The growth of duckweed ( Spirodela polyrrhiza ) was investigated in an outdoor batch system under 15 different conductivities ranging from 200 μ S/cm to 3000 μ S/cm with average 110 μmol/m 2 daylight intensity. The growth was performed in an anaerobically treated domestic wastewater using an initial plants population of 50 fronds. Increase in Relative Growth Rate—RGR—(in terms of fresh weight and number of fronds) had a significant non-linear (polynomial) relationship with the conductivity. The maximum RGR related to fresh weight of 0.176 was observed at the conductiv i ity of 1200 μS/cm while the maximum RGR related to fronds number was 0.193 at the conductivity of 800 μS/cm. The optimum range for duckweeds growth was found to be between conductivities of 600 μS/cm and 1400 μS/cm. The maximal rates of removal of COD of 14.5 mg/day, of 0.65 mg/day, NTK of 15.68 mg/day, faecal coliforms of 100% and turbidity of 80.8% were observed in this range. The COD and PO 4 2- removal rates were highly correlated to the growth rate, with the correlation factor of up to 0.783 and, then to the conductivity. The NTK reduction was positively related to the conductivity.
W. S. Hillman, “The Lemnaceae, or Duckweeds,” The Botanical Review, Vol. 27, No. 2, 1961, pp. 221-287. http://dx.doi.org/10.1007/BF02860083
L. Bonomo, G. Pastorelli and N. Zambon, “Advantages and Limitations of Duckweed-Based Wastewater Treatment Systems,” Water Science and Technology, Vol. 35, No. 5, 1997, pp. 239-246. http://dx.doi.org/10.1016/S0273-1223(97)00074-7
J. R. Caicedo Bejarano, “Effect of Operational Variables on Nitrogen Transformations in Duckweed Stabilization Ponds,” Ph.D. Thesis, The UNESCO-IHE Institute for Water Education, Delft, 2005.
E. Landolt and R. Kandeler, “The Family of Lemnaceae—A Monographic Study: Phytochemistry, Physiology, Application, and Bibliography. (Vol. 2 of Monograph),” Geobotanical Institute of the ETH, Stiftung Rubel, 1987.
E. Landolt, “The Family of Lemnaceae—A Monographic Study: Vol 1: Morphology, Karyology, Ecology, Geographic Distribution, Systematic Position, Nomenclature, Descriptions,” Veroffentlichungen des Geobotanischen Institutes der ETH, Stiftung Rubel, Zurich, 1986, p. 566.
R. M. Harvey and J. L. Fox, “Nutrient Removal Using Lemna Minor,” Water Pollution Control Federation, Vol. 45, No. 9, 1973, pp. 1928-1938.
J. Xu, et al., “Production of High-Starch Duckweed and Its Conversion to Bioethanol,” Biosystems Engineering, Vol. 110, No. 2, 2011, pp. 67-72. http://dx.doi.org/10.1016/j.biosystemseng.2011.06.007
B. Ingemarsson, et al., “Nitrogen Utilization in Lemna II. Studies of Nitrate Uptake Using 13 ,” Plant Physiology, Vol. 85, No. 3, 1987, pp. 860-864. http://dx.doi.org/10.1104/pp.85.3.860
F. A. Nasr, H. S. Doma and H. F. Nassar, “Treatment of Domestic Wastewater Using an Anaerobic Baffled Reactor Followed by a Duckweed Pond for Agricultural Purposes,” The Environmentalist, Vol. 29, No. 3, 2008, pp. 270-279. http://dx.doi.org/10.1007/s10669-008-9188-y
D. Patel and V. Kanungo, “Phytoremediation Potential of Duckweed (Lemnaminor L: A Tiny Aquatic Plant) in the Removal of Pollutants from Domestic Wastewater with Special Reference to Nutrients,” Bioscan, Vol. 5, No. 3, 2010, pp. 355-358.
E. Awuah, “Pathogen Removal Mechanisms in Macrophyte and Algal Waste Stabilization Ponds,” Taylor & Francis, Leiden, 2006.
F. A. Al-Nozaily, “Performance and Process Analysis of Duckweed-Covered Sewage Lagoons for High Strength Sewage: The Case of Sana’a, Yemen,” 2001.
J. Xu, J. J. Cheng and A.-M. Stomp, “Growing Spirodela polyrrhiza in Swine Wastewater for the Production of Animal Feed and Fuel Ethanol: A Pilot Study,” CLEAN— Soil, Air, Water, Vol. 40, No. 7, 2012, pp. 760-765. http://dx.doi.org/10.1002/clen.201100108
S. Sengupta, C. Medda and A. Dewanji, “The Impact of Duckweed Growth on Water Quality in Sub-Tropical Ponds,” The Environmentalist, Vol. 30, No. 4, 2010, pp. 353-360. http://dx.doi.org/10.1007/s10669-010-9293-6
F. H. Papadopoulos and V. A. Tsihrintzis, “Assessment of a Full-Scale Duckweed Pond System for Septage Treatment,” Environmental Technology, Vol. 32, No. 7, 2011, pp. 795-804. http://dx.doi.org/10.1080/09593330.2010.514009
J. Cheng, et al., “Nutrient Removal from Swine Lagoon Liquid by Lemna Minor 8627,” Transactions of the American Society of Agricultural Engineers, Vol. 45, No. 4, 2002, pp. 1003-1010.
R. P. Staves and R. M. Knaus, “Chromium Removal from Water by 3 Species of Duckweeds,” Aquatic Botany, Vol. 23, No. 3, 1985, pp. 261-273. http://dx.doi.org/10.1016/0304-3770(85)90070-1
C. B. Sekomo, et al., “Heavy Metal Removal in Duckweed and Algae Ponds as a Polishing Step for Textile Wastewater Treatment,” Ecological Engineering, Vol. 44, 2012, pp. 102-110. http://dx.doi.org/10.1016/j.ecoleng.2012.03.003
A. Sasmaz and E. Obek, “The Accumulation of Arsenic, Uranium, and Boron in Lemna gibba L. Exposed to Secondary Effluents,” Ecological Engineering, Vol. 35, No. 10, 2009, pp. 1564-1567. http://dx.doi.org/10.1016/j.ecoleng.2009.06.007
P. Skillicorn, W. Spira and W. Journey, “Duckweed Aquaculture: A New Aquatic Farming System for Developing Countries,” Banco Mundial, Washington DC, 1993.
P. van der Steen, A. Brenner and G. Oron, “An Integrated Duckweed and Algae Pond System for Nitrogen Removal and Renovation,” Water science and Technology, Vol. 38, No. 1, 1998, pp. 335-343. http://dx.doi.org/10.1016/S0273-1223(98)00419-3
G. Oron, D. Porath and L. R. Wildschut, “Wastewater Treatment and Renovation by Different Duckweed Species,” Journal of Environmental Engineering, Vol. 112, No. 2, 1986, pp. 247-263. http://dx.doi.org/10.1061/(ASCE)0733-9372(1986)112:2(247)
K. R. Reddy and W. F. Debusk, “Growth-Characteristics of Aquatic Macrophytes Cultured in Nutrient-Enriched Water. 1. Water Hyacinth, Water Lettuce, and Pennywort,” Economic Botany, Vol. 38, No. 2, 1984, pp. 229-239. http://dx.doi.org/10.1007/BF02858838
C. McLay, “The Effect of pH on the Population Growth of Three Species of Duckweed: Spirodela Oligorrhiza, Lemna Minor and Wolffia Arrhiza,” Freshwater Biology, Vol. 6, No. 2, 1976, pp. 125-136. http://dx.doi.org/10.1111/j.1365-2427.1976.tb01596.x
R. M. Wedge and J. E. Burris, “Effects of Light and Temperature on Duckweed Photosynthesis,” Aquatic Botany, Vol. 13, 1982, pp. 133-140. http://dx.doi.org/10.1016/0304-3770(82)90047-X
H. Brix, “Do Macrophytes Play a Role in Constructed Treatment Wetlands?” Water Science and Technology, Vol. 35, No. 5, 1997, pp. 11-18. http://dx.doi.org/10.1016/0304-3770(82)90047-X
E. Ashby and T. Oxley, “The Interaction of Factors in the Growth of Lemna VI. An Analysis of the Influence of Light Intensity and Temperature on the Assimilation Rate and the Rate of Frond Multiplication,” Annals of Botany, Vol. 49, No. 2, 1935, pp. 309-336.
O. Thomas, “Métrologie des eaux Résiduaires,” CEBEDOC, Liège, 1995.
H. White, “The Interaction of Factors in the Growth of Lemna. IX. Further Observations on the Effect of Light Intensity on Growth and Multiplication,” Annals of Botany, Vol. 50, No. 4, 1936, pp. 827-848.
M. L. Boss, M. J. Dijkman and V. B. Theiling, “Aging Studies on Lemna,” Quarterly Journal of the Florida Academy of Sciences, Vol. 26, No. 2, 1963, p. 175.