AU2020102464A4

AU2020102464A4 - A miniaturized air-lift membrane bioreactor for decentralized sewage treatment

Info

Publication number: AU2020102464A4
Application number: AU2020102464A
Authority: AU
Inventors: Wanyin Bao; Jingzhen Luo; Wenlue Miao
Original assignee: Bao Wanyin Miss; Luo Jingzhen Miss
Current assignee: Bao Wanyin Miss; Luo Jingzhen Miss
Priority date: 2020-09-28
Filing date: 2020-09-28
Publication date: 2020-11-12
Anticipated expiration: 2028-09-28

Abstract

In recent years, with the rapid development of rural economy and the improvement of living standards of local residents, the rural sewage discharge tends to concentrate and increase in amount, leading to growing concentration on the issue of rural sewage discharge and reuse. Nevertheless, the progress of sewage treatment has relatively been slow due to the backward level of technical management. In this study, a set of rural decentralized integrated membrane bioreactor system is developed in order to satisfy rural domestic sewage's characteristic of decentralization, including anaerobic tank, membrane bioreactor, clean water tank, aeration fan, suction pump and isolation plate. This invention possesses both technological advantages of the original membrane bioreactor and convenient operation which can be used to purify and to treat the domestic sewage of the scattered households, improving the flexibility of the sewage treatment. 1 MBR equipment process flow chart Refluxed pipe of mixture and sludge Aerator ipe Outlet pipe Intake ipe Regulating pool Anaerobic pool Anoxic pool Aerobic pool Equipment room Figure Schematic diagram of construction Concri cfontmd Oto a rrm vrtlo, Lift 1 eg laI o i lLi) Pn iI I'll wellil, . Figure 2 1

Description

MBR equipment process flow chart

Refluxed pipe of mixture and sludge Aerator ipe Outlet pipe

Intake ipe

Regulating pool Anaerobic pool Anoxic pool Aerobic pool Equipment room

Figure

Schematic diagram of construction

Concri cfontmd Oto a rrm

vrtlo, Lift 1 eglaI o i lLi) Pn iI

I'llwel il, .

Figure 2

TITLE

A miniaturized air-lift membrane bioreactor for decentralized sewage treatment

FIELD OF TECHNOLOGY

This patent is designed for sewage treatment area of water treatment technologies. In

particular, a membrane bioreactor is involved.

BACKGROUND In recent years, the efficiency of sewage treatment has been significantly improved due to the construction and upgrading of sewage treatment plants in China. However, the improvement is limited to the urban area. The sewage of rural areas has not been effectively treated in time in China. In terms of sewage treatment equipment, the effluent quality in some areas is substandard because of the poverty of equipment and the failure in checking, reporting and handling the faults and defects of equipment. For the lack the environmental consciousness, some rural people discharge sewage into the river, making the composition of sewage increasingly complex and the local environment too polluted to inhabit. The discharge of untreated domestic sewage not only poses a potential threat to the drinking water source, leads an important cause of eutrophication of rivers and lakes, but also harms the surrounding soil and people's health.Improving the living environment of the rural people is an important task in the implementation of the strategy of Rural Revitalization. It is an important task to study the suitable sewage treatment technology and carry out the rural domestic sewage treatment to change the disordered discharge of rural domestic sewage and improve the living conditions of farmers. It is also the key to improve the water environment of river basin and region.

There are many decentralized treatment progress for sewage in China, such as constructed wetland, stabilization pond, septic tank, biological aerated filter, hybrid anaerobic biofilter, and so on. The constructed wetland is a natural system, which has good removal effect on solid suspension, low cost and energy consumption, but covers a large area, bears a low treatment load and generate an average treatment effect on BOD. The stabilization pond uses bacteria and algae to jointly remove organic pollutants in wastewater through microbial degradation, organic adsorption, filtration and other functions. Affected by temperature, it is often used in southern China. Similarly, it also covers a large area and takes a long time for hydraulic retention making it to accumulate mud. The septic tank is an integrated system with advantages of easily building, covering less area, generating higher effluent quality.

But it requires more units to work and professional technicians to carry out maintenance management, process control and equipment management. While the scarcity of professional talents in rural areas makes it hard for future operation and management. What's more, sludge output of the biological aerated filter is low and the quality of effluent water is in stable. As for the hybrid anaerobic biofilter, it is a widely used water treatment process in rural decentralized treatment system, which can save energy in operation. It has been found that the mass transfer conditions of microorganism and sewage in anaerobic state are important factor. When there is a certain amount of micro biomass and sufficient time, the effluent can meet the secondary discharge standard of urban sewage treatment plan. But a bad working condition of anaerobic tank may affect the removal effect of COD. In addition, the removal rate of ammonia nitrogen in compound anaerobic biological tank is not satisfactory. Each technology has its own advantages and disadvantages and scope of application. Therefore, the sewage treatment process should be selected scientifically according to local conditions. At the same time, the construction and development of surrounding towns and industrial zones should be fully considered according to the rural conditions, and the corresponding planning scheme should be formulated. For more developed areas with land shortage, the research and development of miniaturized integrated membrane bioreactor process is particularly important.

Therefore, the patent has developed a set of rural decentralized integrated membrane bioreactor system, including anaerobic tank, membrane bioreactor, clean water tank, aeration fan, suction pump and isolation plate. It is expected to apply this system to Jiangsu Province, Zhejiang Province and other regions in China. The system not only has the advantages of the original membrane bioreactor technology, but also is convenient to use. It can carry out sewage evolution treatment for zero retail household sewage, and improve the flexibility of sewage treatment. Therefore, the system has an important role and promotion value in improving the quality of rural water environment in China.

SUMMARY In this innovation design, all sewage is led to specific sewage processing equipment through sewage collection pipeline, after passing away a filtering grid, sewage will be sent to an adjusting pool for measuring homogeneity with a lifting pump, and then will be sent to an integrated sewage purification equipment continuously through a lifting bump. The process of biochemical degradation is conducted inside the facultative oxygen of an integrated sewage purification equipment for further degrading organic pollutants. Aeration equipment is established at the bottom of the pool ,and oxygen necessary for the surviving of microorganism is provided by blast blower inside the house of equipment. This system degrades ammonia nitrogen with denitrifying bacteria, and creates back flow through mixture. All effluent will be further degraded after entering into the MRA membrane, then proceeded with a separation of mud and water, and finally released out after reaching the Standard B of GB18918-2002

DESCRIPTION OF THE DRAWINGS Figure: MBR equipment process flow chart; Figure2: The schematic diagram of infrastructure; Figure 3: The removal rate of 4 test items; Figure 4: Description for Technical Route.

DESCRIPTION OF PREFERRED EMBODIMENT Design principle:

As shown in Figurel, MBR equipment is composed of regulating pool, anaerobic pool, anoxic pool, aerobic pool with MBR components, and equipment room. Anaerobic pool, anoxic pool, and aerobic pool each are isolated by isolation plate. The water inlet pipe passes into the anaerobic pond through the regulating pond. The refluxed pipe of mixture and sludge is inserted into anaerobic pool. The aerator pipe is distributed in anaerobic pool, anoxic pool and aerobic pool.

Figure 2 is the schematic diagram of infrastructure. The regulating tank is located under the MBR equipment. The sewage enters the regulating tank from the inlet. After the initial precipitation, the supernatant of sewage is pumped into the integrated sewage equipment for treatment using the lifting pump.

During the process, the sewage first enters the regulating tank for initial precipitation, and then is introduced into the anaerobic tank through the intake pipe for treatment. The middle passage is used to carry the sewage after aeration from the anaerobic tank to the anoxic tank. After the aeration treatment, the sewage flows into the aerobic pond through the overflow port between the aerobic pond and the anoxic pond, and is purified in the MBR membrane module. Finally, the treated sewage is pumped out through the outlet pipe for use outside.

Main parameters of equipment: Number Name Quantity Facility Requirements The treated water volume (10t/d); integrated sewage treatment equipment. Tank body should 1 Treatment I be made of glass fiber reinforced plastics; equipment plate thickness > 3mm. 1OT /d = 2.5m * 1.5m * 2.2m. Membrane frame: 304 Angle steel; Membrane: immersed flat membrane element; Membrane aperture: 0.1 m; Effective area of a single membrane: 1.0 m2 ;

2 Membrane 1 Membrane material: polyvinylidene fluoride module (PVDF); Supporting plate: acrylonitrile butadiene-styrene copolymer (ABS); Water yield: 400-800L /P*min; effluent turbidity: 1.0Ntu.

3 Submersible 1 Voltage: 220 v sewage pump

Blower aerationdiameter: DN32; 4 1 Temperature range: -20°C-+120°C rotameter Pressure: <0.9mpa

Self-priming 1 Injection-type self-priming pump: 0.37 kW at pump 1.8 m/h

6 Exposure to 1 Vortexfan:<0.81kW air pump

Air duct: DN32 PPR pipe or 304 stainless steel 7 Pipe 4 Water pipe: DN25 PPR pipe or Upvc industrial pipe

The electric control cabinet should be made of carbon steel with a thickness of no less than cntric I1.5mm, including the following features: 8 control 1 system Equipment control can be automatic or manual. Automatic control means the whole process is fully automated without personnel on duty. Manual control means each actuator can be controlled separately. The field control system is equipped with the input and output capabilities of DI, DO, Al and AO as well as the network RJ45 communication interface. Data acquisition: remote data (including transmembrane pressure difference, liquid level, temperature, flow rate, and operation state) can be transmitted and recorded in real time and saved for more than one month, in addition, the system can diagnose and alert abnormal data. Remote control: It can operate the equipment remotely as well as controlling the start and stop of the equipment.

1 Experimental procedures 1.1 The lift pump starts to intake water. Then the activated sludge is taken from the sewage treatment plant nearby and dosed into the aerobic tank. The aeration cycle is 3 days, and meanwhile carbon source is added; 1.2 Observe the growth of activated sludge. When the sludge concentration in the aerobic tank reaches 2000-3000mg/L, the effluent is discharged normally. Add a certain amount of denitrifying bacteria into the anoxic tank, thus improving the nitrification capacity of the system; 1.3 The equipment normally waters in and out, and the bacteria is constantly replenished. When SV maintains at approximately 30%, the equipment operates properly. After testing, the inlet and outlet data are as follows:

Table 1 Inlet data

Sampling Test items (Units: mg/L) point CODcr NH 3-N TP SS

1# 813 57.9 11.3 120 2# 243 60.1 10.4 108 3# 481 136 21.7 142 4# 142 42.4 6.54 67 5# 465 91.2 16.7 85

6# 129 52.6 5.23 63

Table 2 Outlet data

Sampling Test items (Units: mg/L) point CODCr NH 3-N TP SS

1# 21 0.512 0.820 16 2# 20 0.616 0.792 11 3# 21 5.84 0.784 10 4# 5 0.484 0.416 6 5# 10 0.892 0.908 12 6# 24 3.03 0.780 10

2 Data processing Table 3 Inlet and outlet index and removal rate Test items (Units: mg/L) Sampling point CODcr NH3-N TP SS

1# inlet 813 57.9 11.3 120 1# outlet 21 0.512 0.820 16 Removal 97.4 99.1 92.7 86.7 rate %

2# inlet 243 60.1 10.4 108 2# outlet 20 0.616 0.792 11 Removal 91.8 99.0 92.4 89.8 rate %

3# inlet 481 136 21.7 142 3# outlet 21 5.84 0.784 10 Removal 95.6 95.7 96.4 93.0 rate %

4# inlet 142 42.4 6.54 67 4# outlet 5 0.484 0.416 6 Removal 96.5 98.9 93.6 91.0 rate %

5# inlet 465 91.2 16.7 85 5# outlet 10 0.892 0.908 12

Removal 97.8 99.0 94.6 85.9 rate

% 6# inlet 129 52.6 5.23 63 6# outlet 24 3.03 0.780 10 Removal 81.4 94.2 85.1 84.1 rate %

Average RR % 93.4 97.7 92.5 88.4

Standard 60 8 1 20

3 Data analysis and summary 3.1 Attainment of effluent index According to the outlet data in Table 2, the contents of CODcr, NH 3 -N, TP and SS in the effluent of the six sampling points all meet the class I-B standard of GB 18918-2002, satisfying CODcr60mg/L, NH 3-N68mg/L, TPGmg/L and SS< mg/L. The results indicate that the operation is stable and reliable, and can achieve the treatment effect expected.

3.2 Analysis of the removal rate of each index On the basis of the inlet data (Table 1) and outlet data (Table 2), the removal rate of 4 test items at each sampling point is calculated (Table 3) and plotted (Fig. 1 and Fig. 2) respectively. The calculation demonstrate that the average removal rate of CODr is 93.4%, with 4 of the 6 sampling points beyond 95% and 5 in excess of 90%; the average removal rate of NH 3 -N is 97.7%, and the removal rates of all sampling points pass %; the average removal rate of TP is 92.5%, and 5 out of 6 sampling points outstrip 9 0% ; the average removal rate of SS is 88.4%, 2 and 5 sampling points in 6 possess removal rate over 90% and 85%, respectively. In general, the removal rates of each index maintain at a high level and effective removal is achieved. In terms of specific sites, the removal rates of CODr, NH 3 -N and TP in Hujia village (6#) turn out lower than those in other sampling sites, possibly due to the geographical location of the sampling points or difference in the sludge and equipment used.

3.3 Sludge analysis The operation effect of the process indicates that the sludge discharge of the whole process is relatively small and there is no secondary pollution.

3.4 Comparison with other technologies Major sewage disposal technologies currently used in rural areas of China include constructed wetlands, stabilization ponds, biological filters, oxidation ditch, etc. The validity and advancement of the new technology are proven through the comparison of the removal efficiency of COD, NH 3-N, TP and SS between membrane bioreactor and the technologies above.

Table 4 Removal rate of pollutants in domestic sewage by different treatment process COD NH 3-N TP SS

Constructed wetlandError! Reference 75-80 50-60 60-70 85 source not found.

Stabilization pondError! Reference source >55 >70 >50 not found.

Biological filterError! Reference source not found. 78.1 7 •

Oxidation ditchError! Reference source not found. 96.9 88.4 68.3 90

Membrane bioreactor 93.4 97.7 92.5 88.4

The removal rates of COD, NH 3-N, TP and SS in domestic sewage by different treatment processes are listed in Table 4. Compared with other technologies, the effluent quality of membrane bioreactor is at a higher level, with a generally higher removal rate of each pollutant, especially for NH3 -N and TP. The removal rate of TP reaches 92.5%, far higher than that of stabilization pond, biological filter and oxidation ditch. The removal rate of NH 3-N is even high up to 97.7%, ahead of constructed wetland and biological filter. Advanced in sewage treatment, membrane bioreactor would play an important role in improving the quality of rural water environment.

4 Influence factors and control points In membrane bioreactor process, the operating condition of membrane separation is similar to traditional membrane separation, with major control factors including influent quality, temperature, operating pressure, dissolved oxygen, membrane surface velocity, pH, MLSS, etc. The influence and choice of each factor will be individually discussed in the following passage.

4.1 Temperature Classically, the membrane flux enlarges with the increase of temperature, mainly due to the decrease of the viscosity of activated sludge mixture and the resulting reduce in osmotic resistance. The membrane bioreactor system should be operated at -35 °C

4.2 Operating pressure The trans-membrane pressure of submerged MBR should not exceed 0.05Mpa.

4.3 Dissolved oxygen Among different types of MBR process, aerobic, anoxic and anaerobic sections are formed from the mixture in the bioreactor, respectively. The control range of dissolved oxygen in each section of the reaction tank is: below 0.2 mg/L in anaerobic section, 0.2-0.5 mg/L in anoxic section and no less than 2 mg/L in aerobic section.

4.4 Membrane surface velocity With regard to external MBR, the operating condition should be controlled at pressure as low as possible and flow rate as high as possible. The membrane surface velocity should be kept at 3-5 m/s, thus maintaining high water flux and reducing the cleanout and replacement of membrane, which is conducive to the maintenance of membrane.

4.5 pH Generally, the pH resistance of biochemical bacteria in MBR is between 6-9, so the pH value of influent water in membrane bioreactor should maintain between 6-9.

4.6 MLSS The sludge concentration should be kept within a moderate range, because both too high or too low sludge concentration will lead to increase in the filtration resistance and decrease in the membrane flux. The sludge concentration of submerged MBR aerobic tank should be controlled at 3000-20000 mg/L.

Claims

Claims: 1. A miniaturized air-lift membrane bioreactor for decentralized sewage treatment, characterized in that, including: by integrating the membrane separation technology with the traditional wastewater biological treatment technology, this process not only avoids the secondary sedimentation tank, but also greatly improves the solid-liquid separation efficiency, the biochemical reaction rate is improved due to the increased concentration of activated sludge in the aeration tank and the development of dominant flora in the sludge.
2. According to product of claim 1, wherein the equipment is compacted and integrated so suitable for sparse treatment of rural sewage with high quality effluent, which can be recycled for irrigation.
3. According to product of claim 1, wherein advanced ultrafiltration membrane technology and biological simulation technology were integrated in response to the inflow water quality and fluctuation; flat membrane was deployed to improve the membrane flux by more than 30%, reduce the contact angle to below 70 degrees, and optimize the equipment energy consumption with little sludge.
4. According to product of claim 1, wherein air lift is used to carry out backflow and convert air energy into backflow kinetic energy, which resulted in reduced use of the sludge backflow pump in the process; compared with the traditional process, this technology can save 30% energy; it can also reduce equipment failure rate, which leads to reduce the original high maintenance cost as well.
5. According to product of claim 1, wherein, this technology features a high treatment efficiency, small floor area, low energy consumption, and closed equipment; it is suitable for most of mountainous villages, and less restricted by topography and climate conditions.

Figure1

Figure 2

Figure 4 Figure 3