Abstract
System dynamics is considered as a computer-aided approach to policy analysis and design. It includes the response and reaction of a system to external shocks. In the present research, following the sampling and testing phases, a system dynamics model was developed for modeling of phosphorus in facultative stabilization ponds. First, the scheme of soluble reactive phosphorous stock, its specifications and parameters were determined and created in the VenSim PLE 7.1 software. Then, mathematical relations were determined for each process. Finally, the model was calibrated and verified based on the data from the Yazd facultative ponds, Iran. Sensitivity analysis showed that the most important factors affecting phosphorus concentration in the ponds are the phosphorus settling rate, losses caused by algal respiration and excretion, while the losses caused by herbivorous zooplanktons, hydrolysis rate of inorganic carbon, and ratio of phosphorus to chlorophyll-a had the least importance. Results showed that, algal growth rate and phosphorus settling rate were important factors in phosphorus removal. Hence, with appropriate retention time in the pond, it can be managed more properly. The ratio of phosphorus to algae had less importance in the model. The ratio of carbon to phosphorus and rate of respiration of carnivorous zooplanktons did not affect the phosphorus concentration. It is recommended that this model can be used for pond management and overall assessment of facultative ponds.
Highlights
Wastewater stabilization ponds (WSPs) are the simplest and most widespread wastewater treatment plants for stabilizing biodegradable materials (Beran and Kargi 2005; Sah et al 2011)
In a study conducted in vitro, the results showed that Dynamics Models can be used to determine the purification efficiency of stabilized ponds
Since the first facultative pond has the potential for wastewater treatment, sampling and modeling was done in this pond
Summary
Wastewater stabilization ponds (WSPs) are the simplest and most widespread wastewater treatment plants for stabilizing biodegradable materials (Beran and Kargi 2005; Sah et al 2011). WSPs provide suitable conditions for natural wastewater treatment processes by natural forces such as sunlight, wind, temperature, wild plants, and animal life (Samaei et al 2016a). WSPs employ the most basic methods for wastewater treatment in developing countries, especially in the hot climate region (Møller et al 2016; Shahi et al 2013). Shahsavani et al AMB Expr (2019) 9:157 dissolved oxygen while lower layer has anaerobic conditions as a result of lack of dissolved oxygen (Sah et al 2011). FPs have usually depths of 1.5–2.5 m and their retention time is 30 to 70 days (Sah et al 2011)
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