Sanitation interventions: A threat to drinking water supplies in rural India?

Inadequate separation of excreta from human contact can lead to a number of health problems. This is a cause for concern in India because as many as 600 million people defecate in the open despite ongoing national programmes to curb this, and the Prime Minister of India having declared this as a national priority pledging to provide a toilet in every home by 2019. 

The paper titled 'Are sanitation interventions a threat to drinking water supplies in rural India? An application of tryptophan-like fluorescence' published in the journal Water Research, informs that toilets require installation of a sewerage system, which is unfeasible in many developing countries as it requires significant capital investment and piped water supply. Thus, on-site sanitation technologies such as leach pits or septic tanks are often preferred.

However, on-site sanitation can lead to leaching of human excreta directly into the sub-surface within the built up area and may pose as a threat to nearby groundwater derived potable supplies through the introduction of pathogens or elevated concentrations of nitrates. However, there are limited studies that have tried to explore these linkages between on-site sanitation technologies and groundwater contamination.

Faecal contamination of groundwater-derived potable supplies

The paper presents the findings of the study that explored the link between on-site sanitation technologies and groundwater contamination in four villages namely Maksudpur, Shahjahanpur, Sigariyawan and Taraura of Daniyawan block in Patna, Bihar and tested the ability of tryptophan-like fluorescence (TLF) technique as an indicator of faecal contamination in this setting.

The four villages provided an ideal case as sanitation interventions were being promoted within these villages and on-site sanitation installations included latrines and pour flush toilets with disposal into a leach pit or septic tank. These were done within the last two years and had been completed to less than 2 m below ground level. 150 water supply sources were sampled for faecal coliforms by using tryptophan-like fluorescence (TLF), an emerging real-time indicator of faecal contamination. Sanitary risk inspections were also performed at all sites, including whether a supply was located within 10 m of a toilet, the recommended minimum separation.

Findings of the study

• 18% of water supplies contained faecal coliforms, 91% of which were located within 10 m of a toilet. 58% had faecal coliforms above detection limit, and sanitary risk scores were high.
• The area showed low vulnerability to faecal contamination of aquifers due to leaching as the area was made up of unconsolidated aquifers, which were least vulnerable to pathogen contamination. This was because the protective clayey silt overlying the exploited horizon was prohibitive to pathogen transport, and led to long travel times that negated any risk from pathogenic bacteria due to dying off of the pathogens.
• Proximity to a toilet was the only significant sanitary risk factor for faecal contamination. Faecal contamination was considered a result of individual water supply vulnerability such as inadequate headwork completion or sanitary seal, incompetent casing, or poor back fill contact facilitating rapid vertical by-pass down the casing.
• The study found that TLF technique was an effective method to detect faecal coliform.

The paper argues that sanitary interventions in rural areas are very likely to contaminate groundwater-derived potable supplies with excreta, a very worrying prospect as many of the rural communities are completely dependent upon these groundwater resources. Even in low vulnerability hydrogeological settings such as those in this study, contamination can occur due to excreta entering individual supplies as a result of inadequate headworks, poor sanitary seals, and/or incompetent casing. Thus, widespread implementation of current on-site sanitation systems across India will inevitably lead to the faecal contamination of adjacent water supplies, irrespective of the setting.

How can this contamination be dealt with?

• Communities need to be made more aware of the potential risks of on-site sanitation and mitigation measures to ensure that domestic water is clean prior to consumption.
• Communities need to be aware of a range of standard low cost treatment measures such as boiling or solar water disinfection, given that centralised water treatment options might not be feasible in rural areas.
• Water supplies must be adequately protected from faecal contamination through suitable sanitary seals, headworks and subsurface installation. This can be undertaken by raising awareness of the risks and current guidance, and better regulation of the drilling industry.

Lead image source: Sourabh Phadke in CONRADIN, K., KROPAC, M., SPUHLER, D. (Eds.) (2010): The SSWM Toolbox. Basel: seecon international gmbh. URL: http://www.sswm.info

Please download a copy of the paper below.