed with amylase at the outlet of the screw press sludge press to obtain activated sludge containing amylase; the weight of the added amylase is 0.1% of the weight of the activated sludge; (3) hydrolysis of activated sludge, specifically: performing a first hydrolysis on the activated sludge containing amylase at a temperature of 50-55°C for 30-50 minutes; then adding alkaline protease and stirring for a second hydrolysis, wherein the amount of alkaline protease added is 0.1-0.3% of the weight of the activated sludge; the second hydrolysis temperature is 50-55°C for 5-8 hours; and finally heating to 90°C and keeping warm for 30 minutes to inactivate the enzyme and sterilize. (4) re-concentrating the hydrolyzate, specifically: filtering the hydrolyzate obtained in step (3) through a vibrating screen to remove some sand and gravel, and then vacuum concentrating it through a triple-effect rising membrane concentrator to a solid content of more than 60%; (5) Product sterilization and packaging.

2. The treatment process according to claim 1, characterized in that The solid content of the surimi processing wastewater is 1-2% by mass, the added starch solution is 1-5% of the wastewater by mass, and the mass concentration of the starch solution is 0.1-0.2%.

3. The treatment process according to claim 1, characterized in that NaOH is added to adjust the pH value of the hydrolyzate obtained in step (3) to be greater than 10.

0.

4. The treatment process according to claim 1, characterized in that The step (5) specifically comprises: heating the vacuum concentrated material to 90° C. and hot filling the barrel.