Costs of conventional vs. membrane treatment for karstic spring water

Water production technology for the treatment of karstic springs has to cop e with high fluctuations of various water quality parameters, in particular with high turbidity peaks. in addition, natural and manmade dissolved cont aminants such as NOM, pesticides and chlorinated hydrocarbons require compl ex multistage treatment schemes applying conventional process trains like f locculation, granular media filtration, ozonation, granular activated carbo n filtration and final disinfection. Several alternatives using membrane pr ocesses are proposed in order to simplify the plant schemes and to reduce t reatment costs. A cost assessment of existing conventional treatment plants and following membrane systems of the same size is presented: micro-, ultr afiltration with and without powdered activated carbon (PAC) and the integr ated system ultrafiltration-nanofitration (MF, UF, MF/PAC, UF/PAC, UF/NF). Based on full- and pilot-scale experience with karstic spring water, capita l as well as operating and maintenance costs (O&M) for conventional and mem brane plants are evaluated. Detailed cost analysis reveals that compared to conventional systems, membrane treatment leads to a substantial relative i ncrease of O&M fraction. Especially, the dosing of PAC to MF or UF increase s 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 combina tions may not compete with conventional and UF/PAC plants.