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| Issue date:27/05/2010 |
| ATA Journal for Asia on Textile & Apparel - May 2010 Issue |
| Source:Journal for Asia on Textile & Apparel |
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| Researchers say that water scarcity has increasingly become a business risk, and the cost of water is likely to rise significantly in years to come. To minimize the impact, textile and apparel manufacturers are advised to take immediate action and consider some uncostly measures |
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| Four ways to save water were suggested by NRDC experts (Photo: Town of East Hampton, US) |
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| Drought in Guizhou province (Photo: Oxfam HK March 2010) |
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Drought, a severe form of water scarcity, has been observed in more and more regions such as Australia, China and the United States in recent years, China's State Commission of Disaster Relief said this March.
Severe drought has affected over 51 million Chinese people and left more than 16 million people and 11 million livestock facing drinking water shortages. Since autumn last year, southwest China, including Yunnan, Sichuan and Guizhou provinces, Guangxi Zhuang Autonomous Region and Chongqing Municipality, has received only half its annual average rainfall and water stores are depleted.
The "Charting our water future" (2009) report of the 2030 Water Resources Group stated that, by 2030, under an average economic growth scenario and if no efficiency gains are assumed, global water requirements would grow from 4,500 billion m3 today (or 4.5 thousand cubic kilometers) to 6,900 billion m3.
In order to mitigate the water challenge, the report suggested the following directions:
Agricultural productivity is a fundamental part of the solution
Efficiency in industry and water systems for domestic use is similarly critical
Quality and quantity of water are tightly linked.
"Best practices" on saving water identified
Whereas North America and Europe have few textile mills and mature environmental regulatory structures, China and most other developing nations lack the capacity either to adequately monitor the thousands of mills operating locally or to enforce existing standards. In response to the problem, US- based Natural Resources Defense Council (NRDC) partnered with six pioneering multinational apparel retailers and brands to launch the Responsible Sourcing Initiative (RSI), as part of the larger Clean by Design effort to address the environmental impacts of the fashion industry.
In February 2010, NRDC released a report* providing a practical guide for stakeholders in the textile and apparel supply chain for responsible sourcing. Ten relatively easy-to-implement and low-cost practices were recommended. Four of them relate to water use.
Water consumption varies among processes within a textile mill as well as by machine type and setup. Wet processing (i.e. pretreating, dyeing, and finishing) typically accounts for the majority of water consumption and wastewater discharge, the NRDC report says.
Recycling and reuse measures that focus on these processes yield great savings, and, since the water recovered is often hot, these improvements save energy as well. Steam condensate and non-contact cooling water (such as water used to cool a singeing machine) is a second valuable source of water to recover because it is high in both quality and temperature. Finally, water is used for general washing and cleaning throughout the factory, and good housekeeping practices can substantially reduce wasteful use of water in cleaning as well, according to experts at NRDC.
A mill that implemented all of the four practices suggested would save between 27 and 37 tons of water per ton of production—13-24% of its total water use, the report says.
Leak detection, preventive maintenance, improved cleaning
Although individual leaks may not seem important in the overall consumption picture, they can be responsible for a significant loss of resources over the course of a year. For example, one 2mm steam leak with saturated steam of 5 kg/cm2 consumes an estimated 10.34 tons of standard coal per year. Similarly, the power loss from one compressed air leak of about 4 mm with 0.6 mPa pressure is 6.5 kilowatts in electricity, an annual loss of about 52000 KwH.
Based on observations made during the mill assessments, RSI estimated conservatively that leaks of water and steam were responsible for between 1% and 5% of losses of water and energy. In fact, these values could be higher judging from the relevant literature. Additional savings can be expected from improved oversight of the water used in cleaning operations; for example, by installing shut-off valves and turning off hoses when they are not in use.
This practice consists of routinely investigating sources of leaks in water, steam, and compressed air and implementing an effective preventive maintenance program, requiring virtually no investment costs and thus delivering instant payback, according to the NRDC report.
Reuse of non-contact cooling water
Non-contact cooling water should always be recycled. It is high in quality and temperature and can thus be reused beneficially in various processes, such as in desizing, scouring, washing, or rinsing. Furthermore, at a discharge temperature of 45°C and considerable water volume, discharge of cooling water stresses the wastewater treatment system. It is thus highly beneficial to keep such large quantities of hot, clean water out of the treatment system. RSI found that some mills were either not reusing this water at all or were using it in cold water processes that did not benefit from the heat.
RSI identified three sources of non-contact cooling water that can be most beneficially recaptured and reused: water used in singeing, preshrink machines, and in air compressor systems. Other sources of cooling water may be available elsewhere in the mill as well, such as from batch jet dyeing machines.
This practice requires installation of a water reuse system—pipes, valves, pumps, holding tanks, and a control system. Investment costs are estimated at less than US$1,500 and return on investment is less than one month, NRDC report states.
Reuse of steam
Textile mills rely on a large amount of saturated steam in the dyeing process. Some of that steam converts into condensed water (condensate) over the course of its use. This condensate is very high in temperature and purity. One of the best places to collect large volumes of condensate in woven fabric mills is inside the drying cylinders, where fabric is dried by heat from steam. Knitted mills find large sources of condensate primarily in steam traps.
The most efficient use of condensate is to return it to the boiler and convert it back into new steam. However, for companies that buy their steam from an outside supplier or whose boiler is located too far from the process, the condensate can serve as water supply for washing or desizing, thereby recovering both water and heat.
In three mills investigated by RSI, condensate went directly to wastewater without reuse. In one of these mills, the drying cylinders produced condensed water at a speed of 15 kg/h, which translated into 18,975 tons of condensed water per year, 2.5% of the total water consumption in the factory.16 Energy savings accruing from this option are also quite substantial.
This best practice requires installation of pipes and lines to capture and return condensate. Estimates of investment costs have a large range and were difficult to pinpoint in RSI mills because they depend on the particular layout of the mill and the proximity of condensate sources to the boiler. Payback periods are good in all cases, between immediate (less than one month) and less than eight months.
Reuse of process water from bleaching and mercerizing
The water discharged from bleaching and mercerizing machines can be collected and reused for other processes, instead of discharging it directly to wastewater treatment. The quality of water must be evaluated, but can often meet the quality requirements for scouring after simple pretreatment (cleanup of fibers).
This best practice requires purchasing pipes, water tanks, and electrical pumps to store and return water to the process. Estimates of investment cost range from US$3,000 to US$30,000 depending on mill size and layout, but in all cases the investment pays itself back immediately (less than one month). Some mills will not need to purchase new equipment but can adapt existing equipment and systems to this use.
Cold pad batch processing
One mill familiar to RSI assessors converted to cold pad batch dyeing and saved approximately 3,550 tons of steam (equivalent to 461.5 tons of coal) annually with an investment of RMB 256,000 (US$37,500) and a payback time of only four months. However, cold pad batch technology is limited to woven cotton fabric and works best with heavy-weight fabric and dark colors. Because of these limits in applicability, cold pad batch processing is not included in the list of best practices. *Information on the four water-saving practices comes from "NRDC's ten best practices for textile mills to save money and reduce pollution" published in February 2010
Water issues in China and India
What is drought? (Source: Governance Knowledge Centre of India) |
Due to the heterogeneous nature of water problem across countries in the world, several case studies on different countries were conducted for the 2030 Water Resources Group report including China and India.
Demand in India will grow to almost 1.5 trillion m3 by 2030, driven by domestic demand for rice, wheat, and sugar for a growing population, a large proportion of which is moving toward a middle-class diet. Against this demand, India's current water supply is approximately 740 billion m3. As a result, most of India's river basins could face severe deficit by 2030 (unless concerted action is taken), including some of the most populous places such as the Ganga, the Krishna, and the Indian portion of the Indus, according to the report.
China's demand in 2030 is expected to reach 818 billion m3, of which just over 50% is from agriculture (of which almost half is for rice), 32% is industrial demand driven by thermal power generation, and the remaining from household uses. Current supply amounts to just over 618 billion m3. Significant industrial and domestic wastewater pollution makes the "quality adjusted" supply-demand gap even larger than the quantity-only gap: 21% of available surface water resources nationally are unfit even for agriculture. Thermal power generation is by far the largest industrial water user, despite the high penetration of water-efficient technology, and is facing increasing limitations in the rapidly urbanizing basins. |
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| Copyright © Adsale Publishing Limited. Any party needs to reprint any part of the content should get the written approval from Adsale Publishing Ltd and quote the source "ATA Journal for Asia on Textile & Apparel", Adsale Textile English Website - www.AdsaleATA.com. We reserve the right to take legal action against any party who reprints any part of this article without acknowledgement. For enquiry, please contact Editorial Department. |
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| Copyright © Adsale Publishing Limited. Any party needs to reprint any part of the content should get the written approval from Adsale Publishing Ltd and quote the source "ATA Journal for Asia on Textile & Apparel", Adsale Textile English Website - www.AdsaleATA.com. We reserve the right to take legal action against any party who reprints any part of this article without acknowledgement. For enquiry, please contact Editorial Department. |
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