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The treatment and reusing technology of printing and

dyeing wastewater

YI XuenongSchool of Environment and Architecture

University of Shanghai for Science and Technology

Shanghai, China

Zhang YansenSchool of Environment and Architecture

University of Shanghai for Science and Technology

Shanghai, China

AbstractA kind of technology and process of treating printing

and dyeing wastewater with high efficiency and low energy

consumption was presented. Based on the analysis of the current

methods this article summed up the more practical way,

combining theory with practice, to provide some references for

the similar projects.

Keywords-printing and dyeing wastewater; treatment

technology; polyvinyl alcohol

PVA

; wastewater reusing

The printing and dyeing wastewater is a major part of

textile printing industrial wastewater .In recent years, as the

rapid development of dyestuff industry and finishing

technology, new additives, dyes, finishing agents are widely

used in the printing and dyeing industry .In the wastewater

more and more poisonous organic compound are found, andeven some organic matter are carcinogenic, mutagenic, cause

distortion, which has done mankind a great disservice. China

is one of the countries that struggle with serious problems

about water shortage and water pollution .As the water crisisincreasingly, more attention must be paid to reduce pollutant

emissions from the every printing and dyeing processes, useof clean production technologies, recycle of wastewater,

which are of great political and economic significance for

alleviating the water crisis and maintaining sustainable

development.

1 The characteristics and hazards of printing and dyeing

wastewater

According to their sources, printing and dyeing wastewaterpollutants can be divided into two categories: one is from

entrainment material of the fiber material; the other is used in

the processing of slurry, oil, dyes, chemical additives, etc. The

characteristics of printing and dyeing wastewater are complex

composition, high organic matter content , color depth, highchemical oxygen demand ,relatively low biochemical oxygen

demand ,poor biodegradability and large emissions , etc.

1.1Hazards to human health

1.1.1 Cause acute and chronic poisoning

Printing and dyeing wastewater sometimes contains heavy

metal salts which are difficult to degrade using normal

biochemical methods, thus they can long-stand in the natural

environment and endanger human health through the foodchain and so on

[1]. So that the human body poisoning, such as

methyl mercury poisoning (Mina Mata disease), cadmium

poisoning (Itai-itai disease), arsenic poisoning, chromium

poisoning, cyanide poisoning, pesticide poisoning. Of lead,

barium, fluoride can also cause harm to human health. Theseacute and chronic poisoning is the main aspects of causing

serious harm to human health.

1.1.2 Carcinogenesis

Printing and dyeing wastewater contains benzene, amine,

pyrene, polycyclic aromatic hydrocarbons, halogenated

hydrocarbons and other organic pollutants[2]. All thesematerials can be accumulated in suspended solids, sediments

and aquatic organisms. Long-term consumption of water or

food containing these substances may induce cancer. Printing

and dyeing industry use a large amount of Chromium

relatively: dyeing industry often uses it as an oxidant andpotassium dichromate mordant; the preparation of printing

rollers consumes a large amount of Chromium .Chromium has

also been confirmed to cause cancer, we should pay particular

attention to its emissions and utilization.

1.2 The harm to the environment

It is estimated that more than 50 million tons of textile dyesare used all over the world. A large number of wastewater

brought by the process of printing and dyeing is discharged

into the rivers, lakes, seas and surface water. The dye in the

wastewater can absorb light, reducing the transparency of

water and affecting the growth of aquatic life and microbial,

which is not conducive to self-purification of water.Meantime it is easy to create visual pollution and also severe

pollution of water can affect human health. The pollutions and

emissions must be strictly controlled for those things like

resin finishing agent, organic metal flame retardants and

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waterproofing agents containing cadmium which can easily

produce formaldehyde, resulting in badly contaminated but

difficult to treat by the traditional methods.

2 The treatment technology of printing and dyeing

wastewater

2.1 The traditional treatment process and its improvement

2.1.1 Adsorption process

The most widely used physical approaches the adsorption

process. Activated carbon, clay, porous material such as

powder or granules are mixed with water ,or let water through

filter bed composed with granular material, so that waste

water pollutants are adsorbed on the surface of porous

material or filtered to remove . The method for the removal of

dissolved organic matter in waste water is very effective, but

can not remove the water and the hydrophobic colloidal dyes.

2.1.2 Coagulation treatment

They are of two main Methods, flotation and r coagulating

sedimentation. in which the mostly used Coagulant is

aluminum or iron salt-based. The main advantages of

coagulation process is simple, easy operation and

management, equipment investment, covering an small area ,

with high hydrophobic dye decolonization efficiency ;

drawback is that operating costs are relatively high ,sludge

with high water, poor performance and child care, the

treatment effect on the hydrophilic dye worse.

2.1.3 Biological treatment method

Biological treatment methods include aerobic and anaerobic

method. Currently the main method used is aerobic dyeingwastewater treatment. Aerobic is divided into aerobic and

biofilm process. A large number of organic materials are

decomposed by activated sludge, also part of the color. You

can also fine-tune the PH value, operating efficiency and low

cost, water quality is better suited to deal with a high organic

content printing and dyeing wastewater; biofilm

Decolonization of dyeing wastewater higher than the activated

sludge process. Contact oxidation method is a kind of biofilm

characteristics of activated sludge method, the equivalent of

adding aeration tank filling, so filling the surface covered with

a variety of biofilm in the biofilm, the wastewater at the sametime there is a certain amount of suspension the activated

sludge and biofilm detachment, so that waste water to be

purified.

2.2 New treatment technology

2.2.1 Photochemical oxidation

The advantages of photochemical oxidation are with themild reaction conditions (ambient temperature and pressure),

oxidation ability and speed Photochemical oxidation can be

divided into light decomposition, photosensitizing oxidation,

light-induced oxidation and photo catalytic oxidation. Amongthem, the present study is more photo catalytic oxidation. The

research on dyes of photo catalytic degradation is focused on

photo catalyst. Some iron ligand compounds have

photochemical activity. They can be used to degrate organic

compounds. TiO2 is a ideal photo catalyst because of is

stabilization insoluble innocuity etc. The traditional

powder TiO2 is hard to use in practice, because it does notsuit to flow system and hard to separate.

2.2.2 Membrane technology

The technology disposals the wastewater by separating

concentratingrecycling. The membrane technology includes

micro filtration membrane ultra filtration membrane

nanometer membrane and RO membrane. Membrane

technology does not need to plus chemical reagents, in the

process, it does not produce secondary pollution; the process

is simple to operate, it can be carried out under atmosphericpressure with low energy consumption; some salts and dyes

can be recycled from the wastewater and be reused; The

treated wastewater can be directly reused, reducing waste

emissions. But the membrane technology also exists some

problems, such as membrane fouling, membrane flux,

membrane cleaning and the resistance to acid and alkali of the

membrane, etc.

3 The treatment methods of PVA in printing and dyeing

wastewater

The process of printing and dyeing wastewater includes:

desizing, scouring, bleaching, mercerization, dyeing, printingand finishing, etc. The most pollutants in printing and dyeing

wastewater are from the slurries of the process of sizing,mainly PVA slurry. PVA is a kind of organic macromolecular

compounds that is difficult to biochemical degradation, and it

is also an important micro-organisms immobilized material.

Recently, because of its increasing usage, the environmental

problems that PVA causes become increasingly serious. Many

experts and scholars at home and abroad are studying thetreatment methods of PVA wastewater and have made a series

of results[3]

.

3.1 Membrane technology

As is introduced above, membrane separation method is a

method that uses micro porous membrane to filter and

separates the certain substances in the wastewater by the

Selective permeability of the membrane. Feng Bing-ling used

chitosan ultra filtration membrane to treat printing and dyeing

wastewater, the removal rate of COD could reach about 80%,

the decolonization rate exceeded 95%[4]

.

3.2 Ozone oxidation technology

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This method is using ozone to degrade the PVA, the

process is: A long-chain between the molecules cut and the

molecules break into small molecules, so the rate of theBOD5/COD increase, which is favorable to the follow up

biochemical treatment. In the actual operation, it does not just

use the ozone, but also together use other enhanced

technologies, such as ultrasound wave, UV and so on. The

results of an experiment show that, after 12 min treatment, the

degradation rate of PVA with O3/ultrasound, O3/UV synergyis more improved than directly under the O3 oxidation,

showing a good synergistic effect[5]

.

3.3 Chemical condensation technology

PVA is a non-ionic organic polymers, the adsorption of

some electric charge produced by the traditional coagulants is

very weak, merely has no effect to the degradation of PVA. In

the case of containing more salts, salting-out effect makes

PVA separate out. At the same time, borax and PVA

molecules start up double-diol-type combination[6]

. The

experiments show that under the combined effect of the borax

cross linking and Salting-out reaction, the PVA in the

wastewater can be separated out as the gel forms, so as to

achieve the purpose of recycling.

3.4 Biodegradation technology

Although the biodegradability of waste water that contains

PVA is poor, PVA can be degraded under the effect of some

enzymes. As early as 1936, people found PVA can bedegraded into carbon dioxide and water under the effect of the

fungus Fusarium. Using highly efficient degradation bacteria

to deal with PVA-containing wastewater is through screening

and domestication PVA-degrading bacteria, to achieve thePVA completely biodegradable. As is reported, PVA-

degrading bacteria include pseudomonas, brevibacterium,

etc[7]

. The PVA-degrading enzymes isolated from these

degrading bacteria include sec-alcohol oxidasepolyvinyl

alcohol dehydrogenaseB-diketone hydrolase, etc.

4 Printing and dyeing wastewater reuse technology

In order to meet the future demand for printing and dyeing

industry, we must strength the protection, management and

use of existing water resources[8]

. Improve the reuse ratio of

water and development of new water sources can greatlyalleviate the contradiction of the water supply and demand toreduce effluent emissions and the existing water pollution.

The printing and dyeing wastewater reuse technologies

include :AdsorptionCoagulationChemical Oxidation

Electrochemical Biological treatment Photochemical

oxidation Membrane technology Ultrasound

technologyHigh-energy physics method and so on.

The development direction of the reuse of printing and

dyeing wastewater has two paths: Emphasis on the promotion

of the comprehensive management of the waster water andcontinuous optimization of the wastewater reuse program

[9].

In the design of water-recycling facility we should

calibrate the maximum dosage. Water desalination is an

important factor for maintaining balance of circulation system,

ensuring product quality and stable operation of the sewage

system. If not, the largest recycling dosage should be in

control within 30%.

5 Pilot scale study

The process printing and dyeing wastewater treatment is

further introduced in company in Liaoning Province, which

has the similar technics .

5.1 Process of treatment

The investigation shows that concentrations of pollutants in

the production process are very high, especially ,PVA ,whichis as high as 14000mg/L. We apply the chemical treatment-

anaerobic treatment -aerobic treatment process in order to

effectively reduce concentrations of pollutants, which can

obtain good effects. First, it is the pretreatment of biochemical

treatment and that is coagulation with the use of PAM. PVA

residual concentration with different dosage of PAM is in

Table1.( the assumption price of PAM in the market is 20000

Yuan/ton)Table1 Record of experimental data

concentration

of PAM5 3 1 0.5

0.1

0.05

residualconcentration

of PVA

mg/L

4900 6100 7250 8700 9500 10000

cost of PAM

Yuan

1000 600 200 100 20 10

From the table above we know concentration of PAM and

residual concentration of PVA are inverse ratio while cost of

PAM and concentration of PAM are direct proportion.

Considering the high gremoval efficiency of the pollutants in

the follow-up biological treatment we choose 0.5as optical

concentration. Route of process is seen in fig 1:

Fig.1 Process of treating PVA-contained wastewater and reusing

raw water

regulation tank mechanic reactor

anaerobic tankaerobic tanksecondarysedimentation tank

effluent

PAM

returned sludge

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5.2 Interpretation of process of treatment

Sewage generated from the production process firstly flow

into regulation tank, which is responsible for storage andregulation of wastewater to ensure the stable quality and

quantity of wastewater. Then it reaches mechanical reactor

after the addition of

polyaluminium chloride(shortened from PAC).There is a

series of physical and chemical reactions with the help of

mechanical agitation, which also can reduce pollutionconcentration greatly, especially PVA, at the same time. The

anaerobic tank is mainly for decomposing macromolecular

organic into macromolecule organic through the metabolism

of anaerobe, which is good for follow-up treatment. Aerobic

pool is to further decompose macromolecules organics so as

to make effluent up to standard. Finally it flows intosecondary sedimentation tank, separating sludge from effluent.

A part of the sludge will flow back to anaerobic tank and

aerobic pool, other is for beneficial utilization[10]

.

5.3 Treatment effect

After the normal operation of the equipment, recycling rate

of PVA and removal rate of COD can arrive at approximately

80 percent, which decrease concentration of PVA immensely.

It plays a key role in improving the overall treatment effect of

printing and dyeing wastewater and making effluent meets the

standard.

6 Conclusion

From the result of study and discussion above, the proposed

method and technology is feasible for treating the printing

and dyeing wastewater . First we apply phy-chemical methodto treat wastewater of PVA, which can effectively low cost

and investment, decrease treatment load of subsequent

processing structures, increase biodegradability of wastewater.

It can also create conditions for subsequent aerobic and

anaerobic wastewater treatment to obtain higher efficiency.

We are able to enable effluent up to national standard making

use of this technique although initial concentration is as high

as 14000mg/L. Whats more, anaerobic process can produce

biogas, which can be used as new energy and reduce the harm

on environment. At last, the project is set up with recycling

process. Recycling water can be used for landscape irrigation

and production process, which can save precise water and

reduce production cost. Anyhow this technique can gain goodeconomic benefit and social benefit, and have some

promotional value and application prospects.

References

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[3] Zhu Puxin, Yao Yongyi. PVA biodegradability and applicationprospect [J]. Cotton Textile Technology, 2005, 33(2): 62264.

[4] Zhang Huizhen, Liu Bailing, Luo Rong. Recent Advances in theBiodegradability of PVA and its Derivative Material [J]. Journal of theGraduate School of the Chinese Academy of Sciences, 2005, 22 (6):6572666.

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