Environment – Manufacturing more Efficiently –
Water Efficiency
Increase your
profits by reducing your water
Water consumption
can be a major operating cost for manufacturers and could be costing companies
over 1% of business turnover. Yet by using some simple control measures and
inexpensive devices, this can be reduced by as much as 50%. These savings go
straight to your bottom line as well as conserving an increasingly scare global
resource.
Many people
think of water as a free resource, because as individuals we rarely have to
account for its usage at home. In reality water is a utility that is paid for
twice – once on purchase and once on disposal.
Freshwater
resources in the more densely populated and farmed areas are reaching the point
of being fully “allocated” so managing water consumption and minimising waste
is important. The use of water for manufacturing and industry represents 11% of
total demand.
The cost of
water varies from region to region. This includes the suppliers’
operating and maintenance costs, water purchase and waste water disposal.
Disposal costs for the effluent discharged to sewer will vary depending on the
level of waste water treatment provided by the local sewerage utility.
For industry,
there are additional operating costs for using and disposing of water.
On site water
must be:
A reasonable
estimate of the true cost of water is around three times the cost of purchase and disposal.
In the plastics and chemical sector the biggest
use of water is for cooling and steam production. Water is also a major raw
material to make plastic products.
Other significant uses include plant and
vessel washing, product washing, vacuum pumps and air pollution control. Water is used as a
means of transferring material and energy around a processing facility and the
loss of this down the drain can be a significant cost to business. .
At many sites the common use of manual hoses
to wash down equipment and surfaces is an invitation to use water
indiscriminately.
Despite so many
varied applications, water is often only metered as it comes onto site for
billing purposes. Some plants meter process usage as this may be critical to
product quality, and many sites are now aware of the need to meter steam usage
for energy efficiency programmes but cooling water flows are rarely measured.
Having a
comprehensive metering system helps to locate leaks. Many plastics / chemical
plants have developed over a period of years, and underground water mains are
very common. Without a regularly updated distribution network diagram and clear
metering to enable a full water balance to be constructed and reconciled with
the water bill, leaks can go undetected for years. Underground leaks can also
have much more serious impact, including possible erosion of foundations and
roads and, if the leak becomes a serious burst pipe can result in production
losses while the main is excavated and repaired.
Water is in fact the most common solvent used in
industry and while this is extremely valuable to industrial processes, it also
means that while clean water may come onto a site, it is generally dirty,
material laden water that leaves a site as trade waste. Most water used in the plastics / chemical industry is used once
only. After use it is simply discharged to drain and either to sewer or an
on-site treatment plant but it may be perfectly adequate for re-use in another
process or as wash water before discharge.
A "water cascade" can provide opportunities for several
cycles of re-use before it becomes too dirty and must be discharged. Yet every
time that water is re-used, an equivalent volume of clean water does not have
to be bought. By reusing water in the production process, water consumption can
be cut by 50%, 70% or even 90%.
Measure water
use to establish a baseline water usage against which to measure progress. This
will show how and where water is being used and will highlight the those area
which use the most water and indicate where any leaks may be undetected.
Ensure that water use calculations include:
Pumping costs
Maintenance costs
Treatment costs
Whether the waste is hot water or cold water,
and the costs of heating or cooling
Costs of disposal of resultant waste water (i.e.
trade waste charges)
Following this, a simple housekeeping programme can be instituted to
generate immediate savings, raising staff awareness of the commercial importance
of water savings and providing a fund for more capital-intensive measures.
Simple
housekeeping measures which have been used in the plastics / chemical industry
include:
1. Leak
detection programmes
There will be areas where water use is required
but where the amount of water used can be decreased.
2. Process water
usage improved cleaning procedures
Once the water
balance has been completed, it is important to update it regularly so that the
impact of any activities is transparent. This naturally leads on to setting
targets for production and ancillary use with which progress can be monitored
and savings verified.
Sooner or later,
however, capital investment will be required. Some of the most common measures
taken by the chemical industry include:
A six step
approach to reduce water costs:
The
measurement of water usage is essential to highlight trends, abnormalities, the
potential for savings and the effect of water minimization measures.
A number of
water-saving measures and practices are common to all businesses. For example,
it is good practice to keep drains for foul sewage, stormwater and process
effluents separate, so that high sewage or trade effluent charges are not
incurred for "cleaner" water flows. Dry methods should be considered
prior to those which use water, to minimise water use and effluent generation.
When a hose is used to spray equipment or floors, care should be taken that
large quantities of solid or soluble materials are not sent to drain if they
can first be removed by sweeping or scraping. In staff toilets, the
installation of percussion taps or automatic flushing devices for urinals could
be considered.
If you have an Environmental
Management System at your site, water use and disposal might well be
considered a significant impact from your process already. If you haven’t
already done so, consider options for reducing water use at your next
management review.
If you don’t
have an EMS, set yourself or your team a
series of key milestones. Against each action, set a date and a responsibility
for achieving the action.
No comments:
Post a Comment