Complete Guide to MBBR Media: From Material Selection to Process Adaptation for Efficient Wastewater Denitrification

The process of denitrifying water at wastewater treatment plants usually involves the use of small plastic pieces, or MBBR media. These little carriers allow bacteria to colonize the media and thrive. Eventually these bacteria will break down harmful nitrogen compounds and help clean the water. Choosing the right media and installing the system correctly can play a large role in how your plant performs. Once operators understand how the MBBR Biochip Media works, they can often fix issues with poor denitrification or inconsistent performance on a day to day basis.

What is MBBR Media? Core Functions & Industry Application Scenarios

MBBR media consists of small plastic flotation units which live inside of a wastewater treatment tank. They look simple but they work hard cleaning your water. Any MBBR Biofilm Carriers provides tons of small surfaces for good bacteria to live and grow on. These bacteria are what break down organics and remove nitrogen from your water. MBBR media really focuses on giving bacteria a place to live. Many treatment systems will wash out bacteria or they will become stressed if there is any upset in water flow. With MBBR media the bacteria are able to sit still in the tank while the media floats with the water. This flow helps to bring more oxygen and food to the bacteria which makes the treatment process thrive. The second major role that media plays is aiding in the removal of nitrogen, especially during the denitrification stage. Essentially what this means is that bacteria are turning offensive smelling nitrate into harmless nitrogen gas. This step is crucial for meeting discharge limits at most facilities. This system can even handle expansion loads when proper media is chosen and installed into the tank correctly. It's impressive how MBBR systems can be applied effectively everywhere, from food processing plants and aquaculture farms to, as I've seen, even smaller municipal wastewater treatment facilities. Let's say you have a seafood processing plant that discharges highly concentrated organic waste into their wastewater treatment system. You may struggle with foul odors and high ammonia concentrations. By installing an MBBR tank the plant can expect to see less variability in water quality and reduced occurrences of ammonia spikes. Another good example is residential wastewater systems in growing neighborhoods. These systems experience different amounts of flow throughout the day. The MBBR media can help provide consistent treatment when the flow is not steady. Even the shape of the media is something to think about when selecting. More surface area can be gained by using a media with cylindrical or honeycomb-like designs while allowing for proper movement of water. Movement through the system is what helps prevent your bacteria from clogging the system.

Comparison of Mainstream MBBR Media Materials: How to Choose HDPE/PP/Modified Plastics?

MBBR media selection is not only based on what material the media is made of but also the shape of the media. Here are the three most common forms: HDPE, PP, and Modified plastics. Each reacts differently under real wastewater environments, so ideal selection will vary based on the application. HDPE (high-density polyethylene) is very common. It is rigid, flexible, and handles abrasion very well. HDPE media can be found in most plants and will run for years without issue. HDPE is also chemically resistant to many waste chemicals. Because of this, it can be very safe media to default to for most applications, especially municipal wastewater facilities and food processing plants. One downside is HDPE may be heavier, which can affect tank movement in some lightly aerated tanks. PP (polypropylene) is lighter than HDPE and will usually impart more motion in the tank. This increased motion can help improve contact between bacteria and wastewater. In some systems this can allow for faster reaction times. But the downfall to PP is it can become brittle over an extended period of time, especially if there is large fluctuation in water temperature. It's typically used in applications where the operating environment doesn't vary too much and load is not extremely high. Modified plastics are simply plastics that have been modified to overcome limitations of traditional plastic media. Some are blended to create a higher surface roughness while others are modified to promote better biofilm attachment or strength. These media types can be found in harsher environments such as industrial wastewaters with high ammonia concentrations or extreme/ variable loading. These media tend to be more pricey so they are used when the processes need to perform more consistently. In application, engineers will sometimes run small batches of media and see how they perform before pulling the trigger on a media. For example, an engineer could test out HDPE and modified media in a brewery wastewater treatment plant. They may conclude that HDPE works well enough for simple organics removal but the modified media offered a more consistent nitrogen removal during peak production days. Longevity isn't the only factor to consider when selecting the proper media. One should also consider how well the media can match up to the real world conditions.

Matching Media Specifications & Fill Rate Precisely for Different Wastewater Treatment Scenarios

You don't simply pick a media type and you have correctly specified MBBR media. Tank volume internals configuration and fill rate all factor into how well the system will perform. Even great media won't perform if these aren't considered. Media size can often be determined by what the wastewater is like. Highly organic wastewater works well with smaller media. This is because there is more surface area for bacteria to grow on. However, they can be hard to keep moving if your aeration system isn't strong. Larger media handles flow more predictably and can be controlled easier but offer less surface area for bacteria per volume. For example, many small food processing plants creating high organic wastewater loads often opt for smaller carriers. While a municipal plant with constant flow would probably lean more towards a medium-sized media for balance. Shape affects the media as well. Some media shapes focus on providing more internal surfaces. Others look to allow for easier movement within the tank. The result is that bacteria will grow more evenly on some media than others. Uneven flow can cause parts of the tank to be overloaded with bacteria. While other parts will not have enough activity. Fill rate is another factor some operators overlook. Fill rate is how much of the tank is occupied by media. For most systems based on how they are designed, the sweet spot for fill rate is between 40 percent and 70 percent. Below that range, the media won't provide enough surface area for the bacteria to work efficiently. Above that, the media will not be able to move freely and will decrease oxygen transport. We've seen a plant struggle with fluctuating ammonia levels, simply by increasing their fill rate from 40 percent to 60 percent. The increase allowed the system to steady out because there was more room for bacteria to thrive in the tank. But when the same plant tried too much at 75 percent fill rate, the system began to experience backups and lower oxygen levels. Just because you can fit more media doesn't always mean you should. Just like media size, wastewater type also plays a huge factor in what media will work best. High strength industrial wastewater usually requires a higher fill rate and more active aeration. While domestic wastewater that is lighter will flow easily at a low fill rate and aren't as particular about their settings. Media specifications sort of even out when you look at the whole picture. You want to allow your bacteria enough room to breath, enough surfaces to grow on and constant motion for balanced treatment.

Key to Efficient Denitrification: Synergistic Design of MBBR Media & Biochemical Processes

Simply because there is MBBR media in the tank does not automatically result in successful denitrification. Both media and the biochemical reaction need to work together. When these two aspects are balanced, nitrogen removal becomes consistent and hassle-free. There are two key components that the bacteria in a denitrification system need; a place to live and an environment to work in. The MBBR media provides the habitat these little creatures need. Inside the media is the biofilm that is home to many different types of bacteria, including the ones that will convert nitrate to nitrogen gas. But these bacteria also need an area with low dissolved oxygen and a steady source of carbon. If there is too much oxygen throughout the tank, denitrification will be hindered. Process design plays a huge role in this. Most plants have segregated tanks for anoxic and aerobic. Oxygen is supplied during the aerobic stage to help oxidize organics and turn ammonia into nitrate. Then the water is pumped over to the anoxic zone where dissolved oxygen is lacking. Here, the nitrate is used by denitrifying bacteria and turned into harmless gas which is then released into the atmosphere. MBBR media helps bridge these two stages together. Media moves throughout the tank bringing active biofilm with it and promoting contact between bacteria and wastewater. Also the media motion helps eliminate dead spots, which can cause slower treatment rates. A great example of this occurred at a municipal wastewater facility. They were experiencing high levels of nitrates in their effluent. The first thing they did was increase aeration. They thought this would help the treatment process but it actually made the denitrification process worse. Then they adjusted the system to allow clearer anoxic zones and longer retention time for MBBR media in that zone. After this change was made, nitrate levels dropped and stayed under limits. Control of the carbon source is also another important factor. Some facilities will add an external carbon source like methanol or acetate. This is used as a food source for the denitrifying bacteria. If there is not enough carbon, the bacteria will slow down. If there is too much, you can experience excess sludge as well as higher operating costs. Since MBBR media and biochemical requirements work well together while running in the same direction, your system will be more stable. Operators will have to worry less about troubleshooting and more about maintaining consistent performance.