Ospedaletto (PI) Soil Washing Plant

The plant has a capacity that varies according to the granulometric characteristics of the soil to be treated; in particular, it has a capacity of 25 t/h for soils with a silt content of about 36% and a capacity of 50 t/h for soils with a silt content of about 20%.
The contaminated soil washing section involves washing the soils with water and if applicable adding specific detergents (surfactants and soda), or organic de-emulsifiers (in the presence of oily emulsions in the soil) or sodium hypochlorite (for foul-smelling soils) in order to obtain materials suitable for the subsequent direct recovery or subsequent stabilisation treatment.
The washing process removes heavy metals, linear chain and aromatic (BTEX, IPA) hydrocarbons and organochlorine solvents.
The waste, after going through an off-line crusher if applicable, is fed into the loading hopper of the coarse screening system. From here, by means of a conveyor belt equipped with a magnetic separator, it is further screened with a rougher screen with separation and washing of materials larger than 60 mm. The finer fraction, between 2 and 60 mm, is sent to the next washing step. This is followed by going through three hydrocyclones, the washing And vibro-drying of the suspension of water and sand, and separation of the sand.
At the end of the cycle, the washing water is sent to the chemical-physical treatment of the same soil washing plant.
The following fractions are obtained from the soil washing operation:

1. pebbles, gravel and coarse sand (larger fraction): recovered and sent to reuse;
2. fine sands, silt, clays (fine-grained fraction): subjected to either further treatment or disposed of or reused.

The grain sizes of these inert materials that can be recovered are as follows:

1. pebbles > 150 mm;
2. pebbles > 60 mm;
3. gravel 2-60 mm;
4. sand 0.06-2 mm.

According to the directions of the former Ministerial Decree 471/99, materials with a grain size of less than 2 mm is subjected to analyses on the same basis, while material with a grain size of more than 2 mm is subjected to release tests with water saturated with CO2. The analytical results are compared with the limit values indicated by the above Ministerial Decree.
If the aggregates leaving the washing plant do not meet the expected characteristics, the possibility of carrying out an additional washing cycle, or the stabilisation treatment, or of sending them to other treatment or disposal plants, is evaluated.
The following types of waste also originate from the washing process:

1. sludge from the chemical-physical treatment of washing water;
2. sludge with the light fraction from soil washing;
3. ferrous material and coarse material removed.

Waste type approval
Specific waste control procedures apply both when defining contracts with customers (the 'type approval' phase) and upon accepting deliveries to the plant.
The compliance of the quality of the incoming waste with the corresponding approval is checked by means of visual and analytical inspections, carried out instantly, periodically and on a 'spot' basis, including collection of waste samples.
After checking, the waste is sent for the treatments defined in the approval phase.