a b s t r a c tA continuous anaerobic digestion experiment was carried out to investigate the co-digestion of 75% food waste and 25% maize husk at different organic loading rates (OLRs) of 1-4.5 gVS/L/d. Results obtained showed that pH fluctuated between 7.3 and 7.5 and total alkalinity (TA) between 0.4 and 6.7 g CaCO3/L, indicating that the system was not inhibited by acidification. The range of the ratio of volatile fatty acid (VFA) to TA of 0.06-0.25 was also well below 0.4 and showed that the anaerobic co-digestion was stable and feasible. Though there was no significant difference (p < 0.05) between biogas yields at OLRs of 3.5 and 4.5 gVS/L/d, the methane content at OLR of 4.5 gVS/L/d was higher than that of 3.5 gVS/L/d and suggests that carbon dioxide producing microorganisms were more active in OLR of 3.5 gVS/L/d. The OLR of 4.5 gVS/L/d was therefore found to be the most satisfactory for large scale operation of anaerobic digesters for co-digestion of food waste and maize husk. From a separate batch test, the average biogas yield of 0.50 ± 0.04, 0.24 ± 0.02 and 1.31 ± 0.07 L/gVS were obtained from digesters A, B and C, respectively, indicating that the addition of maize husk to digester C significantly improved the production of biogas from food waste when compared to the biogas yield of digester A that contained food waste alone. Digester B with 100% maize husk was by far the least performed digester.

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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.

This work investigated the performance of locally available brewer's spent grain (BSG) as an adsorbent for the removal of Fe (III) from aqueous solution. The brewer's spent grain (BSG) was collected, processed and characterized using scanning electron microscope (SEM) and X-ray fluorescence (XRF) to assess its potential for the removal of Fe (III). Thereafter, batch adsorption technique was employed to evaluate the effects of adsorption variables such as pH, initial metal ion concentration, adsorbent dosage and contact time on the sorption efficiency of BSG. The maximum adsorption time was fixed at 120minutes with a stirring speed of 100rpm. Experimental data obtained were then analyzed using selected isotherms and kinetic models such as Langmuir isotherm, Freundlich isotherm, Pseudo-First order and Pseudo-Second order kinetic models. SEM result revealed the presence of microporous structure within the surface of BSG thus making it a good candidate for metal ion removal. Based on the linear coefficient of determination (r 2), it was observed that the experimental data fitted well with the Langmuir isotherm model (r 2 = 0.9940 for raw BSG and 0.9946 for the treated BSG). In addition, the reaction mechanism that accompanies the adsorption of Fe (III) unto BSG was best described by the pseudo-second order kinetic model (r 2 = 0.9823 for raw BSG and 0.981 for the treated BSG). Finally, maximum adsorption efficiencies of 66% and 77% were obtained for both the raw and treated BSG for optimum adsorption time of 120 minutes, pH 8.0 and adsorbent dose of 1.0g/50ml solution.