MBBR Media Operation & Maintenance Guide: 3 Core Tips to Reduce Loss & Boost Biofilm Growth Efficiency

MBBR works best when the media inside the reactor is healthy, active and balanced. However, when you get out of the lab and into actual operations, problems like media being lost, flow not being uniform, or poor biofilm growth can gradually lower how well things work, and you might not see it coming. Problems usually become obvious once the effluent water quality diminishes or energy usage begins to rise. The good news is that incorporating simple day-to-day operating and maintenance habits can offer significant benefits. Proper care can extend the life of your MBBR Biochip Media while keeping it stabilized in the tank and help promote healthier biofilm growth to keep your treatment process running efficiently.

Slow Biofilm Growth on MBBR Media? Root Causes & Practical Fast Biofilm Cultivation Methods

Systems that take a long time to establish biofilm growth on MBBR media usually have an underlying issue with the entire treatment system being poor. You can have good tanks and still experience cloudy water, poor ammonia removal or erratic performance. What tends to happen in reality is that the problem starts right from the beginning and goes unnoticed during startup or even after rebooting the system. One common issue is low biomass activity to start with. If your waste activated sludge feed is poor or the system is newly seeded, bacteria take a long time to grow on the media. The other reason can be poor oxygen balance. Too low concentration of air limits bacterial growth and too much turbulence will wash out the bacteria before they can settle and cling to media. The quality of water being treated matters too. If organic food source (BOD) is low, bacteria don't have sufficient energy to build a healthy layer. On the other hand harsh chemicals such as disinfectants or pH can destroy the early stages of biofilm formation very quickly. Temperature has an impact too. Naturally bacteria multiply slower in cold water temperature therefore biofilm builds up slower. This is common in outdoor tanks during rainy season or when the weather is cool. Provide high quality seed source to boost biofilm growth faster. Healthy mature plant activated sludge is preferred over week or diluted sludge. DO not reduce aeration after startup, keep it constant by fine tuning so that media does not tumble but rotates inside media. Gentle circular motion allow bacteria to attach to media and stay there. Try to limit exposing the system to high shock loads chemically or big fluctuations in influent load for initial days. Gradually building up organic load helps microbes settle in and multiply within media layers. Some operators even operate the system with slightly higher DO initially which is brought down to normal settings after biofilm is formed. The above case was seen in a small wastewater treatment plant in a simple case scenario. Almost a week to ten days of crappy-nitrification was seen when the system was started up. Improved quality of seed sludge and reducing air turbulence allowed visible growth of biofilm in just a few days and performance kicked in soon after. Be patient and keep conditions stable for biofilm to grow. Biofilm does not rush to grow, but if you give it what it needs it will grow on more and more rapidly.

Media Loss/Damage? Protection Points During Installation & Operation

Operators sometimes do not realize media is lost or damaged until after the system is up and running. At first everything may seem fine but overtime the system may experience fewer carriers in the tank, abnormal movement or ineffective treatment. Some occasions you will even see media in the effluent resulting in performance and maintenance concerns. A common situation happens during the installation process. If there is too large of a screen at the outlet, it's easy for small or broken media to slip through. Some plants utilize low quality retainers that bend or loosen with pressure creating space for media to escape. Abrupt movements while filling the tank can also damage media. Pouring media in too high or too fast can cause pieces to crack on impact before the system even starts operating. Aeration in the tank should also be considered. Too much pressure or uneven distribution can cause the media to collide with great force against each other or tank walls. Over time this will cause cracks and wear on the media surface. Too little aeration can cause media to cluster and create dead zones which also break down the media surface due to friction at that point. Pump and screen maintenance is another helpful factor to reduce media loss. If there is a blocked or broken screen, media can burst through downstream. You might even have small openings that go unnoticed which can cause media to be lost over time without you knowing. We experienced a municipal plant that had media loss a couple months into startup. The problems were identified by noticing there was not fin screen at the outlet and too much aeration at the tank corner. Once the air flow was balanced by fixing the screen and regulating air, media loss was stopped. The plant is operating normally again. The key to taking care of your media while in operation is maintaining steady flow, proper screening and gentle yet purposeful mixing. When installing make sure your retainers are secure and properly sized. These are few things that will help your system run smoothly and allow for easier long term maintenance.

Long-Term O&M: Low-Cost Solutions for Media Cleaning & Regeneration

Over time, buildup will occur on MBBR media. Whether that be gradual dirt, sludge buildups and other contaminants you wouldn't want. This isn't always something that will stop your system dead in its tracks but can inhibit biofilm activity and cause unstable treatment. Many operators jump to the end that they must replace their; however, in many cases some cleaning and revival can be done to help prolong media life without breaking the bank. One method that is easily done is air scouring inside of the tank. Letting your system run a short cycle with intense aeration will help scour off loose sludge that may be on the media surface. This works great for soft buildups, as it will do little for heavy scaling. Just don't overdo it because that can also be damaging to your biofilm layer you're trying not to remove. Offline washing is another inexpensive option. During some plants maintenance tank cleanout, they will take a portion of media offline and place it into another tank filled with clean water and some light agitation. This will help wash out large sludge deposits and reestablish biofilm to more of the media surface. Some operators have even used tank water instead of fresh to not shock the bacteria too much. Adjusting flow patterns inside of your reactor can also play a role in cleaning over time. Development of dead spots either in the corners of your tank or upstream of your baffles can cause sludge to build in that same spot over and over, dirtying your media more each time. Adjusting circulation patterns or moving your aeration locations slightly can help keep your media staying cleaner throughout operation. An industrial plant we run saw elevated ammonia after their first year of operation. Once the media was pulled, it was covered in layers of sludge which reduced the media's active surface. Instead of pulling the whole system offline they decided to air scour for 2 days and followed it up with a partial offline media rinse. Once back in service, normal treatment was restored and they were able to go many months using the same media. These are just a few simple steps you can take to help extend the life of your media. The goal isn't trying to make your media look new again but allowing enough active surface for your bacteria to thrive on.

O&M Data Monitoring: Key Indicators & Abnormality Handling Procedures

Keeping an MBBR system running well isn't just about how good the tank looks but keeping up with how the numbers are performing daily. By keeping proper data you can solve minor problems before they become huge failures. Most plants that have experienced performance problems went unnoticed to these warning signs in basic monitoring. Dissolved oxygen (DO) is one of the first things to look at. If DO sat very low for a long period of time the biofilm activity will decrease and along with it the removal of ammonia. If too high, it can cause extreme turbulence which can stress media and lighten the biofilm wall. Staying within a normal range that correlates with your system design is much better than trying to chase high numbers. Monitoring ammonia and nitrate are also very important as well. If ammonia begins to rise with a consistent flow and load you know there is poor nitrification occurring within the biofilm. This could be from low microbial activity, improper DO or maybe even a recent shock load. Nitrate test results can also help you know that your nitrogen cycle is functioning properly or being hindered at an early stage. Something else to look at would be the TSS (total suspended solids) of the effluent coming from the tank. If this spikes suddenly it could mean media wear, biofilm shedding, or even screen damage allowing particles to pass through. This is one of the first indications you may notice that something isn't right in the reactor. Do not overlook changes in flow rates as well. If there is a sudden increase or decrease you can upset the balance of organic loading to the microbial capacity to treat. The other numbers may look normal but overtime this will affect your biofilm strength with inconsistent flow. On one of our facility audits for a food processing facility, we noticed the effluent ammonia was gradually rising each day. There did not look like anything seemed wrong by just looking into the tank. After checking the DO logs we noticed there was a slow decrease in DO due to a partially plugged diffuser line. After cleaning the air system and returning DO back to normal ranges the effluent ammonia came back to normal operating ranges within a couple days. If any parameters are outside the norm follow these few steps. First check your oxygen levels, then look to see if there were any loading fluctuations. Lastly, start to look at the physical attributes of media movement, screening etc. If you catch it soon enough you can help keep your system balanced and out of long term correction.