R e q u i r e d s u r f a c e a r e a = 0.056 k g B O D d ÷ 0.004 k g B O D m 2 ⋅ d = 14 m 2 {\displaystyle Required\ su{\mathit {rf}}ace\ area=0.056\ {\frac {kgBOD}{d}}\div 0.004\ {\frac {kgBOD}{m^{2}\cdot d}}=14\ m^{2}}