Evaluation of Nano and Micro Zero Valent Iron and Granular Activated Carbon in Household Water Purification System

In order to ensure drinking water meets the standards, utilization of novel treatment technology with low cost and minimum effects on environment is inevitable. Zero-valent-iron in micro and nano scale is extensively used to remove wide range of contaminants from water. Besides the ZVI, granular activated carbon is used in household water purification systems as a low-price, porous medium that adsorbs different contaminants (e.g. organic species and chlorine) and modifies the odor and turbidity of water. The aim of this study is investigation of the efficiency of ZVI and GAC in the treatment of tap water. In this study, the efficiency of zero-valent-iron in scales of nano (NZVI, d50=50 nm) and micro (MZVI, d50=50 µm) and granular activated carbon (GAC, d50=1 mm) in purification of tap water is evaluated. For this purpose, five experimental columns (length=50 cm and inner diameter=2 cm) filled by nano and micro ZVI, and GAC in different mass percentages are prepared, whereas continuous tap water flow of Tehran at the rate of 4.4 ml/min during 28 days (totally 177 liters) is injected through each reactive column. Temporal variations of calcium, magnesium, sodium, potassium, nitrate, and total iron, as well electrical conductivity, pH in the influent waters to and effluent waters from the five reactive columns are sampled and analyzed three times over experimental time at the end of 1st, 7th, and 28th day (totally 18 samples). Simultaneously with the water sampling, the variations of pore water pressure along the columns are measured through pressure gauges. The results indicated that the reactive column containing NZVI (individually or combined with GAC) are proficient in reduction of ions concentration from the influent water in comparison to those containing MZVI and GAC. Decreasing the permeability of reactive materials, reduction of reactivity over time, release of iron into effluent water, and increase of water alkalinity are challenges accompanied by the columns containing NZVI. Results of this study reveal that combinational use of GAC and MZVI in household purification system provides a potentially promising reactive medium with acceptable pollutant removal efficacy and life-time, as well less side effects.