Oxygen transport by aquatic macrophytes in wastewater

Abstract

The macrophytas transports atmospheric oxygen to the rhizofera creating airy environments for the micro-organisms that contribute to the reduction of biological oxygen demand, chemical oxygen demand and suspended solids, also in the removal of organic substances such as nutrients, heavy metals, phenols, formic acid, colorants, pesticides among others. This research aims to evaluate the improvement of wastewater quality in the laboratory, using aquatic plant species of jacinto (Eichhornia crassipes) and water lettuce (Pistia stratiotes). The treatments evaluated were: Plants with Barriers, Plants without Barriers, Barriers without plants and without barriers nor plants. The content of dissolved oxygen in wastewater analysis of variance showed significant difference (p < 0.05) between species and treatment. Jacinto had average values of 2.60 to 5.08 mg l^-l in a nine-day observation period, also the without Barriers treatment shows a higher value from 2.7 to 4.85 mg l^-l. On the other hand, water lettuce showed higher values in the without Barriers treatment, ranging between 2.27 and 4.81 mg l^-l and with Barriers from 1.24 to 1.53 mg l^-l. Jacinto Plants with Barriers and Plants without Barriers showed transferred dissolved oxygen values of 0.46 and 0.45 mg O₂ d^-1l^-1respectively. Jacinto without Barriers, removed the wastewater in a 20.23 % of the biological oxygen demand and with Barriers 19 % at the end of the ninth observation day. On the other hand, the without barriers nor plants treatment removed an average of 63 % of the biological biochemical oxygen demand, while the Barriers without plants treatment was 42 %. Jacinto without Barriers showed higher average of total dry biomass weight (6.06 g) and dissolved oxygen concentration (3.63 - 5.34 mg l^-l) compared with the water lettuce plant without Barriers (3.20 g) and dissolved oxygen (1.7 - 4.81 mg l^-l).