a b s t r a c tA 3-year detailed investigation on the use of water lettuce macrophyte pond for the purification of wastewater from rubber processing industries and the reuse of the final effluent as biofertilizer is presented. Baseline wastewater quality information was collected on a monthly basis and analysed for one year before the introduction of water lettuce to 50% pond surface cover. This was done to reliably determine the parameters that exceeded limits and need treatment. These parameters are: phosphate, nitrates, pH, biological oxygen demand, conductivity, turbidity, total dissolved solid and total suspended solid. The effluents from the macrophyte ponds were then monitored mainly on monthly basis for chemical, physical and biological parameters. The treatment and analyses of parameters with exceedance were carried out in the ponds, using the retention periods of 2 weeks, 4 weeks, 8 weeks and 12 weeks for 1st, 2nd and 3rd inoculations. The result of the study showed a progressive reduction in the level of wastewater contaminants fed into the macrophyte pond. Significant reductions within permissible limits were obtained for most of the parameters except TSS and turbidity. Final effluent from the ponds was also found to boast the height, stem girth, leaf area and biomass yield of maize plant. Maximum plant height of 117.5 ± 7.6 cm was obtained using treatment 2 at 63 day after planting. The weight of cob produced from treatment 2 is 46.2 ± 6.1 g while the weight of cob produced by the control experiment is 21.3 ± 6.7 g. The chemical composition of the resulting water lettuce biomass shows it could be utilized as forage for feeding animals.

One of the significant components of the hydrological cycle is evapotranspiration. Monthly meteorological parameters of 35 years from 19 meteorological stations across the Northern Region of Nigeria (NRN) were obtained and utilized for the calibration of Hargreaves–Samani (HS) model by comparing between potential evapotranspiration (ETo) values estimated from the original HS and the Penman–Monteith (FAO-56 PM) models. The calibrated HS equation was assessed using trend patterns and some statistical indices. The average value of root mean square error (RMSE) and the mean absolute error (MAE) decreased by 37.1 and 40%, respectively, after the calibration of the model. Also, the correlation coefficients (R) of stations that had values > 0.8 increased from 6 to 11 and the minimum R value increased by 12% above that of the original HS equation. The trend and spatial map of the statistical tests conducted also indicate better performance in most climatic regions after calibration. The precision of the HS equation improved significantly after calibration for semi-arid, humid, and sub-humid regions. However, few stations in the semi-arid, humid, and sub-humid regions did not show drastic improvement due to the peculiarity of the location and high variations in the wind speed and relative humidity parameters.

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Background: The demand and cost of domestic energy in Nigeria are on the increase, primarily due to the increasing human population and demand. This is compounded by desertification, increasing the cost of electricity, industrialization, lack of alternative such as solar, wind and nuclear energy.This study was conducted to compare the potential of biogas produced from anaerobic co-digestion of coconut fibre, cocoa pods, maize husk, orange peels, pineapple peels and yeast and to determine the effect of pH and retention time on biogas yield. Methods: During the experiment, five batch reactors/digesters were used. The digesters were labeled A,B,C,D, E and each replicated three times. Digester A consist of 2g of yeast, 4g of coconut fibre, digester B consist of 2g of yeast, 4g of cocoa pods, digester C consist of 2g of yeast, 4g of maize husk, digester D consist of 2g of yeast, 4g of orange peels and digester E consist of 2g of yeast, 4g of pineapple peels. The pH was determined before corking the reactors. Result: The results showed significant differences among the different substrate for biogas yield and methane component. Biodegradability of the different substrate, quality and retention time significantly affected the biogas yield in the five digesters. Digester loaded with maize husk produced significantly higher volume of biogas and methane component compared with other substrate. Increase in biogas yield for maize husk of 4g was 23.33ml with methane component of 61.78% for the 10 days hydraulic retention time. The retention time of 4, 5, 6 and 8 days significantly produced the highest volume of biogas in the other digesters. Based on the findings, maize husk and yeast blend could be a rich source of renewable energy option and would help arrest ecological disaster in addition to control of deforestation.