THE APPLICATION OF THE ROOT-ZONE METHOD FOR THE TREATMENT AND REUSE OF HIGH-STRENGTH ABATTOIR WASTE IN MEXICO

A two-stage system for treating high-strength wastewater from an abatt oir at Pachuca, Mexico is described. The system consists of an anaerob ic digester followed by an artificially-constructed wetland which empl oys horizontal subsurface now through the root zone of emergent hydrop hytes planted in a gravel substrate. The main goals of this study were to monitor the treatment efficiency of the system for the first twelv e months of operation and to assess the suitability of the effluent fo r irrigation purposes. The treatment efficiency during the twelve mont h period was generally good with mean removal efficiencies of 88.5% fo r BOD5, 87.4% COD, 89% suspended solids, 73.6% organic nitrogen and >9 9% faecal coliforms. Removal rates were generally poor for orthophosph ates, NH3-nitrogen and NO3-nitrogen. The differing roles of the two st ages in the treatment process are discussed. Although not suitable for irrigating crops, the effluent is being successfully used for the irr igation of ornamental plants and recreational lands. (C) 1997 IAWQ. Pu blished by Elsevier Science Ltd.