The availability of affordable and reliable clean water is one of the major global issues at present times. Groundwater is increasingly contaminated by various anions, rendering the water unsuitable for human consumption, and posing ecological threats. Anions like nitrate and fluoride are detrimental to human health even at low concentrations and exhibit various levels of toxicity. Traditional groundwater treatment methods like adsorption, ion exchange, membrane filtration and chemical or biological reduction can remove these target pollutants, but they have limitations, such as generating concentrated brine and causing secondary pollution. Further it can be even more challenging to treat contaminated waters such as secondary effluents with low concentration of pollutants.

A Continuous Integrated system consisting of an Ion Exchange Membrane Bioreactor coupled with defluorination unit is implemented that combines advantage ion exchange processes, biological reduction and precipitation using coagulant to effectively eliminate the nitrate and fluoride from the contaminated groundwater without compromising the treated water quality. A unified two step approach for elimination of nitrate and fluoride was implemented. First separation of target pollutants from feed side to receiver using anion exchange membranes, the next following steps focusses on elimination of nitrate and fluoride from the receiver side using biological reduction and coagulation-flocculation respectively.

The synthetic groundwater used for study contained various anions like fluoride, nitrate, sulphate, chloride, alkalinity, and humic acid to replicate the actual composition of the groundwater collected from field. For the separation studies two membranes, FAD PET 75 and FAS PET 75 were used and their removal efficiency under different field conditions were studied with the removal efficiency of more than 95% and 90% for the target pollutant nitrate and fluoride. For the accumulated nitrate and fluoride, bioreactor followed by coagulation-flocculation unit is provided. The bioreactor consists of open pore spiral packing media and is filled with the sludge maintained at anoxic conditions, with the ORP in the range of -50 to -200 mV. The denitrification efficiency of >95% was achieved with glycerol as carbon source, HRT as 2 h and C/N ratio in the range of 1.8 – 2. For the defluorination unit the optimal pH was observed at 8.5 and with the coagulant dosage of 1.5 g/L and turbidity as 20 NTU removal efficiency of >98% was achieved. Once the individual system was optimized the systems were connected to operate in continuous loop. The continuous treated groundwater from the integrated system was obtained at the flow rate of 100 mL/h.