Study of a hybrid process combining zonation and microfiltration/ultrafiltration for drinking water production from surface water

A hybrid process, consisting of zonation and membrane filtration, followed by activated carbon filtration, was studied in pilot scale for drinking water production from river water. The main focus of this study centred on tests to determine the effect of ozone on the filtration and fouling behaviour of ceramic microfiltration and ultrafiltration membranes with pore sizes of 0.1 mu m and 20 kD as well as on the quality of the water produced. The results showed that a certain ozone concentration in the permeate was required to maintain stable and high permeate fluxes during microfiltration and ultrafiltration of river water without backflushing. For the membranes under study, a minimum concentration of 0.05 mg ozone per litre in the permeate was needed. Furthermore, as the ozone dosage was increased, permeate fluxes rose to the values of pure water permeability depending on ozone doses. Ultrafiltration of the river water with the addition of ozone showed that yields of 99% can be achieved without reducing membrane permeability while obviating the need for membrane backflushing. In order to assess the treatment process and the water qualities generated, the most important chemical and microbiological analytical parameters were determined in the feed river water and in the treated water after each treatment stage and were then compared. The results of the analysis showed that, due to this treatment process, the concentration of the organic components in the water, determined as total organic carbon (TOC), chemical oxygen demand as permanganate demand (COD), adsorbable organic halogens (AOX) and spectral absorption coefficient (SAC(254)), could be reduced to values under the respective determination limit. Moreover, microbiological analysis showed that coliform bacteria, E. coli, Pseudomonas aeruginosa, Clostridia and faecal streptococci, which were sometimes present in the river water, could be eliminated completely. Therefore all the parameters analysed for the fresh water produced, fulfilled the requirements of the German Drinking Water Regulations.