The relationship between BOD:N ratio and wastewater treatability in a nitrogen-fixing wastewater treatment system

摘要

A BOD:N:P ratio of 100:5:1 is often used as a benchmark for nutrient addition in nutrient limitednwastewaters. The impact of varying nitrogen levels, whilst maintaining phosphorus constant, wasnstudied in a simulated aerated lagoon (BOD:N of 100:0; 100:1.3; 100:1.8; 100:2.7 and 100:4.9). Ansynthetic wastewater was prepared using methanol, glucose and acetate as the combined carbonnsource, ammonium chloride as the nitrogen source and dipotassium hydrogen phosphate as thenphosphorus source. Nitrogen levels did not impact organic carbon removal, but did stronglyninfluence floc structure. With no supplemental nitrogen, growth was dispersed. Increasing thennitrogen level increased filamentous growth, with a marked change in filamentous speciesnoccurring between a BOD:N ratio of 100:1.8 and 100:2.7. Nitrogen fixation occurred at a BOD:Nnratio of 100:0; 100:1.3 and 100:1.8, with nitrogen loss at BOD:N ratios of 100:2.7 and 100:4.9. At anBOD:N ratio of 100:4.9, ammonium discharge was significantly greater (1.8 mg/L) than at the lowernnitrogen levels (0.04 – 0.18 mg/L). Phosphorus behaviour was more variable, however significantlynmore phosphorus was discharged at the lowest nitrogen level than at the highest (po0.05). Basednon readily available nitrogen, the BOD:N ratio at which nitrogen fixation no longer occurred wasnaround 100:1.9.