45 40 35 30 25 Effluent oil and grease (mg/L) 20 15 10 5 3.5 0 0 0.5 1 1.5 2 2.5 3 Surface loading rate (gal/(min.ft)) Figure Q4-2: Hydraulic loading for oil removal A waste stream flow of 0.57 m/min and a temperature 39.4C contains significant quantities of ton emulsified oil and non-settleable suspended solids. At this temperature the solubility of oxygen = 18.6 mg/L and the fraction of saturation = 0.85. The concentration of oil is 120 mg/L. It is intended to reduce the oil to less than 20 mg/L. Laboratory studies for flotation showed: Alum dose = 50 mg/L Recycle pressure = 515 kPa abs. Solid sludge production = 0.64 mg/mg alum Total solid sludge concentration = 3 wt% The bench-scale batch flotation data and the hydraulic loading for oil removal are shown in Figure 2+1 [8 marks) [8 marks] [10 marks) [4 marks) and Figure Q4-2 respectively. Estimate: i) the recycle rate in m/min, ii) surface area of floatation unit in mand iii) Solid Sludge quantities generated in kg/d iv) Total volume of sludge in L/min