Premium
Oxygen Transport through Aquatic Macrophytes: The Role in Wastewater Treatment
Author(s) -
Reddy K. R.,
D'Angelo E. M.,
DeBusk T. A.
Publication year - 1990
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1990.00472425001900020011x
Subject(s) - effluent , eichhornia crassipes , aeration , macrophyte , wastewater , sewage treatment , biochemical oxygen demand , aquatic plant , sewage , environmental chemistry , environmental science , environmental engineering , chemistry , chemical oxygen demand , biology , ecology , organic chemistry
Laboratory experiments were conducted to determine the effectiveness of three floating and six emergent aquatic macrophytes in improving domestic wastewater quality, based on their capacities for O 2 transport into the effluent. Oxygen transport into the rooting zone of the plants created an oxidized microenvironment, thereby stimulating C and N transformations critical to wastewater treatment. Plants were cultured in flasks containing deoxygenated primary and secondary sewage effluent for an 8‐d period. Oxygen transport by the plants was measured in terms of both O 2 consumed by the effluent (biological O 2 demand reduction—BOD 5 ) and increased effluent dissolved O 2 . Two floating plants, pennywort ( Hydrocotyle umbellata L.) and waterhyacinth [ Eichhornia crassipes (Mart.) Solms], and the emergent plants pickerelweed ( Pontederia cordata L.) and common arrowhead ( Sagittaria latifolia L.), were superior in improving primary sewage effluent quality, by reducing BOD 5 up to 88%, NH 4 ‐N up to 77%, and increasing dissolved O 2 up to 6.1 mg L −1 . Nitrification rates in pennywort‐ and water hyacinth‐based water treatment systems were calculated to be in the range of 12 to 47 kg NH 4 ‐N ha −1 d −1 . Oxygen transport through plants accounted for up to 90% of the total O 2 transported into the effluent. In separate batch experiments, the effectiveness of diffuse mechanical aeration (5 and 50 mL air min −1 ) and of biological aeration (O 2 transport by selected plants including pennywort, waterhyacinth, pickerelweed, and common arrowhead) on the rate of contaminant removal from deoxygenated primary sewage effluent were compared for a 26‐d period. Biological and mechanical aeration effected similar BOD 5 removal. First‐order reaction rate constants for BOD 5 removal were from 0.0066 to 0.0079 h −1 and from 0.0041 to 0.0051 h −1 for biological and mechanical aeration, respectively. Rate constants for NH 4 ‐N removal were from 0.0024 to 0.0107 h −1 for the plant treatments. Virtually complete BOD 5 removal occurred in biological and mechanical aeration treatments within 20 d. Complete nitrification of NH 4 ‐N had occurred within 12 d after mechanical aeration was initiated, but subsequent N‐loss by denitrification was inhibited. In the biological aeration treatments, negligible effluent (NO 3 + NO 2 )‐N levels were measured, but 65 to 100% NH 4 ‐N loss occurred both by plant assimilation and by sequential nitrification‐denitrification reactions.