Page 153 - Industrial Wastewater Treatment, Recycling and Reuse

Advanced Physico-chemical Methods of Treatment for Industrial Wastewaters 127

2.5.3 Application of Cavitation in Reducing Ammoniacal
Nitrogen

Averyimportantproblemwithrespecttomanychemicalindustriesisreducing
ammoniacal nitrogen in wastewaters. Ammoniacal nitrogen (NH 3 -N) is a
measure for nitrogen as ammonia, a toxic pollutant. Ammonia can directly
poison humans and upset the equilibrium of water systems. The nitrogen in
sewage/industrial wastewaters is assessed as ammoniacal nitrogen. This indi-
cates the amount of nitrogenous organic matter that has been converted to
ammonia. The average strength of crude domestic sewage will have a com-
bined nitrogen content of 40-60 mg/L. Ammoniacal nitrogen removal can
be carried out by biological, physical, or chemical methods or a combination
thereof. Available technologies include adsorption, chemical precipitation,
membrane filtration, reverse osmosis, ion exchange, air stripping, breakpoint
chlorination, and biological nitrification and denitrification (Metcalf & Eddy,
Inc. 1991). Conventional methods, however, are not efficient and are cost
intensive.Physico-chemicaltreatmentorionexchange/adsorptionispreferred
over other methods because it is stable, easy to maintain, and reliable. Aguilar
etal.(2002)investigatedphysico-chemicalremovalofammoniacalnitrogenby
coagulation-flocculationusingactivatedsilica,powderedactivatedcarbon,and
precipitated calcium carbonate. They found very low ammonia removal of
around 3–17%, but albuminoid nitrogen (nitrogen in the form of proteins)
removal was appreciable (74–89%), and the addition of coagulant aids reduced
the sludge volume to 42%. Ion exchange resins and some cheaper alternative
natural and waste materials can be used to replace high-cost materials. Various
researchers have studied the effectiveness of a variety of low-cost materials for
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ammonia removal such as clay and zeolite (Aziz et al., 2004; Celik et al., 2001;
Demir et al., 2002; Roz ˇic ´ et al., 2000; Sarioglu, 2005), limestone (Aziz et al.,
2004), natural and waste materials such as waste paper, refuse cement, and
concrete (Ahsan et al., 2001). Thus there is huge opportunity for development
of new materials, processes, and process integration options for cost-effective
industrial separations along with water recycling strategy.

2.5.4 Case Study: Hydrodynamic Cavitation Using a Vortex
Diode in Real Industrial Effluent Treatment

It is instructive to evaluate the performance of newer devices such as the vor-
tex diode in treating real industrial wastewaters. A detailed study was carried
out usingindustrial wastewater fromthe dyeand pigment industry(Hiremath
etal.,2012).Theimportantcharacteristicsofthiswastewateraregivenbelow: