Modeling the system dynamics for nutrient removal in an innovative septic tank media filter

Abstract

A next generation septic tank media filter to replace or enhance the current on-site wastewater treatment drainfields was proposed in this study. Unit operation with known treatment efficiencies, flow pattern identification, and system dynamics modeling was cohesively concatenated in order to prove the concept of a newly developed media filter. A multicompartmental model addressing system dynamics and feedbacks based on our assumed microbiological processes accounting for aerobic, anoxic, and anaerobic conditions in the media filter was constructed and calibrated with the aid of in situ measurements and the understanding of the flow patterns. Such a calibrated system dynamics model was then applied for a sensitivity analysis under changing inflow conditions based on the rates of nitrification and denitrification characterized through the field-scale testing. This advancement may contribute to design such a drainfield media filter in household septic tank systems in the future.

System Dynamics Modeling of Nitrogen Removal in a Stormwater Infiltration Basin with Biosorption‐Activated Media

“…Coupled feedback loops, stocks, and flows are used to structure interactions among variables and to demonstrate the dynamic behavior of the whole system over time. The model was originally developed during the mid‐1950s (Forrester, 1971) and has been extensively used to address a wide variety of environmental and ecological studies, including tree growth (Pan and Raynal, 1995), lake eutrophication assessment (Vezjak et al, 1998), bioavailability of metals in wetlands (Wood and Shelley, 1999), groundwater recharge (Abbott and Stanley, 1999), waste management (Dyson and Chang, 2005), water reallocation (Elmahdi et al, 2007), and wastewater treatment (Xuan et al, 2010, 2011). Thus, system dynamics modeling is well suited for studying N transformations due to the cycling and feedback feature of N species in stormwater management, although few studies have been performed for such purposes.…”

“…In addition to this main loop, a variety of reverse reactions produce internal loops among different compounds, such as N uptake (NH 4 + to ON), dissimilatory nitrate reduction to ammonium (NO 3 – to NH 4 + ) (Canfield et al, 2010), and volatilization (NH 4 + to NH 3 ). To better recognize such a dynamic complex system involving various circular, interlocking relationships among its compounds, system dynamics modeling has been recently applied to “visualize” the nutrient removal process in some semi‐enclosed subsurface treatment facilities (Xuan et al, 2010, 2011).…”