Abstract
Conventional biological nutrient removal processes in municipal wastewater treatment plants are energy-consuming, with oxygen supply accounting for 45–75% of the energy expenditure. Many recent studies examined the implications of the anammox process in sidestream wastewater treatment to reduce energy consumption, however, the process did not successfully remove nitrogen in mainstream wastewater treatment with relatively low ammonia concentrations. In this study, blue light was applied as an inhibitor of nitrite-oxidizing bacteria (NOB) in a photo sequencing batch reactor (PSBR) containing raw wastewater. This simulated a biological nitrogen removal system for the investigation of its application potential in nitrite accumulation and nitrogen removal. It was found that blue light illumination effectively inhibited NOB rather than ammonia-oxidizing bacteria due to their different sensitivity to light, resulting in partial nitrification. It was also observed that the NOB inhibition rates were affected by other operational parameters like mixed liquor suspended solids (MLSS) concentration and sludge retention time (SRT). According to the obtained results, it was concluded that the process efficiency of partial nitrification and anammox (PN/A) could be significantly enhanced by blue light illumination with appropriate MLSS concentration and SRT conditions.
Highlights
The concentration profiles of nitrogen compounds were monitored to understand the characteristics of partial nitrification in the photo sequencing batch reactor (PSBR) illuminated by blue light
Considering the results obtained, it was concluded that partial nitrification was performed in the reactor because of the relatively dominant ammonia-oxidizing bacteria (AOB) community caused by nitrite-oxidizing bacteria (NOB) inhibition with blue light
In the resulted in an ~20% lower removal rate of photo batch reactor (PBR), there was an accumulation of NO2 − -N, but the concentration of NO3 − -N did not a) Bacterial communities were analyzed by for biomass obtained at days
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The mechanisms of NO2 − accumulation resulting in PNMs in stratified open-oceanic water columns have been studied. Two main mechanisms, such as photoinhibition of nitrifying bacteria and NO2 − release by phytoplankton, were found [8,9]. The first mechanism involves the separated oxidation of NH4 + and NO2 − during the nitrification process This results in the accumulation of NO2 − when the microbial populations, such as ammonia-oxidizing bacteria (AOB) and NOB, have different sensitivities to light or different substrate demands within the water column [10,11]. The physiological responses of nitrifying bacteria and the changes in the bacterial community by blue light were monitored to confirm whether blue light may be a new type of NOB inhibition factor for mainstream, partial nitritation
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