1. Process Performance Improvement Study on DAF
The main purpose of the process performance improvement study is to
determine the most optimum and effective DAF operating parameters and the study
was separated into 3 stages as follows:
i. Design calculation review to determine the area of optimization to be
focused in.
ii. Mechanical tuning adjustment study.
iii. Chemical tuning adjustment study
Based on the above design input, the constructed DAF is having
characteristics as follows:
Recirculation pump specification = 4 bar (Dry
mounted/ vertical multistage
pump)
Constructed DAF tank surface area = 6.0 m2
Constructed saturation tube volume = 0.15 m3
Air compressor capacity = 751 lit./min (2,703,600 l/day-
Single stage type)
Design Calculation Review
The original design calculation is shown in Appendix F. The design input of
the DAF system at the initial stage is based on 600m3/day of incoming wastewater flow rate and 200mg/l TSS. And the design output from Appendix F can be
summarized as follows:
Then, a simulation design calculation on the DAF based on the current
WWTP operating condition of 350m3/day incoming wastewater flow rate and 2,000
mg/l of TSS was carried out. The result of calculation is shown in Appendix G and it
is summarized as follows:
Recirculation rate = m3/hr
Recirculation pump pressure = 3 bar
Required surface area = 6.93 m2
Saturation tube volume = 0.76 m3
Air volume required = 87,920 lit./day
When actual constructed DAF specification is compared with the
specification from the design simulation output based on currently assumed WWTP
operating condition, it shows that a lot of compartments of the DAF needed to be
modified or replaced. Based advice from the Chief Designer (Mr. Jeff Ong), the DAF
was operated first without doing any modifications because a lot of design
assumptions at the initial design stage is far higher and has a very high safety factor.
This is mainly due to lacking of wastewater during at the early design stage. As such,
a proper experiment cannot be carried out to determine the design assumptions and
the designer had to set a higher design assumption based on his own experiences.
Recirculation rate = 3.92 m3/hr
Recirculation pump pressure = 3 bar
Required surface area = 5.36 m2
Saturation tube volume = 0.13 m3
Air volume required = 15,072 lit./day

2. To determine a proper design parameters, an experiment using a laboratory
flotation cell is normally needed to be carried out to be used to determine the A/S
ratio- “Volume of air to the mass of solids ratio” (Higbie, 1935), . In the design stage,
the designer assume the optimum A/S ratio to be mL/mg, surface loading rate
of 90 L/m2/min and air saturation time of 120s. These data are gotten from the Joint-
Venture partner associate in Denmark who was previously involved in the design and
construction of DAF in coffee production factory’s WWTP and all these design
assumptions have a high safety factor.
Design Calculation Explanation
The design calculation shown in Appendix F and G is actually based on the
equation as follows:
Equation showing the relationship between A/S ratio and the solubility of air,
the operating pressure, and the concentration of solids for a system in which
there is a pressurized recycle flow(Tchobanoglous et al, 2003):
A / S = [1.3 sa ( f P - 1 )R ] / ( Q Sa )
Where,
A/S = air to solids ratio, mL (air)/ mg (solids)
sa = air solubility, mL/L
f = fraction of air dissolved at pressure P, usually 0.5
P = pressure, atm.
= (p )/ (SI Unit)
= (p )/ 14.7 (US customary unit)
p = gage pressure, kPa (ib/in2 gage)
Sa = influent suspended solids, g/m3 (mg/l)
R = pressurized recycle, m3/d
Q = mixed-liquor flow, m3/d
For a better understanding of the formula, kindly please refer to Metcalf &
Eddy- Chapter 5. Besides that, additional information about the use of flotation for
treating oily wastewater can be found in Eckenfelder (2000).

3. Also how they got this
Parameters
Is that from experience,
or how?
Is this refers to Influent Oil
and Grease Concentration