The ETP is made up of
different stages that ensure that the effluent from the company is well treated
before sending out to the environment. The stages are listed below and its
diagram.
The stages are:
·
Static point
·
Self clearing device (strainer
Device )
·
Oil separation tank
·
Equalization tank
·
Biological tank A
·
Sedimentation Tank
·
Biological tank (B)
·
Final clarification
Firstly, the Nigerian
bottling company has a well organized, functional plant that is
used to treat the effluent from the
company and safety procedure are followed from the entrance of the gate
to the plant location which is done
by a yellow marked line that allows for
a walkway to the plant.
The various components of a
effluent treatment plant have been derived from unit operations. Every unit
operation aims at the removal or reduction of specific objectionable substances
to the desired degree. Depending upon
the kinds and magnitudes of the treatment required, proper unit operations are
selected and arranged in the proper
sequential order for the purpose of modifying the quality of raw water to meet
desired standards.
The company flowrate of
effluent into the plant is 200m3
/hr and the discharge ratio of influent to the environment is 65 to 70m3 /hr and the rest 130m3 /hr is recycled and surface aerators
are used in the tank to remove the odours and
colour from the tank.
The two process used in
these pant is : the constant flow pump and valve
-
The constant flow /buffer tank: Help to
checkmate the rate of flow of the
effluent in the tank while
-
the valve act as an aid for serving there by passing a less concentrated effluent
a flow directly to the biological
tank B when serving and maintenance are needed
The effluent from the Nigerian bottling company
contains pieces of broken
bottles, oil, chemical and
pipes which are screen at the unit operation section known as the static point.
The screening removes or hold
back the floating matter. The NaOH (costic
soda) or Sodium Hydroxide in the
effluent which is poisonous and its basic in nature and will be neutralized by an acid (HCL) thereby
forming salt and water.
While the screening of the
floating matter are holdback, the rest flows down to the self clearing device where plain
sedimentation take place
Plain sedimentation: Simply means that sedimentation is not effected by
the addition of chemical or other
processed in a relatively quiescent state, solids having specific gravity greater than that of
the liquid containing them settle while
solids with specific gravity
lower than that of the liquid
tends to rise. Though the debris are
removed but the effluent still
contain sand and oil. But on reaching the strainer device some of the
debris that escaped are been
trapped by the screen at the strainer device which is
3mm apart each other. It is normally
taken as a batch separation process where some of the sand which where unable
to pass the hole are retain but rest are sent to the oil separation unit but
due to the fact that pressure of effluent
entering into the oil separation tank is on high pressure it tends to push and missed with the oil that is meant to settle after the first process tank but on the third process
tank the separation takes place settling
the sand and floating the oil at the
surface of the third process tank of the
oil separation tank which is
scoop out with net, the water in-between the oil and sand flows into the
fourth stage known as the equalization tanks.
After the separation of sand and oil
the treatment of the effluent start properly at
these stage, the water that flows
into the equalization tank still contain chemical known as sodium hydroxide which is transferred into
the tank. The moment you start agitation
in the equalization tank it helps to reduce the concentration of sodium hydroxide
(NaOH) which is base in nature then manually by hand hydrochloric acid is
coagulated by allowing it to dozed into
the equalization tank. To determine or know the quantity of HCL. (hydrochloric
acid) to be applied in the equalization
tanks is by simply dipping in a meter reader in the tank at the ratio of 1000m3 water you apply 600 liter of hydrochloric acid which is a
standard but can be changed depending
the among of sodium hydroxide present in the equalization tank. Micro-organisms that are present in the effluent are enriched in the Biological
Process A with urea and decomposition process take place producing water, biomass
and carbon iv oxide. carbon iv oxide easily escape to the
atmosphere and leaving behind biomass and water which either sent to sedimentation tank for separation or
to the
belt press room where sludge
is abstracted from biomass and it is
pressed to a sludge cake which is use as
a manure in agriculture. Before the sludge
cake is produced it pass through a ploymaker
unit where polyelectrolyte coagulate
with biomass before sending it to the sludge belt press
at the sedimentation tank which is the sixth stage, normally defined as
a separation of wanted from unwanted.
Sedimentation tank may be considered to consist of four part
·
inlet zone where influent flow and suspended solids disperse over
·
A settling zone where suspended solid settle
·
A bottom zone where settled particles accumulate and are withdrawn
·
An outlet zone through which the
effluent flow out
In the sedimentation tank
there is a cylindrical scaper bridge
machine that rotate and collect the
scum to pit then the sludge (Biomass) to
sludge tank and it take maximum of 6
month/ one year for a sludge to be matured
before sending it to belt press
room for sludge cake.
The effluent is then sent to
the biological tank B which is the
seventh stage and a surface aerator is turned on to stirs, by removing the
odours. The final stage which is the final classification tank where
chlorine is added before send it fish pond or to the lake /river around the
company known as the AJARI RIVER.
Below is the data log for
Nigerian bottling company production record is attached and it shows the weekly report
and necessary precaution obtained if need be.
The following are the
challenges and precautions taken in the effluent treatment plant
CHALLENGES:
-
At the static point the effluent
discharged was overflowing it channel reason being that the pipe was not wide
enough to accommodate the flow
-
At the time of inspection the (HCL) hydrochloric acid needed to prevent the odour from the effluent was not available whereby causing un-conducive environment.
PRECAUTION
-
A wire gaze was constructed to reduce the flow rate coming into the pipes
-
Place order for the replacement of (HCL)hydrochloric acid which was not enough to neutralized
the base (NaOH) sodium hydroxide