environment

By MARTIN KOEPENICK

Proven whitewater recycling and filtration system saves money, reduces costs, and contributes to water management goals in China

SUPER CLEAN WHITEWATER REPLACES FRESH WATER

In China, the motivation is high to minimize wa-

ter usage in paper mills, meeting stricter govern-

mental regulations, combined with the focus to

reduce costs through more efficient water and energy

consumption. Many paper mills are actively pursuing

plans to significantly reduce fresh water use and to

return water to rivers cleaner than it arrived.

One proven approach, the PETAX™ fine filtration

system from Kadant, is gaining popularity as a way to

better manage water resources, including continu-

ously circulating whitewater, and simultaneous

capture of fibers and colloidal material. Management

is assured of reduced costs for incoming and outgo-

ing water, also making a positive contribution toward

the national goal of minimizing industrial water us-

age. Independent of the water treatment system, the

compact PETAX fine filtration system helps deliver

consistently higher paper machine efficiency and

runnability.

A wide range of paper, board, and tissue makers

across Asia have chosen the PETAX to reduce water

usage and save money. A paper and board producer

in Thailand has now installed four units and has

ordered another three.

SAME WATER SOURCE FOR INDUSTRY AND COMMUNIT IES

Usually a mill’s water comes from the same rivers as

fresh water for municipalities and farming. In addi-

tion to increasingly higher fresh water usage costs,

fees continue to rise for effluent discharge. In 2010

41Pulp & Paper International (PPI) S e p t e m b e r 2 0 1 1

With savings of 2,000 m3/day of fresh water,

PETAX filters allow for whitewater reuse significantly reducing effluent load as well

as providing recovery of fiber and heat from whitewater

P&P Int'l - PPI Sept 2011 - p41 to 43.indd 41 8/22/2011 9:19:56 AM

the Chinese government mandated increased recy-

cling of industrial water, and has offered incentives to

achieve desired results faster.

Though national conservation policies have

helped to limit increases, water use nevertheless

climbed to a record 599 billion m3 in 2010. Over the

next decade, according to government projections,

China’s water use will reach 620 to 630 billion m3/yr

, and an announcement earlier this year by the gov-

ernment indicates water use could reach as high as

670 billion m3/yr over the next decade.

Motivated by a desire for sustainable growth, cost

savings, and the need to meet new governmental

standards, more and more mills are progressively

closing water loops and reducing fresh water con-

sumption.

According to Tim Tian, team leader of water

effi ciency projects at Kadant Johnson’s Wuxi facil-

ity, “China is moving quickly toward water saving

systems, making more paper with less water, and

recycling water without any linkage to wastewater

treatment systems. Our PETAX system stands

alone as an economical self-contained unit,

whether there’s a wastewater treatment system or

not. In addition, our wide range of other products,

including gravity strainers, multiple barrel pressure

fi lters and shower systems, contribute to greater

sustainability and smooth operation of mill

equipment.”

The system is capable of processing up to

240 m3/hr of white water with suspended solids in

the range of 100-2000 mg/L. The recycled whitewater

generated by this system can be reused for a wide

range of functions, and does not clog equipment,

such as shower nozzles.

AN AUSTRAL IAN LEAP FOR WARD

PETAX has become a preferred solution on an in-

creasing basis throughout Asia. Based upon increas-

ingly tight water supplies, Australia’s Encore Tissue

looked for the latest technology to reduce water use.

As reported by City West Water, Melbourne,

42 S e p t e m b e r 2 0 1 1 Pulp & Paper International (PPI)

environment

Water conservation in ChinaOverall, water resources in China are becoming scarce, and measures need to be taken to prevent water resources from hampering economic and social development.Water resources per person in China are 2,200 m3/yr, but are projected to decrease by 25%-30% when the population potentially surges up to 1.6 billion. At present in China, there is an annual gap of 36-50 billion m3 in the water supply. Now, and even more so in the coming years, sustainable use of water resources will play an important role not only to improve the quality of human life but also for development of the economy and society. Some of China’s leading paper producers are already taking a wide range of measures to reduce water usage, and enhance water during processes and return it to the local river is a sustainably acceptable way.

As industry and human populations increas-ingly draw from limited fresh water resources, tapping into whitewater is proving to achieve profi tability and environmental performance

P&P Int'l - PPI Sept 2011 - p41 to 43.indd 42 8/22/2011 9:19:58 AM

43Pulp & Paper International (PPI) S e p t e m b e r 2 0 1 1

Encore Tissue, decided to employ the fi ne fi ltration

system in its tissue making process, choosing a sys-

tem that could handle the high volume of suspended

particles, allowing showers to function without build

up or potential blockage.

According to Encore Paper’s mill manager Hugo

Rust, “Petax enabled us to reuse process water in the

manufacturing process without compromising our

water quality.”

REPEAT SUCCESSES IN THAILAND

Thailand’s largest packaging producer, Siam Kraft

Industry, chose PETAX to recycle whitewater used

in the papermaking process via single-stage fi ltra-

tion of liquids containing a high level of suspended

solids. The equipment is similar to that supplied to

them earlier, as well as a sister kraft packaging plant

before that.

Tian adds, “It’s important to note that removing

almost all of the suspended solids over 30 microns in

size in the fi ltrate, is achieved without the addition of

chemical fl occulants, fi ber sweetener stock, or pre-

coats. Just with the fi ltered whitewater itself, optimal

performance of showers on the wires and felts has

been achieved. Our customers are typically seeing up

to 30% savings in water consumption.”

HOW ARE SAVINGS ACHIEVED?

A specially designed felt-like fi lter media is applied

to each of a series of discs. Process water is evenly

distributed into the fi lter vessel across the surface

of each disc. The fi lter vessel, fi lled with process

water, operates under low pressure (0.1-0.3 bar).

The submerged discs slowly rotate, gaining speed as

pressure drops. Cleaned fi ltrate passes through the

media to a hollow space in each disc, from which

it collects in a central hollow shaft at atmospheric

pressure.

Throughout the process, the discs are continu-

ously cleaned in three stages. First, fi lter cakes are

doctored off and pumped away. Then, clean fi ltrate

is pumped back through the media to remove debris,

which is pumped away. Next, a submerged, oscillat-

ing high-pressure shower also cleans the media.

Mills have been operating the fi lter media for

about six months without replacement. Changing the

disc assembly takes only one to two hours. PPI

Martin Koepenick has written about the pulp and

paper industry for more than 25 years visiting mills

around the world: mkoepen@gmail.com

environment

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SYSTEM BENEF ITS

• Reduces fresh water usage and effl uent treatment costs.• Saves energy by reclaiming and reusing process water.• Minimizes shower nozzle plugging.• Polishes save-all’s super, clear-leg white water, DAF water, or cooling tower water.

FUNCT IONAL PARAMETERS• Fluid source: disk save-all super, clear-leg white water• Contaminants: fi nes and fi bers• Application: white water system; showers on wire and felts

Purifi ed whitewater from a Kadant PETAX system can provide for up to a 30% reduction in fresh water, and minimizes wastewater sent back to the effl uent plant. Showers don’t plug, because suspended solids bigger than 30 microns (and even smaller) are removed

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