4.4.3 Biological Treatment
Wastewater undergoes biological treatment after chemical treatment. Domestic
wastewater of the factory is also taken directly to the biological treatment. Urea
and diammonium are added to the wastewater to ensure there is a sufficient amount
of nitrogen and phosphorus phosphate which is necessary for microorganisms in
biological treatment. Carbon source is the organic matter present in the wastewater.
Biological treatment is carried out in two stages: facultative and completely mixed
extended aeration tanks consisting of two independent compartments are served for
this purpose. In the first stage, some portion of the biological and chemical load of
the wastewater is removed in the facultative aeration tank by aerobic microorganisms present at the upper level of the tank to which oxygen is provided with the help
of the surface aerators and by anaerobic microorganisms present at the lower/bottom
level of the tank. Then, wastewater is taken into the first biological clarification basin
and the biomass is removed from wastewater by settling. The supernatant of partially
treated wastewater is directed from this tank to the second completely mixed tank.
The concentration of biomass settled as the waste sludge is measured frequently and
is recycled to the facultative aeration pond. The excess sludge is removed from the
system when the biomass concentration increased.
In the second stage, the organic pollution load of wastewater is removed by
aerobic microorganisms in a completely mixed aerated tank which is mixed by
diffused air provided by the surface and submerged aerators placed at the top and
bottom of the tank, respectively. The mixture of wastewater and activated sludge is
sent to final sedimentation tank, and the excess waste activated sludge settled to the
bottom of the tank is removed while a part of it is recycled back to the aeration tank.
After sedimentation pool of clear supernatant is discharged. There is a sand filtration
unit at the WWTP before clear supernatant storage tank, but in the current case it is
not needed to be used.
4.4.4 Sludge Removal and Dewatering Process
Sludge produced in this WWTP consisted of two different characteristics: chemical
and biological sludge. Sludge coming from chemical treatment was stored in the
sludge thickener for a while for thickening and settlement purposes. Supernatant
above the thickened sludge is recycled back to the chemical treatment while bottom
thickened sludge is taken into bags wherein the sludge is more concentrated. The
excess sludge coming from biological treatment is taken into sludge drying bed
which is a kind of big tank. Sludge dried there is sold to a fertilizer company together
with the sludge of chemical treatment at certain times. Treatment plant flow diagram
and the sampling points taken for wastewater characterization are shown in Fig. 8.9.
Table 8.14 shows the sizes of the tanks and basins in the treatment plant.
According to the results of that study, corn oil refining wastewater treatment
efficiency was 98.1%, 98.5%, 98.2%, 95.47%, and 86.8% for total COD, BOD 5 ,
366
D. Kaya and Y.-T. Hung
Wastewater undergoes biological treatment after chemical treatment. Domestic
wastewater of the factory is also taken directly to the biological treatment. Urea
and diammonium are added to the wastewater to ensure there is a sufficient amount
of nitrogen and phosphorus phosphate which is necessary for microorganisms in
biological treatment. Carbon source is the organic matter present in the wastewater.
Biological treatment is carried out in two stages: facultative and completely mixed
extended aeration tanks consisting of two independent compartments are served for
this purpose. In the first stage, some portion of the biological and chemical load of
the wastewater is removed in the facultative aeration tank by aerobic microorganisms present at the upper level of the tank to which oxygen is provided with the help
of the surface aerators and by anaerobic microorganisms present at the lower/bottom
level of the tank. Then, wastewater is taken into the first biological clarification basin
and the biomass is removed from wastewater by settling. The supernatant of partially
treated wastewater is directed from this tank to the second completely mixed tank.
The concentration of biomass settled as the waste sludge is measured frequently and
is recycled to the facultative aeration pond. The excess sludge is removed from the
system when the biomass concentration increased.
In the second stage, the organic pollution load of wastewater is removed by
aerobic microorganisms in a completely mixed aerated tank which is mixed by
diffused air provided by the surface and submerged aerators placed at the top and
bottom of the tank, respectively. The mixture of wastewater and activated sludge is
sent to final sedimentation tank, and the excess waste activated sludge settled to the
bottom of the tank is removed while a part of it is recycled back to the aeration tank.
After sedimentation pool of clear supernatant is discharged. There is a sand filtration
unit at the WWTP before clear supernatant storage tank, but in the current case it is
not needed to be used.
4.4.4 Sludge Removal and Dewatering Process
Sludge produced in this WWTP consisted of two different characteristics: chemical
and biological sludge. Sludge coming from chemical treatment was stored in the
sludge thickener for a while for thickening and settlement purposes. Supernatant
above the thickened sludge is recycled back to the chemical treatment while bottom
thickened sludge is taken into bags wherein the sludge is more concentrated. The
excess sludge coming from biological treatment is taken into sludge drying bed
which is a kind of big tank. Sludge dried there is sold to a fertilizer company together
with the sludge of chemical treatment at certain times. Treatment plant flow diagram
and the sampling points taken for wastewater characterization are shown in Fig. 8.9.
Table 8.14 shows the sizes of the tanks and basins in the treatment plant.
According to the results of that study, corn oil refining wastewater treatment
efficiency was 98.1%, 98.5%, 98.2%, 95.47%, and 86.8% for total COD, BOD 5 ,
366
D. Kaya and Y.-T. Hung