Costs of conventional vs. membrane treatment for karstic spring water

Abstract

Water production technology for the treatment of karstic springs hasto cope with high fluctuations of various water quality parameters, in particular with high turbidity peaks. In addition, natural and manmade dissolved contaminants such as NOM, pesticides and chlorinated hydrocarbons require complex multistage treatment schemes applying conventional process trains like flocculation, granular media filtration, ozonation, granular activated carbon filtration and final disinfection. Several alternatives using membrane processes are proposed in order to simplify the plant schemes and to reduce treatment costs. A cost assessment of existing conventional treatment plants and following membrane systems of the same size is presented: micro-, ultrafiltration with and without powdered activated carbon (PAC) and the integrated system ultrafiltration—nanofitration (MF, UF, MF/PAC, UF/PAC, UF/NF). Based on full- and pilot-scale experience with karstic spring water, capital as well as operating and maintenance costs (O&M) for conventional and membrane plants are evaluated. Detailed cost analysis reveals that compared to conventional systems, membrane treatment leads to a substantial relative increase of O&M fraction. Especially, the dosing of PAC to MF or UF increases energy consumption and costs for PAC renewal. A comparison of the overall specific production costs shows that for the studied plant capacity in the range of 30–300 m 3/h, the costs for simple membrane treatment with MF or UF are 5% less than for conventional process schemes whereas the costs in combination with PAC are 20% higher. Integrated systems using UF/NF combinations may not compete with conventional and UF/PAC plants.