ANAEROBIC TREATMENT OF WASTE-WATER FROM A FOOD-MANUFACTURING PLANT WITH A LOW CONCENTRATION OF ORGANIC-MATTER AND REGENERATION OF USABLE PURE WATER

Wastewater from a food-manufacturing plant with a low concentration of organic matter below 100 mg/l TOC was first treated at 37 degrees C i n an anaerobic fluidized-bed reactor (AFBR) or in an upflow anaerobic sludge blanket (UASB). The TOC removal efficiency in both reactors dec reased from 85% to 65% as the influent TOC concentration decreased fro m 100 to 35 mg/l at a hydraulic retention time (HRT) of 6 h. Treatment at an HRT of 4 h resulted in an effluent TOC concentration of 11 to 1 5 mg/l. The concentration of suspended solids in the effluent could be reduced to 20 mg/l, which corresponded to 7% of that of the influent. The effluent from both reactors was then treated anaerobically in a f ixed-bed reactor system. The TOC concentration and optical density (OD ) of the effluent from the aerobic treatment were reduced to 5 mg/l an d 0.005, respectively, at an HRT of 2 h. When anaerobically or aerobic ally treated effluent was passed over an activated carbon column, the effluent TOC concentration was reduced to 2 to 3 mg/l. The conductivit y of 1.3 mS/cm in raw wastewater, which was not removed through the ab ove treatments, was reduced to 0.001 mS/cm on an ion-exchange resin co lumn. An effluent quality corresponding to that of ultra-pure water fo r industrial use was finally attained by the treatment in this multi-s tep system.