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1. It can realize sufficient separation of reactor hydraulic retention time HRT and SRT;
2. Small footprint;
3. The system is well nitrated, and the refractory organic matter is further fully degraded;
4. The excess sludge production is extremely low, and theoretically zero sludge discharge can be achieved.
In today's increasingly tight water resources and increasingly serious water pollution, MBR water reuse has enormous social, environmental and economic benefits.
Bathing sewage is a high-quality water source for water reuse, with a large output. It accounts for 71% to 79% of the total water consumption in hotels and restaurants, and the content of organic matter is low. The MBR membrane can be used to realize the recycling of urban sewage treatment. It can be used for greening, rinsing and landscape water replenishment after MBR water reuse treatment.
The improved MBR membrane bioreactor was tested for bath wastewater treatment. The results show that the effluent quality of sewage is good, COD<40mg/L, LAS<0.2mg/L, in line with the water quality standard for domestic miscellaneous waters promulgated by the Ministry of Construction.
I. Traditional MBR Membrane Bioreactor and Improved MBR Membrane Bioreactor
The traditional MBR membrane bioreactor is divided into two types: split type and integrated type. On the basis of the improvement of the common MBR membrane bioreactor, the main components of the improved MBR membrane bioreactor are MBR membrane module and bioreactor.
The deflector is divided into two parts: the biodegradation zone and the membrane filtration water zone. Due to the action of the baffle, the concentration of activated sludge entering the membrane filtration water zone is very low, which greatly reduces the sludge concentration in the biodegradation zone. Membrane fouling can significantly extend the cleaning cycle of the membrane;
The biodegradation zone is a composite type, which combines the characteristics of fixed culture (biofilm) and suspension culture (activated sludge) bioreactor. Studies have shown that compared with pure activated sludge process MBR and biofilm MBR wastewater treatment, composite The performance of the MBR membrane bioreactor is better.
The microfiltration membrane has a pore size of 0.05 Î¼m and is directly suspended from the membrane filtration water zone. The original sewage is filtered through the hair filter, enters the high water tank, and then enters the biodegradation zone through the flowmeter. The organic matter is decomposed by the microorganisms here, and the mixed liquid enters the membrane filtration water zone through the deflector, and passes through the membrane under the suction of the vacuum pump. After filtering, it enters the trough, and the concentrated liquid can be returned to the biodegradation zone through the bottom connecting pipe to form a reflux, and the bottom is aerated by an aerator.
Compared with the traditional MBR, the improved MBR has the following characteristics in structure:
1. Compared with the integrated MBR, the MBR membrane module is relatively independent of the MBR membrane bioreactor, located in the membrane filtration water zone, while the integral MBR membrane module is directly suspended in the MBR membrane bioreactor, the same in that the water passes through Negative pressure suction is taken from the outer surface of the membrane unit into the hollow fiber, and the bottom is aerated to reduce membrane fouling;
2. Compared with the split MBR, there is no need for pump and pipeline connection between the MBR membrane module and the MBR membrane bioreactor, the same is that the MBR membrane module is relatively independent of the bioreactor, and the MBR membrane is less polluted.
The main advantages of the improved MBR membrane bioreactor are:
1. Compared with the integrated MBR membrane, the pollution is greatly reduced, and the split MBR has compact structure, small volume, small working pressure, no water circulation, and energy saving;
2. The processing objects are different. The membrane module of the integrated MBR and the split MBR processes the biodegradable complete mixture in the bioreactor, while the modified MBR membrane module processes the pre-cleared liquid through the baffle, and the SS concentration is reduced, which is beneficial to Reduce membrane fouling without increasing energy consumption. In addition to the biodegradation zone, a small amount of aeration is required for the membrane filtration water zone (the former provides an aerobic environment for microorganisms and the latter is to reduce membrane fouling), so the specific energy consumption of the equipment requires further experimental research.
Second, test water and test methods
The raw water quality of bathing water used in the test is: 6.5-7.0; CODCr: 93-350 mg/L; LAS: 1.0-10 mg/L; NH3-N: 0.6-1.0 mg/L; turbidity: 85-160 NTU; SS: 15 ~ 50mg / L; color gray.
The water quality of this test was 129.0 mg/L for CODCr, 6.4 mg/L for LAS, and 93 NTU for turbidity. After the entire environmental protection equipment system has been running for a certain period of time, the test is carried out, and the membrane module is rinsed with clean water after each test. The monitoring project adopts the standard analysis method of the National Environmental Protection Agency.
Third, test results and analysis
1. Relationship between operating pressure and MBR membrane flux
Membrane flux varies with operating pressure, operating pressures are: 0.01, 0.02, 0.03, 0.04, 0.05 MPa; corresponding MBR membrane flux: 0.72, 3.34, 4.85, 5.44, 6.58 mL / (m2 Â· s) . It can be seen that the MBR membrane flux increases with the increase of the operating pressure, that is, the increase of the operating pressure can effectively increase the membrane flux. Considering that the operating pressure is higher, the required power consumption is higher. In this test, 0.01 Mpa is used as the operating pressure.
2. The relationship between HRT and COD and LAS
Due to the efficient interception of activated sludge by the modified MBR membrane, the sludge concentration in the biodegradation zone is increased, and the COD removal effect is good. At the same time, the removal of COD and LAS is closely related to HRT.
The results showed that the removal rate of COD increased with the increase of HRT, which was 74.99% at 2h and 87.52% at 6h, but the COD of effluent was less than 40mg/L regardless of HRT for 2h, 4h or 6h. Since the HRT is 2h, the membrane filters out too much water, so that the filler is exposed to the water surface, so some of the original bathing wastewater is added, so that the COD removal rate at 4h is reduced to 71.86%, and the fluctuation is generated, but the effluent COD is 36.3mg/L. Still less than 40mg/L, which is the result of the combined action of suspended sludge and attached sludge. It is also a comprehensive manifestation of high sludge concentration and good treatment effect in the improved MBR biodegradation zone, that is, it has good impact load resistance and effluent quality. It is stable and reliable. In addition, the larger the HRT, the lower the LAS concentration in the effluent is less than 0.2mg/L at 2h, which meets the requirements of LAS for the quality of domestic miscellaneous water.
3. Membrane interception of COD
By simultaneously monitoring the water quality of the MBR effluent and the supernatant of the membrane filtration water, the contribution of the membrane to the COD removal rate of the system can be clearly observed. The monitoring results are shown in Table 1. The results showed that the COD of the supernatant was always higher than the COD of the membrane filtrate during the whole test, which fully proved that the membrane had the effect of intercepting soluble COD.
The removal rate of COD in the whole system is composed of the decomposition of organic matter by microorganisms in the biodegradation zone and the interception of COD by the membrane filtration water zone membrane, and the interception effect of membrane filtration water zone membrane makes up for the instability of the treatment performance of the biodegradation zone. To ensure excellent effluent quality, the membrane interception of dissolved macromolecular organic matter is jointly performed by the membrane itself and Fu Xueqi, and other improved membrane bioreactors to treat bathing water to test the gel layer formed on the surface.
The high-efficiency retention of the modified MBR allows almost all of the activated sludge to be trapped in the biodegradation zone, which not only maintains a high sludge concentration, but also greatly increases its volumetric load. The system's COD volumetric load is 1.16kg/(m3Â·d), which is 1.5 to 2.5 times higher than the traditional activated sludge process. It also has good dirt removal effect and strong impact load resistance.
5. Membrane pollution and cleaning
Although MBR has many advantages and has become a research hotspot in today's water treatment technology, the continuous reduction of flux caused by membrane fouling has always been a major obstacle to its promotion and application.
The reason why MBR designed by this test can reduce membrane fouling is:
(1) The biodegradation zone is a composite type, and the membrane fouling in the MBR is mainly caused by the adsorption of dissolved organic matter on the surface of the membrane and the deposition of suspended solid sludge. The higher the concentration of suspended sludge in the reactor, the larger the amount of sludge deposited on the membrane surface, and the sludge deposited on the membrane surface can block the adsorption of dissolved organic matter directly on the membrane surface through the membrane surface, so that the membrane surface adsorbs organic matter. The amount is reduced. Conversely, the lower the sludge concentration in the reactor, the smaller the amount of sludge deposited on the membrane surface, and the more the organic matter is adsorbed on the membrane surface. The volume of sludge in the composite reactor is middle, so the comprehensive effect is better, and the membrane permeability can be maintained at a high level;
(2) The deflector divides the device into two zones.
The function of the deflector makes the sludge concentration in the membrane filtration water zone lower, thus effectively reducing membrane fouling. The membrane cleaning was washed with tap water, the flux was almost completely recovered, and no other cleaning methods were used during the test. It should be pointed out that due to the particularity of the structure of the device, the membrane fouling is mainly based on the adsorption of solid sludge, or the adsorption of dissolved organic matter, or both, and further experimental research is needed.
Fourth, the test conclusion
The results of using modified MBR to treat bathing wastewater show that the removal effect of COD and LAS is obvious. The effluent COD<40mg/L, LAS<0.2mg/L, colorless, odorless, the effluent water quality is stable and reliable, considering the influent In order to ensure excellent effluent quality, the HRT of the system should be controlled at around 3h.
2. The obvious interception effect of membrane on COD has made an important contribution to obtaining excellent effluent quality.
3. Due to the appropriate improvement of the conventional MBR, the concentration of suspended sludge in the membrane filtration water zone is reduced, thereby effectively reducing membrane fouling. The membrane flux can be recovered by tap water cleaning during the test, but the solid sludge and dissolved organic matter are adsorbed. Pollution is the main form and further research and discussion is needed.
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ZHEJIANGGUYUELONGSHAN SHAOXING WINE CO.,LTD. , https://www.chinashaoxingwine.com