MBBR Process vs. Traditional Biochemical Processes: Why Media Is Core to Wastewater Upgrade

Many treatment plants and factories are looking to upgrade their wastewater treatment process. Activated sludge has been around for years and takes up a lot of space. However, it needs continuous attention to keep the process going stable. The MBBR Biochip Media process is allowing for a new process by adding little plastic media to the tank allowing the biofilm to be carried throughout the tank. That is the only change that alters how the bacteria will grow and function. They won't float away but will attach to the media and move along with it. This will allow for a more stable system and much easier to expand without having to start from the beginning.

Limitations of Traditional Biochemical Processes (Activated Sludge Method)

Many wastewater plants have been in operation using the activated sludge method. It is effective, but it also has a number of limits which tend to manifest themselves at the time of demand rise or water quality variation. Space is one of the problems. Activated sludge systems require huge settling tanks and aeration tanks. In the case of small plants, this implies increased cost of construction and reduced growth potential. As a factory increases, the system in most cases does not cope and new tanks have to be constructed. Sensitivity to changes is another challenge. The living microorganisms that are suspended are very essential in this process. The bacteria can become stressed when there is a sudden change in the water load such as a spike in chemicals or flow. Once that occurs, the efficiency of the treatment decreases, and the quality of the effluent gets unreliable. Management of sludge is another ongoing concern as well. Excess sludge must be wasted and treated offsite. This adds to operating expenses and creates another waste stream that must be disposed. Bulking sludge, or poor settling, can occur in some plants making clarification difficult and creating cloudy discharge. Energy requirements is another issue. Aeration is the heart of the process and generally uses the majority of electricity for the plant. Bad oxygen transfer equals wasted energy as no treatment will occur without movement. A good example would be some food processing plants where the daily production rates can change everyday. At times of maximum production, the system can get overwhelmed causing foam or poor settling. The operators then have to adjust air flow and return rates almost everyday just to try and keep everything operating correctly. While these limitations do not mean that activated sludge is an inadequate process, it just excels when operating under constant conditions and where space isn't a luxury. But when dealing with plants that have variable loading, little space, or strict discharge limits, these deficiencies tend to motivate engineers to look for more forgiving processes.

Core Advantages of MBBR Process: Small Footprint/High Load/Strong Shock Resistance

The MBBR process alters the functioning of biological treatment by providing the bacteria with an area to attach and develop on tiny moving media within the tank. This is a very basic concept that has definite benefits particularly to plants that require higher efficiency within less area. The small footprint is among the largest strengths. Since biofilm is cultured on the media, the system is able to accommodate more of the active bacteria within the same media tank. This implies that a plant does not require huge new tanks to expand. It is used by many facilities to upgrade old activated sludge systems without necessarily rebuilding the entire structure. High organic load handling is another benefit. The biofilm attached maintains a vigorous and stable population of the microbe. The system is able to break down the incoming wastewater at a more consistent rate even though the latter includes higher COD or BOD level. This is helpful in industries such as textile, food processing and chemical production whereby water quality is not always constant. Another consideration is shock resistance. In actual practice, the flow and composition of wastewater are usually variable throughout the day. In MBBR media, bacteria are not readily washed away since they are attached to the carrier surface. Although there might be sudden growth in pollutants or a sudden rise in flow, the system will restore quicker than suspended growth systems. A realistic example can be observed in a food processing plant which has peak discharge during cleaning cycles. In a conventional system this can result in unstable effluent hours. Once MBBR media was added to the aeration tank, the plant could manage those peaks without the operators making as many adjustments and more consistently good quality output. The other advantage is operational simplicity. The system is not very dependent on rigid sludge return control. After the media fill rate and aeration are optimally established, the process is more likely to remain stable with time. These benefits make MBBR a good choice in new plants as well as upgrades where space, load variations, and stability are significant issues.

Core Role of MBBR Media in Process Upgrade: Increasing Microbial Biomass

The media is a key component of an MBBR upgrade, as it has a direct impact on the amount of biology that the system can store. Rather than the bacteria floating on the water, the process provides great surface area on which microbes may attach and thrive. It is this change that enables the system to treat additional wastewater in the same tank. Within a conventional tank, the bacteria fight over space and nutrients and remain suspended. Some of them are washed away in the process of settling as they increase in load. The media maintains a stable biofilm layer in an MBBR system. The bacteria remain attached and develop in layers forming a thick community. This increases the total biomass of microbes without the need to expand tanks. The more biomass, the more power of treatment. The decomposition of organic matter takes a shorter time since more active bacteria are simultaneously working. Even within one tank, the biofilm has various layers which carry different tasks. The outer layer is concerned with fresh oxygen and rapid breakdown, whereas inner layers assist in more slow processes, such as nitrification. A basic real example is a municipal plant upgrade. Increased influent load was being exerted on the plant by population growth. They did not construct any new tanks, but instead they placed a portion of the aeration basin with MBBR media. Following the change, the system contained a significantly greater quantity of active biomass, and there was a more stable effluent quality during peak flow periods. Moving on, stability is another key factor. Stability means that sudden changes in flow won't wash out your biomass as easily because it's attached to something. This allows your operators a little more flexibility when it comes to day to day fluctuations. The media will also promote a more active ecosystem within your treatment process. As your biofilm grows it will stratify itself into layers that allow for both aerobic and anoxic reactions to occur in the same tank. Just remember that while the media inside of your tank may look like it's simply taking up space, it's actually creating a much larger biological reactor for waste to be treated.

Process Retrofit Cost Comparison: MBBR Media for Old Plant Retrofit & New Plant Construction

Okay, let's think back on that plant working at full capacity. When we run into problems, the first thing that pops up is usually cost. Do we build new? Do we upgrade existing facilities? MBBR media provides some excellent solutions. Let's begin at existing facilities. Let's say you have an old activated sludge plant. If we upgrade, what that usually means is building new aerators or clarifiers. That is civil work. That translates to tons of downtime while those buildings are built. Not to mention tons of construction cost. Oftentimes you do not have the available space at the plant to grow either. Expansion can be very difficult. Sometimes you have to build new to expand. MBBR media allows you to retrofit your plant in a way never before thought. Rather than building new tanks. You can install media into existing aeration basins. Often times all that is needed is some upgraded aeration or even just screening to keep media from leaving the tank. MBBR media can even change the way you build new plants. Since you can utilize higher concentrations of mixed liquor in a smaller footprint than traditional designs, you can build your tanks smaller. That not only saves you money on civil, but your entire plant can be smaller. Small industrial parks are a perfect example. What if you have multiple factories situated close together on a small piece of land. Rather than building one large centralized treatment plant using traditional technology. They decided to do MBBR retrofits to existing units. They were able to add capacity without expanding the size of the plant. There are many reasons to consider MBBR media. But if you find yourself with an older plant that needs more capacity or want a small footprint when building new. MBBR has some unique advantages.