A. INSTALLATION GUIDE 2. OPERATING PRINCIPLE OF ECOROCK 700->900 UNITS
PAGE
9 / 47
Installation and User guide – ECOROCK 700 to 900 Units – 05-12-2016
2.
Operating principle of an ECOROCK Sewage Treatment Plant
A BIOROCK system is composed of a Primary tank and an ECOROCK treatment unit. Initially the raw
sewage enters the primary tank to provide separation and the breakdown of organic solids (Primary
Treatment). The sewage then passes through an effluent filter before discharging into the ECOROCK
Treatment Unit which incorporates the well proven aerobic digestion process (Secondary Treatment)
and filtration process (Tertiary Treatment).
2.1 THE PRIMARY TANK
The effluent (domestic wastewater composed of black water: origin toilets – and grey water: origin
kitchen, bathroom, laundry) enters the primary tank. This Primary Tank carries out the first basic
phase of wastewater treatment, that is separation of solids and fats by flotation (formation of a
grease layer) and by clarification (the suspended solids sink to the bottom of the tank by natural
settlement). Separated solids building up at the bottom of the primary compartment are called
“primary sludge”. This sludge breaks down in time by anaerobic digestion.
The primary tank should always be equipped with an efficient effluent filter. This filter holds back
remaining suspended solids, fats and other floating matter which enables a higher quality of pre-
treatment.
2.1
.
1
Ventilation of the Primary Tank
Any Primary tank should have a proper unencumbered low level and high level vent. The low level
vent should be connected directly on the outlet side of the tank and the high level on the inlet side
and should not be positioned more than 10 m
1
from the tank and at a minimum height of 4 m
1
with
a wind driven ventilator also fitted. The water inlet should be made air tight. All ventilation should
be checked with a smoke test.
2.1.2
Performance of the Primary Tanks (PT)
If the Primary Tank being used is not a BIOROCK tank, make sure that the quality of the effluent
from the PT meets the BIOROCK requirements. Proper ventilation of a PT is necessary, not only to
avoid smell problems, but also to evacuate the gasses produced. A Primary Tank generates
malodorous gases like hydrogen sulphide (H
2
S). Ventilation of the gasses is necessary to prevent
H
2
S being transformed into harmful sulphuric acid (H
2
SO
4
). Sulphuric acid will harm the biological
process and can cause degradation of the BIOROCK Media.
BIOROCK requires the following performance of a PT in front of the ECOROCK unit:
Composition of normal domestic wastewater (according to EN12566-3+A2 Annex B.3.2):
Variation
BOD
5
*
1
:
150 - 500
mg O
2
/l
COD
*
1
:
300 – 1000
mg/l
S.S.:
200 - 700
mg/l
KN:
25 - 100
mg/l
NH
4
-N:
22 - 80
mg/l
P-Total:
5 - 20
mg/l
*
1
: The ration between BOD
5
and COD should always be < 2
