Diesel Exhaust Fluid – Innovative Stormwater Treatment Trials for High Ammoniacal Nitrogen Concentrations
Stormwater Conference
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Stormwater360 have been working on a treatment solution for high ammoniacal nitrogen concentrations (38 to 132 mg/L) that have been measured in stormwater effluent discharges downstream of existing oil/water separators at refueling truck stops. The high concentrations were identified to originate from urea deposited on the pavement during the Diesel Exhaust Fluid refueling process.
Aquatic organisms are sensitive to ammoniacal nitrogen concentrations and the concentrations entering waterways from truck refueling sites well exceed safe levels for both freshwater and saline environments. ANZECC guidelines list ambient water trigger values at 0.01 and 0.021 mg/L of ammoniacal nitrogen for upland and lowland rivers respectively. The United States Environmental Protection Agency specify acute (1-hour averaged) trigger values for Total Ammoniacal Nitrogen in freshwater and saline environments at 17 mg/L and 11 mg/L respectively.
The paper presents three stages of testing: -
Stage 1 focused on identifying the amount of zeolite media that was required to observably reduce the concentration of ammoniacal nitrogen in solution. At a ratio of 1g of zeolite to 11mg of ammoniacal nitrogen, ammoniacal nitrogen concentrations were observed to decrease from 132 mg/L to 3 mg/L (98% reduction) over 24 hours.
Stage 2 determined the adsorption rate of two different zeolite media blends followed an exponential decay curve relationship with 50% of the total adsorption occurring within the first 4% of the test duration.
Stage 3 established that ammoniacal nitrogen could be removed in a continuous flow arrangement. The testing was conducted using a horizontal flow column (HFC). Influent with 42 mg/L of ammoniacal nitrogen was gravity fed into the HFC at three different flow rates; 1.1, 0.57 and 0.23 l/min.
The research has shown that it is viable to reduce ammoniacal nitrogen concentrations in stormwater effluent flows from truck refueling stops to below the USEPA acute trigger values for freshwater using a proprietary flow-based zeolite media StormFilter cartridge treatment device.