Abstract
Tertiary wastewater treatment could provide a reliable source of water for reuse. Amongst these types of wastewater treatment, deep-bed filtration of secondary effluents can effectively remove particles and organic matter; however, NH4+ and NO2− are not easily removed. This study examined the feasibility of stimulating microbial activity using hydrogen peroxide (H2O2) as a bio-specific and clean oxygen source that leaves no residuals in the water and is advantageous upon aeration due to the solubility limitations of the oxygen. The performance of a pilot bio-filtration system at a filtration velocity of 5–6 m/h, was enhanced by the addition of H2O2 for particle, organic matter, NH4+, and NO2− removal. Hydrogen peroxide provided the oxygen demand for full nitrification. As a result, influent concentrations of 4.2 ± 2.5 mg/L N-NH4+ and 0.65 ± 0.4 mg/L N-NO2 were removed during the short hydraulic residence time (HRT). In comparison, filtration without H2O2 addition only removed up to 0.6 mg/L N-NH4+ and almost no N-NO2−. A DNA metagenome analysis of the functional genes of the media biomass reflected a significant potential for simultaneous nitrification and denitrification activity. It is hypothesized that the low biodegradability of the organic carbon and H2O2 addition stimulated oxygen utilization in favor of nitrification, followed by the enhancement of anoxic activity.
Highlights
The tertiary and advanced treatment of wastewater improves water quality, enabling us to meet environmental concerns and find a potential source of water for reuse [1,2]
The system showed a significant removal of NO2− and NH4+ when H2O2 was added in comparison to the control
We suggest that the typical low biodegradability of the organic carbon at the secondary effluent, which was reflected in the low removal rate of the chemical oxygen demand (COD), BOD, and UVA254, mentioned earlier (Section 3.4, Figure A5a,b in the Appendix A) was a key parameter on the rates of heterotrophic activity [44]
Summary
The tertiary and advanced treatment of wastewater improves water quality, enabling us to meet environmental concerns and find a potential source of water for reuse [1,2]. The filtration of coagulated–flocculated effluent via high-rate deep-bed filters (velocities between 5 and 20 m/h) is widely used for tertiary wastewater treatment [3]. The removal mostly combines particles and some dissolved organic matter (15%–20%) [4]. A hybrid process of filtration and bioactivity, termed biofiltration, allows significant nutrient and organic matter removal in addition to particle filtration [5,6,7]
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