- Understanding influent makeup, concentration, and volume (flow)
- Current and anticipated future effluent discharge requirements
- Potential changes in influent
- Budgetary constrains for capital expenditure and ongoing operations/maintenance
- Life expectancy of the treatment system and ability to modify if needed
Recently, I came across an interesting table from Mara & Pearson (1998) comparing capital expense, O&M, and land requirements for various treatment systems. While the figures are in DM (1996), the relative costs can be extrapolated to current figures.