Use

Rainwater runoff treatment system for outdoor paved area

sized considering a rainfall of 400 l/s*ha and able to convey

the equivalent flow of rainwater (5 mm in 15 minutes as per

Regional Reg. Lombardy no. 4 of 24/03/06) to the oil selection

compartment for drain into watercourses.

Operation

The rainwater containing oils, hydrocarbons, suspended solids

and sediment, enter the selection tank where coarse solids (gravel,

crushed rock) decant, thus ensuring the perfect functioning of

purification in later stages.

The pipe, that from the selection tank leads to the grease trap

is positioned with respect to the bypass pipe in such a way that

it only unloads the

flow equal to the rainwater (the first 5 mm of

rainwater evenly distributed over the entire drainage area served

by the drainage network); the flow rate that exceeds that of the

rainwater is conveyed through the bypass pipe directly into the

final receptor.

The wastewater, which is loaded with oil/hydrocarbons, overflows

into the oil separator suitable for separating by gravity the non-

emulsified oil/hydrocarbons with a specific weight of less than

0.85 g/cm

3

from the drained wastewater through static separation

and coalescing filtration with efficiency increased by 95%.

The rainwater, once treated, is passed through an inspection well

into the final receptor.

COVERED AND UNCOVERED PAVED AREAS

COMPLETE PLANT - DRAIN TO WATERCOURSES

Maintenance

To maintain the proper operation of the plant the flowing checks must

be carried out every six months:

•

the level of the inert substances in the selection tank;

•

the level of the inert substances in the grease separator;

•

the level of oil/hydrocarbons in the grease separator and

cleaning of the coalescing filter;

If an excessive amount of sludge (inert) is found in the various tanks,

proceed to its removal.

If an excessive amount of oil/hydrocarbons are found in the oil

separator, proceed to their elimination.

Specification Item

Supply of rainwater treatment plant (5 mm) for paved surfaces of....

m

2

and suitable for the drain of treated water into watercourses in

compliance with Tab. 3, Legislative Decree 152/06, Annex 5; this

system consists of the following artefacts:

•

flow-splitting chamber suitable to send the rainwater to the

grease separator and send the waters from secondary rainfall,

through bypass piping directly into the receiving body of the

water.

•

oil separator with coalescing filter in which the physical

separation of oils and hydrocarbons by flotation and by

coalescence will take place.

All the artefacts are made of constant thickness polyethylene (12

mm) with the rotational moulding technique and consist of ribs,

which confer resistance for underground use, complete with screw

caps for inspection.

Figure 11

Continuous rainwater collection plant for drain into watercourses

65

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