ALLODUST augmented activated sludge single batch anaerobic reactor (AS-SBAnR) for high concentration nitrate removal from agricultural wastewater

Highlights: • High NO⁻₃-N concentrations in water can contribute to eutrophication. • A new medium was developed to enhance the NO⁻₃-N removal. • ALLODUST can increase the NO⁻₃-N removal efficiency by 77%. • N₂O emission was dropped by 80% in the system contained ALLODUST. Nitrate is among the most widespread contaminants that threaten water bodies and waterways. Under favourable environmental conditions, high nitrate concentrations in water can contribute to eutrophication, thus presenting a high potential for risk to ecosystems and human health. Low-cost allophanic soil material and carbon-based bio-wastes have great potential to reduce nutrient concentrations from contaminated waters. This study investigated the mechanisms that underpin the reduction of nitrate concentrations and nitrous oxide (N₂O) emission in the presence of novel developed media in an activated sludge process. A new operating approach, employing a newly developed media (ALLODUST), was evaluated for enhanced NO⁻₃-N removal from agricultural wastewater. Two anaerobic-aerobic batch reactors were developed, where the coupled bottom aeration method was used for efficient agitation and aeration in the aerobic reactor. The reactor was run at high NO⁻₃-N concentrations (110 mg L⁻¹), under anoxic conditions at low- to long-term contact times (2, 12, and 22 h), while the aerobic period (clarification) was constant for all the experimental designs (2 h). ALLODUST retained its integrity and stability over the long-term operation. Low ALLODUST concentrations (5.95 g L⁻¹) removed 87% of the NO⁻₃-N from the wastewater within 12 h. Further exploration revealed that the same amount of the media was optimal for decreasing N₂O emissions from the anaerobic activated sludge reactor by 80%.