NALDI Ecologia - Model Series LBAR / LBAN -Aerobic and Anaerobic Bacterial Filter

The depurative treatment of sewage by Imhoff pit is very ancient and dates back to the last century, when the first septic tanks appeared. In the past, this type of treatment has found a great diffusion even on plants serving large communities, but currently their use is limited to small rural settlements or as a pretreatment to further purification stages such as percolator beds or biodisks.

The proposed technology does not reach the high purification yields of an activated sludge plant, but it is the most current to obtain a valid improvement compared to an Imhoff tank, in fact a submerged anaerobic bacterial bed is combined with the pollutant load with total absence of energy costs.

The particular bacterial flora that develops in this type of plant remains attached to the biofilter and further demolishes the organic substance present without the need for atmospheric oxygen; there is therefore a real biological reduction of the organic compounds present without the need for any energy cost for blowers or compressors.

The sewage, in order to be effectively purified from this type of plant, must first undergo a pretreatment of clarification: the black sewage coming from the sewage through Imhoff pit and the blond waters coming from the kitchen through a degreaser.

(In the supply the degreaser and the Imhoff pit that may already be present in the settlement are quoted separately).

The drains are then brought together and conveyed by a special distributor pipe on the bottom of the bed and gradually and uniformly run from bottom to top. The purified sewage is collected from a surface collector placed in the upper part of the biofilter and is sent to the drain.

In the past, anaerobic filters were usually made with pebbles of various sizes, which however created considerable difficulty during maintenance and cleaning operations.

NALDI Ecologia, by virtue of experience on industrial plants, uses an inert and  unassailable filling material from chemical and biological agents and with special features specifically designed for this use:

• the sizing of the plants was made considering a capacity of the filter bed equal to 200 l / AE by virtue of the greater surface of the filling bodies or by the formula AE = V * h2 / h as per the Emilia Romagna Regional Law;
• the high permeability and the strong hydraulic load applicable minimize the need to clean the bed which
• can certainly be considered less than 50% of those needed with pebbled beds;
• in relation to the previous points, the purification yields that can be reached with the plastic filtering mass are considerably higher compared to traditional pebbles.

The table below shows some technical data characteristic of the two filling materials:

Selected NALDI Ecology pebbles:

• Vacuum index: 40 - 50% 95%
• Specific surface: 45 - 65 m 2 / m 3 140 m 2 / m 3
• Dry weight: 1,300 kg / m 3 55 kg / m 3
• Weight in operation: 1,400 - 1,500 kg / m 3 300 - 350 kg / m 3

The construction materials in contact with the sludge are all unassailable by the agents present:

• The separation tanks and partitions are completely made of fiberglass (glass fiber reinforced plastic), which guarantees resistance to the aggressions of chemical, biological and natural agents very high, almost eternal and certainly superior to other materials.
• The peculiar characteristics of the materials and the technology used for the construction of the products guarantee a perfect hydraulic seal, thus excluding possible infiltrations and pollution of the water tables.
• The Naldi plant, thanks to the lightness of the materials used and the pre-assembly in the workshop, allows easy transport and installation even by the final user, therefore with extremely low costs.
• The materials used for piping and accessories are made of unassailable plastic and therefore do not require any ordinary maintenance.
• The biofilter is made of isotactic polypropylene, material unassailable by chemical and biological agents present. It can be easily cleaned thanks to the reduced weight, uniformity and dimensions of the individual pieces.