When for economic reasons or for special geographical situations we must abandon the creation of a centralized system, the use of small plants for wastewater treatment for civil use is required.
For the biological treatment of effluent from medium-small residential areas, an ideal process cycle consists of screening, a primary settling tank with a sludge digestion tank (Imhoff tank), a biological purification treatment and the separation of excess sludge.
In the compact biocombi plants with the filtration system offered by MITA Biorulli, the biological treatment occurs through a partially immersed disc (biodisc) on which the biomass forms. In lieu of the final sedimentation tank, the use of a cloth filter is provided which consists of a horizontal perforated metal sheet drum coated with a special filtration cloth equipped with the proper system for the removal of separated sludge.
The most obvious advantages of the system are the minimal energy consumption, maintenance limited to a few simple operations, the small size, the steady performance with regards to variable loads and not least, the absence of noise and unpleasant fumes.
The biological purification phase occurs with a biodisc made of polypropylene parallel discs mounted on a central axis, the diameter of which varies according to the plant size, in a range between 2.00 m to 2.40 m. Forty percent of the surface of the discs is immersed in wastewater and it's well suited for the growth of bacterial flora, the main architect of the biological purification treatment.
The cloth filter replaces the secondary sedimentation tank. The biologically purified water can reach the discharge only by passing through the filter cloth, the surface of which little by little is covered by a layer of sludge which causes the increase in the pressure drops. A level sensor actuates a pump that, through a vacuum unit in contact with the cloth, collects the water necessary from inside the drum to clean the cloth. The sludge removed is released in the primary settling tank, if any, or to another destination (sludge treatment).
Other than the compliance with the legal requirements, the purification system effectively responds to important practical requirements. The maintenance is greatly reduced compared to conventional plants which can be performed by unskilled personnel.
The MITA Biorulli compact plants in the BC series are particularly ideal for small towns or villages, tourist resorts and hotels.