Environmental Engineering Reference
In-Depth Information
water reduction. The use of fog nozzles in continuous cooling units for hot-filled containers
(e.g., jams, drinks, sauces) can result in significant reduction in water use compared to tradi-
tional spraying methods.
Waste when idle
Water left running when not needed, for instance during breaks or when a product is not pre-
sent, is found frequently in food plants. In prewashing and washing systems on conveyor belts,
or in equipment that needs a constant flow of water, the installation of automatic water shut-
off systems when a product is not present can be an effective way of tackling this problem.
Similarly, all equipment can be retrofitted with solenoid valves that shut off the water when
the equipment is not operating. In the case of tubs or vessels, the installation of level control
valves eliminates potential overflows.
Waste in buildings
In buildings, water can be saved by installing water-efficient toilets (e.g., variable flush, inter-
ruptible flush, delayed action inlet valves), low flush urinals, faucet aerators, and low-flow
showerheads.
In exterior areas, water is saved by redesigning landscapes to ones with low-water require-
ment, by installing soil moisture override systems on sprinkler and by calibrating sprinklers,
so runoffs to parking lots and sidewalks are avoided.
Replacing processes with other alternatives
Washing down material to the water flume is a widespread practice that is used to convey
solid residues out of processing plants. Residue may include animal tissue, vegetable peel-
ings, batters, and breadings. When water conservation is a priority, these practices need to
be discontinued for three reasons: (1) large volumes of water are needed to move the
residues, which (2) increase the volume of wastewater and (3) intensify the wastewater solid
content that boosts the biological oxygen demand of the effluent. Instead, dry cleanup prac-
tices need to be set in place, by modifying current systems or by instructing employees to
pick up all the dry waste from the floor and equipment before using water. Dry cleanup
not  only reduces the volume of wastewater with high biological oxygen, but also allows
the recovery of solid materials (mostly protein and carbohydrates) that can be recycled as
animal feed (see Chapter 10).
Once-through process cooling, in which water is circulated once through the equipment
and then discharged as wastewater, can be replaced with closed loops and cooling towers.
An  option is to capture the water from a single-pass cooling system and reuse it for other
applications (e.g., washing and rinsing equipment).
Water has been used to convey fruits and vegetables through the processing plants.
Water transport is consider an inexpensive conveying medium that is also gentle on the
product, but the disadvantages is that it uses large volumes of water that then need to be
treated. Cut fruits and vegetables leach sugars, starches, and acids, so transport water gen-
erally ends up with significant amount of dissolved solids. The best approach to reduce or
eliminate water use in transport systems is by replacing them with dry transport methods.
Conveyor belts can be as effective as water at transporting product efficiently throughout
the plant.
Other water-saving ideas worth considering are the use of steam blanchers instead of
water  blanchers, air cooling after blanching, and the use of evaporative cooling instead of
water cooling.
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