Bank filtration is a natural pre-treatment technology, which enables the utilisation of surface water sources such as lakes or rivers.  The water passes through the natural porous sub-surface (aquifer) to the production well. The porous media serves as a natural filter and reduces the amount of suspended solids and pathogens. Bank filtrate monitored in recent years has shown a significantly higher quality compared to water abstracted directly from surface or groundwater sources. For conventional treatment, high concentrations of organic contaminants requires high (40–60 mg/L) doses of chlorine prior to flocculation thus creating a greater risk for formation of carcinogenic disinfection by-products, as reported in Mathura (Singh et al. 2010) . In such situations BF is advantageous as a pre-treatment in order to reduce the necessary doses of chlorine prior to flocculation. Additional advantages of BF may also be seen during the monsoon season principally in the removal of turbidity and pathogens, as well as in the removal of colour and dissolved organic carbon (DOC), UV absorbance, turbidity, total and thermotolerant coliform counts (Dash et al. 2008 ; Sandhu et al. 2010 ; Thakur et al. 2009a, 2009b ; Dash et al. 2010 ). Bank filtration, however, does not present an absolute barrier to other substances of concern (e.g. ammonium) and some inorganic trace elements may even be mobilized. In Delhi, which has poor surface water quality, extensive post-treatment must be applied to remove high levels of ammonium (Sprenger et al. 2008). Similar aquifer contamination has also been observed in Europe (e.g. Berlin) downstream of sewage irrigation fields. Detailed investigations (Hamann 2009) have shown that even after source water improvement, ammonium will continue to be leached from the soil for decades.

See below a short movie about river bank filtration by the HTW Dresden.

References

Singh P, Kumar P, Mehrotra I, Grischek T (2010) Impact of riverbank filtration on treatment of polluted river water. J Environ. Manage. 91(5), 1055-1062.

Dash RR, Mehrotra I, Kumar P, Grischek T (2008) Lake bank filtration at Nainital, India: water-quality evaluation. Hydrogeol. J. 16(6), 1089–1099. Dash RR, Bhanu Prakash EVP, Kumar P, Mehrotra I, Sandhu C, Grischek T (2010) River bank filtration in Haridwar, India: removal of turbidity, organics and bacteria. Hydrogeol. J. 18(4), 973-983.

Sandhu C, Grischek T, Kumar P, Ray C (2010) Potential for Riverbank filtration in India. Clean Techn Environ Policy doi: 10.1007/s10098-010-0298-0

Sandhu C, Thakur AK, Grischek T, Uniyal HP, Ojha CSP, Kumar S, Schoenheinz D, Eckert P, Kimothi PC (2008) Use of River Bank Filtration for Sustainable Drinking Water Supply in Haridwar, India. Presentation & Proc. International Groundwater Conference: Groundwater Dynamics and Climate Change, 19.-22.03.2008, Jaipur, India

Sandhu C, Grischek T, Schoenheinz D, Ojha CSP, Irmscher R, Uniyal HP, Thakur AK, Ray C (2006) Drinking water production in India—bank filtration as an alternative, Water Digest 1(3), 62–65 Dash RR, Bhanu Prakash EVP, Kumar P, Mehrotra I, Sandhu C, Grischek T (2010) River bank filtration in Haridwar, India: removal of turbidity, organics and bacteria. Hydrogeol. J. 18(4), 973-983

Sprenger, C., Lorenzen, G., Grunert, A., Ronghang, M., Dizer, H., Selinka, H. C. , Girones, R., Lopez-Pila, JM., Mittal, A., Szewzyk, R. (2011) The potential of river bank filtration for reducing viruses and chemicals from river water in mega-cities: The New Delhi Experience. Journal of Water, Sanitation and Hygiene for Development (submitted) Lorenzen, G. Sprenger, C., Taute, T., Pekdeger, A., Mittal, A., Massmann, G. (2010): Assessment of the potential for bank filtration in a water-stressed megacity (Delhi, India). Environmental Earth Sciences, DOI 10.1007/s12665-010-0458-x