(131f) Water Disinfection using Hydrodynamic Cavitation: Influence of orifice shape & inception

Water Disinfection using Hydrodynamic
Cavitation: Influence of
orifice shape
& inception

Vivek Ranade* and Vikrant Gaikwad1

Chemical Engineering and Process Development Division

CSIR ? National Chemical Laboratory

Pune 411008, INDIA; vv.ranade@ncl.res.in

1 Maharashtra Institute of Technology, Pune, India

Hydrodynamic
 cavitation
 offers  distinct  advantages
 for  water
 disinfection  and
 waste  water treatment particularly at large scales of operations. For applying hydrodynamic
cavitation for water
disinfection/ treatment, water stream to be
treated is passed through a fluidic device in which there
exists a low pressure region. Cavities are generated in this region
when the pressure falls below
vapour pressure (in absence of any dissolved gases). These cavities are then collapsed when they travel to regions of higher pressure and lead to very high shear, temperatures and pressures in
localized regions. These high pressure/ temperature as well as high shear facilitate disinfection as
well
as reduction in chemical oxygen demand, color and amonical
nitrogen in the water (Ranade and Bhandari, 2014). In
this work, we have investigated
hydrodynamic cavitation
generated
by
different orifices and have tested their effectiveness for water disinfection.

In this work, five different orifices have been studied which have different orifice shapes with same
fractional open area
(see
Figure 1). Systematic experiments
were
carried out to identify inception
of cavitation.
Measured pressure drop results as a function
of
liquid velocity as well as acoustic signals were used to identify inception points. Different flow regimes such
as no cavitation, inception of cavitation, developed cavitation and super cavitation were identified for varied inlet pressures for each orifice plate. The efficacy of
generated cavitation on water disinfection was quantified
based on measurements of non-pathogenic E Coli colony forming units (CFU/ml).

The  presented
 results
 and 
analysis  will
 be  useful 
for  designing  hydrodynamic
 cavitation  based
systems for water disinfection.

Five orifices with 10%

open area

Typical cavitation inception

References:

Ranade, V.V. and V.M. Bhandari [Editors] (2014) Industrial
Wastewater Treatment, Recycle & Reuse, Elsevier, Amsterdam.