Where nitrogen removal is important, the total nitrogen rate should be kept below 60 lb/ac-d (67 kg/ha-d). To determine the nitrogen loading rate from the hydraulic loading rate, use Equation 8.14:
C = Wastewater nitrogen concentration (mg/L).
D = Number of operating days per year.
For a typical municipal wastewater with 40 mg/L of total nitrogen and an SAT system operated 365 d/yr, the 60-lb/ac-d (67-kg/ha-d) nitrogen loading rate corresponds to a 200-ft/yr hydraulic loading rate.
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