Designing procedure of cascade aeration system
| Cascade aeration = H = R–1/0.11 a b (1 + 0.046 T), R = deficit ratio = Cs-Co/Cs-C Cs = a DO conc. at temp. T (mg/L) Co = DO conc. of influent (mg/L) = 1 mg/L C = required final DO level after post aeration (mg/L) = 6 mg/L Determine the ‘a’ (water quality parameter) -, ‘b’ (weir geometry parameter (for steps)) and Cs values from (Metcalf & Eddy 2003) Appendix D and T selected was 20 °C So, cascade height for 20 °C = H = 2.7 m and Cascade height for 25 °C = H = 3.3 m If height is 1.8–2.4 m then from Table 5–34 (Metcalf & Eddy 2003) step height is 22.3 cm, step length is 33 cm and inclination angle is 40° Thus, we use height of 2.6 m with 11 steps and width of 0.22 m and 0.3 m. |
| Cascade aeration = H = R–1/0.11 a b (1 + 0.046 T), R = deficit ratio = Cs-Co/Cs-C Cs = a DO conc. at temp. T (mg/L) Co = DO conc. of influent (mg/L) = 1 mg/L C = required final DO level after post aeration (mg/L) = 6 mg/L Determine the ‘a’ (water quality parameter) -, ‘b’ (weir geometry parameter (for steps)) and Cs values from (Metcalf & Eddy 2003) Appendix D and T selected was 20 °C So, cascade height for 20 °C = H = 2.7 m and Cascade height for 25 °C = H = 3.3 m If height is 1.8–2.4 m then from Table 5–34 (Metcalf & Eddy 2003) step height is 22.3 cm, step length is 33 cm and inclination angle is 40° Thus, we use height of 2.6 m with 11 steps and width of 0.22 m and 0.3 m. |