CN101376553A - Method for processing low temperature sewerage using low-intensity ultrasonic strengthened membrane bioreactor - Google Patents

Abstract

The invention discloses a method for treating low-temperature sewage by means of a low-intensity ultrasonic enhanced membrane bioreactor, which relates to a treatment method for low-temperature urban sewage. The invention effectively solves the problems of complex process, high treatment cost, large energy consumption and poor denitrification effect existing in the existing low-temperature sewage treatment method. The method of the present invention is as follows: the membrane module (4) is hoisted in the membrane pool (3), and the bottom of the membrane pool (3) is provided with an aeration device (6) to oxygenate and aerate the low-temperature sewage in the membrane pool (3), Low-intensity ultrasonic waves are used to irradiate the low-temperature sewage in the membrane pool (3); the ultrasonic transducers (5) on the low-intensity ultrasonic generating device are arranged on the frames (4-2) on both sides of the diaphragm group (4-1). ); the purified sewage is sucked out by negative pressure through the membrane module and discharged through the intelligent control water outlet system (7), and the concentrated sludge flows back into the anaerobic tank (1). The invention has the advantages of simple process, stable effect, low consumption and high efficiency and good denitrification effect.

Description

Method for treating low-temperature sewage by using low-intensity ultrasound to strengthen membrane bioreactor

technical field

The invention relates to a method for treating low-temperature urban sewage.

Background technique

In cold regions, the temperature of sewage in autumn and winter is low, and the growth and reproduction of activated sludge are affected by water temperature. Generally speaking, the main problems in the activated sludge treatment of low-temperature sewage are as follows: 1. The microbial activity is weakened, and the removal rate of organic matter in the system is reduced; 2. The sludge concentration is low, and the sludge return must be increased. flow rate, which will increase energy consumption and operating costs; 3. The settling performance of activated sludge is reduced, and sludge bulking is prone to occur, resulting in deterioration of effluent water quality; 4. The ability to remove nitrogen and phosphorus is low. Membrane bioreactors have certain advantages in treating low-temperature urban sewage. Due to the interception effect of the membrane, the sludge concentration in the reactor is high, the sludge age is long, the effect of low temperature on the sludge settling performance is small, and the removal effect of organic matter is stable. However, the membrane fouling in the membrane bioreactor is aggravated at low temperature, and the low microbial activity and poor denitrification effect are still problems. For example, the publication number is CN101125723, the publication date is February 20, 2008, and the invention patent application titled "a kind of low-temperature sewage treatment method" is described.

When the effluent of urban sewage treatment plants is introduced into rivers with small dilution capacity as urban landscape water and general reuse water, the A standard of the first-class standard is implemented, that is, COD<50mg/L, BOD ₅ <10mg/L, SS<10mg/L L, TN<15mg/L, NH ₄ -N<5mg/L (8mg/L when the water temperature is lower than 12°C), TP<0.5mg/L. The climate in Northeast my country is very cold in winter, and the average sewage temperature in winter is generally lower than 10°C, and the lowest can reach 5°C. The current A/O, CASS and other processes have poor treatment effects under low temperature conditions. In actual projects, methods such as increasing sludge return flow and prolonging hydraulic retention time are used to improve effluent water quality. These measures will undoubtedly greatly increase the project investment and operating costs of the sewage plant, which violates the environmental protection policy of "energy saving and emission reduction". Moreover, even if the above measures are taken, ammonia nitrogen and total nitrogen are still difficult to meet the standards, and it is imperative to develop a process with better denitrification effect.

At present, most of the methods used in my country to apply ultrasonic waves to sewage biological treatment are high-intensity ultrasonic waves for sludge reduction. The effect of enhanced sewage treatment is divided into two categories. One is for industrial wastewater, which uses ultrasonic pretreatment to decompose refractory high-molecular organic matter and enter the biological treatment device. The other type is used for urban sewage, using conventional activated sludge method or SBR process, with an external ultrasonic radiation device. The method is: take the sludge out of the reaction device with a pump, etc. for ultrasonic treatment, and return the sludge after radiation treatment to the sewage biological treatment facility; or connect the reaction tank equipped with an ultrasonic generator to the secondary sedimentation tank On the activated sludge return pipeline, the sludge structure is destroyed by high-intensity ultrasonic waves to release dissolved carbon sources, nitrogen, etc., or local hot spots produce dissolution and inactivation, so as to achieve the purpose of sludge crushing and reduction and strengthen sludge activity , consumes higher ultrasonic energy.

Contents of the invention

In order to solve the problems of complex process, high treatment cost, high energy consumption, difficulty in reaching standards for ammonia nitrogen and total nitrogen and poor denitrification effect in the existing low-temperature sewage treatment method, the present invention further provides a low-intensity ultrasonic enhanced A method for treating low-temperature sewage with a membrane bioreactor.

The technical scheme adopted by the present invention to solve the above-mentioned technical problems is: the method of the present invention is realized according to the following steps: Step 1, the low-temperature sewage flowing out through the ultra-fine grid flows into the anaerobic pool and the aerobic pool of the membrane bioreactor; Step 2. The low-temperature sewage treated in step 1 flows into the membrane tank of the membrane bioreactor, and the membrane module with a membrane pore size of 0.1-0.2 microns is hoisted in the membrane tank, and the packing density of the membrane is 1.5-2.0m ² Membrane area/m ³ The amount of water to be treated, the sludge concentration in the membrane pool is 8000-15000mg/L, and the bottom of the membrane pool is equipped with an aeration device to oxygenate and aerate the low-temperature sewage in the membrane pool. After 15-20 minutes, the action parameters of the low-intensity ultrasonic wave are frequency 20-28kHz, power density 0.13-0.27W/L; the ultrasonic transducers on the low-intensity ultrasonic generating device are arranged on the frames on both sides of the diaphragm group; Step 4: The purified sewage is sucked out by negative pressure through the membrane module and discharged through the intelligent control water outlet system, and the concentrated sludge flows back into the anaerobic tank.

The present invention has the following beneficial effects:

The invention has the advantages of simple process, stable effect, low consumption and high efficiency and good denitrification effect. The method of the invention combines the biological process and the physical process and can give full play to the respective advantages of the low-intensity ultrasonic wave and the membrane bioreactor. Among them, the integrated membrane bioreactor is used as the main body of low-temperature sewage treatment to remove organic pollutants, nitrogen and phosphorus. Since the membrane bioreactor can hold a high amount of sludge, there is no need to consider the influence of sludge settling performance on solid-liquid separation; the sludge age is long, suitable for the growth of nitrifying bacteria at low temperature, and realizes simultaneous nitrification and denitrification ; Small footprint, and shock load resistance.

The ultrasonic transducer installed in the membrane bioreactor has the following functions: the ultrasonic transducer emits low-intensity ultrasonic waves, and the cavitation effect generated by low-intensity ultrasonic waves can change the permeability of microbial cell membranes and enhance the synthesis and secretion of intracellular enzymes , Accelerate cell metabolism, improve microbial activity. Vibration is generated to promote three-phase mixing and biological mass transfer of water, mud and gas. In the ultrasonic field, filamentous bacteria are large in size, fragile in hyphae, and absorb a lot of energy. They will be cut first to eliminate sludge bulking, reduce sludge viscosity, and reduce membrane fouling at low temperatures. Fundamentally improve the efficiency of membrane bioreactor degradation of organic matter and denitrification at low temperature.

Description of drawings

Fig. 1 is a schematic diagram of the overall structure of the membrane bioreactor of the present invention, and Fig. 2 is a schematic diagram of the positional relationship between the ultrasonic transducer and the membrane module.

Detailed ways

Specific Embodiment 1: As shown in Figures 1-2, the method of using low-intensity ultrasonic enhanced membrane bioreactor described in this embodiment to treat low-temperature sewage is realized in accordance with the following steps: Step 1, the water flowing out through the ultrafine grid The low-temperature sewage flows into the anaerobic pool 1 and the aerobic pool 2 of the membrane bioreactor; step 2, the low-temperature sewage treated in step 1 flows into the membrane pool 3 of the membrane bioreactor, and the membrane pore size is 0.1~ 0.2 micron (submerged) membrane module 4, the packing density of the membrane is 1.5-2.0m2 membrane area/ ^m3 treatment water, the sludge concentration in the membrane tank is 8000-15000mg/L, and the bottom of the membrane tank 3 is equipped with an aeration device 6 Oxygenating and aerating the low-temperature sewage in the membrane pool 3, step 3, using low-intensity ultrasonic waves to irradiate the low-temperature sewage in the membrane pool 3 for 15-20 minutes, the parameters of the low-intensity ultrasonic waves are frequency 20-28kHz, The power density is 0.13-0.27W/L; the ultrasonic transducer 5 on the low-intensity ultrasonic generating device is set on the frame 4-2 on both sides of the diaphragm group 4-1; step 4, the purified sewage is negatively charged through the membrane module The sludge is pumped out under high pressure and discharged through the intelligent control water outlet system 7, and the concentrated sludge flows back into the anaerobic tank 1. The start-up time of the low-intensity ultrasonic generating device is: winter low temperature period (when the water temperature is lower than 12°C), spring and autumn climate mutation period and when the impact load against water quantity and quality changes exceeds 20%. The membrane bioreactor described in this embodiment includes an anaerobic tank 1, an aerobic tank 2, a membrane tank 3, a membrane module 4, a low-intensity ultrasonic generator, an aeration device 6, an intelligent control water outlet system 7, and the membrane module 4 consists of Diaphragm group 4-1 and frame 4-2 are composed, diaphragm group 4-1 is fixed in frame 4-2; oxygen pool 1, aerobic pool 2 and membrane pool 3 are arranged and connected in sequence, and anaerobic pool 1 An underwater push flow device is provided, an aeration device 6 is installed in the aerobic tank 2 and the membrane tank 3, the membrane module 4 is hoisted in the membrane tank 3, and the ultrasonic transducer 5 on the low-intensity ultrasonic generating device is set on the membrane On the frame 4-2 on both sides of the group 4-1, the intelligent control water outlet system 7 is set on the membrane pool 3.

Membrane module 4: the membrane tank 3 is a membrane bioreaction tank enhanced by low-intensity ultrasonic waves. Diaphragm group 4-1 is a polyvinylidene fluoride (PVDF) or polyethylene (PE) hollow fiber microfiltration membrane, the membrane pore size is 0.1-0.2 microns, and the packing density of the membrane is 1.5-2.0m ² Membrane area/m ³ Treated water volume .

Aeration device 6: Install a large-hole or medium-hole aeration device at the bottom of the membrane tank to generate turbulence to wash the surface of the hollow fiber, so that particles fall off the surface of the membrane and reduce the frequency of chemical cleaning of the membrane block. The concentration of dissolved oxygen is controlled between 0.5 and 1.5 mg/L to complete synchronous nitrification and denitrification and strengthen the denitrification effect.

Low-intensity ultrasonic generating device: The ultrasonic wave adopts low frequency and low power. The low-intensity ultrasonic action parameters are selected as follows: frequency 20-28kHz, power density 0.13-0.27W/L (L is the volume of the membrane pool 3), and irradiation time 15-20min. According to the different hydraulic retention time of sewage, the irradiation time interval is 8 or 12h. According to the composition of raw sewage, when the effect of denitrification is mainly considered, the power density should be a low value of 0.13-0.20W/L, and when the effect of organic matter removal is considered, a higher value of 0.20-0.27W/L should be taken. The host of the ultrasonic generator is external, and the ultrasonic transducer is placed on the side of the membrane module bracket parallel to the diaphragm in the pool, fixed on the cross bar, the ultrasonic chip is parallel to the diaphragm, and connected to the generator through wires. The power of a single transducer can be selected from 35W, 50W or 60W. The transducer adopts a trumpet-shaped composite vibrator structure, and the chip and the shell must be corrosion-resistant. Taking a membrane module with a water output of 10t/d (tons/day) as an example, it is necessary to install 4 transducers of 50W, two on each side; a membrane module of 30t/d requires 10 transducers of 60W. Five sides are evenly arranged. The distance between the transducer and the outer frame should not be less than 0.15 meters, as shown in Figure 2.

Embodiment 2: The volume ratio of the anaerobic pool 1, the aerobic pool 2, and the membrane pool 3 in this embodiment is 1:5:2. With this setting, the effect of simultaneous removal of organic matter, nitrogen and phosphorus is the best. Other steps are the same as in the first embodiment.

Specific embodiment three: as shown in Figures 1-2, in this embodiment, the irradiation time interval in step three is 8 or 12 hours. Other steps are the same as in the first embodiment.

Embodiment 4: The technological process of using the method of the present invention to treat urban sewage is: water inlet → pumping station → fine grid → grit chamber → 0.5mm ultra-fine grid (grid spacing is 0.5mm) → biological reaction tank → water outlet . The low-temperature sewage flowing out through the 0.5mm ultra-fine grid flows into the membrane bioreactor into the anaerobic tank 1 and mixes with the sludge flowing out of the membrane tank. The organic matter in the sewage in the anaerobic tank 1 is partially decomposed into VFA under anaerobic conditions (volatile fatty acids), ammonification of organic nitrogen, and anaerobic phosphorus release by phosphorus accumulating bacteria in the activated sludge. According to the phosphorus content of the raw water, a small part of the mixed solution in the anaerobic tank 1 is pumped out and sent to the chemical phosphorus removal system. The mixed solution then flows into the aerobic tank 2 to complete the degradation of organic matter and nitrification of ammonia nitrogen, and finally enters the membrane tank to complete simultaneous nitrification and denitrification to achieve the goal of biological denitrification. Through the intelligent control of the water outlet system, the purified sewage is sucked out by negative pressure through the membrane module, and the concentrated sludge is returned to the anaerobic tank.

Taking the domestic sewage as shown in Table 1 as the treatment object, at 7°C, under the action of the ultrasonic parameters, the COD biological removal rate increased by about 22%, and the TN (total nitrogen) biological removal rate increased by about 3 hours after the ultrasonic irradiation ended. is 23%, and the energy consumption of ultrasonic loading is also small at this time, which realizes the economy of the process.

With the help of ultrasonic waves, the continuous operation of the membrane bioreactor has achieved the standard treatment of low-temperature urban sewage when the HRT (hydraulic retention time) is 3.3 hours. After the ultrasonic wave is set, the COD biological removal rate can be increased by 10% to 15%, and the total removal rate can be increased by 7% to 13%. The TN biological removal rate can be increased by about 14% to 20%, and the total removal rate can be increased by 13% to 16%. Under the action of ultrasonic enhancement, the COD and NH ₃ -N effluent concentrations of the membrane bioreactor were reduced to 10-20 mg/L and 5.8-7.9 mg/L respectively.

Low-intensity ultrasonic irradiation has a certain effect on reducing low-temperature membrane fouling, and can extend the membrane cleaning cycle by 2 days, from 17 days to 19 days.

Table 1 Statistical Table of Domestic Sewage Water Quality

Claims (3)

1. A method for treating low-temperature sewage by using low-intensity ultrasonic waves to strengthen a membrane bioreactor, characterized in that: the method is realized according to the following steps: Step 1, the low-temperature sewage flowing out through the ultrafine grid flows into the membrane bioreactor The anaerobic pool (1) and the aerobic pool (2); step 2, the low-temperature sewage treated in step 1 flows into the membrane pool (3) of the membrane bioreactor, and the membrane aperture in the membrane pool (3) is 0.1 ～0.2 micron membrane module (4), the packing density of the membrane is 1.5～2.0m ² membrane area/m ³ treatment water, the sludge concentration in the membrane tank is 8000-15000mg/L, and the bottom of the membrane tank (3) is equipped with aeration The device (6) oxygenates and aerates the low-temperature sewage in the membrane pool (3), step 3, uses low-intensity ultrasonic waves to irradiate the low-temperature sewage in the membrane pool (3) for 15 to 20 minutes, and the low-intensity ultrasonic The function parameters are frequency 20-28kHz, power density 0.13-0.27W/L; the ultrasonic transducer (5) on the low-intensity ultrasonic generating device is arranged on the frame (4-2) on both sides of the diaphragm group (4-1) Above; step 4, the purified sewage is sucked out by negative pressure through the membrane module and discharged through the intelligent control water outlet system (7), and the concentrated sludge is returned to the anaerobic tank (1). 2. The method of using low-intensity ultrasonic-strengthened membrane bioreactor to treat low-temperature sewage according to claim 1, characterized in that: the anaerobic pool (1), the aerobic pool (2), and the membrane pool (3) The volume ratio is 1:5:2. 3. The method for treating low-temperature sewage by means of low-intensity ultrasonic-enhanced membrane bioreactor according to claim 1, characterized in that: in step 3, the irradiation time interval is 8 or 12 hours.

Images