Quantification and characterization of greywater from
schools
Abdalrahman D. Alsulaili and Mohamed F. Hamoda
ABSTRACT
Survey of schools of different education levels (primary, intermediate and secondary) in Kuwait
showed an average greywater generation rate of 7.3 L/p/d and varied in the range of 2.9–16 l/p/d,
reflecting the school level of education (i.e. student age). The highest rates were observed for
primary schools while the lowest rates were observed in secondary schools where students are
more mature and use the water more wisely. The greywater characteristics indicated waste with low
chemical oxygen demand (COD) and 5-day biochemical oxygen demand (BOD
5
) values but relatively
high solids, conductivity, and sodium content due to excessive use of hand soap. Total coliform
values ranged between 89 and 352 most probable number (MPN)/mL with an average of 196 MPN/
mL while no fecal coliform values were detected. Greywater collected from schools is classified as
light greywater and contains much lower levels of organic matter and nutrients compared to
residential greywater and domestic wastewater. It is suitable for non-potable reuse after minimal
treatment since microbial contamination may pose a serious threat to health if greywater comes into
contact with humans. It also provides a good opportunity for reuse in toilet flushing since it can be
easily collected from wash sinks and fountains, as major sources, and recycled.
Abdalrahman D. Alsulaili (corresponding author)
Mohamed F. Hamoda
Department of Civil Engineering,
Kuwait University,
P.O. Box 5969,
Safat,
13060 Kuwait
E-mail: a.alsulaili@ku.edu.kw
Key words | chemical characteristics, generation rates, greywater, schools, water reuse
INTRODUCTION
Increasing demand for fresh water and scarcity of water
resources in arid and semi-arid regions have created an
urgent need for alternative water resources and optimization
of water use through reuse options. Experience elsewhere in
the world indicates that greywater, which is defined as waste-
water without any input from toilets and kitchens, can be a
cost-effective alternative source of water (Christova-Boal
et al. ). This is primarily related to its availability and
low concentration of pollutants compared to the combined
household wastewater.
Greywater corresponds to wastewater produced in bath-
tubs, showers, laundry machines and sinks, in households,
office buildings, schools, etc. It is estimated that greywater
accounts for about 75% by volume of the combined residen-
tial wastewater (Eriksson et al. ). In the United States,
household, greywater accounts for half of the water con-
sumed for an estimated 114 L/person/d (Beck et al. ).
This fraction of wastewater is less polluted than municipal
wastewater in the absence of feces, urine and toilet paper
(Eriksson et al. ). Substantial volumes of water (15–
55 L/capita/d) can be reused (Nolde ). In addition to help-
ing preserve scarce water resources, greywater reuse can also
reduce water supply costs and decrease the load on centralized
wastewater treatment systems (Beck et al. ).
Characteristics reported by several studies indicate that
greywater has to be considered as dilute sewage because it
has some constituents of raw wastewater (Hrudey &
Raniga ; Christova-Boal et al. ; Eriksson et al.
; Li et al. ; Boyjoo et al. ; Ghaitidak & Yadav
). Greywater characteristics have to be determined
before deciding on its treatment and reuse onsite. Depend-
ing on such characteristics, the type and extent of
treatment can be determined since there are a number of
problems related to the reuse of untreated greywater. The
risk of spreading diseases, due to exposure to microorgan-
isms in the water, will be a crucial point if the water is to
be reused outdoors for irrigation or indoors for toilet flush-
ing and household cleaning (Maimon et al. ). The risk
1973 © IWA Publishing 2015 Water Science & Technology | 72.11 | 2015
doi: 10.2166/wst.2015.408
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