RESIDENTIAL WASTEWATER

PRIMARY TREATMENT

Use

Primary treatment of residential black water.

The Imhoff is installed downstream of the grease traps and/or

drains of sewage (W.C.) to purify the drains through an anaerobic

digestion process.

Operation

The IMHOFF biological tank is a system for primary sedimentation,

accumulation and anaerobic digestion (carried out by organisms

that live in the absence of oxygen) of domestic drains in buildings

that are not served by urban sewage mains. Upstream of the

IMHOFF tank a grease trap should be installed to avoid greasy/oily

substances preventing biological oxidation. Any rainwater drains

must be deviated downstream of the IMHOFF tank.

Maintenance

For the correct management of the Imhoff and to achieve the

required purification results, please follow these guidelines:

•

Regularly inspect the Imhoff to check that there is no gross

material received accidentally to clog the pipes;

•

Remove the excess sludge on a regular basis. 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

Imhoff biological tank for the primary treatment of residential

wastewater manufactured in rotational polyethylene, a single

structure free of joints and reinforcement plating, equipped with

inlet and outlet holes, a sedimentation cone, a digestion tank and

inspection and sampling lids. Suitable for underground installation.

The Imhoff biological tank is 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),

summarized below:

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

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

Sedimentation tank volume

l/PE

40

Digester volume

l/PE

100

Figure 2

Installation of IMHOFF model for domestic use, drainage into public sewers

25

C

i

v

i

l

w

a

s

t

e

w

a

t

e

r

t

r

e

a

t

m

e

n

t