POTENTIAL OF SELECTED MACROPHYTES IN REMEDIATING UNIVERSITY OF ELDORET WASTEWATER USING MULTISTAGE TECHNIQUE

Abstract

Treatment of wastewater is a challenge that has afflicted man ever since he discovered that unsafe management and disposal of wastewater into aquatic ecosystems is detrimental to environment. This research was carried out to establish the ability of various macrophytes to remediate wastewater through multistage phytoremediation technique. Water parameters at the influent and effluent of the University of Eldoret wastewater treatment plant were analyzed using standard methods for a period of eight weeks. These included physicochemical and bacteriological parameters, nutrients and heavy metals. Locally available macrophytes were collected from Marura wetland, identified and used for phytoremediation. The macrophytes were; Azolla pinnata, Typha latifolia, Nymphaea spp. and Ceratophyllum demersum. Wastewater samples were collected from University of Eldoret wastewater treatment plant. Growth chambers containing wastewater samples were prepared in the laboratory. Macrophytes were established in the growth chambers. Wastewater analysis was carried out initially on setting up the experiment and after every five days for a period of 25 days to determine the changes in the levels of physicochemical and bacteriological parameters, mineral nutrients and heavy metals. After the laboratory experiment, a multistage experiment was established with the macrophytes used earlier in the laboratory and University of Eldoret wastewater. Collection points were established at the end of each growth chamber. Wastewater was sampled from these points and analysed for the above mentioned parameters after every 5 days. The means of the data obtained from analysis of mentioned parameters were calculated and analyzed using one way ANOVA and significant means separated using Tukey’s test at 5% level. The results for the influent and effluent were as follows; DO 0.44-1.75 mg/l, 3.03-5.29 mg/l respectively, BOD 432-1396 mg/l, 32-58 mg/l respectively, COD 1204-2654 mg/, 116-156 mg/l respectively, total coliforms 65783-83457 cfu/100ml, 42180 - 62760 cfu/100ml, cadmium 0.044 - 0.109 mg/l and lead 0.06 - 0.153 mg/l. Reduction Efficiency of macrophytes was as follows Azolla pinnata: phosphates, nitrates and lead 100%, cadmium 92.19% (P = 0.00), feacal coliforms 100%. Typha latifolia: lead 100%, phosphates 88.65%, nitrates 89.38% and cadmium 92.19% (P = 0.00), feacal coliforms 100%. Ceratophyllum demersum: phosphates 90.89%, nitrates 92.12%, cadmium 92.06% and lead 100% P = 0.00), feacal coliforms 100%. Nymphaea spp.: phosphates, nitrates, feacal coliforms and lead 100%, cadmium 88.96% (P = 0.00). In the multistage technique, reduction efficiency was as follows; lead 100%, cadmium 83.4% - 100%, phosphates 93.72 - 100% and nitrates 89.79 - 100% (P = 0.00), feacal coliforms 100%. From the results, the University of Eldoret wastewater treatment plant was not efficient in wastewater treatment. The macrophytes investigated were found to be efficient in wastewater treatment. The efficiency of macrophytes was in the following order Azolla pinnata > Nymphaea spp. > Typha latifolia > Ceratophyllum demersum. The multi-stage phytoremediation technique was found to be more efficient than individual macrophyte systems. There is need to introduce multistage phytoremediation ponds after the maturation pond in order to upgrade the University of Eldoret wastewater treatment plant hence improve its efficiency.