CN106007278A - Sludge treatment method - Google Patents

Abstract

The invention discloses a sludge treatment method, which belongs to the technical field of sludge treatment and resource utilization. The method of the present invention mixes the remaining sludge in the secondary sedimentation tank of the sewage plant with partially digested and dewatered sludge, adjusts it to a predetermined solid concentration, and then sends it to the reactor for high-temperature and micro-aerobic digestion, and discharges a certain volume of digested sludge at regular intervals , and the filtrate was collected after concentration and dehydration. After sludge digestion treatment, the removal rate of volatile solids is 26-35%; the filtrate obtained from digested sludge dehydration contains a high concentration of short-chain volatile fatty acids, which can be used as a low-carbon-nitrogen ratio domestic sewage, Dianchi Lake and other non-point source wastewater biochemical An external carbon source for the treatment system.

Description

A kind of sludge treatment method

technical field

The invention relates to a sludge treatment method, which belongs to the technical field of sludge treatment and resource utilization.

Background technique

my country's urban sewage treatment capacity and treatment efficiency have developed rapidly during the "Eleventh Five-Year Plan" and "Twelfth Five-Year Plan" periods, resulting in a rapid increase in sludge production. In 2009, China's urban sewage treatment capacity was 28 billion m ³ , and the output of wet sludge (calculated with a moisture content of 80%) was about 20.05 million tons. In 2015, my country's wet sludge production has reached nearly 40 million tons.

Compared with the rapid growth of sludge production, the construction of sludge treatment and disposal facilities in my country is relatively lagging behind. At present, only about 25% of the sludge in my country's sewage treatment plants has been properly treated, and the phenomenon of untreated sludge being piled up randomly occurs from time to time, which has a serious impact on the surrounding ecological environment. In April 2015, the State Council promulgated the "Water Pollution Prevention and Control Action Plan", which clearly stated that "the sludge generated by sewage treatment facilities should be treated and disposed of in a stable, harmless and resourceful manner, and the sludge in cities at the prefecture level and above should be treated in a harmless manner." The disposal rate should reach over 90% by the end of 2020."

Sludge treatment in developed countries emphasizes resource utilization, Europe and the United States mainly use land, and Japan mainly uses incinerated building materials. With the increasing calls for environmental protection and resource utilization, developed countries have clearly taken land use as an incentive direction for sludge treatment and disposal, and gradually restricted sludge disposal methods such as landfill and incineration. From the perspective of technology development, sanitary landfill after deep dehydration of sludge is only a short-term transitional technical route; sludge drying and incineration has the best reduction effect, but there are problems such as high treatment and disposal costs and difficult treatment of incineration flue gas. Insufficient; land use after sludge anaerobic digestion/aerobic fermentation will be the main way of sludge treatment and disposal due to its high resource utilization efficiency.

Sludge anaerobic digestion can recover energy material—biogas, but the anaerobic digestion process is complicated, the capital investment is high, and the operation management is complicated, so it is only suitable for the stabilization of sludge in large-scale sewage treatment plants. Sludge aerobic digestion treatment has the advantages of fast organic matter degradation rate and flexible operation control, but its energy consumption and operating costs are relatively high, so medium and small urban sewage treatment plants are mostly used. The existing invention patent CN200410066202.2 discloses a sludge high-temperature aerobic digestion device. During the digestion process, the temperature of the reactor can rise steadily to 45-65°C, and the sludge can be stabilized within 5-12 days. This method focuses on the reduction of volatile organic components in sludge. After the sludge is treated with aerobic digestion, the carbon-containing organic components are finally converted into small molecular products such as CO ₂ and H ₂ O. Invention patent CN200910309367.0 discloses a recycling treatment method for organic sludge. The concentrated sludge is digested in a reactor at 48-52°C. The sludge undergoes high-temperature facultative hydrolytic acidification and second reaction zone respectively. High-temperature micro-aerobic digestion in the reaction zone, and the discharged digested sludge is made into mud cake after subsequent dehydration treatment. Dewatered sludge is rich in nutrients such as nitrogen, phosphorus, and potassium, and can be used as a fertilizer or an additive to improve soil for safe agricultural use, thereby realizing the purpose of sludge recycling. Invention patent CN20140067635.3 discloses a high-temperature micro-aerobic-anaerobic digestion device and method for organic sludge. After the organic sludge is digested at high temperature and micro-aerobic, lye is added to adjust the pH value to nearly neutral, and then anaerobic fermentation is carried out. Complete the stabilization treatment of sludge. This method utilizes the limited supply of oxygen in the first-stage high-temperature digestion process of organic sludge to produce a certain amount of volatile fatty acid VFA, which is beneficial to the second-stage anaerobic digestion to produce methane; Due to the complex process and other deficiencies, it is difficult to be popularized and applied in the sludge stabilization treatment of small and medium-sized sewage treatment plants. In the existing sludge biological treatment technology, more emphasis is placed on the biodegradation of organic components in the sludge. After dehydration, the digested sludge can generally meet the agricultural requirements, but the carbon-containing intermediate products produced by the metabolism of the digestion process have not been effectively utilized; In addition, the concentration of ammonia nitrogen in the filtrate obtained from the dehydration process of digested sludge is usually high, which affects its subsequent treatment and utilization.

Contents of the invention

The invention provides a sludge reduction treatment and resource utilization technical method with economical operation cost and relatively simple operation process. High-temperature and micro-aerobic digestion technology is used to treat the remaining sludge in the sewage plant, and the heat released by the oxidation and decomposition of organic matter in the sludge is used to maintain the self-heating and high-temperature state of the reactor. Organic matter is metabolized into short-chain volatile fatty acids (SCFAs) and enters the sludge digestion solution. After the discharged digested sludge is dehydrated, the obtained filtrate has sufficient carbon source, which can be used as an additional carbon source for the low-carbon nitrogen wastewater treatment system; the obtained filter cake has high nutrient content such as nitrogen, phosphorus, and potassium, which meets the needs of land use or agricultural use. need. This technical method can not only effectively solve the problem of carbon source supplementation in the low-carbon nitrogen wastewater treatment system, but also organically combine the stabilization treatment and resource utilization of sewage plant sludge.

The main operating steps and technical contents of the method of the present invention are as follows:

(1) After concentrating the remaining sludge from the sewage plant, send it to the sludge digestion reactor 3, and use the microporous aeration device 9 for low-intensity aeration, and at the same time add the exogenous substance magnesium oxide, the amount of magnesium oxide is 0.5~0.8 kg /(m ³ sludge); The sludge is drawn from the bottom of the sludge digestion reactor 3 and sent back to the sludge digestion reactor 3 by spraying again from the top of the sludge digestion reactor 3 through the sludge return pump 10;

(2) Under the condition of continuous operation of the digestion unit, a sludge discharge operation is performed at regular intervals, and an equal volume of concentrated sludge is added to the digestion reactor. The amount of sludge discharge is based on the effective volume of the sludge and the average residence time of the sludge is 2 to 4 days Determine (the amount of sludge discharged is calculated as the effective volume of sludge ÷ sludge residence time); the discharged digested sludge is sent to the sludge thickening tank 4 for concentration treatment, and then sent to the sludge filter press device 5 for sludge dehydration treatment; The filtrate obtained in the dehydration process is the carbon source in the sludge containing volatile fatty acids; part of the obtained filter residue dewatered sludge is discarded and the other part is passed into the feed mixing tank 2 for mixing with the remaining sludge in the secondary sedimentation tank 8 of the biochemical treatment system And deployment, and then sent back to the sludge digestion reactor 3.

Preferably, the solid content of the feed sludge in the sludge digestion reactor 3 of the present invention is 3.5-6.5%; in order to ensure the micro-aerobic digestion environment of the reactor, the aeration intensity is controlled at 0.6-1.0 m ³ air/( h•m ³ sludge), the microporous aeration plate is evenly installed at the bottom of the reactor; the oxidation-reduction potential (ORP) of the digestion system is maintained at -350~-100mV.

Preferably, the sludge digestion temperature in the sludge digestion reactor 3 of the present invention is 45-60°C; in order to maintain the digestion state of self-heating and high temperature, it is determined according to the energy input density of 180-300 W/( ^m3 sludge) The power of the sludge return pump 10.

The filtrate obtained after the dehydration of the digested sludge in the present invention can be directly used as an additional carbon source of the low-carbon nitrogen wastewater treatment system, mixed with the water to be treated in the adjustment tank 6 of the sewage treatment system in proportion, and then sent to the wastewater biological denitrification reaction unit (7-1 anoxic pool, 7-2 aerobic pool); Compared with the case of no supplementary sludge carbon source, the biological denitrification effect of the effluent of secondary sedimentation tank 8 is increased by more than 54%.

The beneficial effects that the present invention has are as follows:

(1) Magnesium oxide, an exogenous substance, is added to the sludge digestion process to effectively reduce the ammonia nitrogen and phosphate released during the high-temperature micro-aerobic digestion process, and the filtrate after dehydration of the digested sludge can directly serve as additional carbon for the biochemical treatment system of low-carbon nitrogen wastewater source.

(2) After sludge high-temperature micro-aerobic digestion treatment, the dehydrated digested sludge meets the agricultural requirements, and the filtrate obtained from the dehydration process can be used as a carbon source. The removal rate of organic solid components in the sludge is not less than 26%, and at the same time, The reduction, stabilization and recycling of sludge have effectively solved the problem of additional carbon source supplementation in the treatment and disposal of sludge in sewage plants and the treatment of low-carbon nitrogen wastewater. The long-term and stable operation of sewage plants has obvious economic and environmental benefits.

Description of drawings:

Figure 1 Process flow of high-temperature micro-aerobic digestion to release carbon source in sludge to enhance biological denitrification of low-carbon nitrogen wastewater

In the figure: 1—sludge storage tank; 2—feed mixing tank; 3—sludge digestion reactor; 4—sludge concentration tank; 5—sludge filter press device; 6—sewage treatment system regulating tank; 7— Wastewater biological denitrification device (7-1 anoxic tank, 7-2 aerobic tank); 8—secondary sedimentation tank; 9—aeration device; 10—sludge return pump.

detailed description

Below in conjunction with attached accompanying drawing 1, the embodiment of the present invention is described in detail; This embodiment is implemented on the premise of the technical solution of the present invention, has provided detailed implementation and specific operation process, but protection scope of the present invention is not limited to the following Described embodiment.

In the following examples, the evaluation method of releasing the carbon source in the sludge to enhance the biological treatment effect of low-carbon nitrogen wastewater is as follows: the wastewater treatment system adopts the A/O process, and the main operating parameters are: dissolved oxygen DO in the anoxic pool 0.3-0.4 mg/L, Hydraulic retention time HRT 5 h; aerobic tank DO 2.2-3.0 mg/L, pH 7.2-7.6, MLSS 1800-2200 mg/L, HRT 15 h; secondary sedimentation tank supernatant to anoxic tank reflux ratio 200%, sewage The sludge return ratio is 120%, and the sludge age SRT is 40 days. The water quality indicators of low-carbon nitrogen wastewater are as follows: COD 230-250 mg/L, TN 37-40 mg/L, TP 1.8-2.1 mg/L. According to 1/30 of the water flow rate of the A/O system, add the filtrate obtained from the dehydration process of the digested sludge.

Example 1

A cylindrical sludge digestion reactor ³ with an effective volume of 2.0m3 is used. The circulating sludge is drawn from the bottom of the sludge digestion reactor 3, sent to the top of the tower by the sludge return pump 10, and then sprayed back to the digestion reactor. 3 spraying devices are evenly installed, and 3 300mm microporous aeration devices 9 are evenly installed at the bottom of the reactor. The outside of the sludge digestion reactor 3, the air intake pipeline and the sludge return pipeline are all covered with 6cm thick thermal insulation materials To maintain the self-heating high temperature state of the reactor.

(1) When the sludge digestion reactor 3 is started, the remaining sludge of the sewage plant is concentrated (the solid content of the initial feed sludge is 3.5%) and sent to the sludge digestion reactor 3, and the microporous aeration device 9 is used for Low-intensity aeration, while adding magnesium oxide as an exogenous substance, the amount of magnesium oxide is 0.5 kg/(m ³ sludge); the power of the sludge return pump 10 is determined according to the energy input density of 250 W/(m ³ sludge) 500 W, the return sludge is drawn from the bottom of the digestion reactor 3 and sent back to the digestion reactor through the sludge return pump 10 from the top of the sludge digestion reactor 3; the aeration intensity of the sludge digestion reactor 3 is 0.6 m ³ air/(h•m ³ sludge), that is, the total air flow of each branch pipeline is 1.2m ³ /h, and the tail gas generated is sent to the waste gas treatment device of the sewage treatment plant for unified treatment.

(2) After the first batch of sludge in the sludge digestion reactor 3 has been continuously operated for 3 days, it will be operated semi-continuously according to the requirement of sludge residence time of 2.5 days. Discharge 0.8 m ³ of digested sludge every 24 hours, and add an equal volume of fresh sludge (solid content 3.4-3.7%), and add 0.4kg of magnesium oxide at the same time; after 10 days of operation, the discharged digested sludge is sent to the sludge thickener pool 4 for concentration treatment, and then sent to the sludge filter press device 5 for sludge dehydration treatment; the filtrate obtained in the dehydration process contains volatile fatty acids, and the concentration of SCFAs reaches 8450-9380 mg/L; part of the obtained filter residue dewatered sludge is discarded The other part is passed into the feed mixing tank 2 for mixing and blending with the remaining sludge in the secondary settling tank 8 of the biochemical treatment system, and then sent back to the sludge digestion reactor 3 again. During operation, the temperature of the reactor reaches 45-50°C, the ORP value of the digestion system is -290--100mV, and the removal rate of volatile organic compounds in the sludge is 30-35%.

The effluent indicators of the wastewater A/O system with low carbon and nitrogen influent are as follows: COD 82-90 mg/L, ammonia nitrogen 7-10 mg/L, phosphate 0.3-0.4 mg/L; wastewater A/O without sludge digestion solution The concentration of ammonia nitrogen in the effluent of the O system was 18-22 mg/L; compared with the wastewater biochemical treatment system without supplementary carbon source, the biological denitrification effect of the wastewater treatment system after adding carbon source in the sludge increased by 54-61%.

Example 2

A cylindrical sludge digestion reactor ³ with an effective volume of 12m3 is used. The circulating sludge is drawn from the bottom of the sludge digestion reactor 3, sent to the top of the tower through the sludge return pump 10, and then sprayed back to the sludge digestion reactor 3. 7 sprinklers are evenly installed on the top of the tower, and 5 300 mm microporous aeration devices 9 are evenly installed at the bottom of the reactor. Thick insulation material to maintain the self-heating high temperature state of the reactor.

(1) When the sludge digestion reactor 3 is started, the remaining sludge from the sewage plant is concentrated (the solid content of the initial feed sludge is 6.5%) and sent to the sludge digestion reactor 3, and the microporous aeration device 9 is used for Low-intensity aeration, while adding exogenous substance magnesia, the amount of magnesia is 0.7 kg/(m ³ sludge); determine the power of the sludge return pump 10 according to the energy input density of 180 W/(m ³ sludge) 2.2kW, the return sludge is drawn from the bottom of the digestion reactor 3 and sent back to the digestion reactor by spraying from the top of the sludge digestion reactor 3 through the sludge return pump 10; the aeration intensity of the sludge digestion reactor 3 is 1.0 m ³ air/(h·m ³ sludge), that is, the total amount of aeration in the sludge digestion reactor 3 is 12 m ³ /h, and the tail gas generated is sent to the waste gas treatment device of the sewage treatment plant for unified treatment.

(2) After the first batch of sludge in the sludge digestion reactor 3 has been continuously operated for 3 days, the semi-continuous operation shall be carried out according to the requirement of the sludge residence time of ³ days, and 4.0m3 digested sludge shall be discharged every 24 hours, and an equal volume of fresh sludge shall be supplemented (solid content 6.4-6.7%), and add 2.8kg of magnesium oxide at the same time; after running for 10 days, the discharged digested sludge is sent to the sludge concentration tank 4 for concentration treatment, and then sent to the sludge filter press device 5 for sludge Dehydration treatment; the filtrate obtained during the dehydration process contains volatile fatty acids, and the concentration of SCFAs reaches 9130-11600 mg/L; part of the obtained filter residue dewatered sludge is discarded and the other part is fed to the remaining sludge in the secondary sedimentation tank 8 of the biochemical treatment system. Mixing and blending are carried out in the mixing tank (2), and then sent back to the sludge digestion reactor 3. During operation, the temperature of the reactor reaches 51-55°C, the ORP value of the digestion system is -340--130 mV, and the removal rate of volatile organic compounds in the sludge is 26-32%.

After adding the filtrate obtained from the dehydration process of digested sludge to supplement the carbon source, the effluent indicators of the low-carbon nitrogen wastewater treatment system are as follows: COD 83-92 mg/L, ammonia nitrogen 7-9 mg/L, phosphate 0.3-0.4 mg/L; The concentration of ammonia nitrogen in the wastewater A/O system of sludge digestion liquid is 19-23 mg/L; compared with the wastewater biochemical treatment system without supplementary carbon source, the biological denitrification effect of the wastewater treatment system after adding carbon source in the sludge is nearly 60%.

Example 3

A cylindrical sludge digestion reactor ³ with an effective volume of 2.0 m3 is used. The circulating sludge is drawn from the bottom of the sludge digestion reactor 3, sent to the top of the tower by the sludge return pump 10, and then sprayed back to the sludge digestion reactor 3 , 3 spraying devices are evenly installed on the top of the tower, and 3 300 mm microporous aeration devices are evenly installed at the bottom of the reactor 9; heating pipes and temperature controllers are installed around the sludge digestion device to control the sludge digestion reaction temperature at 60 °C.

(1) When the sludge digestion reactor 3 is started, the remaining sludge of the sewage plant is concentrated (the solid content of the initial feed sludge is 5.0%) and sent to the sludge digestion reactor 3, and the microporous aeration device 9 is used for Low-intensity aeration, while adding magnesium oxide as an exogenous substance, the amount of magnesium oxide is 0.8 kg/(m ³ sludge); the power of the sludge return pump 10 is determined according to the energy input density of 200 W/(m ³ sludge) 400W, the return sludge is drawn from the bottom of the digestion reactor 3 and sent back to the digestion reactor by spraying from the top of the sludge digestion reactor 3 through the sludge return pump 10; the aeration intensity of the sludge digestion reactor 3 is 0.8m ³ air/(h•m ³ sludge), that is, the total amount of aeration in the sludge digestion reactor 3 is 1.6m ³ /h, and the tail gas generated is sent to the waste gas treatment device of the sewage treatment plant for unified treatment.

(2) After the first batch of sludge in the sludge digestion reactor 3 has been continuously operated for 3 days, the semi-continuous operation shall be carried out according to the requirement of the sludge residence time of 4 days, and 0.5m ³ of digested sludge shall be discharged every 24 hours, and an equal volume of fresh sludge shall be supplemented. sludge (solid content 4.9-5.2%), and 0.4 kg of magnesium oxide is added at the same time; after 10 days of operation, the discharged digested sludge is sent to the sludge thickening tank 4 for concentration treatment, and then sent to the sludge filter press device 5 for Sludge dehydration treatment; the filtrate obtained during the dehydration process contains volatile fatty acids, and the concentration of SCFAs reaches 8570-9690mg/L; part of the obtained filter residue dewatered sludge is discarded and the other part is passed into the remaining sludge in the secondary sedimentation tank 8 of the biochemical treatment system The feed material is mixed and prepared in the mixing tank 2, and then sent back to the sludge digestion reactor 3 again. During operation, the sludge digestion reactor controls the digestion temperature to 60°C through the heating tube and the temperature controller, the ORP value of the digestion system is -320--120 mV, and the removal rate of sludge volatile organic compounds is 34-39%.

The effluent indicators of the wastewater A/O system with low carbon and nitrogen influent are as follows: COD 80-91 mg/L, ammonia nitrogen 8-10 mg/L, phosphate 0.3-0.4 mg/L. The concentration of ammonia nitrogen in the effluent of the wastewater A/O system without adding sludge digestion solution is 18-22 mg/L. Compared with the wastewater biochemical treatment system without supplementary carbon source, the biological denitrification effect of the wastewater treatment system after adding the carbon source in the sludge increased by nearly 55%.

Claims (5)

1. a processing method of sludge, is characterized in that, specifically comprises the following steps: (1) Concentrate the remaining sludge from the sewage plant and send it to the sludge digestion reactor, use a microporous aeration device for low-intensity aeration, and add exogenous substance magnesium oxide at the same time, the amount of magnesium oxide is 0.5~0.8 kg/( ^m3 sludge); the sludge is drawn from the bottom of the sludge digestion reactor and sent back to the sludge digestion reactor by spraying from the top of the sludge digestion reactor through the sludge return pump; (2) Under the condition of continuous operation of the digestion unit, a sludge discharge operation is performed at regular intervals, and an equal volume of concentrated sludge is added to the digestion reactor. The amount of sludge discharge is based on the effective volume of the sludge and the average residence time of the sludge is 2 to 4 days Determined; the discharged digested sludge is sent to the sludge thickening tank for concentration treatment, and then sent to the sludge filter press device for sludge dehydration treatment; the filtrate obtained during the dehydration process is the carbon source in the sludge containing volatile fatty acids; the obtained Part of the filter residue dewatered sludge is discarded and the other part is mixed with the remaining sludge in the secondary sedimentation tank of the biochemical treatment system into the feed mixing tank for mixing and deployment, and then sent back to the sludge digestion reactor. 2. The sludge treatment method according to claim 1, characterized in that: in the sludge digestion reactor, the solid content of the feed sludge is 3.5 to 6.5%, and the aeration intensity is 0.6 to 1.0 m ³ air/(h· m ³ sludge), the oxidation-reduction potential (ORP) of the digestion system was maintained at -350~-100mV. 3. The sludge treatment method according to claim 1, characterized in that: the sludge digestion temperature in the sludge digestion reactor is 45-60°C. 4. The sludge treatment method according to claim 1, characterized in that: the power of the sludge return pump is determined according to the energy input density of 180-300 W/(m ³ sludge). 5. The sludge treatment method according to claim 1, characterized in that: the filtrate obtained after dehydrating the digested sludge can be directly used as an additional carbon source for the low-carbon nitrogen wastewater treatment system.