Effects of Lemna and Azolla as Biofilters of Nitrogen and Phosphate

[Melody]

The attached study was published in 2008, The Effects of Two Aquatic Floating Macrophytes (Lemna and Azolla) as Biofilters of Nitrogen and Phosphate in Fish Ponds.

Abstract:

Effects of different fish–edible floating aquatic macrophytes on water quality in aquaculture ponds through biofiltration of organic pollutants was studied for a period of four months from July to November 2001. Lemna sp. and Azolla sp. were used in treatment 1 and treatment 2 respectively, and treatment 3 was remained as control. The stocking density of Rohu (Labeo rohita), Catla (Catla catla), Mrigal (Cirrhina mrigala), Thai sharpunti (Puntius gonionotus) and feeding regimes (rice bran and mustard oil) and fertilization rate were the same in all treatments. The values of dissolved oxygen, temperature, nitrate-nitrogen, phosphate-phosphorus, chlorophyll-a, alkalinity and plankton abundance varied among the treatments. It was observed that the lowest concentration of PO4-P (0.01 mg/L) and chlorophyll-a (26.99 µg/L) were found in treatment 1 and treatment 2 followed by treatment 3. This was probably due to the utilization of nutrients by the experimental aquatic macrophytes. Lowest concentration of NO3-N was found in treatment 2 during July, but the fortnightly average values of NO3-N were mostly found lower in treatment 1 followed by treatment 2 and treatment 3. The phytoplankton were composed of Euglenophyceae, Cyanophyceae, Bacillariophyceae and Chlorophyceae. Throughout the experimental period the dominant genus were Euglena, Anabeana and Microcystis. These macrophytes also appeared as a nutrient filter for absorption of nitrogen and phosphorus and removed the excessive amount of nutrients from the waterbody in treatments 1 and 2 and the aquatic environment remained in a sustainable conditions.

[Melody]

Same topic, different floating macrophytes.

Abstract:

The potential of three floating aquatic macrophytes to improve thewater quality of anaerobically digested flushed dairy manure wastewater (ADFDMW) was evaluated. In undiluted ADFDMW (total chemical oxygen demand 2010 mg/l), growth of water hyacinth (Eichhornia crassipes) was inhibited and both pennywort (Hydrocotyle umbellata) and water lettuce (Pistia stratiotes) failed to grow. In a 1:1 dilution of ADFDMW, all three plants grew successfully. However, growth of pennywort and water lettuce was limited while water hyacinth growth was robust. High salinity appears to be the principal reason for inhibition, as well as possibly uncharacterized soluble compounds. In terms of reductions in nutrients, chemical oxygen demand (COD), solids and salinity, water hyacinth performed better than water lettuce and pennywort in diluted ADFDMW. Reduction in nutrients and COD followed first-order kinetics, with water hyacinth exhibiting the highest rates. For water hyacinth, total Kjeldahl nitrogen was reduced by 91.7%, ammonium by 99.6%, total phosphorus by 98.5%, and soluble reactive phosphorus by 96.5% in 31-day batch growth. A polyculture of the three plant species in 1:1 diluted ADFDMW exhibited the next best performance. The high biomass yield of the diluted water hyacinth culture corresponded with high EC and Na+ reductions, suggesting that EC measurement might be a simple tool to monitor performance of water hyacinth growth and nutrient reduction under high plant growth rate conditions.

Nutrient removal by floating aquatic macrophytes cultured in anaerobically digested flushed dairy manure wastewater (http://dairy.ifas.ufl.edu/other/files/Sooknah-and-Wilkie-EcolEng-22_1_-2004.pdf)