Organic substances constitute the major source of pollution of discharge water. Nature reacts spontaneously to such forms of pollution by developing bacteria which decompose the organic refuse.However the bacteria find themselves in competition with other forms of aquatic life so far as oxygen requirement is concerned. If the oxygen is lacking the bacteria do not survive and the water quality is severely affected as a result.
The determining factor of the state of health of the water is thus the oxygen, and consequently the degree of pollution is expressed in terms of BOD, i.e. biological oxygen demand.

Trickling filters came into being to satisfy this biological oxygen demand before the water is discharged into the receiving water courses and reservoirs, thus avoiding the damaging effects of eutrophication on rivers, lakes and seas.

margherita trickling filter fill is the result of the evolution of fills used in the past, such as, for example, stones and wood. By employing this new fill material one can make much higher structures, with much greater specific surfaces and with a reduced risk of blockage.

The bioset structured fill material is composed of an alternating series of flat and/or undulated sheets in PVC, glued together in order to provide a light-weight, robust and rigid structure. Such modules therefore prove to be able to sustain high loads.

These structures, the result of a precise design, provide high active surface for bacterial growth in a relatively small volume and possess free spaces for flow passage sufficiently large to avoid such bacterial accumulation as could cause blockage of the trickling filter.
The flow of the percolating/trickling liquid can be vertical or cross-flow, depending upon the models: the structure of the Bioset fills is such that the direct crossing of the entire module is prevented. Moreover corrugations have been inserted in the sheets to permit an easier attachment of the biomass and increase local turbulence, which enhances the exchange of oxygen between the air and the liquid.

In practice, the liquid is uniformly distributed over the blocks which prevent its free fall and facilitate the flow, wetting the entire useful surface with a uniform and fine film. The liquid, which contains organic residues, is in continuous contact with an airflow created by natural draught which provides a constant oxygen supply. In this manner, the bacteria which develop on the fill surface have all the elements necessary for their growth.

Thanks to the modular structure and limited weight, the Bioset blocks can be easily handled, stored and installed in trickling filter towers.

Random plastic fill for trickling filters.

margherita trickling filter random fill offers a high growth and development surface for the biomass in trickling filter beds. It is entirely manufactured from polypropylene and possesses a high ratio of voidage. Its particular geometric form allows optimum distribution within circular cross-section trickling filter beds, with simple and rapid fill installation procedures.

Features

• Construction material: polypropylene
• Maximum diameter of a single piece: 175 mm
• Height of a single piece: 50 mm
• Unit weight: 100 gr
• Weight per equivalent volume: 50 kg
• Specific surface: 120 m²/m³
• Ratio of voidage: 95%

Structured fill for trickling filters in plastic material.

bioset structured fill for trickling filters offers a high surface area for growth of the biomass in the trickling filter bed. It is entirely manufactured from PVC and possesses a high ratio of void. Its rectangular form permits optimum usage of the space within trickling filter beds of square or rectangular format, with simple and rapid fill installation.

The standard version envisages the supply of rectangular blocks. For supply to distant countries there is the possibility of shipping unglued sheets; their assembly can be performed on site by means of equipment easy to use even for non-qualified personnel.

Available models

• BS 27
• BS 60

System advantages

• High efficiency
• Low energy consumption
• No blockage problems
• Low investment costs
• Simplicity of installation
• Minimum maintenance
• Possibility of revamping existing installations

Application fields

• Trickling filters for biological treatment installations on municipal discharges: trickling filter beds represent one of the oldest biological treatment systems for household waste water coming from the discharges of small communities. Up to now they have been used for small-to-medium sized plants and are characterised by very low energy consumptions. In these treatment systems the active bacteria require a support surface on which to develop and grow. MITA Biorulli’s margherita random and bioset structured fill is an ideal support medium, considering the large surface developed and its significant mechanical resistance to being squashed. margherita and bioset fills for trickling filter beds are ideal both for circular and rectangular or square-shaped tanks. The various bioset profiles which MITA Biorulli offers allow the construction of filter beds with layers of different specific surfaces, in order to differentiate between the active bacteria according to the different loads the effluent water contains.
• Trickling filters for industrial biological treatment installations: trickling filter beds represent one of the oldest biological treatment systems. Still today they are employed by industries where low installation and operating costs are necessary and where limited maintenance is a pre-requisite. They are used more and more as a first stage of coarse load reduction, followed by a secondary, finer treatment of the waste water. MITA Biorulli’s margherita random and bioset structured fill is an ideal support medium, considering the large surface developed and its significant mechanical resistance to being squashed. margherita and bioset fill for trickling filters is perfectly compatible both with circular and rectangular tanks. The various bioset profiles which MITA Biorulli offers allow the construction of filter beds with layers of different specific surfaces, in order to differentiate between the active bacteria according to the different loads contained in the effluent water.
• Revamping and upgrading of existing trickling filters: trickling filters system was a means of waste water treatment widely used in the past. Years ago “poor” materials found in nature such as wood, small stones etc. were used as a support surface/fill. Nowadays such materials are replaced with structured fills of the bioset type, which provides enormously superior contact surfaces in the same volume with significantly lower specific weights. margherita and bioset fills are employed preferably for rectangular and/or square-shaped trickling filters: they are simple to install and can increase the trickling filter treatment efficiency by as much as 10 times. Their format allows optimisation of the filling of the tank without the risk of dead zones or short-circuits. The various profiles with different densities and specific surfaces allow the construction of filter beds with layers differentiated by types of biomass and  according to the inlet load.