Page 154 - Industrial Wastewater Treatment, Recycling and Reuse

128 Industrial Wastewater Treatment, Recycling, and Reuse

– Dark brown color with unpleasant odor
– Presence of organics, salt, and other unknown contaminants
– High COD ( 36,000 mg/L).
For conducting an effluent trial using the vortex diode, the following process
parameters were set.
– Flow rate¼3800 LPH

– Initial temperature¼28 C
– Pressure drop¼155 kPa.
It was found that COD removal is highly dependent on the nature of the
industrial effluent. This is not unexpected since there is lot of variation in
the quality of wastewater, including dissolved and suspended solids apart
from unknown pollutants present in the wastewater such as organics and
metals. This, therefore, requires in-depth analysis of the wastewater and
causes uncertainty in the removal behavior since most of the time data is
not made available in this regard for every pollutant present in the wastewa-
ter. The presence of solids in the wastewater is believed to cause damage to
the cavitation device through mechanical erosion in prolonged operations
and needs to be accounted for. Nontoxic wastewater is traditionally charac-
terized in terms of major parameters such as BOD, COD, and ammoniacal
nitrogen. The present case study, therefore, is an attempt to verify the use-
fulness of cavitation technology in treating industrial wastewater mainly
through reduction in COD and ammoniacal nitrogen. An attempt was
also made to compare different wastewater treatment technologies in treat-
ing the same industrial wastewater in order to get at least some idea about the
implementation of these technologies alone or used in a process integration
strategy. The general observations made in this regard can be compiled
as below:
Reduction in COD
– Coagulation: 65%
– Ion exchange/adsorption: up to 90% or more
– Cavitation: 20–95%
– Process integration (Ion Exchange/Adsorption+Cavitation): >97%.
It may be noted here that although adsorption or ion exchange can be useful
in removing a large percentage of COD in some cases, the capacity for
removal is limited, requiring huge quantities of material and making it
impractical for direct application. Thus these processes can be best used
in integration with other processes such as cavitation. The progress of color
removal with time using cavitation alone is shown in Figure 2.19.