The study was carried out to assess the feasibility of using an
anaerobic hybrid reactor for the treatment of slaughterhouse wastewater. The
reactor, consisting of an Upflow Anaerobic Sludge Blanket (UASB) at the bottom
and an anaerobic filter at the top, was seeded with the digested sewage sludge
and was initially fed with neutralized acetic acid for the activation of
methanogens. Subsequently slaughterhouse waste was fed to the reactor. The
experiments were conducted in five different phases by varying the hydraulic
retention time (HRT) from 24 hours to 18, 12, 8 and 4 hours. Influent chemical
oxygen demand (COD) was increased from 760 mg/L to a maximum of 4200 mg/L. The
organic loading was progressively increased from a low of 0.76 kg
COD/m
$^{3}$
d
$^{-1}$
to a maximum of 20.24 kg COD/m
$^{3}$
d
$^{-1}$
.
In the first phase of
the study the organic loading rate (OLR) was increased from 0.76 kg
COD/m
$^{3}$
d
$^{-1}$
to 2.88 kg COD/m
$^{3}$
d
$^{-1}$
and an HRT of 24 hours was maintained.
The COD removal efficiency increased from 47.3% to 96% when the reactor
achieved steady state conditions. For the next three phases the OLR was
increased from 2.24 kg COD/m
$^{3}$
d
$^{-1}$
to 12.6 kg COD/m
$^{3}$
d
$^{-1}$
by decreasing
the HRT to 18, 12 and 8 hours. The COD removal efficiency dropped for few days
but regained within a short time and was around 95% for each loading rate.
However, as OLR was increased to 20.24 kg COD/m
$^{3}$
d
$^{-1}$
and HRT was decreased
to four hours, the COD removal efficiency decreased (64%). It is seen that the
reactor performed well over a wide range of OLR and a COD and BOD removal
efficiency of 95% was achieved till an HRT of eight hours. The solids removal
efficiency was 73%. It is concluded that higher organic loadings can be applied
to the reactor up to an HRT of eight hours and slaughterhouse waste can be
successfully treated using anaerobic hybrid reactor. However additional units
in series are required to bring the BOD level to permissible values.
