Performance of pilot-scale gravel and sponge bed hydroponic systems vegetated with Duranta erecta treating wastewater in a developing country, Ethiopia, Africa

Abstract

This study aimed to assess the performance of hydroponics vegetated with Duranta erecta in removing nutrients from domestic wastewater in a pilot-scale study. Domestic wastewater was fed to four lines of hydroponic-constructed filter systems (HCFS). The lines 1 and 3 were filled with gravel, but the lines 2 and 4 were filled with polyester sponges. The experimental biofilters (lines 1 and 2) were planted with Duranta erecta, and the control biofilters (lines 3 and 4) were unplanted. This experiment was operated at hydraulic retention times (HRT) of 1, 3, 5, and 7 days which were conducted sequentially. Results indicated that the planted biofilters in gravel media removed nutrients better than the other planted biofilters in sponge media. Better removal efficiencies of 55 and 47% for total nitrogen (TN) and of 32 and 26% for total phosphorus (TP) removal by planted and control lines, respectively, were obtained at 7 days HRT. At the end of the experiment, TN and TP accumulation in the plant biomass sample increased from 132 to 216 g TN/Kg of dry weight, and from 53to 86 g TP/Kg of dry weight, respectively at 7 days HRT. Hence, it can be concluded that nature-based hydroponic filters planted with Duranta erecta might have a promising potential, mainly with gravel media. HCFS represents a very welcome technology to treat domestic wastewater at a decentralized level in developing countries, including Ethiopia.