What Is MBBR Wastewater Treatment And How Dose It Work?Detailed Explanation Of MBBR Process

MBBR is the basic principle of using the biofilm method. By adding a certain amount of suspended carriers to the reactor, the biomass and biological species in the reactor are increased, thereby improving the treatment efficiency of the reactor. Since the density of the filler is close to that of water, it is completely mixed with water during aeration, and the environment where microorganisms grow is gas, liquid, and solid.

 

This article will closely examine the MBBR process, explaining how it works, how it compares to other techniques.

 

 

1.Principle of MBBR process

 

The MBBR process principle is to increase the biomass and biological species in the reactor by adding a certain amount of suspended carriers to the reactor, thereby improving the processing efficiency of the reactor. Since the density of the filler is close to that of water, it is completely mixed with water during aeration, and the environment for microbial growth is gas, liquid and solid three phases. The collision and shearing effect of the carrier in the water makes the air bubbles smaller and increases the utilization rate of oxygen. In addition, each carrier has different biological species inside and outside, with some anaerobes or facultative bacteria growing inside, and good cultivating bacteria outside, so that each carrier is a micro-reactor, so that nitrification and denitrification reactions exist at the same time. , Thereby improving the treatment effect.

 

The MBBR process combines the advantages of both traditional fluidized bed and biological contact oxidation method. It is a new and efficient sewage treatment method. It relies on the aeration in the aeration tank and the lifting effect of the water flow to make the carrier in a fluidized state, and then form a suspension The growing activated sludge and the attached biofilms make the moving bed biofilm use the entire reactor space, give full play to the advantages of both attached phase and suspended phase organisms, so that they can make use of their strengths and avoid weaknesses to complement each other. Different from the previous fillers, suspended fillers can come into contact with sewage frequently and many times, so they are called "moving biofilms".

 

2. The advantages and disadvantages of MBBR

 

Compared with the activated sludge method and the fixed-filler biofilm method, MBBR not only has the high efficiency and operational flexibility of the activated sludge method, but also has the characteristics of impact load resistance, long sludge age and less residual sludge in the traditional biofilm method.

 

Advantages：

 

(1) Packing characteristics

 

The fillers are mostly made of polyethylene, polypropylene and their modified materials, polyurethane foam, etc. The specific gravity is close to that of water, mainly cylindrical and spherical. It is easy to hang the film, does not agglomerate, does not block, and is easy to peel off.

 

(2) Good denitrification ability

 

An aerobic, anoxic and anaerobic environment is formed on the packing, and nitrification and denitrification reactions can occur in one reactor, which has a good effect on the removal of ammonia nitrogen.

 

(3) Good effect of removing organic matter

 

The sludge concentration in the reactor is relatively high, and the general sludge concentration is 5-10 times that of the ordinary activated sludge method, which can be as high as 30-40g/L. Improve the efficiency of organic treatment, and strong impact load resistance.

 

(4) Easy to maintain and manage

 

There is no need to install filler brackets in the aeration tank, which facilitates the maintenance of the filler and the aeration device at the bottom of the tank, and saves investment and floor space at the same time.

 

Disadvantages

 

(1) The filler in the reactor is in a fluidized state by the lifting effect of aeration and water flow. In actual engineering, the phenomenon of local filler accumulation is prone to occur. In order to avoid packing accumulation, it is necessary to improve the arrangement of the aeration pipeline and the structure of the reactor. The structure of the reactor largely determines its hydraulic characteristics. In actual engineering, when the aspect ratio of a single reactor is about 0.5 and the length is not more than 3m, it is beneficial for the filler to move completely. In actual engineering design, a large number of experiments should be conducted to optimize the structure and hydraulic characteristics of the reactor, reduce energy consumption, and further improve the economic benefits of MBBR.

 

(2) The effluent of the reactor is often equipped with grids or grids to avoid the loss of fillers, but it is easy to cause blockage. In the actual project, movable grids can be set up for regular manual cleaning, or an air blowback device can be set up to prevent clogging.

 

 

1. Adhesion of biofilm

 

Biofilm adhesion capacity-the most important indicator for evaluating the quality of the filler. Bio-attachment amount = protected surface area (related to the design and operating state of the filler) × biological attachment amount per unit surface area (related to the performance of the filler)

 

2. Packing performance

 

Filler performance-the most important index for evaluating the biological adhesion of filler

 

(1) Filler surface performance

 

1. Surface structure: It is generally considered that the surface roughness is large and the film hanging speed is fast.

 

2. Surface potential: Generally, microorganisms are negatively charged, and the surface of the filler is positively charged, which is suitable for the growth of microorganisms.

 

3. Hydrophilicity: Microbes are hydrophilic particles, and the filler has good hydrophilicity and is suitable for microbial growth and filming.

 

(2) Hydraulic performance

 

1. Porosity: The volume occupied by the filler, the porosity is high.

 

2. Shape and size: Affect the flow state of water flow and air flow.

 

(3) Fluidization performance

 

It is related to the density of the filler. The density of the filler should be 0.97-1.03, and fluidization can be achieved with less aeration or stirring.

 

3. Identification of maturity of hanging film

 

 

(1) Visual judgment:

 

The biofilm is evenly distributed on the surface of the carrier, and the closer it is to the surface of the carrier, the denser it is, otherwise the looser it is. At the same time, the color of the carrier becomes              darker, which indicates that the carrier film has entered the mature stage.

 

(2) Judgment by microscopy:

 

The biofilm has a dense structure and diverse microbial species. The number of sessile ciliates, bellworms, and cladworms are the majority. The appearance of a small number of rotifers and swimming                ciliates signifies the maturity of biofilms.

 

2. The cultivation stage of biofilm

 

The so-called cultivation of biofilm is to produce and accumulate a certain amount of microorganisms in the treatment system through certain means, so that the biofilm on the filler reaches a certain                thickness, and its cultivation methods mainly include static cultivation and dynamic cultivation.

 

*Static cultivation

 

The so-called static culture is: in order to prevent the new microorganisms from running away with the water, as much as possible to provide the contact time between the microorganisms and the filler       layer, in order to accelerate the formation of biofilms, in the initial stage, in order to avoid the single nutrition of wastewater, so C:N: P=100:5:1 ratio of adding nutrient substrates such as urea, diamine and sugar. First, inoculate sludge (10% biochemical effective volume) and waste water pump into the biochemical tank, and then start aeration culture. The stacking volume of the filler in the biochemical tank is 35%-40% of the effective volume of the reaction tank. Let stand for 4-5h without aeration to inoculate immobilized microorganisms on the filler, then aerate for 1h, then stand for 2h, aerate for 1h, and repeat the operation. After 4-5 days, the surface of the filler has all been covered with biofilm. Continuous small water inflows started from 6 days.

 

*Dynamic training

 

After 6 days of boring culture, a thin layer of yellow-brown biofilm has grown on the surface of the filler, so it is changed to continuous water inflow, dynamic cultivation, adjust the amount of water, and control the dissolved oxygen between 2~4mg/L (use Dissolved oxygen meter measures dissolved oxygen). After about 15 days, there were some amoeba and roaming insects on the filler (observed with a biological microscope), and the filler felt sticky and slippery when touched by hand. After 20 days, protozoa such as flagellates, bellworms, and paramecium free bacteria appeared. After 20 days of cultivation, metazoans such as rotifers and nematodes appeared, which indicated that biofilms had grown. Can start continuous industrial operation

 

3.The domestication stage of biofilm

 

The purpose of domestication is to select microorganisms that adapt to the actual water quality, eliminate useless microorganisms, and make nitrifying bacteria, denitrifying bacteria, and phosphorous accumulating bacteria become the dominant flora through domestication for treatment processes that have the function of denitrification and phosphorus removal. The specific method is to maintain the normal operation of the process first, and then strictly control the process control parameters. The average DO should be controlled between 2~3mg/l, and the aeration time of the aerobic tank should not be less than 5 hours. During this process, do it every day For the determination of various water quality indicators and control parameters, when the average thickness of the biofilm is about 0.2-0.5mm, the biofilm cultivation will be successful, until the effluent BOD5, SS, CODCr and other indicators meet the design requirement

 

 

1. How long does it take for the filler film to hang during low-temperature debugging in winter?

 

In one month, it can achieve the standard well. If the film is hanging, it is actually a process. We divide the film into two angles. The first is that our naked eyes can see the obvious biofilm on the filler. This time will take seven days; the second is that the standard is up to the standard. Time, this time is probably within one month in winter; the third is the time when the biofilm is fully mature, this will be longer, because from a professional point of view, the full maturity of biofilm requires at least one winter and summer alternation. The colony on it can finally achieve stability. To sum up, although from an academic point of view, our stability is probably after a winter and summer. From the point of view of our effect, the water can reach the standard within 30 days, and from the point of view of naked eyes, it is about seven days.

 

2. Does the MBBR process need to add additional biological agents?

 

In the strict sense, MBBR does not require the addition of bacterial agents, so it can be naturally enriched through reasonable optimization parameters, such as our nitrifying bacteria or denitrifying bacteria, because of its biological Membrane conditions are conducive to the attachment of related bacteria, such as anammonia. Under certain conditions, it is conducive to the attachment of our anammonia bacteria. Then, under special water conditions, for example, there are some difficult-to-degrade water quality or water quality. The source is relatively single, and there are some obligate inoculants that have special effects. In this way, inoculants can be added as the initial inoculation, and subsequent additions are not required. To sum it up, it is not necessary under the conditions of domestic sewage, and under some specific wastewater conditions, it can be used as a research proposition to do related research.

 

3. Does MBBR need denitrification and flushing?

 

The biggest advantage of MBBR is that compared with traditional biofilms, it does not need backwashing, because its biofilms are automatically shed. From our research, we found that when your biofilms are more active, their cells There will be more secretions of the outer polymer, and its stickiness will be strong. Then when it ages, the extracellular secretions decrease, and its viscosity weakens, it will automatically fall off during the process of fluidization, and then a new biofilm will grow up, so it does not need to be washed.

 

4. What is the core of MBBR?

 

The core of MBBR is two, one is filler and the other is fluidization. The filler is used as a carrier. There is no unified research to show how much influence its performance has, but its shape will have an impact on fluidization. Therefore, the most widely used fillers are flat cylindrical fillers at home and abroad, so the research on fillers has been continuing. You can try to see which different fillers have the best effect. But from the perspective of engineering, the dimensions to be evaluated are performance, filming speed, final stabilization effect, life, wear resistance, etc., so from now on, the core of the suspended carrier is still fluidization.

 

5. What is the filling rate of MBBR system?

 

The limit filling rate that has been verified so far is 67%, the largest aerobic zone that can be achieved in the project is 60%, and the hypoxic zone is 50%.

 

6. Does the filler of MBBR have to be modified?

 

I think that fillers do not need to be modified. Existing fillers are no problem. Sprun has proved through many engineering practices that fillers can still achieve good results. In my eyes, filler modification is still a research category. Not yet in the engineering category.

 

7. Can MBBR still run when the water temperature is 3 degrees?

 

The currently practiced cases are in Xinjiang, where the water temperature is around 7 to 8 degrees Celsius is able to operate stably. The water temperature of 3 degrees has not been encountered in China, but it is understood that the inlet water of the Norwegian Nordheim Wastewater Treatment Plant (which serves the Winter Olympics) abroad is ice and snow melt water, and the water temperature is 3 degrees. After practice, it can stably meet the standard.

 

8. Will the filler be prone to sludge expansion?

 

The main reason for the formation of sludge bulking is filamentous bacteria, so reports from abroad show that fillers help to weaken sludge bulking because it can break the "long-like" filamentous bacteria in the sludge system. It is a normal sludge floc, and the size of the sludge floc is much smaller than the size of the filler, it will not break the sludge, so from foreign research, MBBR is beneficial to improve the sludge settling property, and from our engineering In practice, it has not been found that the system using MBBR has obvious characteristics of sludge bulking

 

 

*MBBR is a moving bed biofilm reactor, which uses a free-floating plastic film medium to make microorganisms adhere to grow. The plastic film medium needs to remain suspended, so the material needs to have a density close to that of water, and continuous aeration to make good contact between the pollutants and the attached biofilm, so as to effectively remove BOD.

 

Features of MBBR:

 

1. Simple construction and convenient operation.

 

2. The removal efficiency of organic matter is high, and the effect of nitrogen and phosphorus removal is good.

 

3. It is not easy to be blocked and does not need to be backwashed regularly.

 

4. A precipitation process is required after the treatment.

 

*MBR stands for membrane bioreactor, which is a process that combines separation membrane technology with activated sludge. Most of the membrane bioreactors are immersed in sewage, and the organic matter in the sewage is treated by the microorganisms that grow on the surface of the membrane.

 

Features of MBR:

 

1. It can operate under high volume load and low sludge load, and the remaining sludge output is low (theoretically, zero sludge discharge can be achieved), which reduces the cost of sludge treatment.

 

2. High MLSS concentration can be maintained in the reactor, and the volume load of the processing device is high, thereby reducing the floor space.

 

3. High microbial biomass requires sufficient aeration, so operation energy consumption is also higher.

 

4. It is easy to cause membrane fouling, which requires regular membrane cleaning or backwashing.

 

*FBR fixed-bed biofilm reactor, its working principle is similar to MBBR, the difference is that the biofilm is attached to the fixed solid material block. Aeration under the solid material block provides the oxygen required for the growth of the biofilm and controls the cleaning of the film block.

 

1. It can adapt to wastewater with large changes in the influent water volume and organic content.

 

2. It is more convenient to operate than MBBR and has lower energy consumption (because of direct aeration at the bottom).