Grey Water Urban Solution

  Grey water is a valuable resource, especially in water scarce regions such as Bangladesh.  Grey water is anything that has previously been used but has not come into contact with feces, which is called “black water” and should be sent to a waste water treatment plant. Grey water can be used almost anywhere fresh water is being used, as long as it is not being directly ingested.  Grey water has been applied in a number of small scale projects throughout the world. One case study has shown that grey water use in rural schools in India was feasible and fifty to sixty percent of their total water consumption can be reused as grey water, significantly decreasing total water use overall.  The cost of implementing the grey water system in this study was offset in under two years.  A study of the feasibility of grey water use in Dhaka shows a similar setting as the Indian case study; both case studies can be found at the links below.  Sixty to seventy percent of water use in Dhaka can be reused as grey water.  "The reuse of grey water is an attractive solution to minimize the deficit between demand and supply of water in Dhaka city." This deficit is illustrated in figure 7 as the demand is consistently greater than the supply of water and both are increasing steadily.  With minimal filtration, Bangladesh could benefit from grey water by using it to flush toilets, water plants, and as one study suggested, to replenish the groundwater.  The use of grey water will not increase the water supply of Bangladesh.  What it will do is make the water already being used go farther and become more productive.  Overall less water would be needed to maintain a more comfortable lifestyle.

Figure 7 Image from:  http://www.iebconferences.info/345.pdf

Drawbacks and Unintended Consequences

While the use of grey water to minimize the gap between supply and demand of water is feasible, implementation issues may arise.  The cost of a household grey water system would depend upon if water infrastructure is already in place and just needs to be reworked, or if a new system would need to be installed.  Both options could cost a fair amount of money, and depending on if there are subsidies and assistance provided by the government or NGOs, some lower income families may not be able to afford this solution.  Grey water being used improperly could lead to health issues.  Grey water should not be ingested and should only be used for non-contact activities, such as flushing a toilet.  These practices would be taught in the education part of our solution, however if water is scarce these guidelines may not abided by and the user could become ill.

Timeline

Grey water use could be put into implementation fairly quickly, with a single household unit up and running in a day.  Total implementation throughout the country as a general practice could take upwards of five years, depending on funding and enthusiasm.   

Grey Water Use in Rural Schools:

http://neeri.res.in/pdf/greywater.pdf 

Grey water generation and quality measurement at a specific site in Dhaka city:

http://www.iebconferences.info/362.pdf

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