Post treatment of domestic sewage with Spirodela polyrhiza macrophytes

Abstract

Wastewater treatment systems for domestic effluents have high efficiency for removal of solids concentrations, COD, BOD and other organic compounds, however, are customarily deficient for removal of nutrients such as nitrogen and phosphorus. Aquatic plants can be used in wastewater treatment plants, especially with regard to the post-treatment of effluents, in order to removal nutrients and other parameters not previously remedied. Thus, the aim of this study was to evaluate the efficiency of post-treatment wastewater by aquatic macrophyte Spirodela polyrhiza, still an understudied plant for this purpose. The experiment was carried out between March and May of 2016, for 42 days at Toledo-PR. To this purpose, 250 liters of post-treated wastewater were placed in a polyethylene reactor operating in batch. Effluent samples were performed due to the hydraulic retention time (HRT), every 7 days. In effluent were evaluated the following parameters: OD; temperature; pH; turbidity; total solids, fixed solids and volatile solids; COD; total Kjeldahl nitrogen and total phosphorus concentrations. The results obtained during the experiment were satisfactory, observing maximum efficiency for removal of turbidity, N, P and COD of 99%, 100%, 100% and 88% respectively. It was observed that the plant senescence process might have been responsible for changes in turbidity and DO parameters. The macrophyte proved to be a great option for post-treatment of domestic sewage, as it requires for its development high levels of nutrients, thus assimilating these nutrients from the environment to which they belong. More studies are needed, as in Brazil Spirodela polyrhiza is still poorly studied.