Browsing by Author "Mekonnen, Andualem"

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Kinetic analysis of anaerobic sequencing batch reactor for the treatment of tannery wastewater
(Academic Journals, 2017-06-30) Mekonnen, Andualem; Leta, Seyoum; Njau, Karoli
A pilot scale anaerobic sequencing batch reactor (ASBR) was operated at different organic loading rate (1.03, 1.23, 1.52 and 2.21 kg.m-3.d-1) in order to determine the chemical oxygen demand (COD) removal and methane production kinetic models. The system was operated at mesophilic temperature. The wastewater was fed using submersible pump in every twenty four hours and agitated with hydraulic pump for fifteen minutes in every one hour. The COD removal efficiencies was found to be between 69-85% and the methane yield was also between 0.17±0.2 and 0.30±0.02 m3/kg COD removed. In the kinetic studies, modified Stover-Kincannon and second-order models were found to be the most appropriate model for ASBR treating tannery wastewater than first order model. The saturation value constant and maximum COD removal rate found in Stover-Kincannon model were 5.57 and 5.56 kg of COD m-3.d-1, respectively. The kinetic studies of volumetric methane production showed that Michaelis-Menten model was found to be capable of predicting the volumetric methane production in ASBR that treat tanney wastewater.
Wastewater treatment performance efficiency of constructed wetlands in African countries: a review
(IWA Publishing, 2015-01-01) Mekonnen, Andualem; Leta, Seyoum; Njau, Karoli
In Africa, different studies have been conducted at different scales to evaluate wastewater treatment efficiency of constructed wetland. This paper aims to review the treatment performance efficiency of constructed wetland used in African countries. In the reviewed papers, the operational parameters, size and type of wetland used and the treatment efficiency are assessed. The results are organized and presented in six tables based on the type of wetland and wastewater used in the study. The results of the review papers indicated that most of the studies were conducted in Tanzania, Egypt and Kenya. In Kenya and Tanzania, different full-scale wetlands are widely used in treating wastewater. Among wetland type, horizontal subsurface flow wetlands were widely studied followed by surface flow and hybrid wetlands. Most of the reported hybrid wetlands were in Kenya. The results of the review papers indicated that wetlands are efficient in removing organic matter (biochemical oxygen demand and chemical oxygen demand) and suspended solids. On the other hand, nutrient removal efficiency appeared to be low