This Brazilian work evaluates the influence of specific operational conditions on the performance of a spiral-wound ultrafiltration pilot plant for direct drinking water treatment, installed at the Guarapiranga reservoir in the Sao Paulo Metropolitan Region.
Results from operational tests show that the volume of permeate produced in the combination of periodic relaxation with flushing and chlorine dosage procedures was 49% higher than the volume obtained when these procedures were not used.
Two years of continuous operation demonstrated that the ultrafiltration pilot plant performed better during autumn and winter, with higher permeate flow production and reduced chemical cleaning frequency.
Observed behaviour seems to be associated with the algal bloom events in the reservoir, which are more frequent during spring and summer, confirmed by chlorophyll-a analysis.
Concentrate clarification using ferric chloride was quite effective in removing natural organic matter (NOM) and turbidity, allowing its recirculation to the ultrafiltration feed tank. This procedure made it possible to reach almost 99% water recovery considering a single 54 hour recirculation cycle.
Water quality monitoring demonstrated that the ultrafiltration pilot plant was quite efficient, and that potential pathogenic organisms, E. coli and total coliforms, turbidity and apparent colour removals were 100%, 95.1%, and 91.5%, respectively.
