Use

Secondary treatment of residential black water.

Aerobic percolating filters are to be installed downstream of the

Imhoff tank to allow the drain of purified water directly into a

surface watercourse, without the risk of polluting the environment.

Operation

The anaerobic percolating filter is a biological treatment system

consisting of a tank containing plastic media for the high specific

surface area. The clarified water from the Imhoff tank flow into

the anaerobic percolating filter; these filter through the fill media

forming a layer of microbial slime (biofilm). In this way, the contact

surface between the biofilm and the anaerobic microorganisms

increases and thus the exposure of the biodegradable material

to microorganisms increases. These anaerobic bacteria (that is,

which do not require oxygen for growth) adhere to the fill media

and feed on the organic substances contained in the wastewater,

purifying it.

Maintenance

For the correct management of the FAN and to achieve the

required purification results, please follow these guidelines:

•

Regularly inspect the FAN to check that there is no gross

material received accidentally to clog the pipes;

•

With the passing of time, the organic substances, some

mineralized, accumulate in the bottom of the tank or between

the interstices of the random fill media, and the functionality

of the system can reduce. It is, therefore, necessary to wash

the random fill media with water under pressure, aspirating

the washing water at the same time. The backwash of the

random fill media and the removal of mineralized sludge

should be carried out at least once every five years. 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

Anaerobic percolating filter manufactured in rotational polyethylene

for secondary treatment of residential black water. Monolithic

structure, free of joints and with reinforcement plate, with entry and

exit hole, with plastic random fill media with a specific surface area of

120 m

2

/m

3

and inspection and sampling lids. Suitable for underground

installation. The anaerobic percolating filter is dimensioned according

to the instructions contained in Legislative Decree no. 152/2006 and

summarized below:

RESIDENTIAL WASTEWATER

SECONDARY TREATMENT - DRAIN TO WATERCOURSES

PROJECT PARAMETERS

Water supply per P.E.

lt/d

200

Average flow (Q24) per P.E.

lt/h

8,3

Peak flow (Qp) per P.E.

lt/h

20

Specific organic load

gr BOD

5

/P.E.x d

42

Concentration of the biodegradable fraction

mg/l

240

COD/BOD

5

1,67-2,2

Total daily nitrogen load per P.E.

kg/P.E.x d

<0,012

Total surfactant concentration

mg/l

<15

Concentration of oils and fats

mg/l

<10

Specific surface of the random fill media

m

2

/m

3

120

Digester volume

l/PE

100

Figure 3

System composed of DG-PRO, IMHOFF, FAN models for domestic use, with drain into watercourses

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