RESIDENTIAL WASTEWATER
SECONDARY TREATMENT - DRAIN TO THE GROUND
Use
Secondary treatment of residential black water.
Air blown aerobic trickling filters are to be installed downstream of
the Imhoff tank to allow the drain of purified water directly into the
ground, without the risk of polluting the environment.
Operation
The air blown percolating filter is a biological purification system
consists of a tank containing plastic random fill media, fine bubble
diaphragm air diffuser and linear diaphragm blower. The clarified
water from the Imhoff tank
flow into the aerobic 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 aerobic microorganisms increases and thus the exposure of
the biodegradable material to microorganisms increases. The
aerobic environment is ensured by the linear diaphragm blower
that, connecting to the tubular fine bubble diaphragm air diffuser
on the bottom of the container, ensures the oxygenation of the
system. These aerobic bacteria (that consume oxygen for their
growth) adhere to the random fill media and they feed on the
organic substances contained in wastewater, purifying it.
Maintenance
For the correct management of the FPAI SUPERIOR and to achieve
the required purification results, please follow these guidelines:
•
Regularly inspect the FPAI SUPERIOR to check that there is
no gross material received accidentally to clog the pipes;
•
Regularly check that no anomalies have occurred to the
electrical panel if present;
•
Verify that the diaphragm blower works properly, that is,
movement must be observed in the volume of oxidation
coinciding with the operating time;
•
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
Air blown aerobic percolating filter manufactured in rotational
polyethylene for secondary treatment of residential black water.
Monolithic structure, free of joints and reinforcement, with entry and
exit hole, with plastic random fill media with a specific surface area
of 120 m
2
/m
3
, linear diaphragm blower connected to one or more
air tubular diffusers and inspection and sampling lids. Suitable for
underground installation. The aerobic environment is ensured by the
linear diaphragm blower (or side channels depending on the model)
that, connecting to the tubular fine bubble diaphragm air diffuser on
the bottom of the container, ensures the oxygenation of the system.
The plant has been designed in compliance with the indications given
by experience, and in particular, it has an oxidation time of about
15 hours and an airflow supplied of approximately 0.45 m
3
/h for
Population Equivalent.
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
Retention time in the treatment stage
h
approx. 15
Air flow supplied to the process per P.E.
m
3
/h
0,45
Oxygen fed to the system per P.E.
m
3
/h
0,09
Plant for domestic use, drain into the ground composed of the DG, IMHOFF, 3) FPAI SUPERIOR models
1
2
3
1
2
3
Figure 7
41
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