Total Nitrite Nitrogen Research Articles

Application of principal component analysis (PCA) to the assessment of parameter correlations in the partial-nitrification process using aerobic granular sludge

For the first time, principal component analysis (PCA) was used to extract relevant information hidden in the partial-nitrification process using aerobic granular sludge. The objectives of this research are (a) to determine total ammonia nitrogen (TAN), total nitrite nitrogen (NO2–N), nitrate nitrogen (NO3–N), and other water quality parameters; (b) to identify the diversity of nitrification and denitrification bacterial community of wastewater samples during the partial-nitrification process using aerobic granular sludge and; (c) to analyze the correlation of available parameters using PCA. The nitrite accumulation ratio was determined from TAN, NO2–N, and NO3–N. Other water quality parameters were mixed liquor volatile suspended solids (MLVSS), alkalinity, total nitrogen (TN) and sludge volume index (SVI), pH, and dissolved oxygen (DO). The identification of bacterial community was conducted using 16S rRNA gene-based pyrosequencing by GS Junior Sequencing system. The water quality parameters were computed for PCA using software MATLAB. A nitrite accumulation ratio (NAR) between 0.55 and 0.85 was determined while maintaining the aerobic granular sludge's compact and dense structure. The PCA was used to reduce the data dimensionality from the original 8 variables to 2 principal components explaining 75% of the total data variance. Applying PCA to the data analysis in biological wastewater treatment can support detecting data anomalies and separating useful information from unwanted interferences.

Substrate inhibition and pH effect on denitritation with granular biomass

Abstract Undissociated HNO2 (up to 2 mg dm−3) was confirmed as substrate inhibitor for granular biomass from a denitritation upflow sludge bed reactor used for biological removal of nitrite. On the contrary, total nitrite nitrogen (N-NO2 up to 500 mg dm−3) and methanol (COD up to 2000 mg dm−3) were not proven to be inhibitors. pH also affected the denitritation efficiency (optimal pH was 5.9). Reduction of HNO2 concentration in the reactor by effluent recycling is recommended.

High-performance system for partial nitritation of reject water resistant to temperature fluctuation

A sequencing batch reactor (SBR) applying partial nitritation for reject water treatment was operated for 330 days at a laboratory scale. The system was repeatedly exposed to sudden temperature drops from 24 to 17 °C. The nitrogen loading rate (NLR) was increased incrementally from 0.4 to 1.5 kg/(m3 day) with the aim to evaluate temperature stability of the process at different NLR value. Total nitrite nitrogen (TNIIIN) represented 94–99% of oxidised nitrogen in the effluent throughout the entire operation of the reactor. It was found that the pH profile during the SBR cycle, nitrogen removal efficiency and concentration of N-species in the effluent did not show significant changes following temperature decreases occurring within the entire applied range of the NLR. Simultaneously, the nitrogen removal rate increased proportionally with the NLR where the nitrogen oxidation efficiency reached 48–58% regardless of actual temperature and NLR. These observations clearly demonstrate the temperature stability of applied partial nitritation system during the tested temperature fluctuations.

A model for determination of operational conditions for successful shortcut nitrification.

Accumulation of nitrite in shortcut nitrification is influenced by several factors including dissolved oxygen concentration (DO), pH, temperature, free ammonia (FA), and free nitrous acid (FNA). In this study, a model based on minimum dissolved oxygen concentration (DOmin), minimum/maximum substrate concentration (Smin and Smax), was developed. The model evaluated the influence of pH (7-9), temperature (10-35°C), and solids retention time (SRT) (5days-infinity) on MSC values. The evaluation was conducted either by controlling total ammonium nitrogen (TAN) or total nitrite nitrogen (TNN), concentration at 50mgN/L while allowing the other to vary from 0 to 1000mgN/L. In addition, specific application for shortcut nitrification-anammox process at 10°C was analyzed. At any given operational condition, the model was able to predict if shortcut nitrification can be achieved and provide the operational DO range which is higher than the DOmin of AOB and lower than that of NOB. Furthermore, experimental data from different literature studies were taken for model simulation and the model prediction fit well the experiment. For the Sharon process, model prediction with default kinetics did not work but the model could make good prediction after adjusting the kinetic values based on the Sharon-specific kinetics reported in the literature. The model provides a method to identify feasible combinations of pH, DO, TAN, TNN, and SRT for successful shortcut nitrification.