Low-Cost Sanitation – At what Cost ?
The impetus given to sanitation promotion in India over last two decades is considerable
in terms of investments made as well as physical infrastructure built. Often, on-site
sanitation, using various models of leach pit latrines, has been the technology choice in
many sanitation promotion projects in rural and peri-urban areas. Economy of
investments and affordability of users are the major reasons cited for promoting low-cost
options of on-site sanitation. The Total Sanitation Campaign initiated in recent years by
the Ministry of Rural Development, Govt. of India also promotes mostly twin-pit pour
flush latrines costing around Rs.2850 per unit. The units are subsidized heavily and lakhs
of such latrines are being constructed in a short span of time.
Unlike septic tanks, the leach pits of twin-pit latrines are not sealed. Pits are provided
with a honeycombed brick lining that permit the leaching of effluents to soil. Thus, soil is
exposed to the solid excreta having high nitrogen compounds, while absorbing the
bacteria loaded liquids. The honeycomb-like brick structure of these pits allows the
pathogens and nitrogen compounds escape to the surrounding soil on a continuous basis.
These latrines may cause severe groundwater contamination, predominantly of pathogen
bacteria and nitrogen. Pathogen contamination is widely proven in numerous disease
outbreaks, but the implications of nitrogen contamination of groundwater and health
hazards of nitrogen in water supplies did not receive desired attention.
The World Health Organization specified 50 mg/l as the permissible level of nitrogen in
drinking water. In excess of this, nitrogen could cause serious health hazards. People in
densely populated habitations in small towns and rural areas are most vulnerable because
of consumption of water from local shallow open and bore wells. As per one estimate, a
properly functioning septic system contributes an average of 13 kg of nitrogen per
household per year to groundwater. The nitrogen leaching out from leach pit latrines
could be much higher than this. This was confirmed by some studies, wherein densely
scattered leach pit latrines in an area were found to raise the nitrogen concentrations from
negligible levels to dangerous levels.
One such example is the phenomenal increase of nitrogen levels in groundwater due to
dense on-site sanitation in Bermuda. Researchers found about ten-fold increase in
nitrogen concentration in the public water supplies made from local wells over the period
1973-1984. The concentration increased from 2.5 mg/l to as high as 40 mg/l in some of
the bore wells in the area. Similar specific findings were reported from Peri-urban Dhaka
(Bangladesh) and Uganda during 1999. During 1982-86, few Indian scientists related
abnormal levels of nitrogen in groundwater in 3 cities, Hyderabad, Nagpur and Lucknow,
to the predominant unsewered and on-site sanitation infrastructure.
1
A model developed by the author on the soils of a peri-urban area of Bangalore, namely
Mallathahalli, estimated that 75% of the nitrogen leached out from an isolated latrine can
reach the shallow groundwater in the form stable nitrate. Consequent drying and wetting
of unsaturated soils (by intermittent rains) accelerate nitrate leaching towards shallow
groundwater.
Potential health hazards due to excess consumption of nitrate are methemoglobinaemia in
children; oesophageal and gastric cancer; IDDM (diabetes); hypertrophy of thyroid; and
negative reproductive outcomes. Nitrates were found to have direct affects on central
nervous system and vasodilator cardio-vascular system. The human body reduces the
nitrate to nitrite, which in turn oxidizes iron in haemoglobin. The resulting
mathaemoglobin reduces the ability of blood to carry oxygen to different parts of body
leading to cyanosis. Nitrites can react with amines and amides to form nitrosamines and
nitrosamides. Most nitroso-compounds were tested to be carcinogenic in wide range of
animal species.
In a specific study, researchers in Department of Preventive Medicine and Biometrics,
University of Colorado Health Sciences Center, Denver studied 1280 children less than
18 years old from 63 countries in Colorado during 1992 and established that exposure to
nitrogen through drinking water may play a role in promotion of etiology of IDDM.
All these studies and findings points out that the hazards of nitrogen shall be paid due
attention in the interest of public health. The evidence of incidence of more persistent
diseases shall put us on extra caution in promoting on-site sanitation options. One such
technological possibility is “Nitrogen Removal System”, which contain the nitrogen from
the leach pits. They have been tried world over and found to be working satisfactorily.
According to the statistics released by Maryland Coastal Bays Program, Maryland the
nitrogen release from a sanitary latrine can be reduced by 50% by using the nitrogen
removal system.
The promoters of low-cost leach pit models shall rethink on their ecological and public
health implications, instead of justifying only based on economic criteria of sanitation
promotion. Promotion and dissemination of technology for mass application shall take in
to account the ecological implications as well. Otherwise, such interventions may largely
negate the expected public health benefits from those programs though it may appear to
meet the immediate sanitation coverage targets.
-oOo-
2