Abstract
Improving the effect of microbial denitrification under low-temperature conditions has been a popular focus of research in recent years. In this study, graphene oxide (GO)-modified polyvinyl-alcohol (PVA) and sodium alginate (SA) (GO/PVA–SA) gel beads were used as a heterotrophic nitrification–aerobic denitrification (HN–AD) bacteria (Pseudomonas fluorescens Z03) carrier to enhance nitrogen removal efficiency levels at low temperatures (6–8°C). The removal efficiency of and and the variations in concentrations of extracellular polymeric substances (EPS) under different GO doses (0.03–0.15 g l−1) were studied. The results indicated that the addition of GO can improve the efficiency of nitrogen removal, and the highest removal efficiency level and highest carbohydrate, protein, and total EPS content levels (50.28 mg, 132.78 mg and 183.06 mg (g GO/PVA–SA gel)−1, respectively) were obtained with 0.15 g l−1 GO. The simplified Monod model accurately predicted the nitrogen removal efficiency level. These findings suggested that the application of GO serves as an effective means to enhance nitrogen removal by stimulating the activity of HN–AD bacteria.
Highlights
The heterotrophic nitrification–aerobic denitrification (HN–AD) process is widely considered one of the most ground-breaking technological innovations for removing nitrogenous pollutants from sewage
The modified gel beads under optimized preparation conditions are shown in figure 2, and their apparent characteristics are shown in table 1
graphene oxide (GO)/PVA–sodium alginate (SA) gel beads were used as Pseudomonas fluorescens Z03 carriers to enhance nitrogen removal efficiency levels at low temperatures (6–8°C)
Summary
The heterotrophic nitrification–aerobic denitrification (HN–AD) process is widely considered one of the most ground-breaking technological innovations for removing nitrogenous pollutants from sewage. This removal process involves heterotrophic microorganisms oxidizing ammonia nitrogen into nitrate nitrogen and nitrous nitrogen while nitrous nitrogen is reduced to nitrogen by anti-nitrification in the oxygenated environment. With significant nitrogen removal capabilities, these functional bacterial strains have a higher growth rate than autotrophs and can resist high organic loads [7,8]. The HN–AD process offers many potential advantages, some researchers have indicated that the survival, growth and reproductive characteristics of microorganisms could be inhibited at low temperatures, which might create difficulties for highly nitrogenous wastewaters in the biodegradation stage [9]
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