Performance Evaluation of a Subterranean Arsenic Removal (SAR) Community Water Treatment Plant: A Sustainable Long-Term Approach to Removing Arsenic from Drinking Water

Subterranean arsenic removal (SAR) is a low-cost, zero-waste, and ‘easy to operate’ process that can remove arsenic and iron from groundwater without using any adsorption bed. The SAR plant creates an aerobic high Eh bed in the aquifer by recharging oxygenated groundwater, thereby supporting the growth of arsenic and iron oxidizing aerobic bacteria. The arsenic and iron are immobilized in the aquifer sand in the forms of As (V) and Fe(III), respectively. This work reports the key performance data of a SAR plant installed at Ghetugachi village in West Bengal, India under an increased demand three times above the designed production volume. The naturally occurring water has an As concentration of 154 ppb, which was decreased to 13 ppb for 3000 L per day (LPD) water during the period of 2009 to 2015. However, with an increase in demand of up to 10,000 LPD, due to an increase in local consumer population, the As in the SAR treated water increased to 30 ppb. In order to control the As and Fe levels, a novel HAIX-nano Fe resin bead media filter (Lehigh University) was installed in line with the SAR plant thereby reducing the As and Fe in delivery water to 6 ppb and 240 ppb, respectively. This resulted in low filter cost, no filter clogging over the past 6 months, and a lower maintenance cost of both the SAR plant and HAIX media filter. The combined SAR-HAIX plant has been able to maintain a favourable Eh–pH value of the water in order to immobilize the arsenic and iron consistently over the last 6 months of the study. Locally, ~600 people and two schools depend upon the safe water supplied by this plant and the operating cost comes to about $30.00 US dollars a month to produce 10,000 L of safe water per day.