RESIDENTIAL WASTEWATER

SECONDARY TREATMENT - DRAIN TO THE GROUND

Use

Secondary treatment of residential black water with drain into the

ground according to Table 4, Legislative Decree 152/06, Annex 5.

The sub-irrigation system is a complete system for drain into the

ground composed of Grease Trap, Imhoff, Flush Tank and Sub-

irrigation.

Operation

The Subi biological treatment system, complete with grease trap

and septic tank is used downstream of the primary treatment

through a grease trap where a first separation takes place by

flotation of fats and oils in the water from sinks, showers, kitchens

(grey water) except those of the wc (black water), and through

the Imhoff which consists of two compartments, the upper one of

sedimentation, where the bodies with a density higher than that

of water will tend to settle and a lower compartment (digester)

where settled elements will be digested by anaerobic bacteria.

Subsurface irrigation is effectively made up from the

flush tank,

which will cause the wastewater to be sent intermittently inside

the drainage pipes at a certain speed so that the drainage pipes

can be affected by the flow for their entire length. The wastewater,

once in the drainage pipes, will be permeated using filtration to

the surrounding ground where it will undergo purification thanks

to the same bacteria naturally present in it.

Maintenance

For the correct management of the Subi and to achieve the

required purification results, please follow these guidelines:

•

Regularly inspect the grease trap, the Imhoff tank and the

flush tank to check that there is no gross material received

accidentally to clog the pipes;

•

Remove the excess sludge on a regular basis from the Imhoff

and the grease trap. The removal of sludge must be carried

out by a specialized company;

•

Check the flush tank and test the operation (remove the

sludge accumulated if necessary);

•

As provided for by the Consolidated Act on Water (Legislative

Decree 152/06 as amended), and suggested by the normal

hygiene practice, periodically inspect and wash the inspection

well.

Specification Item

The Subi biological treatment system is a purification system used

downstream of the primary treatment and Imhoff septic tank,

constructed with a corrugated container for greater underground

resistance and walkable ribbed maintenance lid made of 100%

recyclable polyethylene with rotational moulding technology. The

systems are complete with inlet and outlet waste piping and relative

gaskets, which guarantee a perfect Gasket. A flush tank made of

100% recyclable polyethylene with rotational moulding technology

with underground resistance and completed with a perforated pipes

system with non-woven fabric suitable for the dispersion of the

wastewater into the ground.

NOTE The pipe lengths and consequently the m

2

of the non-woven

fabric, must be requested later after a detailed analysis by an

authorised geologist who will be obliged to know the hydrogeological

characteristics of the soil on site.

Here is a table of the pipe length depending on the type of soil (taken

from: Annex V the Interministerial Committee resolution of 04/02/77).

PIPE LENGTH DEPENDING ON THE TYPE OF SOIL

TYPE

SOIL TYPES

L (m) /P.E.

1

(STANDARD)

FINE SAND, LIGHT FILLING

MATERIAL

2

2

COURSE SAND AND GRAVEL

3

3

FINE SAND WITH CLAY

5

4

CLAY WITH A LITTLE SAND

10

5

DENSE CLAY

not suitable

1

2

3

1

2

3

Figure 8

Plant for domestic use, drain into the ground composed of the DG, IMHOFF, 2) SUBI models

43

C

i

v

i

l

w

a

s

t

e

w

a

t

e

r

t

r

e

a

t

m

e

n

t