Invasion moving boundary problem for a biofilm reactor model

The work presents the analysis of the free boundary value problem related to the invasion model of new species in biofilm reactors. In the framework of continuum approach to mathematical modelling of biofilm growth, the problem consists of a system of nonlinear hyperbolic partial differential equations governing the microbial species growth and a system of semi-linear elliptic partial differential equations describing the substrate trends. The model is completed with a system of elliptic partial differential equations governing the diffusion and reaction of planktonic cells, which are able to switch their mode of growth from planktonic to sessile when specific environmental conditions are found. Two systems of nonlinear differential equations for the substrate and planktonic cells mass balance within the bulk liquid are also considered. The free boundary evolution is governed by a differential equation that accounts for detachment. The qualitative analysis is performed and a uniqueness and existence result is discussed. Furthermore, two special models of biological and engineering interest are discussed numerically. The invasion of Anammox bacteria in a constituted biofilm inhabiting the deammonification units of the wastewater treatment plants is simulated. Numerical simulations are run to evaluate the influence of the colonization process on biofilm structure and activity.Comment: 20 pages, 11 figures, original pape

Aeration strategies to improve nitrogen removal using deammonification process in EGSB reactor.

Anaerobic digestion technology for stabilization and organic matter removal from swine slurry is widely used and long known, but this method not degrades nitrogen compounds present in abundance in the digestate. So, deammonification is being studied as an alternative for post treatment. In this process, two groups of bacteria nitrifying bacteria (aerobic microorganisms) and anammox (anoxic microorganisms) have to cooperate to complete ammonia remove. In this process, the ammonia oxidation by partial nitrification (PN) generate substrate to anammox activity, so there must have PN control to prevent nitrite accumulation. This way making the dissolved oxygen (DO) supply an important key to control and stabilization process. The present study aimed to test the aeration effect on the nitrogen removal using deammonification process in an EGSB reactor. The results show the use of DO control to avoid nitrite accumulation in a deammonification single reactor is a good strategy to increase anammox activity

Small aggregates can cause nitrite accumulation in one-stage partial nitritation and anammox

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Generation of (synthetic) influent data for performing wastewater treatment modelling studies

The success of many modelling studies strongly depends on the availability of sufficiently long influent time series - the main disturbance of a typical wastewater treatment plant (WWTP) - representing the inherent natural variability at the plant inlet as accurately as possible. This is an important point since most modelling projects suffer from a lack of realistic data representing the influent wastewater dynamics. The objective of this paper is to show the advantages of creating synthetic data when performing modelling studies for WWTPs. This study reviews the different principles that influent generators can be based on, in order to create realistic influent time series. In addition, the paper summarizes the variables that those models can describe: influent flow rate, temperature and traditional/emerging pollution compounds, weather conditions (dry/wet) as well as their temporal resolution (from minutes to years). The importance of calibration/validation is addressed and the authors critically analyse the pros and cons of manual versus automatic and frequentistic vs Bayesian methods. The presentation will focus on potential engineering applications of influent generators, illustrating the different model concepts with case studies. The authors have significant experience using these types of tools and have worked on interesting case studies that they will share with the audience. Discussion with experts at the WWTmod seminar shall facilitate identifying critical knowledge gaps in current WWTP influent disturbance models. Finally, the outcome of these discussions will be used to define specific tasks that should be tackled in the near future to achieve more general acceptance and use of WWTP influent generators

Совершенствование биотехнологий удаления азота и фосфора из городских сточных вод

Изложены теоретические основы удаления из сточных вод соединений азота, основанные на процессах аммонификации, нитрификации и денитрификации, а также более современное направление – ANAMMOX-технология, отмечены условия, благоприятствующие каждому процессу. Указана необходимость чередования анаэробиоза и аэробиоза и другие условия, необходимые для удовлетворительного протекания биологической дефосфотации. Проведен обзор современных направлений совершенствования биотехнологий очистки городских сточных вод от соединений азота и фосфора. Одним из направлений повышения эффективности биологической дефосфотации считается увеличение содержания летучих жирных кислот. Это обеспечивается предварительной ацидофикацией сырого осадка либо размещением загрузки в анаэробной и аноксидной зонах. Важным фактором повышения степени очистки сточных вод с одновременным снижением энергетических затрат является предварительный контакт исходных сточных вод с циркуляционным активным илом в условиях аэрации. С целью снижения энергетических затрат на очистку сточных вод предложены ступенчатая денитрификация и технология с карусельной зоной. Реализация в одном объеме нитрификации и денитрификации упрощает инженерное оформление, гибкая адаптивная система расположения блоков позволяет получить лучшие результаты очистки. Использование повышенных доз активного ила и прикрепленных микроорганизмов, применение мембранных методов позволяет существенно увеличить производительность сооружений при уменьшении их объема