Page 39 - Industrial Wastewater Treatment, Recycling and Reuse

22 Industrial Wastewater Treatment, Recycling, and Reuse

containing refractory pollutants. This problem can be completely cir-
cumvented through appropriate process modification that may involve
raw materials/solvent substitution, or recovery of by-products. The goal
of process modification is to qualitatively change wastewaters from toxic
to nontoxic and use better and more efficient catalysts for optimization of
reactions and raw material use.
2. Reaction/separation equipment modification: Along with process modifica-
tions, product yield can be improved by incorporating the most efficient
and environment friendly equipment and control devices. This involves
mainly installing equipment that produces little or no waste, suitable
modification or newer designs for equipment to enhance recovery or
recycling options, and improving the operating efficiency of equipment.
3. Separate flushing of water stream: Segregation of clean water is very impor-
tant, especially from the recycling and reuse point of view. There are
certain wastewater streams that result from washing or flushing and
may not contain appreciable quantities of pollutants. Such water can
be separately treated and reused for the cleaning/flushing of plant equip-
ment or for any other suitable purpose. Further, segregation of clean
water offers substantial reduction in the requirement of fresh water
and subsequently reduction in cost of fresh water.
4. Avoid leaks/spills/wastages: Thisisquiteeasyandcomesunderefficientplant
operation/maintenance. It can save appreciable quantities of water every
day apart from ending the streams in the effluent that need treatment.
5. Isolation and segregation of noncompatible waste streams: This can also help in
water recycling and reuse through the appropriate selection of methods
for biologically treatable waste and chemically treatable wastewaters,
consequently drastically reducing the load on any single effluent treat-
ment option. In general, for ordinary wastewaters, primary treatment
combined with coagulation/clarification followed by biological or
chemical treatment methods is usually satisfactory to make water suitable
for discharge. If priority pollutants are present, necessitating the final pol-
ishing step in the form of methods such as adsorption/ion exchange to
meet statutory limits, these have to be considered before discharge to
surface waters. Alternatively, polishing methods could also be used for
water recycling and reuse in the same plant facility by appropriately
reducing the pollutant levels. The toxic wastewaters have to be treated
using special methodologies or ultimately destroyed by incinerating.
6. Isolate concentrated and dilute streams: It is desirable to isolate and segregate
concentrated waste streams for recovery of valuable components. Such