Identifying an interfering factor on chemical oxygen demand (COD) determination in piggery wastewater and eliminating the factor by an indigenous Pseudomonas stutzeri strain

Aims: This study attempted to demonstrate nitrite interference on chemical oxygen demand (COD) determination in piggery wastewater, and the capability of aerobic denitrification of the SU2 strain which is capable of promoting the efficiency of nitrogen and COD removal from piggery wastewater. Methods and Results: This study was performed in a 17-litre reactor with a 30% packing ratio, with a ratio of immobilized SU2 cells to sludge of 100 : 1. The ratio of aeration to nonaeration was 4 : 1.5. Removal efficiency of COD was 86.8%. Removal efficiency of BOD and SS was higher than 90%, and r emoval efficiency of NH4+-N and TKN was almost 100%. Conclusions: NO2--N interference is significant when its concentration in p iggery wastewater exceeds 100 mg l(-1). COD in piggery wastewater can be in directly reduced following nitrite reduction by SU2 strain. Significance and Impact of the Study: Utilizing immobilized SU2 cells in co ordination with an SBR system simultaneously reduces nitrite and COD concen trations.