Magnetic nanosorbents such nZVI proved to be effective in different contaminant removal from aqueous solutions. The prepared nZVI was characterized using SEM, XRD, EDAX and UV-Vis scanning spectrum. This study explores different adsorption and kinetic models that can describe the adsorption process of COD into nZVI. The nZVI and standard COD solution were prepared in the laboratory. The effect of nZVI on COD removal was studied at different absorbent dose, contact time, temperature, stirring rate, pH, and initial COD concentration. The results indicated that nZVI is effective in the removal of COD from aqueous solution, where removal efficiencies of 66 and 92% were achieved for 800 ± 10.2 and 100 ± 1.27 mg/L initial COD concentration, respectively, after 20 min of contact time using dose 0.6 g/L at pH 6, temperature 35 ˚C with fixed stirring rate 200 rpm. The isotherm studies were determined using nine nonlinear models. The kinetic data were evaluated using five nonlinear models including pseudo first, second order, Elovich, Avrami and Intraparticulate models. The adsorption data of COD fitted well to Freundlich model with lowest summation of error of 0.842 and pseudo second order kinetic model with lowest summation of error of 0.057. Artificial Neural Network (ANN) with a structure of 7 - 2 - 1 was used to predict the COD removal efficiency. The proposed ANN was found to be effective in simulating the performance of nZVI for COD removal, where a sum of squares error 0.092 and 3.204 for testing and training, respectively with relative error 0.030 and 0.256, respectively. RSM result showed R2 0.898 indicated that model was significant with experimental data. ______________________________________________________________ The effect of solid waste disposal on Nworie river Journal of Environment & Biotechnology Research, Vol. 7, No. 2, Page 23-29, Apr 2018
O.L. Nwaneri, M.I. Nwachukwu, N. Ihua, C.E.I. Nwankwo
Generally, there is a marked decrease in the volume of surface water due to reasons ranging from global warming to anthropogenic activities. The present study evaluated the effect of waste disposal on Nworie River. The potability of the river was studied in terms of bacteriological and physicochemical parameters. A cross-sectional descriptive study design was used. Sample collection from surface and sediment at three different points of the river and at three different times were performed. Conventional microbiological methods of culture, morphological and biochemical assays for isolation and identifications were used. Also, APHA standard analytical methods for the physicochemical assay were employed. Total heterotrophic bacterial count was highest at point A (4.4 x 103 CFU/mL) and lowest at C (3.0 x 101 CFU/mL). Similarly, all other examined bacteria (Coliform, Shigella and Vibrio) were highest at point A and lowest at point C. There was an even distribution of all bacteria both in the surface and sediments across all sampling points A, B and C. Most physical and chemical attributes of the river studied had deviated from acceptable limits for potable water. The domestic and other wastes dumped into Nworie River adversely affected the water body standard. The presence of certain pathogenic bacteria, as well as indicator organisms, has compromised the potability of Nworie River. Further, the physico-chemical properties support the contamination of this water body and suggest unsuitability for human consumption. ______________________________________________________________