Natural Engineered Systems: A Sustainable Alternative for Drinking Water Treatment

Natural engineered systems for groundwater and surface water treatment have the potential to provide safe drinking water in the rural developing country context. A “natural” system treats the water through soil passage, utilizing the subsurface as a naturally available filter. (In)organic compounds are removed from the water by soil passage through processes of filtration, adsorption, oxidation and biodegradation. Therefore, natural engineered systems can have substantial benefits for decentralized applications since they combine two important aspects of water supply: quality improvement and protected storage. Bank filtration and artificial recharge have been found to achieve a 4 log or more reduction of protozoa, bacteria and viruses. Subsurface iron and arsenic removal combines oxidation and adsorption to retain these inorganic constituents on the soil grains. Natural engineered systems have not yet found widespread implementation in the developing world, but they are robust, inexpensive and safe alternatives to conventional drinking water treatment. At existing locations, long-term effects, such as clogging of the subsurface, have not proven to threaten the sustainable application of these technologies. Nevertheless, there is still a need for engineering guidelines to improve the removal efficacies and expand the lifespan of natural systems in the diverse hydro(geo)logical settings.