Abstract
The aim of the present paper is to develop a reliable and accurate model of the wastewater biochemical treatment process and to explore the behaviour through a general dynamic simulation environment, namely the INtegrated Simulation Environment Language (INSEL), for the analysis of the energy demand of the whole wastewater treatment plant. In particular, the presented model pays special attention to the chemical kinetics involved in the activated sludge process for the reduction of nitrogen and carbon compounds. According to the best practices, the plant configuration considered in this work includes the denitrification-nitrification process, performed by completely mixed reactors. In particular, the process analysed in this paper is based on the Ludzak-Ettinger process. The biological process is simulated according to the well-known method widely used in the literature, namely the Activated Sludge Model No 1 (ASM1). The model includes a set of equations for the calculation of aerobic growth of heterotrophs, anoxic growth of heterotrophs, aerobic growth of autotrophs, decay of autotrophs, ammonification of soluble nitrogen, hydrolysis of entrapped organics, and hydrolysis of entrapped organic nitrogen. All these equations, along with energy and mass balances, are solved by the explicit Euler method. The developed model is validated using literature data, showing a great accuracy (deviation below 1%). As for the temperature, results show that, between 15 and 25 °C, in the initial part of the process, transport effects dominate the consumption ones. When the temperature is higher than 30 °C, nitrate consumption is so fast that biomass growth is limited by this effect. Conversely, in case of low temperatures (5–10 °C), biomass growth is not limited by nitrate availability. Finally, results also showed that temperature significantly affects the denitrification process, whereas the effect on the oxygen is lower.
Highlights
The majority of Countries implemented several actions to avoid the disposal of wastes and wastewater without treatment in land and water bodies, since it determines harmful effects on the health of environment, humans and animals [1]
The validation of the anoxic tank and aerobic tank model, as well as the validation of the whole process, was performed on seven days of simulations, according to the available data. These data are included in a fully defined simulation protocol developed as a tool for evaluating activated sludge wastewater treatment control strategies
Results showed that biomass growth is only slightly affected by the selection of the kinetic constant, which should increase from 0.001 to 10 gm−3 in order to detect a relevant effect on the growth of the biomass
Summary
The majority of Countries implemented several actions to avoid the disposal of wastes and wastewater without treatment in land and water bodies, since it determines harmful effects on the health of environment, humans and animals [1]. Conventional wastewater treatment plants are extremely intensive energy consumers [2], since their processes require large amounts of electrical and thermal energy. Data from Germany as well as from Italy show that electricity demand for wastewater treatment accounts for about 1% of total consumption of the country [3]. The high energy consumption in wastewater treatment plants is mainly due to their heavy mechanical systems, such as pumps and aeration systems, for moving and treating wastewater [4]. Due to the high energy consumption of the wastewater treatments plants, more sustainable and energy-efficient treatments have been developed [5]. For example the production of biological energy by-products, such as biogas or biomethane, is obtained by the conversion of wastewater into a stabilised waste [6].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
