Promoting Resource Efficiency in Small & Medium size ... - UNEP

Step 3: Benchmark Performance
Benchmarking is a process of comparing your organisation’s
operational formance to that of other organisations to become ‘best in
class’ and make continual improvements. Benchmarking is more than
simply setting a performance reference or comparison; it is a way to
facilitate learning for continual improvement.
Benchmarks for the selection of unit operations listed below, are
included in Chapter 8 of this handbook and in the electronic PRE-SME
resource kit that accompanies this handbook:
• Paper
• Food processing
• Textile industry
• Leather manufacturing
• Metal manufacturing
Benchmarks for the selection of unit operations listed below are
included in the accompanying electronic PRE-SME resource kit:
• Boilers
• Cooling towers
• Sanitary use
Step 4: Consider Options
Many general approaches exist for identifying water-saving opportunities.
The installation of meters is the essential first step for monitoring usage
and providing motivation for operators to save water. In addition to fixing
leaks and stopping unnecessary use, the approaches listed below can be
applied to become water efficient at any site.
Sanitary/Sewage Uses:
Often overlooked, are the water and cost savings achievable by reducing
sanitary and sewage water usage by employees at commercial and
industrial facilities. While water efficiency measures should begin with
the most water-intensive operations such as cooling, cleaning, rinsing
and heating, many businesses miss the benefits of the ‘low-hanging
fruits’ that can be had in sanitary/sewage water consumption points
such as toilets, urinals, sink faucets and showers. Sanitary/sewage
water use at industrial and commercial facilities may range from a few
percent in a food processing industry to more than 50% in an office
setting. Average daily domestic demands in commercial and industrial
settings range between 75 and 130 litres per day per employee, and a
savings of 25 to 35% in this domestic usage is readily achievable.
Boilers:
Impurities in water add significantly to the cost of effectively operating
a boiler. As steam is lost and water is added to the boiler to replace it,
the concentration of impurities in the water ‘cycle up’, quickly moving
beyond the concentration at which they can be adequately treated by
chemicals. To prevent this, high-solids water must be bled from the
boiler to maintain a manageable level of solids in the boiler water. This
process is known as ‘blowdown’. Unfortunately, blowdown – in addition
to releasing high solids – also releases money that has been invested
in the water. Specifically, the heat energy that brought the water up to
temperature and the chemicals required to treat the water are lost during
the blowdown process.
Improving condensate return is one way to minimise blowdown and
maximise cycles of concentration at which a boiler operates. By
increasing condensate return, operators will decrease chemical usage,
decrease blowdown and conserve the heat contained in the hightemperature
condensate.
Cooling:
The use of open cooling systems represents the largest use of
water in industrial and commercial applications. Closed cooling
water cycles that, are back-cooled with cooling towers, remove heat
from air conditioning systems and from a wide variety of industrial
processes that generate excess heat with less water. While all cooling
towers continually cycle water in a closed loop, there is constant
evaporation to take away the heat. Cooling towers can consume 20
to 30% or more, of a facility’s total water use. Optimising operation
and maintenance of cooling tower systems can offer facility managers
significant savings in terms of water consumption. To minimise purge
losses measure conductivity of the water in the sump. Try to minimise
the input of salts with the cooling water.
Cleaning and Rinsing Applications:
Most industrial and commercial businesses have a variety of cleaning
and rinsing applications that can consume large volumes of water.The
water-efficiency techniques presented in Section 4.4 address general
water efficiency for process changeovers, equipment clean-out, parts
rinsing, tank rinsing, line flushing, floor cleaning and other applications.
They include dry pre-cleaning, collection and cascaded use of water,
(automatic) control of the contents of impurities of wastewater e.g. by
conductivity measurement and control of chemicals or detergents to
make optimum use of water. CIP (Cleaning in place) – plants recover
soda lyes for reuse and the last rinsing water for pre-rinsing of the next
cleaning sequence.
Reuse and Reclamation:
Maximising utility of in-process water is accomplished by using it more
than one time to do work. Water quality characteristics will determine
if multifunctional use of in-process water is acceptable for achieving
necessary product quality control/assurance. Fortunately, many watertreatment
technologies can provide cost-effective opportunities to
reduce water-supply demand and the resultant savings can be used to
justify capital costs. A simple approach in rinsing is the use of counter
low cascades. Depending on water-quality requirements for the stage of
use, water may simply be recirculated or require only basic treatment
such as solid settling, oil skimming and/or filtration using cartridge,
bag, disk, indexing fabric or sand filtration.
Water efficiency options for specific sectors within an industrial plant
and its processes are included in detail in the electronic version of the
toolkit.
To ensure that water consumption is optimised, consumption should
be monitored on a regular basis. It is helpful to install water meters
for separate departments and even for individual processes or pieces
of equipment. Whether this is feasible depends on the level of water
consumption and the expected savings in each instance.
Water consumption can be reduced by 10 – 50% simply by increasing
employees’ awareness and by educating them on how to reduce
unnecessary consumption.
After the option generation (Plan) a draft implementation programme
(Do) has to be made – see Basic Module PDCA.
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