Field study on N₂O emission from subsurface wastewater infiltration system under variable loading rates and...

Area of Science:

• Environmental Engineering
• Wastewater Treatment Technologies
• Greenhouse Gas Emissions

Background:

• Subsurface wastewater infiltration (SWI) systems are vital for wastewater treatment.
• Nitrous oxide (N₂O) is a potent greenhouse gas emitted during wastewater treatment.
• Understanding factors influencing N₂O emissions in SWI systems is critical for environmental protection.

Purpose of the Study:

• To investigate the impact of influent loadings and drying-wetting cycles on N₂O emissions in SWI systems.
• To quantify N₂O emissions under various operational conditions.
• To determine optimal loading ranges and drying-wetting cycles for minimizing N₂O production.

Main Methods:

• Field study employing static chambers and gas chromatography to quantify N₂O emissions.
• Systematic variation of hydraulic loading (HL) and pollutant loading (PL).
• Analysis of pollutant removal ratios (COD, NH₄⁺-N, NO₃^--N, TN) alongside N₂O emissions.

Main Results:

• N₂O conversion rate decreased with increasing hydraulic loading (HL).
• N₂O conversion rate initially increased with pollutant loading (PL) then decreased, indicating nitrification-denitrification interaction.
• Optimal ranges identified: HL 0.08-0.12 m³/m²·d, PL 3.2-3.7 g N/m²·d, and 12h:12h drying-wetting cycles.
• Influent nitrogen to N₂O conversion ratio in SWI systems ranged from 4.5% to 7.0%.

Conclusions:

• Hydraulic loading, pollutant loading, and drying-wetting cycles significantly influence N₂O emissions in SWI systems.
• Optimized operational parameters can effectively reduce N₂O production during wastewater treatment.
• The study provides crucial data for designing and operating SWI systems with reduced environmental impact.