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 = 10m3/hr @ 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 = 22.86 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

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 0.008 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 + 101.35)/ 101.35 (SI Unit) = (p + 14.7)/ 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).

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