Using Plants for Wastewater Treatment

Using plants for water and wastewater treatment is common. Literature shows that different plant species like Water Hyacinth (Eichhornia crassipes), Water Lettuce (Pistia stratiotes L.), Duckweed (Water Lemna), Bulrush (Typha), Vetiver Grass (Chrysopogon zizanioides) and Common Reed (Phragmites Australis) have been used for the treatment of water and wastewater.

A bachelor’s thesis by Ajibade Fidelis of the University of Ilorin, Nigeria on use of water hyacinth for wastewater treatment, makes an interesting reading. The abstract, which is somewhat protracted, is as follows:

The effectiveness of water hyacinth (Eichhornia crassipes) for the purification of sewage was investigated. The study was carried out in the Department of Agricultural and Biosystems Engineering. Three treatments of water hyacinth replicated two times were used in the study. These treatments include no water hyacinth (control), 1kg and 2kg water hyacinth plant density cultures. The system was designed based on Completely Randomized Design (CRD). Sewage samples were collected during the growth of water hyacinth. Purification of water hyacinth (Eichhornia crassipes) on sewage was rapid during the first three weeks in the sewage cultured with water hyacinth (especially 2kg water hyacinth plant density) and there was low absorption in nutrients in the last two weeks when attaining maturity. Parameters such as Cl, Fe, Cu, Mn, Pb, K, F, Nitrate and Sulphate were drastically reduced from 9mg/l to 3.33mg/l, 1.25mg/l to 0.36mg/l, 0.3mg/l to 0 mg/l, 0.5mg/l to 0.08mg/l, 0.2mg/l to 0.01mg/l, 1.7mg/l to 0.17mg/l, 0.7 mg/l to 0.08mg/l, 8.6mg/l to 0.03mg/l, 17.5mg/l to 6.20mg/l respectively throughout the course of the study. The purification by water hyacinth had no effect on the bacteriological parameters (Agar count, E-coli, Coliform). Also, the 2kg water hyacinth plant density cultured in the sewage purifies more compared to the 1kg water hyacinth plant density which is moderate and minimal in the control treatment. One way analysis of variance was used to compare the means of the parameters tested. It shows that parameters like CO2, Mn, lead and sodium have significant difference between the control treatment with both the 1kg and 2kg water hyacinth plant density culture while parameters like pH, magnesium hardness, calcium hardness and calcium total have no significant difference between the no water hyacinth culture( control) with the 1kg and 2kg water hyacinth plant density culture. Finally, sewage parameters like BOD, COD, dissolved oxygen, Cu, F - , nitrate, phosphate, potassium, dissolved solids, suspended solids, sulphate, iron, Cland magnesium total were not affected.

The thesis touches the basics of wastewater treatment, and as such, is expected to be useful for young sanitary engineers. The thesis is attached

F H Mughal