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.
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