Elbi - AQUA Pura

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 drained sub-irrigation system is a complete system for drain

into the ground composed of Degreaser, Imhoff, and drained sub-

irrigation.

Operation

Drenasub is a drained subsurface irrigation system used

downstream of the primary treatment and the Imhoff septic tank,

constructed of 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 seal. A flush tank made

100% recyclable polyethylene of rotational moulding technology

with underground resistance and a complete perforated pipes

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

wastewater into the ground.

Maintenance

For the correct management of Drenasub and to achieve the

required purification results, please follow these guidelines:

•

Regularly inspect the grease trap and the Imhoff 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. Such removal must be carried out by a

specialized company;

•

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 Drenasub biological treatment system, complete with grease

trap and septic tank is installed 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). With

Imhoff which consists of two compartments, the upper one of

sedimentation, where the bodies with a higher density than that

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

where settled elements will be digested by anaerobic bacteria.

The subsurface irrigation is composed of the flush tank of 300 lt

and perforated pipe (DN 110 mm for the dispersing pipe and DN

90 mm for the drainage pipe) of non-woven fabric.

On the gravel surface where the wastewater is filtered, you will

have the establishment of aerobic biomass that will metabolize

organic substances in solution. Aerobic conditions will be created

with the insertion of the ventilation pipes.

The filtered wastewater will be conveyed to the drainage pipe

towards a drainage well and then to the receptor body (stream,

watercourse or river basin).

Laying of the dispersant pipe and the drainage pipe

Dig a trench of 110 cm in height and 60 cm in width and the length

equal to the Elbi drained sub-irrigation model (Length equal to the

length of the drainage pipe).

Insert a layer of 10 cm of clay or geomembrane in the bottom of the

trench.

Place a layer of 20 cm of crushed stone or gravel of 6-8 cm in size

where the draining pipe should be “buried” (D 110 mm) with a gradient

of 0.2-0.3%.

Place a second layer h = 40 cm where a layer of gravel/crushed stone

of 3/6 cm in size will be placed.

Place a further layer of about 20 cm of thick gravel of 6-8 cm in size

where the dispersant pipe will be buried.

Insert the plug at the end of the dispersant pipe. In this last layer, the

pipe aerators should be positioned (one every 3 metres).

Lay the non-woven fabric on this last layer and cover up completely

with the excavated soil (the non-woven fabric prevents the ground

above from falling into the interstices of the gravel so that later

filtration of the wastewater is not prevented).

NOTE subsurface irrigation is a good alternative to the drained

subsurface irrigation in case IMPERMEABLE soils are present in the

site (e.g. Compact clay).

The installation location of the plant is also important, taking into

account that:

•

the distance of the bottom of the trench excavation is > 1 metre

from the maximum groundwater level;

•

pipes for drinking water are > 30 metres distant from tanks;

Given the circumstances set out in this note, it is, therefore, essential

that the determination of the soil and the hydrology of the area be

carried out by an authorised geologist.