Purification of Anaerobic Digester Effluent through Intensive Production of Forage Crops in a Soilless Nutrient Film System

M.T. Alhattab; A.E. Ghaly
Animal production is becoming more intensive and increases in efficiency have created a number of environmental and health problems. However, the efficiency of animal production and the quality of the environment must be tied together. A soilless nutrient film system was designed and constructed to purify the effluent from an anaerobic digester through the intensive production of forage crops. The system was composed of a growth chamber which consisted of three shelves each of which carried two hydroponic troughs. Each trough was divided into three compartments, each of which held a perforated tray used as a plant support medium. The lighting system was designed to provide an optimal level of illumination to the plants for growth. The effluent from the anaerobic digester was applied to the trays by means of fully automated wastewater application system. Tests showed that the system has the potential of producing 3.7 kg of forage per tray in 28 days and reducing the chemical oxygen demand from 23700 mg/L to less than 2220 mg/L (90.7 %), the total solids form 23920 mg/L to less than 1900 mg/L (90.7 %), the TKN form 3400 mg/L to less than 230 mg/L (93.8 %) and NH4-N from 520 mg/L to less than 110 mg/L (78.9 %). Based on the results, an annual yield of 8 670 kg/ha of forage could be produced which is 35 times greater than the yield obtained from field production. The system also eliminates the need for land, fertilizer, harvesting and transport equipment and the storage facilities associated with field production of forage crops.
Purification; Wheat; Plant growth; Animal feed solids; COD; Nitrogen
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