The Need for Sustainable Sanitation Solutions
Improved sanitation is associated with better health and nutritional status. Evidence shows that improved sanitation substantially reduces childhood illnesses and deaths and can improve nutritional status. It does this primarily by acting as a barrier, keeping excreta away from people who, if exposed to the pathogens in faeces, become ill (Esrey, 2001).Source: Esrey et al, 2001
The barrier approach to sanitation prevents faeces from gaining access to environmental vectors such as fingers, flies, fields and fluids (see diagram alongside). These vectors carry pathogens from faeces to food or directly to humans. When faeces contaminate the environment, the vicious cycle of people contaminating the environment and becoming infected by the contaminated environment continues.
All improved sanitation systems, whether of the 'drop and store' or the 'flush and discharge' types reduce contamination. Pathogens are prevented from spreading to three potential vectors: flies, fields and fluids. Without such a source based approach personal hygiene and water disinfection measures will not have much effect.
Of the 3.5 million people who died of diarrhoeal diseases in 1999, it is estimated that forty percent of them could have been saved through the introduction of basic improved sanitation. Infant mortality could drop by as much as 50 percent due to the introduction of sanitation in some communities.
Ecological toilets are very effective in the elimination of pathogens, not just from the domestic environment, but also from areas downstream. They have the added advantage over 'drop and store' as well as 'flush and discharge' systems, that they effectively sanitise the excreta on the spot. Therefore their effect is not only felt in the community where they are introduced but also in surrounding areas as the amount of pollution is reduced.
Health problems arising from the use of Linear sanitation systems
Nutrients enter water bodies from return flows. This causes 'blue baby syndrome' (methemoglobinemia), reproductive problems in women and reduced growth in children.
Chemicals used to treat contaminated water, such as chlorine, produce by-products which are carcinogenic.
Drug and drug metabolites enter the water system from the recycling of sewerage water. These can have a variety of effects, depending on the type of drug and have been linked to an increase in pathogens resistant to antibiotics.
Nutrients which could have been used in the production of crops are lost. This can have a negative impact on nutritional levels in rural areas,
Half of the world's population live within 50 km of a coastline. Most sewerage from these settlements is released, raw, into the ocean, causing the destruction of marine life and the coastal ecosystem. This also has a negative impact on nutritional status.
Global warming and ozone depletion, caused by gasses formed by nutrients escaping into the atmosphere, pose a variety of health risks.
Health Risks from Excreta
One Gram of faeces can contain:
1,000 Parasite cysts
100 Parasite eggs
These pathogens cause infections diseases which lead to over 13 million deaths world-wide annually. Children and the imuno-depressed are the most vulnerable to the organisms which contribute to this burden, specifically bacteria, viruses and parasites. Some of these organisms remain alive in the ecosystem for a long time, either with or without the need for an immediate host. The presence of E.coli in water indicates that it is contaminated with faecel matter. Two other types of of organisms which are also present in faeces are bacteriophages, an indicator and Ascaris eggs, a pathogen. As mentioned above, small amounts of faecel matter can contain large quantities of dangerous organisms. Therefore it is important that it is made safe before it is used as fertiliser on fields.
In human excreta faeces contain almost all the pathogens, while urine is sterile and contains the bulk of the nutrients. Faeces can be made safe in several ways, either at the point of excretion or at a later stage. Separation of the faeces from the urine and the subsequent addition of absorbents which raise the pH and cause dessication, such as lime or ash, is a very effective method for killing off pathogens. Recent studies conducted in Vietnam show that the median die off rate of Ascaris eggs is about 9 weeks while for bacteriophages it was about 5 weeks. This was at an average pH of 9.5 to 10. The pH was found to have more of an influence on the rate of die off of pathogens than the impact of moisture and temperature. The pH is also affected differently by different materials. A study in China has indicated that plant ash is better than coal ash, sawdust or soil for destroying pathogens.
If urine and faeces are to be kept together and then sterilised later a different approach needs to be followed. The carbon-nitrogen ratio in excreta is not viable for composting as there is too much nitrogen present. Therefore additional carbon containing material, such as leaves plant matter and old food has to be added to the mix. This will help promote composting which destroys the harmful pathogens, making humus which can safely be applied to fields (see photo alongside).
Urine is generally considered safe for use, if it is kept free of faeces. Very few organisms are passed through the urine. Those that are passed in urine include Salmonella typhi (typhoid), Salmonella paratyphi (paratyphoid fever) and Schistosoma haematobium (biharzia). The first two do not survive long once outside the body and will be eliminated from urine after it has been stored for a couple of days. The bilharzia cycle is broken if people urinate in water which does not contain the intermediate host to complete transmission (usually snails). Therefore if urine is stored for a few days and the storage tank is drained at intervals the risk of contamination from one of the above organisms is minimal. If cross-contamination with faeces does occur, storage of urine for two to three months will render it safe.