Microbial analysis and chemical composition of maize (Zea mays, L.) growing on a recirculating vertical flow constructed wetland treating sewage on-site

Microbial analysis and the chemical composition of maize (Zea mays L.) hybrid (Beck-5444VT3) planted at 107,000 seeds ha−1 on a recirculating vertical flow constructed wetland treating sewage on-site were examined. Maize ears were sampled for microbial analysis of the cob surface, and homogenisation of the kernels. The microbial analysis included plate count for aerobic total bacteria (TB), total coliform (TC), faecal coliform (FC), Escherichia coli (EC), Listeria spp. (LIS) Pseudomonas aeruginosa (PA), Salmonella spp. (SB), mould (MO), and yeast (YS). The nutritional chemical composition of the maize kernels included ash, crude protein, crude fat hydrolysis, sugar profile, and carbohydrates (starch). The most predominant microbial biota found on both the surface and homogenised of the kernels were PA, TB and MO. The biota having low values included TC, FC, EC and YS. None of the samples tested positive for LIS and SB. There were no major changes in nutrient value of the maize compared to expected standards. The results of this study suggest that subsurface irrigation of maize plants with pretreated sewage effluent recycled nutrients as fertilisers and reclaimed water, producing maize with no adverse effects on microbiological content or change in nutrients. These two findings could make the kernels acceptable for further applications such as biomass processing or to produce biofuel.

► Maize was planted on top of a recirculating vertical flow constructed wetland treating sewage on site. ► Subsurface irrigation of maize with treated sewage recycled nutrients as fertilisers and reclaimed water. ► Maize was harvested with no adverse effects on microbial content. ► The nutrient composition of the harvested kernels was similar to expected standards.