Treatment of Maize Processing Industry Wastewater by Percolating Columns

Abstract

Primary and secondary treatments of the maize processing industry wastewater using gravity percolating columns have been studied. The packing materials used were, respectively, bark, soil, and sawdust in the primary treatment percolators (PTP), while Sphagnum peat moss, soil, and sawdust, respectively, were used in the secondary treatment percolators (STP). Percolating columns with a combination of two or three layers of different materials were also used. Experiments lasted 60 days for PTP and 240 days for STP (until packing saturation). The soil/bark/sawdust combination percolating column was the most efficient in primary treatment for the removal of CODt (an average of 45% CODt removal for a period of 8 weeks with a peak >80% CODt removal during the sixth and the seventh weeks). Sphagnum and sawdust/Sphagnum percolators were efficient (49% CODt removal) in secondary treatment during fifth to seventh months. Soil/Sphagnum and soil/sawdust/Sphagnum packed columns worked with efficiencies of 41 and 43% CODt removal, during the fourth to fifth months, respectively. The treatment efficiency of both systems increased with time. Through primary treatment using these percolator columns, the pH of the wastewater was reduced from 11 to 5 to 6. In the secondary treatment, the pH remained around 5 to 6.4. The electrical conductivity of the effluents from all PTP and STP columns increased compared to their influents probably due to the ions liberated by the decomposition of the packing materials. Saturated packing materials can be disposed of in sanitary landfills since they can be naturally degraded. This low-cost treatment looks promising for small-scale corn mills that cannot afford costlier treatment systems.

Keywords:

• Percolating columns
• primary and secondary treatment
• Sphagnum
• peat moss
• bark
• soil
• sawdust