阅读说明：本技术 一种促进城市剩余污泥厌氧发酵生产挥发性脂肪酸的方法 (Method for promoting anaerobic fermentation of municipal excess sludge to produce volatile fatty acid ) 是由 陶雪 熊小燕 于 2020-05-27 设计创作，主要内容包括：本发明公开了一种促进城市剩余污泥厌氧发酵生产挥发性脂肪酸的方法,包括：(1)将从污水厂取回来的城市剩余污泥进行浓缩,然后将接种污泥和城市剩余污泥混合,装入六个发酵瓶,分别向发酵瓶中投加不同量的电石渣,以此调节发酵系统的碱性条件；(2)将发酵瓶充氮气使其保持厌氧环境,密封发酵瓶,每镉24小时投加电石渣调节发酵瓶的pH到需要的碱性条件,进行碱性发酵；(3)采用高速离心机将步骤(2)中的发酵液混合,在离心速度为10000r/min和离心温度为4℃条件下离心,离心后的上清液即为含有VFAs的城市污泥发酵液。本发明的方法可降低污泥发酵成本,生产的挥发性脂肪酸具有广阔的应用前景,且实现以废治废的目的。(The invention discloses a method for promoting anaerobic fermentation of municipal excess sludge to produce volatile fatty acid, which comprises the following steps: (1) concentrating municipal excess sludge taken from a sewage plant, mixing inoculated sludge and the municipal excess sludge, filling the mixture into six fermentation bottles, and adding different amounts of carbide slag into the fermentation bottles respectively so as to adjust the alkaline condition of a fermentation system; (2) filling nitrogen into the fermentation bottle to keep the fermentation bottle in an anaerobic environment, sealing the fermentation bottle, adding carbide slag every 24 hours to adjust the pH of the fermentation bottle to a required alkaline condition, and performing alkaline fermentation; (3) and (3) mixing the fermentation liquor obtained in the step (2) by adopting a high-speed centrifuge, centrifuging at the centrifugation speed of 10000r/min and the centrifugation temperature of 4 ℃, and obtaining the centrifuged supernatant, namely the municipal sludge fermentation liquor containing VFAs. The method can reduce the sludge fermentation cost, the produced volatile fatty acid has wide application prospect, and the purpose of treating wastes with processes of wastes against one another is realized.)

1. A method for promoting anaerobic fermentation of municipal excess sludge to produce volatile fatty acids is characterized by comprising the following steps:

step (1) preparation of fermentation substrate: concentrating municipal excess sludge taken from a sewage plant, mixing inoculated sludge and the municipal excess sludge, filling the mixture into six fermentation bottles, and adding different amounts of carbide slag into the fermentation bottles respectively so as to adjust the alkaline condition of a fermentation system;

step (2), during the fermentation stage of the municipal excess sludge: filling nitrogen into the fermentation bottle to keep the fermentation bottle in an anaerobic environment, sealing the fermentation bottle, adding carbide slag every 24 hours to adjust the pH of the fermentation bottle to a required alkaline condition, and performing alkaline fermentation;

obtaining the supernatant containing VFAs in the step (3): and (3) mixing the fermentation liquor obtained in the step (2) by adopting a high-speed centrifuge, and centrifuging by using the centrifuge to obtain supernatant fluid, namely the sludge fermentation liquor containing VFAs.

2. The method for promoting anaerobic fermentation of municipal excess sludge to produce volatile fatty acids according to claim 1, wherein: the residual sludge is taken from secondary sedimentation tank sludge of a water treatment plant, is taken back to be stood for 24 hours at the temperature of 4 ℃ in a refrigerator, and the sludge obtained after supernatant liquid is removed is a fermentation substrate.

3. The method for promoting anaerobic fermentation of municipal excess sludge to produce volatile fatty acids according to claim 1, wherein: the inoculated sludge in the step (1) is granular sludge containing microorganisms including proteus, bacteroides and sclerenchyma bacteria.

4. The method for promoting anaerobic fermentation of municipal excess sludge to produce volatile fatty acids according to claim 1, wherein: according to VSS, the mixing ratio of the municipal excess sludge to the inoculated sludge in the step (1) is 1:1, the corresponding pH values of the added carbide slag are 8, 9, 10, 11 and 12 respectively, and a fermentation bottle without the added carbide slag is used as a control group.

5. The method for promoting anaerobic fermentation of municipal excess sludge to produce volatile fatty acids according to claim 1, wherein: and (3) filling nitrogen into the fermentation bottle for 5-10min under the fermentation condition of the step (2), then placing the fermentation bottle in a gas bath constant temperature oscillator, controlling the temperature to be 35 +/-1 ℃, stirring at the speed of 120r/min, and fermenting for 10 days.

6. The method for promoting anaerobic fermentation of municipal excess sludge to produce volatile fatty acids according to claim 1, wherein: and (3) centrifuging at a centrifugal speed of 10000r/min and a centrifugal temperature of 4 ℃ under the centrifugal conditions, wherein the centrifuged supernatant is the municipal sludge fermentation liquor containing VFAs.

Technical Field

The invention relates to a method for promoting anaerobic fermentation of municipal excess sludge to produce volatile fatty acid, and belongs to the technical field of solid waste recycling.

Background

The municipal excess sludge is a main byproduct of a sewage treatment plant, wherein the management and disposal cost of the sludge accounts for more than 1/3 of the total capital construction cost and the operation cost of the sewage treatment plant, and the sludge amount generated by the sewage treatment plant is increasingly large along with the improvement of the human society and the living standard of people. The conventional sludge treatment technology mainly comprises incineration, landfill and the like. The sludge contains a large amount of organic substances (mainly including proteins, polysaccharides and the like). Due to the demand for sustainable development, the treatment of sludge is shifting to resource utilization, where the production of energy and high-value chemical products through anaerobic fermentation of sludge is receiving increasing attention. Compared with methane and ethanol produced by fermentation, the method for producing the volatile fatty acid by sludge fermentation has the advantages of short fermentation time, high added value of products, easy control, simple operation, low cost, high efficiency and wider application prospect.

Regarding the technology of producing volatile fatty acid by anaerobic fermentation, in the prior patent literature, CN101314783 invented by chenjiangjian et al at the university of south of the Yangtze river discloses a method for producing volatile fatty acid by anaerobic fermentation after thermal-alkaline pretreatment of organic waste with high solid concentration, the scheme takes municipal sludge as a model substrate and adopts thermal-alkaline pretreatment, then anaerobic acidification sludge after thermal stress treatment and acclimatization is inoculated as seed sludge for anaerobic fermentation, the solid mass concentration of the treated municipal sludge can be 3.7-12.0%, the highest yield of the volatile fatty acid can reach 0.23g of volatile fatty acid/g of organic matter, and the acid production is improved by 20.1-61.0% compared with the acid production by fermentation of sludge without pretreatment.

In addition, CN103194494B invented by king aijie et al of the university of harbin industry discloses a method for producing volatile fatty acid by co-fermentation of agaricus bisporus fungus chaff and excess sludge, so as to solve the problems of low acidification efficiency of the independent anaerobic fermentation of the excess sludge and disposal and utilization of the agaricus bisporus fungus chaff at present. The method comprises the following steps: firstly, preparing a sludge sample; secondly, preparing a mushroom bran sample; thirdly, adding a fungus bran sample; and fourthly, completing the method for producing the volatile fatty acid by co-fermenting the agaricus bisporus fungus chaff and the excess sludge. According to the method, the agaricus bisporus fungus chaff is used as an external carbon source to condition the excess sludge, and the yield of volatile acid in the excess sludge fermentation process is obviously improved by improving the carbon-nitrogen ratio of an excess sludge system.

CN110452936A, a method for improving the yield of volatile fatty acid by controlling anaerobic fermentation of kitchen waste water under negative pressure, is proposed by Huangjialong et al of the university of agriculture in Huazhong, and the method is used for extruding and filtering the kitchen waste of families or restaurants to obtain the kitchen waste water; collecting the collected matter, removing pollutants in the collected matter, and then fermenting for 6-8 days under the anaerobic environment condition; placing the pretreated sludge in a high-pressure steam sterilization pot for high-temperature sterilization, and cooling to 30 ℃; adding culture medium, and heating and culturing in water bath at 37 deg.C; placing anaerobic sludge and kitchen wastewater in a fermentation tank, using N2 to discharge air in the fermentation tank to create an anaerobic environment, using a negative pressure control device to reduce the atmospheric pressure in the fermentation tank to 0.02 +/-0.005 MPa, and placing the fermentation tank in a water bath for anaerobic fermentation; obtaining a supernatant; namely the volatile fatty acid. The method can increase the yield of volatile fatty acid by 20-50%, and increase the proportion of acetic acid, propionic acid and butyric acid in the volatile fatty acid by 4-10%.

However, the following aspects are not considered in the above prior arts: anaerobic fermentation of sludge is usually carried out in three stages, hydrolysis, acidification and methane production, the hydrolysis stage being the rate-limiting step of the whole fermentation process, volatile fatty acids being produced from the acidification stage. Most organic matters in the sludge are limited by the sludge flocculent structure and the cell wall shielding effect and are difficult to release, so the fermentation efficiency is reduced, and the yield of volatile fatty acid is reduced. In order to improve the hydrolysis of the sludge, different pretreatment methods are applied to the sludge treatment, which mainly comprise chemical pretreatment (alkali and acid), physical pretreatment (heating and high-pressure homogenization), biological pretreatment (enzyme and microorganism) and the like, wherein the alkali in the chemical treatment method has good effect, and can break the sludge structure to rapidly decompose non-soluble granular organic matters in the sludge into micromolecular soluble substances which are then utilized by the microorganism. In the traditional alkali treatment, high-cost sodium carbonate such as sodium hydroxide, calcium hydroxide and the like is mainly adopted, and the addition of the sodium carbonate increases the cost of sludge treatment during large-scale anaerobic sludge fermentation. Therefore, it is of great significance to find an alkaline substance to replace the traditional soda ash to treat the sludge to promote fermentation and produce volatile fatty acid.

The carbide slag is strong-alkaline industrial waste slag, the main component of which is calcium oxide, and the carbide slag is dissolved in water to form calcium hydroxide. The carbide slag pretreatment is a good choice for replacing the traditional alkali pretreatment, the alkali cost of the alkali pretreatment is reduced, the waste is treated by waste, and meanwhile, high-value chemical products are produced, which is the thinking and development direction of sludge treatment at present and in the future, and provides a certain theoretical basis for the research of a new technology for resource utilization of organic wastes.

Disclosure of Invention

The invention aims to provide a pretreatment method for sludge fermentation by using carbide slag pretreatment, which promotes the interpretation of sludge water to release organic matters, improves the yield of volatile fatty acid in sludge fermentation, and realizes the reduction and recycling of carbide slag and municipal excess sludge. The method can reduce the sludge fermentation cost, and the produced volatile fatty acid has wide application prospect and realizes the purpose of treating wastes with processes of wastes against one another.

The invention is realized by the following steps:

the invention provides a pretreatment technology for producing VFAs by fermenting municipal excess sludge under alkaline conditions by taking carbide slag as sludge, which comprises the following steps:

step (1) preparation of fermentation substrate: concentrating municipal excess sludge taken from a sewage plant, mixing inoculated sludge and the municipal excess sludge, filling the mixture into six fermentation bottles, and adding different amounts of carbide slag into the fermentation bottles respectively so as to adjust the alkaline condition of a fermentation system;

step (2), during the fermentation stage of the municipal excess sludge: filling nitrogen into the fermentation bottle to keep the fermentation bottle in an anaerobic environment, sealing the fermentation bottle, adding carbide slag every 24 hours to adjust the pH of the fermentation bottle to a required alkaline condition, and performing alkaline fermentation;

obtaining the supernatant containing VFAs in the step (3): and (3) mixing the fermentation liquor obtained in the step (2) by adopting a high-speed centrifuge, centrifuging at the centrifugation speed of 10000r/min and the centrifugation temperature of 4 ℃, and obtaining the centrifuged supernatant, namely the municipal sludge fermentation liquor containing VFAs.

VFAs in the municipal sludge fermentation liquor containing VFAs in all fermentation bottles in the step (3) mainly comprise acetic acid and propionic acid (the proportion of the VFAs in the total VFAs is more than 63%), and the concentration of the VFAs in the fermentation bottles added with the carbide slag can reach 330.54mg COD/gVSS, which is improved by 8.4 times compared with a control.

The invention has the advantages that:

the carbide slag adopted by the invention is a low-cost strong-alkaline waste, is dissolved in water to form an alkaline condition, when the carbide slag is added into a fermentation bottle for mixing municipal excess sludge and inoculated sludge, the sludge alkaline environment formed by the carbide slag can break a sludge floc structure and break sludge cells, so that organic matters are released into fermentation liquor, more fermentation substrates are provided for acid-producing microorganism fermentation acid production, the periodic addition of the carbide slag can prevent VFAs generated by fermentation from reducing the pH value of the fermentation bottle to inhibit the activity of acid-producing bacteria, and the alkaline condition can inhibit the activity of methane production and reduce the consumption of the VFAs. The method simultaneously utilizes two wastes (municipal excess sludge and carbide slag), adds the carbide slag into the municipal excess sludge fermentation system, promotes anaerobic fermentation of the sludge to produce VFAs, realizes reduction and recycling of the municipal excess sludge, simultaneously expands application of the carbide slag, and reduces cost for producing the VFAs by fermentation. More importantly, the produced VFAs are important platform substances, have wide application value, can be used as an external carbon source to supplement the deficiency of the carbon source in the process of nitrogen and phosphorus removal of sewage, can be further converted into energy substances such as methane, ethanol and the like, and can also be used for synthesizing long-chain fatty acids, paints, other chemical products and the like, thereby further realizing the resource utilization of the urban excess sludge. The invention provides a new way for realizing reduction and resource utilization of the municipal excess sludge, and also provides ideas for widening the application of the carbide slag.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Materials such as carbide slag and instruments for measuring VFAs in the following examples are commercially available. The carbide slag is purchased from Henan Hengyang Yongjie science and technology Limited liability company, and is sieved by a 325-mesh sieve, and the main component of the carbide slag is CaO (70.06%) measured by an X-ray fluorescence spectrometer (AXIOS, Netherlands). The inoculated sludge is granular sludge and is purchased from a certain granular sludge manufacturing plant in Shandong. The municipal excess sludge is taken from a secondary sedimentation tank of a Yongfeng sewage treatment plant in the Haizu area of Beijing, the following municipal excess sludge in each embodiment is taken from a water plant, then precipitated for 24 hours in a refrigerator at 4 ℃, and then the sludge after supernatant liquid is removed is taken as a fermentation substrate, and the sludge is characterized by comprising the following components: the pH value is 7.30 +/-0.04, the TSS is 17853.33 +/-249.87 mg/L, the VSS is 12183.337 +/-165.03 mg/L, the SCOD is 290.87 +/-17.38 mg/L, the soluble protein is 8.40 +/-0.77 mg/L, and the soluble polysaccharide is 4.86 +/-0.22 mg/L.