139,063 research outputs found

    Amperometric Determination of Chemical Oxygen Demand

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    A method is described for measuring the low level --5 to 50 ppm-- chemical oxygen demand (COD) of water samples by amperometric titration. The method involves digestion of the sample with potassium dichromate in a 50% sulfuric acid solution using one-fifth the reagents and sample required for the standard COD method. This is followed by an amperometric titration using a standard ferrous ammonium sulfate solution and employing a rotating platinum electrode in a three-electrode potentiostatic system. The titration is carried out at a potential of +0.80 volts versus a saturated calomel electrode, thus eliminating the need for O2 purging of the polarographic cell. The electrochemical method is compared to the standard method with respect to precision, sensitivity, cost and waste disposal

    Seasonal and Spatial Variations in Water Quality and Its Ecological Implications on Challawa River, Nigeria

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    The water quality of Challawa River, Kano, Nigeria at three sites was investigated for a period of eighteen months (January, 2005 - June, 2006). Results obtained showed some degree of variations along the river course. The pH, colour, temperature, bicarbonate and turbidity valuesincreased from sample site I (upstream), through site III (downstream) of the river. Levels of dissolved oxygen and phosphate decreased down the stream while biochemical oxygen demand, chemical oxygen demand, electrolytic conductivity, nitrate and sulphate fluctuated between sites. Significant differences (P < 0.05) between both sites and seasons for colour, pH, temperature, electrolytic conductivity, bicarbonate and sulphate exist while no significant difference (P > 0.05) was observed on both sites and seasons for turbidity, nitrate and phosphate. However, dissolved oxygen, biochemical oxygen demand and chemical oxygen demand were significantly different (P < 0.05) only between seasons. The implications of the results were discussed.Keywords: Physico-chemical quality, seasonal, spatial, variation, Challawa River, Kano

    Potential of duckweed for swine wastewater nutrient removal and biomass valorisation through anaerobic co-digestion

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    Over the last decades, phytodepuration has been considered an efficient technology to treat wastewaters. The present study reports a bench scale depuration assay of swine wastewater using Lemna minor. The highest observed growth rate obtained in swine wastewater was 3.1 ± 0.3 gDW m−2 day−1 and the highest nitrogen and phosphorus uptake were 140 mg N m−2 day−1 and 3.47 mg P m−2 day−1, respectively. The chemical oxygen demand removal efficiency in the swine wastewater assay was 58.9 ± 2.0%. Furthermore, the biomass valorisation by anaerobic co-digestion with swine wastewater was assessed. Results showed a clear improvement in specific methane production rate (around 40%) when compared to mono-substrate anaerobic digestion. The highest methane specific production, 131.0 ± 0.8 mL CH4 g−1 chemical oxygen demand, was obtained with a mixture containing 100 g of duckweed per liter of pre-treated swine wastewater. The water-nutrients-energy nexus approach showed to be promising for swine waste management.info:eu-repo/semantics/publishedVersio