This research was aimed at assessing the fertilizer quality and public health implications of using digestate biofertilizer from the anaerobic digestion of food wastes and human excreta. Twelve (12) kg of food wastes and 3kg of human excreta were mixed with water in a 1:1 w/v to make 30-l slurry that was fed into the anaerobic digester to ferment for 60days at mesophilic temperature (22-31°C). Though BOD, COD, organic carbon and ash content in the feedstock were reduced after anaerobic digestion by 50.0%, 10.6%, 74.3% and 1.5% respectively, nitrogen, pH and total solids however increased by 12.1%, 42.5% and 12.4% respectively. The C/N ratios of the feedstock and compost are 135:1 and 15.8:1. The residual total coliforms of 2.10×10(8)CFU/100ml in the digestate was above tolerable limits for direct application on farmlands. Microbial analysis of the digestate biofertilizer revealed the presence of Pseudomonas, Klebsiella, Clostridium, Bacillus, Bacteroides, Penicillum, Salmollena, and Aspergillus. Klebsiella, Bacillus, Pseudomonas, Penicillum and Aspergillus can boost the efficiency of the biofertilizer through nitrogen fixation and nutrient solubility in soils but Klebsiella again and Salmollena are potential health risks to end users. Further treatment of the digestate for more efficient destruction of pathogens is advised.

This study was aimed at establishing a water quality database in the study area where none existed previously. Groundwater samples from bore-holes, hand-pump, and hand-dug wells of four densely populated towns in SouthWestern Nigeria were analyzed in respect to physicochemical factors, biological factors, and the metals Nickel (Ni), Lead (Pb), Cadmium (Cd), Zinc (Zn), Copper (Cu), and Iron (Fe) for six consecutive months from September 2012 to February 2013 to give mean values for each town and water source. Total aerobic plate, total coliform bacteria, and Escherichia coli (E. coli) were detected in most of the water samples from the different towns and sources considered. Except for total suspended solids and total solids, the physicochemical parameters of all the samples were within permissible limits. The concentrations Pb, Ni, Cr, and Cd were above the minimum permissible limits. The presence of coliforms and E. coli in the groundwater samples indicates fecal contamination. The microorganisms isolated in this study include Enterobacteriaceae, Staphylococcus aureus, E. coli, Citrobacter, Klebsiella, Pseudomonas, Bacillus, that bore-hole water samples were safer for drinking that water samples from hand-pump, and hand dug wells across the communities.

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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