Abstract：The change law of the inorganic nitrogen in the stable shortcut nitrification and denitrification systems was researched with sequencing batch activated sludge reactor (SBR). Wavelet denoising method was used to preprocess the near infrared spectra of inorganic nitrogen and interval partial least square (iPLS) method was used to establish the mathematical prediction models of inorganic nitrogen content. The results indicated that wavelet denoising method could partially remove the noise of original spectra and improve the accuracy of the model. The interval partial least squares (iPLS) was used to model the preprocessed spectra, to decide the optimum wavelength range and divide the spectrum into 20sub-interval. The optimum wave number range of the ammonia was 8243~8663cm-1while the nitrite nitrogen was 4000~4420cm-1.The correction coefficients of the models for the ammonia nitrogen and nitrite nitrogen were 0.9582 and 0.9544, respectively, and root mean square errors of cross validation (RMSECV) were 0.0321 and 0.0406, respectively, and the prediction coefficients were 0.9184 and 0.8816 with the root mean square errors of prediction (RMSEP) of 0.0790 and 0.0451. When real wastewater was used as raw water in the process, the prediction coefficients of the models for the ammonia nitrogen and nitrite nitrogen were 0.9190 and 0.8739, respectively, and root mean square errors of cross validation (RMSECV) were 0.0578 and 0.0229. The prediction effects of the model on ammonia nitrogen and nitrite nitrogen were better. The method of wavelet denoising and iPLS can effectively not only reduce the variable numbers for establishing models and short operation time, but increase the accuracy of the model, thus providing a feasible analysistechnique for the rapid determination of inorganic nitrogen.
