Emerging countries frequently afflicted by waterborne diseases require safe and cost-efficient production of drinking water, a task that is becoming more challenging as many rivers carry a high degree of pollution. A study was conducted on the banks of the Yamuna River, Delhi, India, to ascertain if riverbank filtration (RBF) can significantly improve the quality of the highly polluted surface water in terms of virus removal (coliphages, enteric viruses). Human adenoviruses and noroviruses, both present in the Yamuna River in the range of 10(5) genomes/100 mL, were undetectable after 50 m infiltration and approximately 119 days of underground passage. Indigenous somatic coliphages, used as surrogates of human pathogenic viruses, underwent approximately 5 log10 removal after only 3.8 m of RBF. The initial removal after 1 m was 3.3 log10, and the removal between 1 and 2.4 m and between 2.4 and 3.8 m was 0.7 log10 each. RBF is therefore an excellent candidate to improve the water situation in emerging countries with respect to virus removal.

Waterborne diseases are frequent and recurrent episodes in developing countries with deficient sanitary conditions affecting drinking water. Waterborne epidemics might affect thousands of persons, like the Hepatitis-E-epidemics of Kuntra (Naik et al. 1992) and Delhi (Ramalingaswami and Purcell, 1988) with 79,000 and 25,000 ill persons respectively. It is not by chance that both epidemics occurred after drinking water treatment suffered a failure, allowing contaminated drinking water to reach the consumers. In order to ameliorate the consequences of water scarcity and poor sanitary conditions, systems for obtaining drinking water are needed which are efficient, robust, and require only low-cost technology. River Bank Filtration (RBF) is a process during which surface water is induced to infiltrate into the subsurface, either due to a natural hydraulic gradient or the depression cone of an abstraction well. During infiltration and soil passage, the quality of the surface water is substantially improved thanks to a combination of physical, chemical, and biological processes such as filtration, dilution with genuine groundwater, sorption and biodegradation of pollutants Apart from pathogens, organic trace compounds are widespread pollutants in rivers and lakes. The capacity of RBF to effectively or even completely remove both, pathogens and many organic contaminants has been confirmed in numerous investigations (e.g., Matthess et al. 1988). Its low costs in technology and labor makes RBF a very suitable drinking water treatment tool for developing countries. The aim of this study was to ascertain if RBF kept its power to remove pollutants and pathogens even in highly polluted waters as they are encountered in many urban agglomerations in developing countries.