TW201838936A - Method of converting sewage sludge to improved soil material converting the sewage sludge containing heavy metals which reduces contamination - Google Patents

Abstract

Disclosed is a method of converting sewage sludge to improved soil material, which includes sequential steps: preparation, mixing, high temperature fermentation, turning and decomposition, and finish. The disclosed method is to remove impurities from the sewage sludge, remove heavy metals by means of using an electric power reaction tank, then mix the sewage sludge up with an organic additive in order to form a first mixture. The first mixture is fermented at high temperature and turns into a second mixture; then the second mixture is turned and decomposed, and finally converts into an improved soil material. Accordingly, the disclosed has advantages of being able to completely convert the sewage sludge containing heavy metals which reduces contamination, and being environmental-friendly to mix plural wastes for reuse and recycle purpose.

Description

Method for converting sewage sludge into soil improvement material

The invention relates to a method for converting sewage sludge into soil improvement materials, in particular to a method for fully converting heavy sewage containing sewage sludge to reduce pollution, and mixing with several kinds of wastes to recycle and reuse recycled sewage sludge to convert soil Methods of improving materials.

In general, sewage sludge is regarded as a common source of pollution in sewage treatment plants. In addition to producing bad odors, it also contains heavy metals and pathogenic microorganisms. In addition, sewage sludge contains a large amount of plant growth. Organic substances and rich nutrients (such as nitrogen, phosphorus, potassium, etc.). In addition, without affecting the quality of the project, the treated sewage sludge can also be used as a substitute for raw materials, such as cement admixtures, asphalt mixtures, and construction materials such as permeable tiles. Sewer sludge is the sediment in the sewer system, which of course contains many effluents that have been treated by the septic tank. Since the sewage sludge contains high nutrients (for crops) and organic matter, it can be used as an agricultural soil improver, building material, etc., and has considerable economic benefits. However, the sewage sludge produced in sewage treatment sites contains heavy metals and other toxic substances in addition to the above-mentioned components of economic value. If these hazardous substances in sewage sludge cannot be removed, not only can they not be used for agricultural composting, but also need to be treated in the form of hazardous waste, and the cost of subsequent treatment will also increase significantly. If it is accidentally discharged into the environment, it will lead to soil or groundwater pollution, the impact level is extremely wide, and the consequences are unimaginable. Heavy metals are commonly used in industry today, and once they cause pollution, they may not improve over time. Unlike organic matter, heavy metals are destroyed by microorganisms and destroyed, so that the original toxic effects disappear completely. Heavy metal pollution environment can be removed by physical, chemical and biological methods, and the considerations for the selection of treatment methods are: treatment cost, pollutant characteristics, technical feasibility and sewage sludge characteristics. The degree of processing also varies depending on the subsequent use requirements. In recent years, there have been many studies to explore the application of technology to remove sewage sludge containing heavy metals, and it has also proved its feasibility. Electric power technology is used to treat environmental pollution, mainly to repair contaminated soil, sewage, solid waste, etc. It can also be applied to saturated, unsaturated, and contaminated soil, sewage, and groundwater, and for low permeability The samples to be processed have a good remediation effect (eg Guedes et al., 2014). This technique is to insert positive and negative electrodes at both ends of the contaminated area and apply direct current. Under the action of the applied electric field, the more positively charged heavy yang will move toward the cathode, and the yin in the sewage sludge will move toward the anode. The electric field between the positive and negative electrodes generates the electroosmotic flow and ion migration mechanism of the electrochemical principle to guide the flow of the electrolyte solution in the sewage sludge to remove or concentrate the pollutants to a limited range to facilitate subsequent treatment and achieve the removal The purpose of the pollutant (eg Choi and Luib, 1995). In addition, the principle and reaction mechanism of electrodynamic technology, because the surface of the sewage sludge is negatively charged and is a porous medium, when an electric field is added, the relative movement between the electrolyte fluid and the sewage sludge is generated. All belong to the scope of electrodynamics, and various electrochemical reactions will occur during the treatment of sewage sludge by the electrodynamic method. The principles and reaction mechanisms of the electrodynamic technology include: electric double layer, electrolysis, electroosmotic flow, and ion migration. This electric power technology and reaction mechanism are conventional technologies and will not be repeated here. In addition, many existing poultry manure materials (such as chicken manure, duck manure, goose manure), waste space bags after shiitake mushroom cultivation, waste wood chips, etc. are difficult to dispose of, and it is also wasteful if directly discarded. Therefore, it is necessary to develop new technologies to solve the aforementioned disposal problems of sewage sludge and organic waste.

The purpose of the present invention is to provide a method for converting sewage sludge into soil improvement materials, which has the advantages of sufficiently converting sewage sludge containing heavy metals to reduce pollution, and is quite environmentally friendly with the recycling of several kinds of waste. In particular, the problem to be solved by the present invention is that the traditional sewage sludge and organic waste cannot be effectively reused. The technical means to solve the above problem is to provide a method for converting sewage sludge into soil improvement materials, which includes the following steps: 1. Preparation steps; 2. Mixing step; three. High temperature fermentation steps; 4. Steps of turning the pile into rot; and V. Complete the steps. The above objects and advantages of the present invention are not difficult to gain an in-depth understanding from the following detailed description and drawings of selected embodiments. The following examples and drawings are used to explain the present invention in detail:

Referring to Figures 1 and 2, the present invention is a method for converting water sludge into soil improvement materials, which includes the following steps after the start: 1. Preparation Step S1: Take out the sewage sludge from the sewage treatment plant 91 of the sewage system, which is defined as a first sewage sludge 81, and after removing impurities from the first sewage sludge 81, it becomes a second sewage Sludge 82; The heavy metals in the second sewage sludge 82 are then removed to form a third sewage sludge 83. two. Mixing step S2: The third sewage sludge 83 after removing heavy metals is mixed with an organic additive 71 to form a first mixture 61. three. High-temperature fermentation step S3: Put the first mixture 61 into a high-temperature fermentation device 92 to form a second mixture 62 after high-temperature fermentation. The fermentation temperature of the high-temperature fermentation device 92 is between 100 and 160 degrees Celsius. And the fermentation time is between 1 and 24 hours. four. Step S4: The second mixture 63 is subjected to a process of turning and maturing for at least 3 days. Fives. Step S5 is completed: finally converted into a soil improvement material 63. In practice, the preparation step S1 can be further subdivided into: [a] Pre-treatment of sewage sludge Step S11: At room temperature, flatten the first sewage sludge 81 for at least 24 hours and remove impurities After grinding and crushing, it passes through the screen to become the second sewage sludge 82. [b] Step S12 of removing heavy metals: refer to FIG. 3, and set up an electrodynamic reaction tank 93 (for example, as described in the "System and Method of Electrodynamic Power Remediation of Heavy Metal Contaminated Soil by the Republic of China Invention Patent No. I249441"). The sewage sludge 82 is placed therein; a pair of electrode plates 93A are provided in the electrodynamic reaction tank 93, and an electrolyte 93B (as shown in FIG. 4) is supplied, then the second sewage sludge 82 and the Electrolyte 93B is mixed. In addition, at both ends of the distributed heavy metal region A (see FIG. 4, the irregular clusters are only for illustration), a DC positive terminal 931 and a DC negative terminal 932 are respectively connected, with a predetermined interval between 0 and 100V Voltage (or predetermined current from 0 to 200mA). When carrying out electrokinetic reactions, many positively charged heavy positive ions will move towards the DC negative terminal 932, while the negative ions in the sludge will move toward the positive DC terminal 931, and the electrochemistry is generated by the electric field between the positive and negative electrodes The principle of electroosmotic flow and ion migration and other action mechanisms guide the flow of the electrolyte solution in the second sewage sludge 82, and finally the concentrated heavy metal B can be obtained at the DC negative electrode end 932 (as shown in Figure 4 The state is only for indication, and may include other pollutants), and the purpose of removing pollutants (removing heavy metals contained in the second sewage sludge 82) is achieved. The heavy metal system includes at least one of cadmium, nickel, copper, lead, chromium, and zinc. The organic additive 71 is at least one item selected from the group consisting of waste space bags after planting shiitake mushrooms, waste poultry dung, and waste wood chips. This technology uses water sludge under heavy metals as the main target pollutant in the remediation test. It uses electric power technology to remove heavy metals from sewage sludge, and discusses the impact of different operating conditions to achieve the removal of heavy metals in sludge. The results, and the use of sewage sludge after removing heavy metals to retain its high nutrients and organic matter, combined with high-temperature fermentation technology, convert it into soil improvement materials. Here are some examples: The samples used in this experiment were collected from the sludge produced by a water resource recovery center (that is, the first sewage sludge 81). The collected sludge sample is pre-treated, and the sample is flattened and air-dried at room temperature for at least 24 hours. After removing impurities such as paper dust, gravel, weeds and hair from the sludge, it is crushed with ceramic grinding equipment and Pass the standard screen of ASTM No. 10 (2 mm) for subsequent tests. The basic properties of sludge are analyzed according to standard methods. The analysis items include: sludge pH, sludge conductivity, water content, organic matter content, and full-scale analysis of heavy metals. The basis and results of various basic analysis methods of sludge are listed in Table 1 below. The pH value of the sludge sample in this study was 6.11, the moisture content was 78%, the sludge organic content was 47%, the heavy metal cadmium concentration was 5.60 mg/kg, the chromium concentration was 317 mg/kg, the nickel concentration was 830 mg/kg, and the copper concentration It is 533mg/kg, the lead concentration is 147mg/kg, and the zinc concentration is 2501mg/kg. (Table I) The relevant instruments and equipment used in the test are shown in Table 2 below: (Table 2) Among them, the pH meter and the conductivity meter are used to measure the pH value and conductivity of the sludge sample and the electrolyte, respectively. The flame atomic absorption spectrometer is used for the analysis and measurement of heavy metal concentration; the multi-stage variable-speed oscillator is used for sludge oscillation extraction. After the centrifuge oscillates and extracts the sludge, the solid and liquid of the sludge are separated by centrifugation for subsequent analysis and use. The pumping pump is used for the extraction of heavy metals in the sludge, and the sludge particles are completely filtered out, so that the subsequent samples can be analyzed on the machine. The DC power supply provides the DC power required for the operation of the electrodynamic treatment system for this test; the electronic balance provides the weighing of the test drugs and sludge samples; the deionized water manufacturing machine serves as the preparation of test drugs, sample analysis and experimental instruments Equipment cleaning and use. The electromagnetic stirrer is mainly used to prepare the electrolyte in the system, so that the test drugs and reagent water are evenly mixed; the ultrasonic cleaner is used to wash experimental glassware and laboratory instruments that are not easy to clean; the oven is used for the analysis of moisture content in sludge samples . The test drugs used in this institute are shown in Table 3 below: (Table 3) Sodium carbonate is formulated to a concentration of 0.01 M and used as an electrolyte in the electric power system. The manufacturer is Sigma-Alorich with a purity of 99.8%. The manufacturers of nitric acid and hydrochloric acid are all produced by Merck with purity of 65% and 37, respectively. %, mainly used for the preparation of aqua regia of heavy metal detection method-aqua regia digestion method (NIEA S321.63B, 2003). Regarding the test of the removal of heavy metals in sewage sludge by electrodynamic technology, the electrodynamic treatment system in this study was tested under the conditions of 0.01 M sodium carbonate electrolyte, with graphite electrode plates (Graphite) and iridium dioxide plate (Dimensionally Stable Anode, referred to as DSA), Stainless Steel plate (Stainless Steel) as electrodes, with different voltage gradient operating factors: 1.0V/cm, 1.5V/cm and 2V/cm, 2.5V/cm. Regarding electromotive technology equipment and materials, the electromotive treatment system (as shown in Figure 3) designed in this experiment is equipped with an electromotive treatment system tank (ie, the electromotive reaction tank 93) made of polyvinyl chloride (PVC). The specifications are 26cm in length × 11cm in width × 11cm in height (inner diameter), and the sample storage tank is separated by a PVC separator in the tank body. The treatment system is supplied with DC power by a DC power supply, and a gauze-covered porous PVC plate is used as an interval between the polar plate and the sludge sample. After filling in the sludge sample to be processed and the operating electrolyte, the final voltage is passed Direct current. Regarding the test process of electrodynamic technology (as shown in Figure 2), the pretreatment of sludge and the analysis of basic physical and chemical characteristics, including the full analysis of the pH value, water content, organic matter content and heavy metal concentration of the sludge, will be carried out. The mud sample is placed in the sample storage tank of the mold field (about 450 g of sludge), and 0.01 M sodium carbonate electrolyte is injected around the electrolyte storage tank, with different operation electrode plates (graphite electrode plate, iridium dioxide electrode plate and (Stainless steel plates) The purpose of the test is to find the ideal plate type as the operating parameter of the system. After selecting the electrode plate with better operation effect, the experiment is conducted with the operation parameters of different voltage gradients. During the test, the system voltage and current changes are recorded daily and the pH value and conductivity of the electrolyte are measured. An appropriate amount of electrolyte is also injected daily. In addition, the sludge samples are taken once a day (about 3 g), and the collection points are respectively near the anode end (that is, the DC positive pole end 931), the center of the storage tank, and near the cathode end (that is, the DC negative pole end 932). After the sludge sample is dried, the heavy metal content of the sludge can be analyzed. Through the process of finding out the appropriate parameters of the electrodynamic technology processing system, the transmission mechanism of the electrochemical reaction occurring in the system is discussed in more depth. Remove heavy metal from the sludge and use it as a raw material for high temperature fermentation, then use it with the waste space bag (or waste poultry manure, waste wood chips) for planting Xiangru, heat it at 130 ^o C under high temperature fermentation, and add high temperature resistance The bacterium completes the transformation within 2 hours and develops non-toxic and harmless soil improvement materials. The key point is that this test is to explore the test of removing heavy metals in sewage sludge by using different types of electrode plates and applying different voltage gradients and other parameters. Based on the test results and related theories, appropriate operating conditions are sought to To achieve effective removal of heavy metals in sewage sludge. The best results are obtained as follows: [a] The concentration of heavy metals in the sludge treated by electrodynamic technology increases with the distance from the anode plate, and it can be seen that the electroosmotic flow of the electrochemical principle is generated by the electric field between the positive and negative electrodes And ion migration and other action mechanisms can effectively remove or concentrate heavy metal contaminants to a limited range. [b] In this study, when different electrode plates are used as the operating parameters of electrodynamic technology, the removal efficiency is better when using iridium dioxide electrode plates as electrode plates, among which the removal efficiency of heavy metals nickel, cadmium and chromium is the most significant, respectively 72.22% , 56.76% and 38.59%. [c] In this study, a five-day electrodynamic test was conducted under different voltage gradients. Cadmium, nickel, copper and lead had good removal rates at a voltage gradient of 2.0V/cm, which were 100%, 96.67%, and 17.89, respectively. % And 52.88%; the removal effect of chromium and zinc at 2.5V/cm is more significant, the removal rate is 80.07% and 44.09%. [d] In this test, 0.01 M sodium carbonate was used as the electrolysis operating fluid, iridium dioxide electrode plate was used as the anode plate, and stainless steel was used as the cathode plate. The test for removing heavy metals in sewage sludge by electrodynamic technology was performed. Cadmium and nickel were removed at a higher level The removal rate of cadmium can reach 100% under the voltage gradient of 2.0V/cm. [e] Use electrodynamic technology to treat heavy metals in sewage sludge, conduct a one-day test with different operating voltage gradients (2.0V/cm and 2.5V/cm), and the cost of electricity consumption if 100mg/kg heavy metals are removed About 0.93-99.6 yuan. [f] This product assists Wufeng Elementary School in greening the campus, and the results have been affirmed by the school. The advantages and effects of the present invention are as follows: [1] Full conversion to water sludge containing heavy metals can reduce pollution. The invention uses electric power technology to remove heavy metals from sewage sludge, and then converts them into soil improvement materials through steps such as mixing, high-temperature fermentation, and pile-over rot, to reduce pollution. Therefore, full conversion to water sludge containing heavy metals can reduce pollution. [2] Mixing several kinds of wastes for recycling is quite environmentally friendly. The invention removes the heavy metal from the sewage sludge and mixes it with waste (organic additives) of at least one of the discarded space bag, discarded poultry dung material and discarded sawdust after planting shiitake mushrooms. It can be recycled and reused after the steps of high temperature fermentation and pile rot. Therefore, it is quite environmentally friendly to mix and recycle several types of waste. The above is only a detailed description of the present invention through the preferred embodiment. Any simple modifications and changes made to this embodiment will not deviate from the spirit and scope of the present invention.

S1‧‧‧Preparation steps

S11‧‧‧Pretreatment steps of sewage sludge

S12‧‧‧Step of removing heavy metals

S2‧‧‧Mix step

S3‧‧‧High temperature fermentation step

S4‧‧‧ Steps of rot

S5‧‧‧Complete steps

61‧‧‧The first mixture

62‧‧‧Second mixture

63‧‧‧ Soil improvement materials

71‧‧‧ organic additives

81‧‧‧First sludge

82‧‧‧Second sewage sludge

83‧‧‧The third sewage sludge

91‧‧‧Sewage treatment plant

92‧‧‧High temperature fermentation device

93‧‧‧Electrodynamic reaction tank

93A‧‧‧electrode plate

93B‧‧‧Electrolyte

931‧‧‧DC positive pole

932‧‧‧DC negative terminal

A‧‧‧Heavy metal distribution area

B‧‧‧ more concentrated heavy metals

Figure 1 is a flow chart of the present invention. Figure 2 is a block diagram of the process of processing water sludge into soil improvement materials under the present invention. Figure 3 is a schematic diagram of an electrodynamic reaction tank. Figure 4 is a water sludge under Figure 3. Schematic diagram before and after heavy metal treatment

Claims (4)

A method for converting sewage sludge into soil improvement materials includes: 　一. Preparation steps: Take out the sewage sludge from the sewage treatment plant of the sewage system. This is defined as a first sewage sludge. After removing impurities from the first sewage sludge, it becomes a second sewage sludge; then Heavy metals in the second sewage sludge are removed to form a third sewage sludge; 　二. Mixing step: mixing the third sewage sludge after removing heavy metals with an organic additive to form a first mixture; 　三. High-temperature fermentation step: Put the first mixture into a high-temperature fermentation device to form a second mixture after high-temperature fermentation. The fermentation temperature of the high-temperature fermentation device is between 100 and 160 degrees Celsius, and the fermentation time is between Between 1 and 24 hours; 　四. Step of turning and composing: the procedure of turning and composing the second mixture for at least 3 days; 　Five. Completion steps: Finally converted into a soil improvement material. The method for converting sewage sludge into soil improvement materials as described in item 1 of the scope of patent application, wherein the preparation steps include: 　[a] Pretreatment step of sewage sludge: at room temperature, the first sewage sludge The mud is flat and air-dried for at least 24 hours, and after removing impurities, it is ground and crushed and then passed through a screen to become the second sewage sludge; 　[b] Step of removing heavy metals: setting up an electrodynamic reaction tank, the second sewage sludge Placed in it; a pair of electrode plates are arranged in the electrodynamic reaction tank, and an electrolyte is fed, then the second sewage sludge is mixed with the electrolyte. In addition, at both ends of the distributed heavy metal region, a DC positive terminal and a DC negative terminal are respectively connected, and there is a predetermined voltage between 0 and 100V; when electrodynamic reaction is performed, more than positively charged heavy 金 is positive Move toward the negative end of the DC, and the yin in the sludge moves toward the positive and negative end of the DC. The electro-osmotic flow and ion migration of the electrochemical principle are generated by the electric field between the positive and negative electrodes to guide the second launch. The electrolyte solution in the sludge flows, and finally concentrated heavy metals can be obtained at the end of the DC negative electrode to achieve the purpose of removing pollutants. The method for converting water sludge into soil improvement materials as described in item 2 of the patent application scope, wherein the heavy metal includes at least one of cadmium, nickel, copper, lead, chromium, and zinc. The method for converting water sludge into soil improvement materials as described in item 1 of the patent application scope, wherein the organic additive is at least one selected from the group consisting of waste space bags after planting shiitake mushrooms, waste poultry manure, and waste wood chips.