Potentials of using duckweed (Lemna gibba) for treatment of drainage water for reuse in irrigation purposes

• Published in: Desalination and water treatment Vol. 57; no. 1; pp. 459 - 467
• Main Authors: Allam, A., Tawfik, A., El-Saadi, A., Negm, A.
• Format: Journal Article
• Language: English
• Published: Abingdon Elsevier Inc 02-01-2016; Elsevier Limited
• Subjects: Ammonia; Aquatic plants; Arid regions; Constants; Continuous flow; Drainage; Drainage water; Duckweed; Duckweed-based treatment system; Effluent treatment; Effluents; Floating plants; HRT; Irrigation; Irrigation water; Nitrification; Ponds; Protein; Retention time; Wastewater treatment; HRT; Arid regions; Protein; Duckweed-based treatment system; Nitrification
• ISSN: 1944-3986; 1944-3994; 1944-3986
• DOI: 10.1080/19443994.2014.966760

The potential use of duckweed (Lemna gibba) for the treatment of drainage water was investigated. Three continuous flow duckweed-based treatment systems (one-pond, two-pond, and three-pond) were used. Removal efficiencies of CODtotal and ammonia in the two-pond system were significantly higher (60.2 ± 6.1% and 80.2 ± 1.4%) than that found for single-pond system (30.6 ± 7.9% and 56.8 ± 3.3%), respectively, at a total hydraulic retention time (HRT) of 14 d. Performance of three-pond system connected in series was evaluated at different HRTs of 21, 14, and 7 d. Results showed that increasing the HRT and area of duckweed pond to pond depth (Aduckweed/dpond) ratio from 7 to 14 d and from 63.83 to 127.66 substantially increased the removal efficiency of CODtotal from 59.7±3.29 to 88.34 ± 1.82%, respectively, resulting an effluent quality of 13.6±2.3 mg COD/L in the treated effluent. However, the removal efficiency of CODtotal remained almost constant when increasing the HRT from 14 to 21 d and Aduckweed/dpond from 127.66 to 191.49. This was not the case for nitrification efficiency, where ammonia removal increased from 32.6±7.95 to 71.75 ± 6.1% and from 71.75±6.1 to 85.6 ± 4.6% when increasing the HRT from 7 to 14 d and from 14 to 21 d, respectively.