Coagulation/flocculation is an auspicious procedure for microalgae biomass harvesting. However, the issues of coagulant cost, toxicity, and the large volume of contaminated, nonrecyclable culture medium that is usually generated negate the industrial applications. Therefore, a biocoagulant with frother properties [i.e., the fruit seed extract of Margaritaria discoidea (MDE)] was evaluated as a green biocoagulant to obviate these challenges. The harvesting efficiency (HE %) and the rate parameters were determined in samples collected from a eutrophicated fish pond. The MDE-harvested biomass characteristics were compared with that of the nonchemical approach. Apatococcus lobatus, Arthronema africanum, and Aphanocapsa sp. were the suite of microalgae in the eutrophication system, and the MDE induced the floatation of the microalgae floccule. HE of 98% was achieved and the process obeyed the first-order flotation kinetic. The galactomannans fraction of the MDE flocculated the microalgae cells via the adsorption and bridging mechanism, while the saponin fraction served as the frother that enabled the floatation of the microalgae floccule. The inorganic fraction of the MDE biomass was higher than that of the biomass obtained from the non-chemical method, but the proximate an elemental composition were comparable with the non-chemical method. As shown in the FTIR analysis, no extraneous functional group was introduced into the MDE-harvested biomass. The settleability and filterability of the harvested biomass were comparable with the biomass of other algae species harvested with other types of coagulants.
This study identified areas where different types of herbicide were used for municipal weed control in selected residential communities in Akure, Akungba-Akoko and Owo in Ondo State, Nigeria. A survey of the communities was carried out to identify sites maintained with herbicides (test sites) and those without herbicide history (control sites). Composite soil samples collected from each site were analyzed using standard laboratory procedures for the determination of selected soil physical and chemical properties. The data obtained were subjected to statistical analysis of variance (ANOVA). Results obtained indicated that the soil texture of the study sites were mostly sandy loam while pH ranged from slightly acidic to neutral. Significant differences (P < 0.05) were observed in the organic carbon (OC) contents of soil samples from Owo as against the samples from Akure and Akungba-Akoko though Owo had the highest OC (24.48 ± 9.36 g kg-1) followed by Akungba-Akoko (21.21 ± 10.36 g kg-1) and Akure (18.10 ± 7.75 kg-1) which was the lowest. However, no significant differences (P < 0.05) were observed in the values of the micronutrients and exchangeable cations across all the sites. Conclusively, application of herbicides to weeds did not have significant effect on the soil fertility (in all the sites) in the short run (2013-2015) but more aggressive application could have deleterious effects in the long run because leaching is encouraged as a result of the sandy nature and low organic carbon content of the soil in the study areas.
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