Effectiveness of point-of-use (POU) filter system for removal of contaminants from water

Abstract

Groundwater supplies most of the drinking water in the small settlements in the Danubian plain region of Bulgaria. The region is mostly agricultural, leading to chemical pollution, mostly with nitrogen, of the shallow groundwater. Direct health concerns, linked to nitrates contamination of water, determine the increased popularity of drinking water point-of-use (POU) filtration pitchers. The objective of this study was to evaluate the effectiveness of a commercial pitcher filtration system in removing select pollutants, such as metal ions, namely, copper and iron, nitrate nitrogen, and suspended solids (algal culture of Monoraphidium contortum) from augmented tap water. In addition, we have studied the effects on electrical conductivity and pH of water. The POU system of choice was a widely used brand name in Bulgaria, providing cartridges that fit most of the European pitcher filter brands. We have evaluated the performance of the filters at three different exploitation intervals – pre-washed new filter (0%), 50%, and 100% of the exploitation capacity set according to manufacturers’ claims of recommended volume of water, as well as at different contact times between the water and the filter media. The results indicate that the efficiency of the filters diminishes with aging and increases with increasing contact time – multiple filtrations. The efficiency in terms of electrical conductivity and amount of iron decreases proportionally with filter age, and in terms of phosphates, the maximum effect is observed in filters at 50% capacity. Water filtration reduced water conductivity by 12% in a single filtration and stabilized the pH values towards the neutral range. The effect on pH values is inversely proportional to the buffering capacity of the water. The filters removed 85–98% of copper ions and 20% of iron ions. Nitrate removal efficiency averages 40% and doubling the contact time increases the efficiency to 70%. The efficiency of removing suspended solids is on average 17%, mainly due to the small size of the particles. Overall, the POU systems are an effective way to purify water at home. The filter cartridges effectively reduce contaminants, such as metals and nitrates, which are particularly problematic in areas supplied by groundwater sources.