Wastewater-nitrogen removal using polylactic acid/starch as carbon source: Optimization of operating parameters using response surface methodology

Abstract

The use of PLA/starch blends for nitrogen removal was achieved.

The influence of different operating parameters on responses was verified using RSM.

The conditions for desired responses were successfully optimized simultaneously.

Blends material may have a promising application prospect in the future.

Nitrogen removal from ammonium-containing wastewater was conducted using polylactic acid (PLA)/starch blends as carbon source and carrier for functional bacteria. The exclusive and interactive influences of operating parameters (i.e., temperature, pH, stirring rate, and PLA-to-starch ratio (PLA proportion)) on nitrification (Y₁), denitrification (Y₂), and COD release rates (Y₃) were investigated through response surface methodology. Experimental results indicated that nitrogen removal could be successfully achieved in the PLA/starch blends through simultaneous nitrification and denitrification. The carbon release rate of the blends was controllable. The sensitivity of Y₁, Y₂, and Y₃ to different operating parameters also differed. The sequence for each response was as follows: for Y₁, pH>stirring rate>PLA proportion>temperature; for Y₂, pH>PLA proportion>temperature>stirring rate; and for Y₃, stirring rate>pH>PLA proportion>temperature. In this study, the following optimum conditions were observed: temperature, 32.0°C; pH 7.7; stirring rate, 200.0 r·min^-1; and PLA proportion, 0.4. Under these conditions, Y₁, Y₂, and Y₃ were 134.0 µg-N·g-blend^-1·h^-1, 160.9 µg-N·g-blend^-1·h^-1, and 7.6 × 10³ µg-O·g-blend^-1·h^-1, respectively. These results suggested that the PLA/starch blends may be an ideal packing material for nitrogen removal.

Graphical abstract

Keywords

Nitrogen removal / Polylactic acid / Starch / Carbon source / Response surface methodology

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Acknowledgements

This study was supported by the National Natural Science Foundation of China (Grant No. 41505124) and Fundamental Research Funds for the Central Universities (Grant No. FRF-TP-15-044A1).

Funding

RIGHTS & PERMISSIONS

2014 Higher Education Press and Springer-Verlag Berlin Heidelberg