The influence of pH on the sodium removal rates of three crops grown in a brewery effluent treatment system

Richard P. Taylor, Clifford L.W. Jones and Mark Laing

Agricultural Water Management, 2019, vol. 226, issue C

Abstract: Cabbage (Brassica oleracea), saltbush (Atriplex nummularia) and Japanese millet (Echinochloa esculenta) were grown in recirculating hydroponic systems to determine their capacity to remove sodium from brewery effluent (BE). Each treatment was irrigated with post-anaerobically digested effluent, where the pH was either adjusted to 6.5 or unadjusted. The irrigation solutions from the hydroponic systems planted with saltbush had the lowest concentration of sodium (708.54 ± 6.18 mg/l), whereas the systems planted with millet and cabbage had a similar sodium concentration (729.01 ± 5.17 mg/l). The pH adjustment of BE significantly decreased the sodium leaf content of cabbages, saltbush and millet plants by an average of 633.33 mg/kg. This could have been due to two reasons; firstly the addition of H + would decrease the ratio of Na/positively charged ions thus, decreasing the sodium electrochemical gradient between the root plasma and rhizosphere; and secondly, the addition of H + may enhance sodium efflux. Halophytes such as saltbush have been shown to assimilate sodium from soil water complexes. Saltbush planted hydroponic systems resulted in the lowest increase in effluent sodium concentration which corresponded to saltbush leaf tissue having the highest sodium concentration. However, the sodium concentration in all hydroponic systems increased during each cycle. The rate of sodium assimilation into the halophyte plant tissue was slower than the concentrating effect caused by evapotranspiration, which accounted for the increase in sodium in all the treatments. Hydroponic systems, which aim to remove sodium from effluent, need to be designed to minimize evaporation.

Keywords: Phytoremediation; Halophytes; Hydroponics; Wastewater (search for similar items in EconPapers)
Date: 2019
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Persistent link: https://EconPapers.repec.org/RePEc:eee:agiwat:v:226:y:2019:i:c:s0378377419305840

DOI: 10.1016/j.agwat.2019.105813

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