Application of response surface methodology for simultaneous carbon and nitrogen (SND) removal from dairy wastewater in batch systems

Abstract

The application of batch systems to the direct treatment of dairy wastewater was investigated. Batch experiments were conducted to study the organics removal and simultaneous nitrification and denitrification (SND) process. The experiment was conducted by varying four independent parameters (mixed liquor suspended solids, chemical oxygen demand [COD]/N ratio, aeration time and cycling time), using a central composite design under response surface methodology. The process responses of five dependent parameters (COD, Total kjehldahl nitrogen (TKN), NO₃ ⁻, effluent NO₃ ⁻ and effluent total nitrogen) were studied, and in each case, the percentage removal in batch runs was determined with each process displayed in contour plots. Finally, after optimizing the process conditions, the best treatment of dairy wastewater under optimized conditions was established and the responses were shown. This study shows that microbial granules cultivated under the alternating aerobic/anaerobic conditions in batch systems could efficiently remove organic carbon and convert all the ammonium to nitrogen gas.

Keywords:

• Nutrient removal
• Dairy wastewater
• SBR
• RSM

Acknowledgements

The research was made possible through a grant from the Tarbiat Modarres University (TMU), sponsored by the Ministry of Science, Iran. The authors wish to thank Mrs. Haghdoust (Technical assistant of Environmental Laboratory) for her assistance and Ellen Vuosalo Tavakoli (University of Mazandaran) for editing the English text.