Technology comparison for the sustainable treatment of municipal wastewater in small communities of Costa Rica: Surface requirements, building cost and operating and maintenance cost

Abstract

This article discusses the sustainable treatment of sewage for small communities in Costa Rica. Although recent efforts show a political interest in improving the country's historical lag in sanitation infrastructure, there are few references that guide the selection process of the most appropriate technology and scale for the systems to be installed. This work provides an analysis of three technologies for wastewater treatment plants (WWTP) of feasible application in the country. For this, the area demand (AD), the building cost (BC) and the operation and maintenance cost (O&MC) of STPs at different scales were estimated. It was shown that systems with constructed wetland have the highest AD and the lowest BC and O&MC. The systems with upflow anaerobic sludge blanket reactor followed by trickling filter (UASB + TF) had a larger AD than those of activated sludge with extended aeration (ASE), with BC smaller for the first technology and CO&M 50 to 100% higher for ASE. The study found that the current practice of extended use of small-scale ASE systems is not the most sustainable option. Thus, it is advised that future WWTP consider larger scales and alternative technologies, emulating some recent successful experiences in countries with similar conditions.