KR20100111787A - Method for co-treating pretreated sludge and organic wastewater - Google Patents

Abstract

PURPOSE: A method for emerging pre-treated sludge into organic wastewater is provided to reduce the amount of the sludge and purify the organic wastewater by increasing the generating amount of methane. CONSTITUTION: A heating process is processed with respect to 10L of sludge at 120 degrees Celsius for one hour in order to perform a pre-treatment for the sludge. The heating process is selected from an ultrasonic process, a thermo-chemical process, and a thermal treatment process. 20 to 200 weight by parts of organic wastewater is added into 100 weight by parts of the pre-treated sludge. A common anaerobic digestion process is performed at 30 to 40 degrees Celsius.

Description

Method for Co-treating Pretreated Sludge and Organic Wastewater}

The present invention relates to a method for co-treatment of a combination of pretreated sludge and organic wastewater. More specifically, after pretreatment of sludge generated in a sewage treatment plant, the organic wastewater is combined and anaerobic digested to improve anaerobic digestion efficiency of sludge. The present invention relates to a method for co-treatment of organic wastewater combined with pretreated sludge to enhance.

Sludge generated during the treatment of sewage is composed of 40 ~ 90% of organic matter and organic matter, and its water content is 97 ~ 99%. In addition, when decay, severe odors and substances harmful to humans and organisms are generated, excessive treatment costs are generated when treating them.

In order to solve this problem, the number of sewage sludge treatment plants is increasing, and the amount of sewage sludge generated is increasing rapidly, but the sludge is recycled and reused up to now despite the huge investment in socioeconomic costs. And sludge is a serious social problem because there is no clear method or countermeasure against the reduction.

Recently, sludge reduction technologies by anaerobic digestion in connection with solubilization technology by pretreatment of sludge as well as recycling of sewage sludge have been steadily developed.

In addition to stabilizing and reducing sludge, anaerobic digestion has the advantage of producing methane gas as a byproduct. Methane is produced through hydrolysis, acid fermentation and methane fermentation of sludge. At this time, when the sludge is used, ammonia (NH ₃ ) and hydrogen sulfide (H ₂ S) are generated due to nitrogen and sulfur contained in the sludge. Ammonia and hydrogen sulfide are highly toxic substances, and their concentration increases the inhibition of acid fermentation and methane fermentation bacteria involved in the anaerobic reaction, thereby preventing smooth anaerobic digestion. Therefore, in order to reduce their inhibitory effect, the generated ammonia and hydrogen sulfide should be selectively removed or their inflow should be lowered. In this way, the method of anaerobic digestion by mixing the sludge removed from the high concentration organic wastewater with low nitrogen and sulfur content or the primary sedimentation tank with high organic content with surplus sludge or concentrated sludge is considered.

On the other hand, anaerobic treatment technology is widely used as a method of treating high concentration organic wastewater, and there is an advantage that methane gas can be obtained as a by-product. However, when the wastewater treatment, the wastewater and the active microorganism must be sufficiently in contact with each other, and there is a problem in that the start-up time of the reactor operation is long for adaptation to the high concentration wastewater.

Conventional technology related to sludge stabilization and weight reduction during sewage and wastewater treatment is a method to completely decompose organic matter in a short time while melting it with alkaline agent added by injecting high temperature steam steam into a pre-treatment pyrolysis tank. Chemical treatment method (Korea Patent No. 10-393284), “Sewage / Wastewater sludge extinguishing system” (Korea Patent No. 10-485639) and “ Continuous organic acid production apparatus and method from sewage sludge using thermal oxidation ”(Korean Patent No. 10-507990). In addition to this, "Soil treatment device and sludge reduction device" (Japanese Patent Laid-Open No. 2005-144231 and Japanese Patent Laid-Open No. 2006-346556) and "Sludge heat decomposing sludge by operating the hydrolysis reactors installed in parallel are alternately operated. Hydrolysis methods and apparatus ”(US Patent Publication No. 2005-6966985).

 However, in the case of anaerobic digestion tanks installed in existing sewage treatment plants, they can be applied only to high concentrations of wastewater and wastes with high solids concentration, and methane gas can be obtained as a byproduct. Due to the disadvantages such as poor utilization of the gas is not practically used for reduction and energy recovery, and does not contribute to the improvement of dehydration.

As described above, one of the reasons why the anaerobic digestion process of sewage sludge does not exhibit great efficiency is because the substrate is blocked by the thick cell walls of the microorganisms constituting the sludge, which does not facilitate biological hydrolysis. Anaerobic digestion is stabilized through the stages of hydrolysis, acid production and methane production. In the case of sewage sludge digestion, biological hydrolysis is the rate suggesting step. Due to the slow hydrolysis, long residence time of sludge and huge capacity digestion reactor Required. In addition, as mentioned above, as the concentration of ammonia and hydrogen sulfide increases, they play a role in inhibiting anaerobic digestion.

Therefore, the present inventors have diligently tried to solve the problems of the prior art, and as a result of anaerobic digestion by combining organic wastewater when anaerobic digestion after pretreatment of sludge, the rate of methane production is increased, and the sludge in the anaerobic digestion period and anaerobic digester It was confirmed that the residence time can be shortened, and that the amount of methane produced in the anaerobic digester can be increased to increase the anaerobic digestion efficiency, thereby completing the present invention.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for treating sludge generated in a sewage and wastewater treatment plant with a high concentration of organic wastewater.

The present invention to achieve the above object, (a) pretreatment of sludge; And (b) adding 20 to 200 parts by weight of organic wastewater to 100 parts by weight of the pretreated sludge, followed by co-anaerobic digestion at a temperature of 30 to 40 ° C. To provide.

According to the present invention, due to the combined anaerobic digestion of pretreated sludge and organic wastewater, the rate of methane production is increased during the anaerobic digestion process, which reduces the residence time of the sludge in the anaerobic digestion period and the anaerobic digester, and increases the amount of methane produced to efficiently Sludge reduction and organic wastewater purification can be carried out.

The present invention in one aspect, (a) pre-treating the sludge; And (b) adding 20 to 200 parts by weight of organic wastewater to 100 parts by weight of the pretreated sludge, followed by co-anaerobic digestion at a temperature of 30 to 40 ° C. (A) of FIG. 1.

The term 'joint anaerobic digestion' as used herein means the simultaneous anaerobic digestion of pretreated sludge and organic wastewater in an anaerobic digester.

As used herein, the term 'combined co-treatment' refers to the purification of the pretreated sludge and organic wastewater by anaerobic digestion at the same time.

In the present invention, sludge means sludge generated in sewage and wastewater treatment facilities.

Organic wastewater in the present invention means a high concentration of organic wastewater generated from livestock, manure, leachate, sewage and wastewater treatment plant and various industrial facilities, specifically, it is characterized by high concentration organic wastewater of 1,000 ~ 25,000mg BOD / L You can do

When anaerobic digestion of sludge and organic wastewater is carried out jointly, adding less than 20 parts by weight of organic wastewater to 100 parts by weight of sludge does not have an effect of increasing methane generation or shortening of anaerobic digestion, and exceeds 200 parts by weight of organic wastewater. There is no benefit from increasing the amount added. Further, preferably, the sludge and the organic wastewater can also anaerobicly digest the same amount (1: 1 ratio).

In addition, if the temperature during anaerobic digestion is less than 30 ℃, the anaerobic digestion efficiency is lowered, if it exceeds 40 ℃ there is a problem that the energy consumption increases.

In the present invention, the pretreatment may be selected from the group consisting of heat treatment, ultrasonic treatment and thermochemical treatment.

In the present invention, the pretreatment of the sludge is performed to compensate for the disadvantage that the anaerobic digestion effect of the sludge and the organic wastewater is poor due to the characteristics of the sludge which is slower than the organic wastewater. Sludge is composed mostly of solids, whereas most organics are dissolved in wastewater, including organic wastewater. Solubilization is known as the rate-limiting step of anaerobic digestion in order to convert these solids into methane by anaerobic digestion. The sludge anaerobic digestion rate is slow because it has to go through the process. Therefore, in the present invention, the sludge is physically and chemically pretreated to increase the solubilization rate, thereby rapidly producing methane and stabilizing sludge in the anaerobic digestion tank through joint anaerobic digestion with organic wastewater.

As a result, in the present invention, by increasing the solubilization rate of the sludge through the pretreatment of the sludge, it can be expected to reduce the anaerobic digestion time and the residence time in the anaerobic digestion tank.

In the present invention, the heat treatment may be carried out at a high temperature of 100 ~ 180 ℃.

The pretreatment of the sludge using heat causes the solids constituting the sludge to be hydrolyzed by the high temperature so that the anaerobic digestion can be rapidly changed. At this time, if the heat treatment temperature is less than 100 ℃ hydrolysis of the sludge does not occur sufficiently, if the temperature exceeds 180 ℃ caramelization (sludge) of the sludge occurs, or the energy consumption is high, the anaerobic digestion does not proceed properly There is this.

 In the present invention, the ultrasonic treatment may be performed using an ultrasonic wave of 300 ~ 1,000 kj / L.

The pretreatment of the sludge by the ultrasonic treatment is to irradiate the sludge with ultrasonic waves so that the solid particles constituting the sludge are mechanically broken and decomposed so that the anaerobic digestion can be rapidly changed.

At this time, if the ultrasonic wave is less than 300kj / L, the hydrolysis of the sludge does not occur sufficiently, if the ultrasonic wave exceeds 1,000 kj / L there is a problem that the energy cost for the ultrasonic treatment is excessively increased.

In addition, the ultrasonic treatment time may be characterized in that the 30 minutes to 2 hours 30 minutes, the ultrasonic treatment time is less than 30 minutes, the ultrasonic treatment efficiency is lowered, if the time exceeds 2 hours 30 minutes, the energy consumption cost of the ultrasonic treatment is excessive There is a problem.

In the present invention, the thermochemical treatment may be performed by adding an alkali agent of 1 ~ 5g / L while heating the sludge to a temperature of 40 ~ 160 ℃.

In pretreatment of sludge by thermochemical treatment, heat and alkaline agents cause the solids constituting the sludge to change into a form in which anaerobic digestion can proceed rapidly.

The alkaline agent may be selected from the group consisting of NaOH, CaO, Ca (OH) ₂ and mixtures thereof, but is not limited thereto.

At this time, if the temperature of the heat applied during the pretreatment by the thermochemical treatment is less than 40 ℃ hydrolysis of the sludge does not occur sufficiently, if the temperature exceeds 160 ℃ excessive hydrolysis proceeds there is a problem that does not proceed anaerobic digestion normally. If the concentration of the alkaline agent is less than 1g / L does not sufficiently hydrolyze the sludge, if the concentration exceeds 5g / L there is no benefit from the increase in the concentration of the alkaline agent.

In the present invention, in the step (a), 10 to 90% of the total sludge may be pretreated, and the rest may be characterized by anaerobic digestion without pretreatment.

In other words, in the present invention, sludge is not 100% pretreated, but only 10 to 90% of the sludge is pretreated and introduced into the anaerobic digestion stage, and the rest is introduced into the anaerobic digestion stage without pretreatment, thereby co-anaerobic digestion with organic wastewater ( (B) of FIG. 1). Pre-treatment costs can be reduced if only a portion of the sludge is pretreated and the sludge is introduced into the co-anaerobic digestion stage.

As a result, joint anaerobic digestion of sludge and organic wastewater with improved solubilization rate by pretreatment increases the rate of methane production, which can shorten the anaerobic digestion period and shorten residence time in the anaerobic digester. You can expect the effect. In addition, the amount of methane produced can also be increased to enhance the overall anaerobic digestion efficiency.

Hereinafter, the present invention will be described in more detail by way of examples. These examples are intended to illustrate the present invention in more detail, and it will be apparent to those skilled in the art that the scope of the present invention is not limited to these examples.

Example 1 Sludge Solubilization Rate According to Pretreatment Method

The sludge solubilization rate according to the pretreatment method was compared by different methods of pretreatment. The sludge used in the experiment was surplus sludge from the sewage treatment plant in Chuncheon. The COD was 20,690 mg / L. As the pretreatment tank used for the experiment, a reaction tank having a capacity of 10 L was used. The pretreatment method used in the experiments was heat treatment, sonication and thermochemical treatment using heat and alkali.

As a heat treatment method, 10 L of the excess sludge was introduced into a pretreatment tank, and heat at 120 ° C. was applied for 1 hour to pretreat the excess sludge.

As an ultrasonic treatment, 10L of the excess sludge was introduced into a pretreatment tank, and then irradiated with ultrasonic waves having a frequency of 28 kHz for 1 to 2 hours at a power of 87.5 W / L (ultraviolet irradiation of 400 to 800 kj / L) to produce excess sludge. Pretreatment.

As a thermochemical treatment using heat and an alkaline agent, 10 L of the excess sludge was introduced into a pretreatment tank, followed by applying heat at a temperature of 120 ° C. for 1 hour and injecting 1.6 g / L of NaOH as an alkaline agent to pretreat the excess sludge. .

The solubilization rate of excess sludge after pretreatment by each pretreatment method was investigated. The solubilization rate was calculated using the following solubilization rate formula (I) based on the dissolved COD in the sludge.

Solubilization rate (%) = (SCOD-SCODo) / (TCODo- SCODo) × 100 ------------ (I)

SCOD = dissolved COD after sonication (mg / L)

SCODo = dissolved COD before sonication (mg / L)

TCODo = total COD before sonication (mg / L)

As a result, as shown in Figure 2, the solubilization rate of the excess sludge according to the pretreatment method was 29% in the heat treatment, 41% in the ultrasonic treatment, and 64% in the thermochemical treatment using heat and alkaline agents.

As a result, it was found that the solubilization rate of the sludge was improved by the pretreatment. In particular, in the case of heat treatment, the solubilization effect by alkali injection was increased at the same time as the heat treatment.

Example 2 Measurement of Methane Generation and Sludge Reduction Efficiency by Joint Anaerobic Digestion of Sludge and Organic Wastewater

Anaerobic digestion of sludge and joint anaerobic digestion of sludge and organic wastewater were conducted to compare the methane production and sludge reduction efficiency according to the anaerobic digestion method. The sludge used in the experiment was excess sludge from Chuncheon sewage treatment plant. The COD was 20,690 mg / L, and the organic wastewater was discharged from the food manufacturing plant. The COD was 6,600 mg / L. The anaerobic bioreactor with a capacity of 10L was used as the anaerobic digester used for the experiment. A magnetic stirrer and a gas collector were mounted, so that gas including methane gas generated in the anaerobic digester was transferred to the gas collection tank. It was made to quantify and the temperature was kept at 35 ° C (Fig. 5).

10L of the excess sludge, 5L of the excess sludge, and 5L of the organic wastewater were added to two anaerobic digesters of the same type, and the single anaerobic digestion of the excess sludge and the joint anaerobic digestion experiment of the excess sludge and the organic wastewater were conducted.

After 21 days from the start of the anaerobic digestion experiment, the methane production and sludge reduction efficiency produced as a result of single anaerobic digestion and joint anaerobic digestion were measured. Methane emissions were measured and calculated using gas generation volume and gas chromatography, and the sludge reduction efficiency was calculated by measuring the total suspended solids of sludge before and after anaerobic digestion using a scale after drying the sludge in an oven. .

As a result, when anaerobic digestion of excess sludge alone as shown in Figure 3, while the amount of methane generated by anaerobic digestion is about 29.4g CH ₄ / kg VSS, when the excess sludge and organic wastewater jointly anaerobic digestion, The amount of methane produced by anaerobic digestion was about 35.0g CH ₄ / kg VSS, indicating that methane production was increased by 20% compared to the case of anaerobic digestion of excess sludge alone.

In addition, as shown in FIG. 4, when anaerobic digestion of excess sludge alone reduced 51% of sludge, 58% of sludge was reduced when anaerobic digestion of excess sludge and organic wastewater was performed. It was confirmed that the sludge reduction efficiency of about 14% compared to the case of anaerobic digestion alone.

As a result, co-anaerobic digestion of sludge and organic wastewater increased the methane generation and sludge reduction efficiency compared to the case of anaerobic digestion of sludge alone.

Example 3: Methane Formation Rate and Methane Production by Co-anaerobic Digestion of Pretreated Sludge and Organic Wastewater

Methane production rate and methane generation rate were measured by co-anaerobic digestion of pretreated sludge and organic wastewater. In particular, methane production rate and methane generation rate were compared according to the pretreatment ratio of organic wastewater and sludge co-anaerobic digestion.

The sludge used in the experiment was excess sludge from Chuncheon sewage treatment plant. The COD was 20,690 mg / L, and the organic wastewater was discharged from the food manufacturing plant. The COD was 6,600 mg / L. Pretreatment methods used in the experiments were heat treatment, sonication and heat and alkaline treatment. As the pretreatment tank used for the experiment, a reaction tank having a capacity of 10 L was used. As anaerobic digester, an anaerobic bioreactor with a capacity of 10L was used, and a magnetic stirrer and a gas collector were installed so that gas, including methane gas, generated in the anaerobic digester was transferred to the gas collection tank. The temperature was kept at 35 ° C.

Methane generation was measured and calculated using gas generation volume and gas chromatography, and sludge reduction efficiency was calculated by measuring the total suspended solids of sludge before and after anaerobic digestion using a scale after drying the sludge in an oven. It was.

3-1. Joint Anaerobic Digestion of Sludge and Organic Wastewater Pretreated by Heat Treatment

For pretreatment of the sludge, 10L of sludge was heat-treated for 1 hour at a temperature of 120 ° C. 5 L of the heat treated sludge and 5 L of organic wastewater were introduced into an anaerobic digester for co-anaerobic digestion. At this time, the ratio of the sludge pretreated by the heat treatment method of the sludge introduced into the anaerobic digester was 0%, 20%, 40%, 60%, 80% and 100% of the total sludge was carried out. That is, experiments were performed when the sludges pretreated in 5L of total sludge to be anaerobic digested were 0L, 1L, 2L, 3L, 4L, and 5L.

As a result of the anaerobic digestion of the heat treated sludge and the organic wastewater, as shown in FIG. 6A, the organic wastewater was stabilized by anaerobic digestion for the first 7 days after the start of anaerobic digestion, and the sludge was 21 days after the start of anaerobic digestion. Afterwards it stabilized. Stabilization of anaerobic organic wastewater was confirmed by changes in the amount of COD remaining and the amount of cumulative methane gas generated in the wastewater. As shown in Table 1, the amount of methane generated during the first 7 days corresponds to 2/3 or more of the total methane generated. In addition, the methane production rate during the initial 7 days of the anaerobic digestion period was also six times more than the methane production rate during the 14 days in the methane production rate. In addition, the higher the pretreatment ratio of the sludge by heat treatment was shown to improve the anaerobic digestion efficiency.

Methane Formation and Methane Formation Rate after Joint Anaerobic Digestion of Heat Treated Sludge and Organic Wastewater Pre-treated (heat-treated)
Sludge ratio Methane generation
g CH ₄ / kg VSS Methane production rate
g CH ₄ / Lday Initial 7 days 14 days after initial 7 days Initial 7 days 14 days after initial 7 days 0% 20 11 0.20 0.05 20% 44 12 0.46 0.06 40% 71 15 0.74 0.09 60% 88 18 0.92 0.10 80% 113 25 1.19 0.14 100% 122 39 1.27 0.22

The comparison of the co-anaerobic digestion of untreated sludge with organic wastewater shows that the pretreated sludge ratio in the table above is 0% and can be compared with other pretreatment ratio values. In conclusion, considering that methane generation rate and methane production rate are high in the early stage of anaerobic digestion, co-anaerobic digestion of pretreated sludge and organic wastewater by the heat treatment method can shorten the duration of anaerobic digestion, and the ratio of pretreated sludge will be high. It was confirmed that the higher the anaerobic digestion efficiency can be increased. On the other hand, when only organic wastewater was anaerobic digested, methane was only 1/3 of the pretreated sludge due to the low COD of organic wastewater.

3-2. Joint Anaerobic Digestion of Sludge and Organic Wastewater Pretreated by Ultrasonic Treatment

For the pretreatment of the sludge, 10L of sludge was introduced into the pretreatment tank, and then ultrasonic waves with a frequency of 28 kHz were irradiated for 1 to 2 hours (with 400 to 800 kj / L ultrasonic waves) at a power of 87.5 W / L. It was. 5 L of the sonicated sludge and 5 L of organic wastewater were introduced into an anaerobic digester for co-anaerobic digestion. At this time, the ratio of the sludge pretreated by the ultrasonic treatment method of the sludge introduced into the anaerobic digester was 0%, 20%, 40%, 60%, 80% and 100% of the total sludge was carried out. That is, experiments were performed when the sludges pretreated in 5L of total sludge to be anaerobic digested were 0L, 1L, 2L, 3L, 4L, and 5L.

As a result of the anaerobic digestion of the ultrasonically treated sludge and the organic wastewater, as shown in FIG. 6 (b), the organic wastewater was stabilized by anaerobic digestion for the first 7 days after the start of anaerobic digestion, and the sludge was 18 after the start of anaerobic digestion. After days stabilized. In addition, as shown in Table 2, the amount of methane generated during the initial seven days corresponded to two-thirds or more of the total methane generated. Stabilization of anaerobic organic wastewater was confirmed by changes in the amount of COD remaining and the amount of cumulative methane gas generated in the wastewater. Also, in the methane production rate, the methane production rate during the initial 7 days of the anaerobic digestion period was 6 times or more than the methane production rate during the 14 days after the initial 7 days. In addition, the anaerobic digestion efficiency was improved as the pretreatment ratio of the sludge by the ultrasonic treatment is increased.

Methane Formation and Methane Formation Rate after Joint Anaerobic Digestion of Ultrasonicated Sludge and Organic Wastewater Pretreated (ultrasound)
Sludge ratio Methane generation
g CH ₄ / kg VSS Methane production rate
g CH ₄ / Lday Initial 7 days 14 days after initial 7 days Initial 7 days 14 days after initial 7 days 0% 20 11 0.20 0.05 20% 44 14 0.24 0.07 40% 68 17 0.46 0.09 60% 88 18 0.72 0.11 80% 128 27 0.92 0.16 100% 133 40 1.34 0.22

In conclusion, considering that methane generation rate and methane production rate are high in the early stage of anaerobic digestion, the joint anaerobic digestion of pretreated sludge and organic wastewater by ultrasonic treatment can shorten the duration of anaerobic digestion, and the ratio of pretreated sludge will be high. It was confirmed that the higher the anaerobic digestion efficiency can be increased.

3-3. Joint Anaerobic Digestion of Pretreated Sludge and Organic Wastewater by Thermochemical Treatment Using Heat and Alkaline

For the pretreatment of sludge, 10L of sludge was introduced into the pretreatment tank, and then heat was applied at a temperature of 100 to 160 ° C. for 1 hour, and 1.6 g / L of NaOH was injected as an alkaline agent, followed by heat and alkali treatment. . The heat and alkaline treated sludge 5L and 5L of organic wastewater were introduced into the anaerobic digester to co-anaerobic digestion. At this time, the ratio of the sludge pretreated by heat and alkaline treatment method in the sludge introduced into the anaerobic digester was 0%, 20%, 40%, 60%, 80% and 100% of the total sludge was carried out. . That is, experiments were performed when the sludges pretreated in 5L of total sludge to be anaerobic digested were 0L, 1L, 2L, 3L, 4L, and 5L.

As a result of the anaerobic digestion of the heat and alkaline treated sludge and the organic wastewater, as shown in FIG. 6 (c) and Table 3, the rate of methane production for the first 7 days after the start of anaerobic digestion was Only 14 times the methane production rate for 14 days. The rate of methane production during the initial 7 days was only twice that of 14 days because the pH of the sludge was corrected by alkali treatment so that the microorganisms needed time for the microorganisms to adapt. It seems to be. In the methane production, methane production continued to increase in the latter part of anaerobic digestion, indicating that anaerobic digestion continued. In addition, the higher the pretreatment ratio of the sludge by heat and alkaline treatments, the higher the anaerobic digestion efficiency was.

Methane Generation and Methane Production Rate after Co-anaerobic Digestion of Sludge and Organic Wastewater Treated with Thermochemical Alkaline using Heat and Alkaline Pretreated (heat and alkaline)
Sludge ratio Methane generation
g CH ₄ / kg VSS Methane production rate
g CH ₄ / Lday Initial 7 days 14 days after initial 7 days Initial 7 days 14 days after initial 7 days 0% 20 11 0.20 0.05 20% 51 15 0.53 0.11 40% 85 16 0.88 0.12 60% 106 15 1.11 0.23 80% 108 71 1.14 0.43 100% 109 102 1.15 0.64

In conclusion, considering the large amount of methane produced and the rate of methane production in the early stage of anaerobic digestion, joint anaerobic digestion of sludge and organic wastewater pretreated by heat and alkaline treatment methods can shorten the anaerobic digestion period, and It was confirmed that the higher the ratio can increase the anaerobic digestion efficiency.

However, the methane production rate during the first 7 days after the start of anaerobic digestion was only twice that of the methane after 7 days, and the methane production was steadily increased in the latter part of the anaerobic digestion. Sludge pretreatment may contribute to the increase in final methane production, but it is considered to be somewhat inefficient in improving methane production rate compared to pretreatment such as heat treatment and sonication.

Example 4 Joint Anaerobic Digestion Efficiency of Pretreated Sludge and Organic Wastewater According to Pretreatment Method

By comparing the sludge pretreatment method, the anaerobic digestion efficiency of the pretreated sludge and organic wastewater was compared. Anaerobic digestion efficiency was compared by measuring methane generation and sludge reduction efficiency.

The sludge used in the experiment was excess sludge from Chuncheon sewage treatment plant. The COD was 20,690 mg / L, and the organic wastewater was discharged from the food manufacturing plant. The COD was 6,600 mg / L. The pretreatment tank used in the experiment was a 10L reactor, an anaerobic bioreactor with a capacity of 10L, and was equipped with a magnetic stirrer and a gas collector. Gases, including methane gas, were transferred to the gas collection tank for quantification and the temperature was maintained at 35 ° C. Pretreatment methods used in the experiments were heat treatment, sonication and heat and alkaline treatment.

As a heat treatment method, 10 L of the excess sludge was introduced into a pretreatment tank, and heat at 120 ° C. was applied for 1 hour to pretreat the excess sludge.

As an ultrasonic treatment, 10L of the excess sludge was introduced into a pretreatment tank, and then irradiated with ultrasonic waves having a frequency of 28 kHz for 1 to 2 hours at a power of 87.5 W / L (ultraviolet irradiation of 400 to 800 kj / L) to produce excess sludge. Pretreatment.

As heat and alkaline agent treatment, 10 L of the excess sludge was introduced into a pretreatment tank, and then heat was applied at a temperature of 120 ° C. for 1 hour, and 1.6 g / L of NaOH was injected as an alkali agent to pretreat the excess sludge.

Anaerobic digestion was performed in five cases: untreated sludge, organic wastewater, heat treated sludge and organic wastewater, ultrasonically treated sludge and organic wastewater, heat and alkaline treated sludge, and organic wastewater.

4-1. Methane Generation by Pretreatment Method

After performing anaerobic digestion for 21 days, methane generation in each of the five cases was calculated using gas generation volume and gas chromatography.

As a result, as shown in (a) of FIG. 7, methane generation amount was 34.54 g / kg VSS when the sludge was not pretreated but was anaerobic digested, and methane was 118 g / kg VSS when the wastewater was anaerobic digested. The anaerobic digestion of the bay stabilized within 7 days after the start of anaerobic digestion because it was easy to use microorganisms. In the case of co-anaerobic digestion of heat-treated sludge and organic wastewater, the amount of methane produced was 164 g / kg VSS, which was 4.7 times higher than that of sludge but anaerobic digestion, and 175 g / kg VSS when sonicated. It was 5.1 times higher, and heat and alkaline treatments were 231 g / kg VSS, which was 6.7 times higher. In other words, when co-anaerobic digestion of pretreated sludge and organic wastewater showed higher methane generation than anaerobic digestion of only untreated sludge alone, these results indicate that organic wastewater is easy to decompose.

4-2. Sludge Reduction Efficiency According to Pretreatment Method

After 21 days of anaerobic digestion, four cases of untreated sludge, heat treated sludge and organic wastewater, ultrasonically treated sludge and organic wastewater, heat and alkaline treated sludge, and organic wastewater were treated. The weight loss efficiency was measured. The sludge reduction effect was calculated by measuring the VSS of the sludge before the experiment and measuring the VSS after the experiment. For quantitative comparison, the reduction effect of sludge was calculated on the basis of 21 days when sludge was relatively stabilized.

As a result, as shown in (b) of FIG. 7, anaerobic digestion of only untreated sludge showed 55% of sludge reduction effect, and 61% of co-anaerobic digestion of heat treated sludge and organic wastewater. The sludge reduction effect was shown, and the co-anaerobic digestion of sonicated sludge and organic wastewater showed 62% sludge reduction effect. The sludge reduction effect was shown.

As a result, methane generation and sludge reduction efficiency increased when pretreatment of sludge with organic wastewater rather than anaerobic digestion of sludge alone showed an increase in anaerobic digestion efficiency. In addition, in the pretreatment method, when the sludge was treated by heat and alkaline treatment, it was confirmed that the anaerobic digestion efficiency of the pretreated sludge and organic wastewater was high.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereby. something to do. Thus, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

1 is a schematic diagram of a process for co-anaerobic digestion by combining pretreated sludge and organic wastewater (a: 100% pretreatment of sludge and then co-anaerobic digestion by combining with organic wastewater, b: pretreatment of a portion of sludge Co-anaerobic digestion by incorporation into organic wastewater without some pretreatment).

2 is a graph showing the solubilization efficiency of the sludge according to the pretreatment method.

3 is a graph showing the amount of methane generated by the sole anaerobic digestion of sludge and the co-anaerobic digestion of sludge and organic wastewater.

Figure 4 is a graph showing the sludge reduction efficiency by the sole anaerobic digestion of sludge and joint anaerobic digestion of sludge and organic wastewater.

Figure 5 shows a schematic diagram of the anaerobic digester used when co-anaerobic digestion of sludge and organic wastewater in the present invention.

6 is a graph showing methane production by co-anaerobic digestion of sludge and organic wastewater according to the pretreatment method (a: when the sludge was pretreated by the heat treatment method, b: when the sludge was pretreated by the ultrasonic treatment method, c: heat and Pretreated sludge with alkaline).

7 is a graph showing the anaerobic digestion efficiency according to the pretreatment method (a: comparison of methane production after anaerobic digestion according to the pretreatment method, b: comparison of sludge reduction efficiency according to the pretreatment method).

Claims (8)

Combined co-treatment of pretreated sludge with organic wastewater comprising the following steps: (a) pretreating the sludge; And (b) adding 20 to 200 parts by weight of organic wastewater to 100 parts by weight of the pretreated sludge, followed by co-anaerobic digestion at a temperature of 30 to 40 ° C. The method of claim 1, wherein the organic wastewater is a high concentration organic wastewater of 1,000 ~ 25,000mg BOD / L. The method of claim 1 wherein the pretreatment is selected from the group consisting of heat treatment, sonication and thermochemical treatment. The method of claim 3, wherein the heat treatment is characterized in that for heating the sludge at a high temperature of 100 ~ 180 ℃. The method of claim 3, wherein the ultrasonic treatment irradiates the sludge with an ultrasonic wave of 300 to 1,000 kj / L. The method of claim 3, wherein the thermochemical treatment adds 1-5 g / L of alkaline agent at a temperature of 40-160 ° C. 5. 7. The method of claim 6, wherein the alkali agent is selected from the group consisting of NaOH, CaO, Ca (OH) ₂ and mixtures thereof. The method of claim 1, wherein in step (a), 10 to 90% of the total sludge is pretreated, and the remainder is anaerobic digested without pretreatment.

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