Page 155 - Industrial Wastewater Treatment, Recycling and Reuse

Advanced Physico-chemical Methods of Treatment for Industrial Wastewaters 129

Figure 2.19 Examples of the extent of color removal using hydrodynamic cavitation.

Overall, with the use of an appropriate technology or a combination,
more than 95% reduction in color and more than 97% COD reduction
in some cases can be accomplished for real industrial wastewaters. The final
result in the above example of industrial wastewater treatment is shown in
Figure 2.20, where practically clear water can be obtained using process
integration with cavitation and ion exchange.
As far as the removal of ammoniacal nitrogen is concerned, the hydro-
dynamic cavitation with a vortex diode appears to be far more effective and
produced near total removal of ammoniacal nitrogen from the real industrial
wastewaters in some cases (Table 2.4, Figure 2.21). The performance was
again substantially dependent on the type of effluent. However, the utility
of the vortex diode in hydrodynamic cavitation appears to be beyond doubt
(Ranade et al., 2013).
The hydrodynamic cavitation device is simple in construction, without
any moving parts, and easy to operate. More importantly, hydrodynamic
cavitation devices are amenable to scale-up and can be designed for treating
large volumes of industrial effluents. The vortex diodes have already been
3
tested using up to 40 m /h flow rates (Ranade and Bhandari, 2013). Hydro-
dynamic cavitation is therefore perceived to be an energy efficient and quite
effective technology for wastewater treatment, especially in view of its capa-
bility to degrade refractory pollutants. It can also be conveniently combined