|
Greywater Reuse and Water Safety Plans: A case study from
Madhya Pradesh, India
Madhya Pradesh is a state in central India that suffers recurrent water quantity and quality problems. Over exploitation of groundwater resources is resulting in the leaching of chemical (fluoride) contaminants into groundwater sources. Microbial contamination is also a problem with low levels of sanitation coverage. The lack of available freshwater in schools has resulted in UNICEF, in collaboration with Governmental and non-Governmental (1) partners, exploring the use of greywater (defined in this context as shower, bath, sink and laundry water) for domestic purposes such as toilet flushing, handwashing and cleaning (2).
Non-potable greywater reuse in tribal residential schools
Sanitary complexes in many tribal boarding schools in Madhya Pradesh are non-functional due to the lack of available water. UNICEF has developed greywater treatment technology to provide water-scarce residential schools in the province with water recycling. The objective is to ensure sufficient water availability for hand washing, toilet cleaning and washing of floors.
The water reuse systems:
- provide recycled water to improve coverage of “sustainable” school sanitation
- reduce demand on “fresh” groundwater sources
- are cost effective
Greywater quantification results from the schools indicate greywater usage of 40-50 litres/student/day compared to 5 litres/student/day for drinking water (3). To treat or reuse this water, a greywater system comprising of an equalization cum settling tank and filtration units (comprising local media and storage tanks with baffles for aeration) has been developed. The total cost of the system is US$500.
View a schematic diagram of the UNICEF Water reuse system .
Figure 1: A school greywater treatment system in Madhya Pradesh.
Greywater Management - Water Safety Plans (WSPs)
The World Health Organisation noted that the most effective means of consistently ensuring the safety of both fresh and greywater is through the use of comprehensive risk assessment and risk management (4). These approaches are termed Water Safety Plans. They describe the minimum requirements of safe practices to protect consumer health and/or derive numerical 'Guideline Values' for constituents of water or indicators of water quality. In this light, the third edition of the World Health Organisation (WHO) Guidelines for Drinking Water Quality published in 2004, has moved towards a risk-based approach to chemical water safety (4).
Water Safety Plans comprise two main components namely risk assessment and risk management. Outlined below are examples from preliminary work undertaken by UNICEF at the residential schools in Madhya Pradesh (5).
1) Risk Assessment
The first stage of development of Water Safety Plans requires the establishment of health-based criteria. These criteria or targets are established by undertaking Quantitative Risk Assessments. In Madhya Pradesh, UNICEF performed a Quantitative Microbial Risk Assessment (QMRA) to assess the risk of microbial contamination.
The risk assessments involve hazard identification in greywater systems through the use of Sanitary and Hazard inspections. Then, based on identified hazards an exposure assessment is undertaken to determine the hazardous exposure to the population. These hazards are then prioritised based on a dose-response model founded on Disability Adjusted Life Years.
Finally, a relative risk value is assigned to prioritise which hazard and which water quality parameters are of priority for a specific system. For example, monitoring turbidity (a physico-chemical parameter) because low filtration in the water reuse system (a hazard) can result in high turbidity and potential breakthrough of bacteria. The approach has been simplified to encourage children to use Water Safety Plans as a means of monitoring the risk of the grey water system (see figure 2 and 3).
Figures 2 and 3: Children's Water Safety Plans for the greywater system.
2) Risk Management (Water Safety Plans)
In Madhya Pradesh, UNICEF has developed the monitoring component of Water Safety Plans through school Water Safety Clubs. Each school paints a Water Safety Plan matrix on the outside wall of their school building (see figure 4). The Water Safety Plan is then managed and monitored daily by the Water Safety Club (comprising of both teachers and students).
Figure 4: A school Water Safety Plan board in Madhya Pradesh.
Figure 5: Water Safety Plan framework for a Water Recycling System.
Figure 6: Learning about filtering greywater through play.
 The following risk management measures are proposed:
1. Different colour pipes for grey water
2. The addition of a light colour dye to the recycled water
3. Pictorial warning signs for hazards
4. Clear marking of taps
5. Teacher-controlled pumping system
6. Corrective actions by children
In summary, greywater treatment and reuse is effectively improving sanitation in school and Water Safety Plans are a useful tool as they provide a scientific and practical approach to resolving water quality problems affecting greywater system.
References
1. The non-governmental partners were: National Environmental Engineering Research Institute (Nagpur), National Centre for Human Settlement and Environment (Jhabua) and Public Health Engineering Department (Madhya Pradesh).
2. Weizhen L,Y. T. Leung, A., (2003) A preliminary study on potential of developing shower/laundry wastewater reclamation and reuse system, Environmental and Public Health, Vol. 52, Issue 9, pp 1451-1459
3. Godfrey, S., Saxsena, A., Kumar, P., Swami, A. and Joshi, N. (2005) A preliminary study on potential of greywater reuse system in water scarce and fluoride contaminated rural areas of Jhabua, Madhya Pradesh, India Group, I. W. R. S. Water Reuse and Reclamation for Sustainability (WRRS) South Korea, IWA
4. World Health Organisation (2004) Guidelines for Drinking Water Quality – Edition 3, Geneva, Switzerland
5. Godfrey S, Kumar, P., Swami, A., Wate, S R. and Dwivedi, H.B (2005), Water Safety Plans for rainwater and greywater reuse, Presented at XII International Rainwater Catchment Systems Conference, November 15-18, 2005, New Delhi
6. Birks, R., Colbourne, J., Hills, S., Hobson, R. (2004) Microbiological water quality in a large in building water recycling facility, DEFRA, UK
For more information please contact Sam Godfrey (sgodfrey@unicef.org)
|
