The MITA Cloth Pile Filter is the latest technology for achieving low Total Suspended Solids (TSS) and Phosphorous Removal. The MITA Cloth filter combines provides high quality with high performance for the filtering of both municipal and industrial wastewaters as well as water re-use applications.
The MITA filter produces high quality filter effluent of less than 5mg/l Total Suspended Solids (TSS) and can help reduce BOD5 as this is normally tied to the solids content of the effluent. Phosphorous Removal (P-Removal) is becoming the set standard for tertiary treatment and the MITA Pile Cloth Filter can achieve P-Removal rates as low as 0.10mg/l.
What is Pile Cloth Filtration?
Simply put, it is a layer of Polstoff microfibres which are designed to remove suspended solids from final effluents.
MITA Pile Cloth Filters are available in a range of models to cover a wide range of filtration applications from the smallest TF2 Drum Filter to the mid-range MSF2 PECV-VM (Vertically Mounted Filter) to the largest MSF32/160 which is for the larger applications. The filter units are usually constructed in 304 or 316L stainless steel, although special materials like super duplex, which is saltwater resistant, are also available on request.
On the MSF range the cloth is mounted on the plastic segments, 6 segments forming a single disc, with up to 32 discs per filter. Each disc has a filtration area of 5 m2, with the 32-disc filter providing 160 m² of filtration area per unit. As the discs are 100% fully submerged in the effluent, the full disc surface area is available for the filtration process.
The water flows through the filter cloth segments from the outside and into the central discharge tube where it then passes to the riser chamber before discharging the filter itself and all by gravity flow.
Backwashing takes place when the chamber water level increases, which indicates the cloth needs to be cleaned. The MITA filter is unique, in that it can backwash in both clock and anti-clockwise directions, which helps to remove more solids. The backwash water is the water which has already been filtered, by the cloth. The backwash time varies depending on the number of discs, but the filter never stops operating, the backwash water is normally returned to the head of the works.
During normal operation, the solids increase on the cloth and as the hydraulic resistance builds on the cloth, the water level increases in the chamber. When the level difference between incoming and clean water reaches 250mm the cleaning of the filter will begin. The filter discs are slowly rotated, and the solids attached to the cloth are removed by the backwash shoe, which is a suction device, operated by the pump. Any settled solids in the filter tank are removed using the sludge pump which are provided with every filter unit.
The structure of the pile cloth fabric is such, that when the filtration process is taking place, the fibres lay flat to form a compact layer of fibres, which provides excellent filtration characteristics, similar to a deep bed sand filter.
During the backwash or cleaning process, the fibres of the cloth are lifted by the backwash shoe via suction delivered from the pump. This allows the retained solids to be easily removed. The MITA cloth can be supplied in varying sizes, with 10µm and 5µm the most common. With 5µm being the finer cloth, it therefore retains correspondingly higher filtration efficiencies. The MITA filter, only uses power (max 2,2kw per machine), when the filter is in its backwash mode. The disc filter is rotated via a non-metallic chain and sprocket and the pumps are initiated to clean the cloth.
The filter is supported at each end via two sets of non-metallic rollers, to ensure there is no possible chance of a bearing failure. The segments can be easily removed via two nuts to make cloth replacement simple and quick. The pump or the backwash shoe can be completely and easily removed for service purposes.
MITA filters offer good hydraulic throughput and are excellent at handling shock loadings and offer low backwash frequencies.
Advantages of the MITA Filter