Cloth filters


The final water filtration that comes from the purification plants offers many advantages and compensates for the lack of possible process.
High values of Suspended Solids (SS) always involve negative changes even of other parameters.

Requirements such as improving final effluent quality, adapting plants to new operating conditions and recovering water for industrial or agricultural use are the new needs that present themselves to operators of wastewater treatment plants. Corrective interventions are often conditioned by the lack of space.

MITA Biorulli proposes a simple and effective cloth filtration system to solve these problems. This process is similar to sand filtration because of the results attained. Furthermore, the cloth filters manufacturing concept permits backwashing during the operation without stopping the machine and then the filtration; it allows for minimum head loss (max 0.5 m c.l.), reduced energy consumption and minimum space requirements.

The cloth filters are made of a support structure (drum or disc), coated with a special polstoff filtration fabric consisting of synthetic fibers having a thickness of 4 - 5 mm.

The filters are equipped with a cloth backwashing device commanded by level sensors. Numerous models are available with a working capacity ranging from 10 m3/h up to over 800 m3/h for a single filtration unit.

The technology and the application experience of MITA Biorulli offer high reliability machines that are simple to use, with very low investment, operation and maintenance costs.

Functioning description

cloth filtersThe cloth filter is made up of a drum or alternatively of filter discs mounted on a central hollow shaft. The filtration is done by gravity with an idle machine and uses the level difference between the input and output of the machine. The discs (or the drum) run completely immersed in the water to be treated.

During the filtration phase, the solids are held back by the special polstoff cloth. The minimum water level in the tank containing the filter is controlled by a weir placed on the side of the clean water outlet. With the increase of deposit of solids on the cloth, the hydraulic resistance increases in passing and therefore the difference between the levels of entry and exit.

When a difference of 15 ÷ 20 cm between these levels is reached, it automatically activates the cleaning process of the cloth.

To clean the cloth which is necessary to restore its filtering capacity, the discs (or drum) are rotated slowly. The solids are removed as a result of the backwash passage through the cloth, the water already filtered by a suction pump; this pump is connected to special suction nozzles, which by adhering to the walls of each disc or drum causes the free fiber of the cloth filter to stretch facilitating the release of the sludge particles retained therein.

The contact of the suction nozzle with the cloth filter generates the recompression of the free fibers and the consequent formation of an even filtration panel.

The cloth filter of the drum or disc filters is made of polstoff free fibers (fiber length from 10 to 12 mm and a diameter of 13 to 27 µ fastened to a large weave fabric that serves as support). The type of filtration obtained is comparable to the deep filtration of sand filters and not the surface filtration of the monofilament cloth filters.