Abstract
We evaluated the processing capacity of a water purification system for low-organic-content wastewater from a poultry grading and packing facility. The system comprised vertical-flow intermittent feeding constructed wetlands connected in series. The BOD (Biochemical Oxygen Demand) of the water treated in the first stage was 6.8 mg•L-1. After stabilization at the facility, it was about 2-3 mg•L-1, for a decrease in BOD of 90% or more. SS (Suspended Solid) and BOD were removed in Wetland 1, where coarse particles were used as filter material, but D-BOD (Dissolved BOD) removal tended to occur in Wetland 2, where fine particles were used. The NH4-N concentration at each survey point was low, but the NO3-N concentration tended to increase with downstream flow. NH4-N generated by mineralization was rapidly nitrified. The average OTR (Oxygen Transfer Rate) value was 6.5 g•m-2•day-1, which is much less than 28 g•m-2•day-1, the standard in the United States and Europe, but the upper load limit was not confirmed. Filling the wetlands with water took longer in winter than in summer. The decomposition of solid organic materials is delayed by clogging in winter, but the water temperature rises in summer, suggesting an improved discharge capacity owing to organic matter decomposition.
