Cost and Land Functions for Wastewater Treatment Projects: Typical Simple Linear Regression versus Fuzzy Linear Regression

This paper analyzes cost data pertinent to the municipal wastewater treatment plants (MWTP) in Greece. First, data have been collected with onsite visits and contain the land size necessary for a MWTP, the construction cost, and the operation and maintenance cost of existing wastewater treatment facilities. Second, they come from analytical budgeting of natural wastewater treatment system units. Twelve equations of the form ln Yi = A0i + A1i ln Xi are estimated both with ordinary least squares (OLS) and fuzzy linear regression (FLR). The root mean square error and the mean absolute error are used as fitting measures for the comparison of the OLS with the fuzzy estimations. It is shown that the FLR did produce very similar estimates but slightly inferior to those of OLS in most of the cases for these particular datasets.