The obtained high values for ABmax (76%) and maximum COD
removal in the UASB reactor (84%) showed the potential of the
UASB reactor in grey water treatment. Moreover, the results
demonstrated that a high CODt removal (52–64%) was obtained
in the UASB reactor at HRT between 6 and 16h and wastewater
temperature of 30 1C. Accordingly, the UASB reactor has a
significantly higher CODt removal at a short HRT as compared
to the septic tank, the common system of grey water pretreatment.
The temperature of grey water ranges between 18
and 38 1C (Eriksson et al., 2002) and it can be considered similar
to that applied in this research, if short connection between
the grey water sources and the UASB reactor, and proper
isolation of this connection are applied. Consequently, installing
of the UASB reactor treating grey water in the cellar of the
buildings will be a suitable option. Thus, the losses in the
wastewater temperatures can be minimised and the energy
losses from warm water in the buildings can be utilised for
extra heating of the reactor, when it is required. For keeping
the temperature of the reactor at about 30 1C and minimising
the heat loss, a good insulation is required. Accordingly, the
thermal resistance of the insulator should be X5Km2/W. For
each insulator, the thermal resistance is known and, therefore,
its thickness can be determined.