A Framework Based on Finite Element Method (FEM) for Modelling and Assessing the Affection of the Local Thermal Weather Factors on the Performance of Anaerobic Lagoons for the Natural Treatment of Swine Wastewater

Anaerobic lagoons are natural wastewater treatment systems suitable for swine farms in small communities due to its low operational and building costs, as well as for the environmental sustainability that these technologies enable. The local weather is one of the factors which greatly influences the efficiency of the organic matter degradation within anaerobic lagoons, since microbial growth is closely related to temperature. In this manuscript, we propose a mathematical model which involves the two-dimensional Stokes, advection–diffusion-reaction and heat transfer equations for an unstirred fluid flow. Furthermore, the Anaerobic Digestion Model No1 (ADM1), developed by the International Water Association (IWA), has been implemented in the model. The partial differential equations resulting from the model, which involve a large number of state variables that change according to the position and the time, are solved through the use of the Finite Element Method. The results of the simulations indicated that the methodology is capable of predicting reasonably well the steady-state of the concentrations for all processes that take place in the anaerobic digestion and for each one of the variables considered; cells, organic matter, nutrients, etc. In view of the results, it can be concluded that the model has significant potential for the design and the study of anaerobic cells’ behaviour within free flow systems.

Modeling and recycling simulation of the wastewater treatment plant of the city of Mrirt

This work focuses on the wastewater treatment plant (WWTP) in the city in Morocco called ‘Mrirt’. This WWTP produces quite noticeable odors especially from the anaerobic ponds, leading to the search for a solution to reduce odors. The location is not far from habitations. The solution chosen is the recycling of effluent from the exit of the plant towards the anaerobic ponds. The study consists in modeling the effect of recycling wastewater. Modeling discussed is to bring the operation of the anaerobic and facultative ponds by mathematical models that can then be used to perform simulations of the projected order to determine the impact on the recycling wastewater solution. Recycled effluent and its injection into anaerobic lagoons is a process and a new experience in Morocco. The simulation results of this new principle are quite promising and may thus constituted a platform for future projects of sewage treatment plants on the one hand and for projects and solutions to reduce odors from anaerobic lagoons on the other hand. It should be noted that it was very difficult to choose the parameters used as input data for modeling anaerobic lagoons.