In the Republic of Panama there are many schools located in rural areas where there are no municipal sewage systems. Many project contractors take as a reference the septic tank system as the most versatile primary system in terms of wastewater treatment plant management. This study presents a comparative modeling between an Imhoff Tank treatment system and the Upflow Anaerobic Sludge Blanket Sludge Reactor system for schools. Results indicates that the second treatment system is more economically efficient having an advantage of 48% in terms of construction cost per square meter, 2% less than the first system (Imhoff Tank) and an advantage as an anaerobic system in the removal of solids with 76.7% (87.11 mg/L) of capacity.