Dairy effluent polishing by aquatic macrophytes

In dairy industry, primary and secondary treatment methods are quite common for effluent treatment. However, this type of treatment is not effective in filtering the nutrients from the dairy waste water. Nutrient removal capacity of some important macrophytes i.e. Eichhornia crassipes, Lemna minor and Azolla pinnata have been tested individually as well as in combinations under microcosm investigations. Percentage nitrogen removal values by E. crassipes, A. pinnata and L. minor were 71.8 +/- 0.20, 62.5 +/- 0.39 and 60.13 +/- 0.48. Corresponding figures for phosphorus were 63.2 +/- 0.98, 58.8 +/- 0.57 and 56.3 +/- 0.51. Maximum removal was observed in combination studies, involving E. crassipes and L. minor (78.8 +/- 0.18% nitrogen and 69.4 +/- 0.11% phosphorus). Analysis of variance revealed significant (p < 0.001) variation among different incubation periods, both for nitrogen (F = 395985) and phosphorus (F = 196767) removal by a combination of E. crassipes, and L. minor. E. crassipes and A. pinnata removed 74.1 +/- 0.11% of nitrogen and 68.7 +/- 1.0% of phosphorus, whereas, it was recorded 70.0 +/- 0.25% nitrogen and 66.7 +/- 0.95% phosphorus by combination of L. minor and A. pinnata.