Abstract
Denitrifying phosphorus removal was realized in sequencing batch reactors using different carbon sources (acetate, propionate, and a mixture of acetate/propionate). Nutrient removal and nitrous oxide (N2O) production were investigated, and the factors affecting N2O production were explored. Nitrogen removal was 40.6% lower when propionate was used as the carbon source instead of acetate, while phosphorus removal was not significantly different. N2O production was greatly reduced when propionate was used as the carbon source instead of acetate. The emission factor in the propionate system was only 0.43%, while those in the acetate and mixed-carbon source system were 16.3% and 1.9%, respectively. Compared to the propionate system, ordinary heterotrophic organisms (i.e., glycogen-accumulating organisms) were enriched in the acetate system, explaining the higher N2O production in the acetate system. The lower nitrite accumulation in the propionate system compared to the acetate system was the dominant factor leading to the lower N2O production.
Highlights
In order to control the eutrophication in surface water, nitrogen and phosphorus are continuously removed from wastewaters in many countries
We investigated the long-term influences of organic substances on accumulation during anaerobic/anoxic/oxic sequencing batch reactors (SBRs) were established, and acetate, propionate, or a mixture of acetate and propionate was used as the carbon source, respectively
N2O production during denitrifying phosphorus removal (DPR) process was reduced when propionate was used as the carbon source instead of acetate
Summary
In order to control the eutrophication in surface water, nitrogen and phosphorus are continuously removed from wastewaters in many countries. Biological nutrient removal (BNR) is a widely applied process to simultaneously remove nitrogen and phosphorus through a combination of nitrification/denitrification and enhanced biological phosphorus removal (EBPR). The competition for carbon sources between the denitrification and EBPR processes limits the efficiency of nutrient removal and increases the cost (Wang et al 2015). Denitrifying phosphorus removal (DPR) is attracting considerable attention as a novel BNR process. In this process, denitrifying phosphorus-accumulating organisms (DPAOs) was enriched. It can use nitrite/nitrate instead of oxygen as the electron acceptor for phosphorous removal to achieve the simultaneous removal of nitrogen and phosphorus (Wang et al.2011). Compared to the conventional BNR process, DPR process exhibits reduced sludge production and lower demand for oxygen and carbon, making it suitable for treating wastewater with a low ratio of chemical oxygen demand (COD) to nitrogen
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