Carvalho VCF, Kessler M, Fradinho JC, Oehmen A, Reis MAM. Achieving nitrogen and phosphorus removal at low C/N ratios without aeration through a novel phototrophic process.
Sci Total Environ 2021;
793:148501. [PMID:
34171805 DOI:
10.1016/j.scitotenv.2021.148501]
[Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 06/12/2021] [Accepted: 06/13/2021] [Indexed: 06/13/2023]
Abstract
Conventional wastewater treatment technologies for biological nutrient removal (BNR) are highly dependent on aeration for oxygen supply, which represents a major operational cost of the process. Recently, phototrophic enhanced biological phosphorus removal (photo-EBPR) has been suggested as an alternative system for phosphorus removal, based on a consortium of photosynthetic microorganisms and chemotrophic bacteria, eliminating the need for costly aeration. However, wastewater treatment plants must couple nitrogen and phosphorus removal to achieve discharge limits. For this reason, a new microalgae-bacterial based system for phosphorus and nitrogen removal is proposed in this work. The photo-BNR system studied here consists of a sequencing batch reactor operated with dark anaerobic, light aerobic, dark anoxic and idle periods, to allow both N and P removal. Results of the study show that the photo-BNR system was able to remove 100% of the 40 mg N/L of ammonia fed to the reactor and 94 ± 3% of the total nitrogen (Influent COD:N ratio of 300:40, similar to domestic wastewater). Moreover, an average of 25 ± 9.2 mg P/L was simultaneously removed in the photo-BNR tests, representing the P removal capacity of this system, which exceeds the level of P removal required from typical domestic wastewater. Full ammonia removal was achieved during the light phase, with 67 ± 5% of this ammonia being assimilated by the microbial culture and the remaining 33 ± 5% being converted into nitrate. The assimilated P corresponded to 2.8 ± 0.23 mg P/L, which only represented, approximately, 1/9 of the P removal capacity of the system. Half of the nitrified ammonia was subsequently denitrified during the dark anoxic phase (50 ± 24%). Overall, the photo-BNR system represents the first treatment alternative for N and P from domestic wastewater with no need of mechanical aeration or supplemental carbon addition, representing an alternative low-energy technology of interest.
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