NUR and our relationship in BNR processes with sewage at different temperatures and its design application

Model based evaluation of plant improvement at a large wastewater treatment plant (WWTP)

In this work, the effect of the improvement carried out at a large-scale wastewater treatment plant (WWTP) was evaluated, by means of modelling works, with the aim to determine the influence of the modernization over the process performance. After modernization, the energy consumption due to the aeration decreased about a 20% maintaining the effluent quality. In order to double-check the good effluent quality, modelling works were carried out at the full-scale plant. After calibration, the model was applied to the upgraded full-scale plant obtaining deviations lower than 10%. Then, the performance of the main biochemical processes was evaluated in terms of oxygen uptake rate (OUR), ammonia uptake rate (AUR), and chemical oxygen demand (COD) consumption. The rate of the main processes depending on the aeration, that is OUR and AUR, were about 22 gO₂/(kg VSS·h) and 2.9 gN/(kg VSS·h), respectively.

Microbial population response to changes of the operating conditions in a dynamic nutrient-removal sequencing batch reactor

A nutrient-removal sequencing batch reactor operated with short anaerobic/aerobic cycles was subjected to different operating conditions, namely, cycle length, feeding pattern and feed composition. The changes in microbial population, as well as the contribution of microbial groups to the total nutrient removal, were estimated using the kinetic parameters obtained in this study. Denitrifying polyphosphate-accumulating organisms (DPAOs) were detected in the system, representing a fraction of 23% of phosphorus-accumulating organisms (PAOs). The results suggest that DPAOs and non-DPAOs are different microorganisms. The presence of nitrate in the feed stimulated DPAOs to predominate over non-DPAOs. Feeding the reactor with a mixture of organic substrates also stimulated DPAOs. Glycogen-accumulating organisms (GAOs) were likely to be present in the system and their development over PAOs was apparently favoured by increasing the aeration time and feeding during the aerobic phase. In contrast, the presence of propanoate in the feed apparently favoured PAOs over GAOs.