Use

Primary treatment of residential black water.

The septic tank is installed downstream of the grease traps

and/or drains of sewage (W.C.) to purify the drains through an

anaerobic digestion process. The septic tanks can be installed in

series (individual, dual chamber and three chambers).

Operation

ST septic tanks are particularly indicated to purify drains in

residential settlements of small size. Inside of septic tanks,

the process of separation of oils and greases comes through

flotation, while the separation of solids occurs through

sedimentation. Furthermore, a process of anaerobic digestion

(without the presence of oxygen) takes place. The output will

result in wastewater with solubilized and dispersed solids. Battery

installation increases the treatment efficacy and significantly

reduces the amount of suspended solids.

Maintenance

For the correct management of the ST and to achieve the required

purification results, please follow these guidelines:

•

Regularly inspect the ST to verify that no coarse materials

have accidentally blocked the pipes;

•

Remove the excess sludge on a regular basis (as per local

regulations). 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

RESIDENTIAL WASTEWATER

PRIMARY TREATMENT

Septic tank manufactured in rotational polyethylene, in a single

structure, free of joints and reinforcement plating, equipped with

inlet and outlet holes and inspection and sampling lids. Suitable for

underground installation. Septic tank constructed in accordance

with the descriptions and purification capacity indicated by the

Committee of Ministers for the Protection of waters against

pollution (Ordinary Supplement to Official Journal no. 48 of

21/02/77 paragraph 4).

PROJECT PARAMETERS

Water supply per P.E.

lt/d

150/200

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

60

Concentration of the biodegradable fraction

mg/l

300

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

Retention time during the treatment stage

h

12 c.a.

Figure 1

Installation in series of model ST for domestic use, drainage into public sewers

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