Feasibility Study on Grey Water Reuse
Jiang, J., Acheampong,B., He,Q., Balazs, T. and Bancroft, T., Faculty of Physics Science, University of Surrey, UK
(free)
Greywater is defined as wastewater streams from baths, showers, basins, laundries and kitchens but not
wastes from toilet flushing which has been termed as black water. In various studies, per capita
consumption (PCC), as litres water per person per day, has been used to quantify the water consumption.
The PCC in the UK in 2001 was 149 based on the UK OFWAT 2001report. In the same year the French
average was 125. In the US, the water consumption is higher than most European countries, the PCC
reaches 382 (Lazarova et al, 2003).
Table 1 compares the breakdown of water consumption ratios in US, UK and Germany. Strong similarity
can be observed within the shown values. It can be seen that water usage for toilet flushing is set out
around 1/3 of all water consumption. Laundry operational water falls between 10 and 15% while
bath/shower/basin consumptions reveal higher variation within 20 and 37%, yet it ought to be noted that `US data may contain extensive irrigational water usage in the “Other” section, hence the slightly lower
values at every point. This small, farming practice is probably the cause of very high PCC value as well. By
the data analysis as shown above and considering the regional differences it can be summarised that
water used for toilet flushing is no more than 30% of total water consumption. Projecting this ratio onto
the characteristic of generated wastewater, it can be stated that the amount of generated greywater is
higher than blackwater. Thus it could be estimated that by toilet flushing alone, at least 30% of the total
household water consumption might be saved by the grey water recycling activity.
