Table 4. Variation in unit electricity consumption for different sizes of wastewater treatment plants (Goldstein and Smith 2002b). Larger wastewater treatment plants exhibit economies of scale with lower energy requirements per volume of wastewater treated.

  Electricity Consumption (kWh/ML)†
Wastewater Treatment Plant Size
(ML/d)‡
Trickling Filter Activated Sludge Advanced Wastewater Treatment Advanced Wastewater Treatment with Nitrification
3.8 480 590 690 780
19 260 360 420 510
38 230 320 370 470
76 200 290 340 440
190 180 280 320 420
380 180 270 310 410


†kWh/ML: kilowatt-hours per megaliter
‡ML/d: megalitres per day