Modeling and Comparison of the Modified Ludzack–Ettinger Process with Septic Tank Integration for Wastewater Treatment in Small Communities Using GPS-X

Aim: 
Wastewater treatment in small-population communities has challenges. The current study aims to modeling and comparison of the Modified Ludzack–Ettinger (MLE) process with septic tank (SEP) integration for wastewater treatment in small communities using GPS-X.
Methods: 
In this study, two scenarios MLE and SEP-MLE processes for wastewater treatment were simulated using the data of the Noshabad city wastewater treatment plant as a small community and GPS-X software. In this model, the removal of total suspended solids (TSS), chemical oxygen demand (COD), total nitrate (TN), and total phosphorus (TP), the effect of quantitative and quality variations of influent wastewater in shock load conditions on the effluent quality were investigated.
Results: 
Removal efficiency of TSS, COD, TN, and TP for SEP-MLE processes were 96.7, 92.8, 68.3, and 47.1%, and for MLE were 98, 93.6, 69.3, and 52.9%, respectively. The SEP-MLE process demonstrated superior quantitative shock resilience (40%) compared to the MLE process (18%), whereas both processes displayed comparable qualitative shock resilience (17%). The MLE process generated a larger volume of sludge (21 m³/day) with a lower concentration (0.8%) and volatile solids reduction (35%) compared to the SEP-MLE process (2.5 m³/day, 5%, and 38%). Furthermore, the SEP-MLE process incurred reduced initial investment costs ($1084 compared to $1328) and decreased operational costs ($32 compared to $34) relative to the MLE process.
Conclusions: 
According to the results, a septic tank and MLE combination were an effective process for wastewater treatment in small communities.