Abstract
Absence of microbial indicators from groundwater does not always mean absence of contamination. Research in sub-Saharan Africa warns against generalized assumptions - and solutions. Faecal contamination of groundwater is only significant if a threat to human health is posed; it is possible that there may be contamination without posing such a risk (raised nitrate levels, though still complying with water quality standards, and an absence of pathogens). The resource management issue here would be whether the long-term trend was for nitrate levels to exceed quality standards. It is also important to note that research has yet to be carried out correlating the persistence and transport of standard microbial indicators (faecal coliforms and faecal streptococci) with actual pathogens. Whilst there are currently no better alternatives to these standard indicators, the assumption that an absence of indicator species equates to an absence of pathogens may be unsafe. Research at the Robens Centre (in collaboration with Birmingham University) into enterovirus occurrence and transport in groundwater is ongoing. Whilst it is accepted that the provision of on-site sanitation facilities will have a positive impact on human health, it is equally clear that impacts on groundwater quality will result. Experience has shown that once contaminated, groundwater is often extremely costly to treat. To maximize public health benefits, an integrated approach to sanitation and groundwater management is required, based on a long-term cost-benefit decision-making process. It is vital to this process that further progress is made on the understanding of the persistence and transport of sewage contaminants in groundwater.