Nutrients removal by floating macrophytes (lemna minor and azolla pinnata) from Egerton University generated effluent, Kenya

Abstract

Floating macrophytes have the capacity to improve wastewater quality by absorbing nutrients thus purifying pre-treated wastewater and have been found to be more appropriate for effluent in developing countries. This is due to their effective and extensive root system and moderate capital investment required in their engagement in wastewater treatment. They are especially appropriate for tropical countries due to the warm climate experienced in these regions which support rapid plant growth and microbial activities that enhance uptake of nutrients and other pollutants from the wastewater. Being dependent on uptake of nutrients by the wetlands vegetation, the efficiency of wastewater treatment systems in wastewater purification is therefore influenced by the type of flora growing in them and how effective these flora are in the uptake of nutrients from the wastewater. Many of macrophytes are normally found growing together in a single wetland and the nutrient removal efficiency of individual plant species has not been effectively determined yet this is important in promotion of the effluent treatment technology. This study assessed the nutrient removal efficiency of two floating macrophytes (Lemna minor and Azolla pinnata) in Egerton University generated effluent. The key research question to be answered was; was there a significant variation in nutrients concentration in the wastewater after treatment by the selected floating macrophytes? In answering this question, randomized complete block design was used. In all cases, American Public Health Association standard protocols for sampling, sample processing and analysis were used. The data generated was analyzed using both descriptive and inferential statistics. The nutrients removal efficiency was determined using one-way ANOVA and Tukey test. In all determinations, the level of confidence was 0.05. The wastewater physicochemical parameters varied slightly during the study period. Increase in biomass for the selected macrophytes was noted suggesting that there was significant uptake of nutrients (Azolla pinnata: F= 621.713, P= 0.00; Lemna minor: F= 786.494, P= 0.00). Decreases in ammonia, total nitrogen, total phosphorous and soluble reactive phosphorous concentration were noted whereas an increase in nitrates and nitrites concentration was observed. Azolla pinnata proved to be better than Lemna minor in the uptake of soluble reactive phosphorous where the nutrient uptake was statistically significant (F= 35.183, P= 0.044). Based on the study results we can conclude that Azolla pinnata and Lemna minor are efficient in nutrient removal and therefore good in wastewater treatment. Thus we recommend increasing the population of the two floating macrophytes in the treatment of