Not all cloth disk filters are created equal. With several competitors in the field, Nexom is showcasing the benefits of selecting the MITA filter for your municipal wastewater project. For over 20 years, the MITA system has installed and serviced over 800 filters throughout the world. MITA’s evolution of the 'tried-and-true' cloth disk filter delivers the highest reliability in the smallest footprint in its class.
So, what is MITA and why should this technology be considered for future projects? According to Nick Janous (Nexom representative), "The MITA name is not really well known in North America just because they just entered the market. However, if you were to compare the MITA filter to competitor companies in the United States, the MITA has actually built more filters worldwide than any of the companies or suppliers here in the United States."
"The MITA filter has over 800 installed all around the world, which is an impressive number. Currently, we are approaching 100 MITA installs since the partnership with Axius Water in North America. We are getting a nice installation base under us, and we are building the foundation for a great product here in the United States. In the last year, we already have more than 30 projects that are going to be going in the ground and that is just in the first year of entering the U.S. market. Admittedly, it’s been a bit of an uphill battle. We can beat our competitors on all specs and the MITA is very cost effective. Oftentimes we are anywhere from 15 to 30% less expensive than a lot of the legacy brands in the U.S."
Why would people consider using MITA?
There are several manufacturers of cloth disk filters in the wastewater industry. Why would you consider a new technology compared to an established technology? "In the Midwest, we are very aware of these total phosphorous limits and some emerging TN limits to really control and reduce the amount of algae forming in our waterways. The MITA has been proven to reduce phosphorus down to <0.1 mg/L. Another emerging area to apply the MITA filter is stormwater treatment or overflow treatment process. The MITA can treat the water that the sewers can’t handle if there is nowhere else to put it. Run the stormwater through a filter and disinfect. Combined sewer overflow (CSO) is becoming a solution that is needed in some of these bigger cities."
Another reason to consider new technology is the ability to efficiently meet new limits
and regulations. "A big driver for facilities who selected the MITA filter is water reuse. We have a lot of areas in the world that have very limited water resources, particularly out of California and Southwest. They are using wastewater for reuse, not necessarily for potable reuse, but irrigation and other types of water reuses."
Is Nexom testing the MITA on wastewater treatment for currently unregulated wastewater items? "Yes, we are testing microplastics because it is a hot topic. We don’t know if microplastics will have an eventual limit or a permit from the DNR, but that is something we are studying. We have some data collected that demonstrates that we do some microplastic removal or sequestration."
Key features that get your attention
Lowest head loss profile in its class
Smallest footprint in its class
Compared to the other cloth disk filter company, we can reduce our footprint by 30% over our competition. This is because of how tight we can pack our disks together and with lower profile head we can get a nice skinny package of filters that can reduce the footprint.
Amazing amount of factory integration prior to getting to the site
For example, when other disk filters show up on site, they have separate pumps and piping for backwash and controls that need to be hooked up and wired. A lot of these items are prebuilt in the MITA factory. It is pre-piped so when it shows up on site, you have one phalange and one electrical connection and that’s all you need for your contractor.
Very simple system
Safety and reliability is key. We have access ways and walkways right above the filters that make any sort of maintenance or inspection makes it easy and safe for operators.
Cloth pile is Title 22 certified, water reuse approved for the southwestern part of the United States.
We are finding that other states are requiring Title 22 as well even though they know they won’t be reusing the water, it’s just a standard they use.
Free fiber cloth has a fine texture, not spongy. Made of polyester and very durable.
Fiber pore sizes available in both 5 or 10 microns.
Additional benefits of the MITA filters include maximized factory configuration, reduction in required construction effort, and the unit is mostly factory assembled on delivery. Customization is encouraged with the MITA filter. You have an infinite way to customize the number of racks and the number of disks on the filter. There are a variety of disk units (see picture below). "Here we have the roller bearings we have to support the disk. They never have to be replaced, no maintenance, no greasing. These are designed to easily last 20 years. The backwash pumps and drive assembly all come installed. There are no external control valves to install."
How does it work?
"The water filters outside in. It goes through cloth into the disk, which feeds into the central tube. That central tube takes the filtrate water and puts it into a small chamber with a weir to control the water elevation. The water doesn’t sit too high above the disk itself. You really don’t need a ton of driving head to get water to go through that large surface are of the disks."
Source: MITA Cloth Disk Filter - Nexom
"At the very top, we have a walkway that is integrated into the entire rack. When the entire system gets installed in the tank, that is where the operators can go up there and tie off to a railing and they can do all of their maintenance. It is only less than a foot to access the filters if you need to do maintenance or membrane replacement. This equipment is extremely safe. You don’t need a ladder to climb in, you don’t need any extra equipment to move around the platform."
Besides the safety, what additional benefits does the MITA have over the competition? "We have multiple backwash pumps that are integrated into the entire rack. They are submersible pumps, and they are really easy to replace and maintain. The MITA system doesn't need any sort of external pumping. Everything is in the tank. A special feature is the unique molded backwash system. The entire rack of disks will rotate around a fixed backwash shoe, which is what takes the solids off the filters. The disks rotate both clockwise and counterclockwise. Why is that important? The reason why they do that is because you get better cleaning when the shoe can pull those piles back and forth. It's similar to vacuuming your carpet at home. It is better to pull them back and forth to release the solids from different angles. Lastly, we link our backwash pumps in groups of twos, so each pump can do two to three filters each and you simply have a control built in that says you can turn them on individually."
"Rather than having the valves that would open up and isolate the disks that are being backwashed, you could have a submersible pump that is assigned to every three or four disks. The control logic turns on, runs for a minute or two and turns off. Then it goes to the next one. All of the backwash reject is sent out through the top pipe, and it gets sent out of the filter. There is a well on the end for the sludge pump with a submersible pump that occasionally pumps sludge to same reject line and back to the front of the plant. I want to stress this design is extremely simple. The installation is a breeze for contractors."
Is direct piping needed for the MITA filter? "The backwash pumps sit right inside the equipment and draw from the treated water, so you’re not having to pipe water to this system." Another common question is the longevity of the pumps and items that need replacing. Nexom is in the process of building out their EDI location in Columbia, Missouri. This will be headquarters for production for BABA projects as well as a warehouse for spare parts. According to Nexom, "The pumps and the bearings are the only moving parts on the filter. These items have no replacement schedule and should easily last the 20+ year lifecycle of the MITA filter."
Footprint and sizing
The secret to the tight footprint of the MITA filter is the unique backwashing system. "We don’t need a lot of room between the disks in order to get our backwash arm in there. Other companies that have back wash arms, they require more room. Our backwash systems are molded, so they have a tight profile to get more square footage of filters in the same volume of tank."
"In terms of footprint, we pride ourselves on having the smallest footprint of all of the manufacturers. Here is an example: 65 MGD facility in Italy. With twelve, 24-skis filters, they are taking up approximately 15,500 square feet. Another large installation we have is located in Naples Italy. This is the largest cloth media filter in Europe. The MITA filter is located at an 150 MGD activated sludge plant, featuring sixteen 32-disk filters, and covering 28000 square feet of filter area."
The Nexom MITA filter reduces construction costs by up to 30%. How?
"Reducing footprint with the unique backwash scheme is the key. We competed against the other big cloth filter company, and the engineers were originally at 60% design. Our technical team talked to the engineer. Everyone looked at the competitors piping gallery with the pumps and valves. It is just a very complex system feeding into the reject line. With our MITA design, you have one pipe coming out from each bank of filters which is your reject line. You simply have a weir where the treated effluent comes out. When you put them side by side, everyone could see it was a no-brainer for the engineer. The Nexom technical team drew the design for them, highlighted the cost and footprint savings. In the end, the engineer changed from 60% design around the competitor company to 100% committed to MITA."
MITA filter design options
Depending on your facility and environment, most wastewater equipment comes with additional design options to ensure the technology works seamlessly for you. "We have an option we call the Organ weir, because it looks like keys on an organ. Instead of having a single line of a weir, our design is longer and provides better water coming over the top of the weir. If you are concerned about algae growth or UV light exposure, we have solutions. The Nexom team has designed exterior covers that you can lift or design a system to raise them up with a motor or system. Most of the MITA filters come with a double chain and double sprocket. Our competition only has a single chain and single sprocket. MITA has found that the chain has a tendency to stretch over time and wear because you are really applying a lot of force to that single chain. Doubling up the chain helps reduce the need to replace the chain and reduce maintenance. Bigger racks with 20, 25, 30 different disks, that require a lot of torque to rotate the system. The double chains are much safer way to turn your system without replacing the chain or doing extra maintenance."
MITA maintenance, safety and accessibility
How easy is it to maintain a MITA filter? "This is what the cloth looks like, there are two stainless steel bolts that go all the way through to the top with washers and nuts. You just remove those two washers and nuts on top and slide this piece out, swap fabric out and put it back in. It is pretty quick. The only parts that need service or replacement are the pumps and cloth. Cloth needs replacement every five to eight years depending on application."
The safety of your employees is important to Nexom. "In Europe they are very conscious about safety. They design the systems to be easily maintained, without employees having to go into confined spaces or be at risk."
All backwash pumps, backwash valves, and filter segments are accessible from the platform. In this picture, you can tie off on cables for extra safety. All the controls and cables are tightly confined in these channels above the walkway. Your chain drive, level sensors, level switches, backwash pumps are under the hatch.
OPEX savings over time
Operational expenses are a large consideration when selecting new wastewater filtration equipment. Nick stated, "There are several OPEX advantages with MITA. MITA offers a double chain drive for shorter backwash cycles. Because of the clockwise and counterclockwise motion with the molded backwash shoe, it is possible to achieve longer media life by removing more solids every time you do a backwash. Operators can reduce backwash by 20-40% in terms of the interval. You are essentially wearing less on the fabric because of fewer backwashes. This also means you can extend your chemical cleaning by 50%. You don’t have to do a stand in place chemical cleaning as often you can extend it by 50% because you are getting more of the solids out and you are making cloth cleaner each time."
Maintenance also impacts operational expenses. "Our filter is manufactured at an ISO 9000 (quality management) production facility. This ensures the quality of the products is superior and the employee work in a very safe environment. We understand that bigger filters require bigger the tanks. We can place the filters in concrete tanks, stainless steel SS304 or SS316 tanks. Another consideration for operational expenses is the drive chain. Roller bearings on both ends of the filtrate shaft mitigate any lifetime bearing issues. The drive chain, motor, filters, and pumps are easily accessible through a little hatch under the walkway."
If you are interested in learning more about Nexom and the MITA cloth disk filter, please contact the ICS Group for a custom presentation for operators and engineers.