Effluent Treatment in Textile Industry-2

Bleaching and Dyeing

It is estimated that to dye 1 kg of cotton with reactive dyes, 0.6-0.8 kg of NaCl, 30-60 grams of dyestuff and 70-150 liter of water is required. Once the dyeing operation is over, the wastewater must be treated before reuse. Coagulation and Membrane Technique ( nanofilteration  or reverse osmosis) are among the processes suggested for the treatment of water. 

Coagulation and Flocculation

Natural and wastewater contain small particles. They are suspended in water in a form called as a colloid. These particles carry the same charges, and repulsion prevents them from combining into larger particles to settle. Thus, some chemical and physical techniques are applied to help them settle. The phenomenon is known as coagulation. A well known method is the addition of electrolyte. Charged particulates combine with ions neutralizing the charges. The neutral particulates combine to form larger particles, and finally settle down. Historically Alum is used for this purpose but it makes the pH of the solution slightly basic. 

Another method is to use high-molecular-weight material to attract or trap the particulates and settle down together. Such a process is called flocculation. Starch and multiply charged ions are often used.

Here the basic advantage is that the dye molecules themselves are removed which is better than other methods where dye molecules are decomposed and produce harmful and toxic aromatic compounds. 

The disadvantage is that in coagulation process, large amount of sludge is created which may become  a pollutant itself and increase the treatment cost.

This method is useful for removing the insoluble dyes, but the cost of treating the sludge increases.

Ultrafilteration and Nanofilteration


Ultrafilteration filters substances with sizes less than  than 10^-7 to 10^-8 m . It can effectively remove suspended organic solids. It can not remove multivalent ions. It needs low water pressure to operate.

Nano filteration filters substances with size less than 10^-8 to 10^-10 m. It can remove multivalent ions. 

Reverse Osmosis

It can remove substances with size less than 10^-9 to 10^-11m. It can remove multivalent as well as monovalent ions.

When a compartment containing a dilute solution is connected to another compartment containing a concentrated solution by a semipermeable membrane, water molecules move from the dilute solution to concentrated solution. This phenomenon is called osmosis.

By applying pressure in the higher concentration solution, water molecules migrate from a high concentration solution to a low concentration solution. This method is called reverse osmosis water filter system. ( Source )

An excellent FAQ on Reverse Osmosis can be found here .

Previous    Next

Now that you've finished reading this post, what are you going to do? You should join the Forum.

Effluent Treatment in Textile Industry-1

The idea for this topic is triggered by the news of discovery of treatment of textile effluent by a combination of biological and physico-chemical methods.

Speaking simply, the effluent control is effected by two approachs, physcial and chemical. However these methods are expensive and non effective. Using both biological and chemical methods, one can achieve effective effluent control. 

Read the full story here .

Industrial Textile processing comprises several processes which include pretreatment, dyeing, printing and finishing processes. Besides consuming large amount of energy and water, these processes generate lot of waste products.  

Generally the effluents generated in textile processes have the following shorcomings:

- Heavily Colored

- Contain High concentration of Salts

- Exhibit High BOD ( Biochemical Oxygen Demand) and COD ( Chemical Oxygen Demand)

Understanding COD and BOD

COD is the total measurement of all chemicals in the water that can be oxidised.  BOD is supposed to measure the amount of food ( or organic matter ) that bacteria can oxidise. Permissible limit of COD is 250 to 500 ppm and BOD is 30mg/l.

To explain it further, the microbes present in polluted water consume the dissolved oxygen for respiration and nitrification. These bacteria consume pollutants and then use dissolved oxygen to convert the pollutants into energy. Other bacteria consume ammonia to nitrate a process called nitrification. Please see the pictures here for illustration.

This is important to control COD and BOD as a water high in BOD can deplete oxygen in the receiving waters, causing fish kills and ecosystem damages. Low BOD also helps in further treatment.

A typical textile mills effluent has a pH of 9.8 to 11.8, Total alkalinity as CaCO3 17-22 mg per liter, BOD 760-900 mg/l, COD 1400-1700 mg/l, total solids 6000-7000 mg/liter and total chromium 10-13 mg/l.

Three methods are suggested to reduce pollution

1. Use of new, less polluting technologies

2. Effective Treatment of effluent

3. Recyling waste several times over before discharge. 

The following are the most common causes of generation of effluent wasts in textile industry:

Desizing

In general 50% of the water pollution is due to waste water from desizing. 

Problem with Effluent from Desizing

It has high BOD which renders it unsuitable. 

Solutions to Control

- Using enzymes that degrade starch into ethanol. This can be recovered by distillation

- Using oxidative system like H2O2 that degrade startch to CO2 and Water. 

- Using Electro-oxidation

- Treatment with Mixed activated Sludge system. 

In mixed activated sludge system, microorganisms are introduced which convert carbon in the effluent into suspended solids and carbon dioxide and water. The solids are then separated from the wastewater in the settling tank and then recovered.

As most of the dyes are not biodegradable, this method of using activated sludge is not always successful. 

Mercerisation

Problems:

The effluent has high concentration of NaOH

Solutions:

- Recovering NaOH from waste water using membrane techniques. 

- Use of Zinc Chloride during mercerisation

Source: 1

next

Now that you've finished reading this post, what are you going to do? You should join the Forum.

Buti and Buta Motifs in Jodhpur Textile Printing

1. Sada:  This motif is used by Bishnoi community of Jodhpur.

2. Oul : This motif is worn by Chaudhari Community.

3. Ankuri : This motif is worn by Kalbelia and Jat Community

4. Makhi : This Motif is used by Choudhary community.

5. Gulbuta : This motif is used by Jain and Choudhary community

6. Kapa: This motif is worn by widows of Rabari Community

7. Bhalka: This motif is ued by Gadiya Luhar community.

8. Jali : This motif is used by Gadiya Luhar community

Now that you've finished reading this post, what are you going to do? You should join the Forum.

Traditional Striped Motifs in Jodhpur Textile Printing

Boriya

Boriya Motif- Used by Mali Kaum in Rajasthan

Ilaicha

Ilaicha Motif- Worn by Sirvi in Rajasthan

Jodhpuri Katar

Jodhpuri Katar- Worn by Rabari Kaum

Makoda

Makoda- Worn by Rabaris

Mehndi

Mehndi Motif- Worn by Sindhi Muslim- Ghagras

Methi

Methi Worn by Choudhari Community in Rajasthan

Nimboli

Nimoli Motif- Used by Choudhary Women in Jodhpur

Phooli

Phooli Worn by Rebari ( Raika) in Rajasthan

Rakhri

Rakhri - Worn by Rebaris in Rajasthan

Rata Katar

Rata Katar- Worn by Sirvis

Sada Chint

Sada Chhint- Worn by Vaishnav

Samundar

Samundar- Worn by Merat Kaum in Rajasthan

All these pictures are courtesy Mr. Chhipa Yasin- who has developed a bed sheet using thirty of these now-forgotten motifs.

Now that you've finished reading this post, what are you going to do? You should join the Forum.

Motifs of Jodhpur Printing- Phetiya ( Fetia, Phetia)

Phetiya is one of the most popular motifs used in block printing in Jodhpur. There are various variations of Phetiya are available. Some of them are as given below:

1. Panihari Phetiya

In this motif, Indigo and Alizarin are prominent Colors. It is a traditional costume of Sirvi ( Chaudhary) Community in Rajasthan. The word Sirvi means share cropper (A sharecropper is a farmer who doesn't own the lands he farms). Sirvi people speak Marwari. The men wear cotton thread around their waist, called bell or dhaga, having eleven knots. They believe that this dhaga symbolizes their community deity Jagadhamba of Rajasthan.

2. Nanna Phetiya

It comprises of natural colors like Indigo, Alum, Haldi and Alizerin. Availability of good water enhances this kind of block printing. It is a favourite among the women in the Choudhari community who carry these prints in their traditional Ghaghras.

3. Genda Phetiya

The genda print is seen mostly in the traditional dresses of Rabari community. Some natural colors like alum or indigo are used in Dabu technique of printing.

4. Gunda Phetiya

The Gunda Phetiya kind of block prints are vividly seen in the traditional attires of the Mali Jat in Rajasthan. Simple yet unique prints with Shades of alizerin and indigo enhance the simplicity of the fabric.

5. Bavliya or Guddi Phetiya

The Bavliya kind of print is mostly seen in the traditional outfits of the women in the Choudhari ( Godwal)  community of Rajasthan. The prints are made with finely carved blocks using natural Colors.

Now that you've finished reading this post, what are you going to do? You should join the Forum.

How Neel or Ultramarine Blue Whitens Fabrics

What is Neel

Neel is used very commonly in washing of the white clothes. It is interesting to know the chemical and other facts about this chemical. 

Neel is a chemical called Ultramarine Blue. It is a blue pigment consisting primarily of a double silicate of aluminium and sodium with some sulfides or sulfates. It is the most complex pigment found in nature. It is found in the natural state in the mineral of Lapis Lazuli. Now it is also produced artificially. 

The name Ultramarine essentially means "Beyond the Sea", because it was imported from Asia by sea. 

How it Effects Fabrics

White fabrics become yellow or grey after some washing. Since blue and yellow are complementary colors in the subtractive color model of color perception, adding a trace of blue color to the slightly off-white color of these fabrics makes them appear whiter. Ultramarine has a red undertone which means it reflects at both the blue and red end of the spectrum but absorbs only the unwanted yellow component. Most other blues are having green undertone. In addition to absorbing the yellow component they also absorb the red and therefore cannot give such a balanced correction as ultramarine does. 

Ultramarine is a pigment and not a dye. It is insoluble in water and keep itself only by agitation. Upon washing some of the ultramarine particles become trapped in the fabric which gives it blue undertone. Next washing these particles come out and new particles take their place. Thus it is an auto correcting Mechanism. 

If too much of the ultramarine is added, it will give a pale blueness to the fabric, instead of brilliant whiteness. If a rapid correction is required, rinsing with some lime or vinegar will easily remove the excess blue color.  

Particle size is also important. If particle size is less than 1 micron, then in the next washing the particles do not get washed out and blueness keeps on increasing. Ideally a size of 2-3 micron is recommended. 

It should be remembered that Ultramarine improves the whiteness of the fabric, but not the brightness. In fact as it subtracts the absorption of yellow light, it reduces the brightness making the fabric appear dull. 

Brightness can be increased by using some optical brighting agent.

Sources : Wikipedia, 1, 2

Now that you've finished reading this post, what are you going to do? You should join the Forum.

Textile Analysis for Forensic Testing

Textile as used in Forensic Evidence

Fibers represent one of the forensic evidences known as trace evidence.

The forensic examiners must handle a victim with care, to minimize fiber loss. Retrieving the victim's clothing as soon as possible is very necessary to prevent as much fiber loss as possible. Fibers are typically collected using adhesive tape.

The following details are particularly noted when analysing fibers. This helps to determine the source of the fibers.

1. Fiber Type: The presence of less common fibers at a  crime scene or on the clothing of victim or suspect increases its significance.

2. Fiber Colors: It greatly influences the significance of fiber comparison. Fading and discoloration further adds significance to a fiber association.

3. Number of Fibers: The greater the number of fibers on the body of a suspect or victim,  the more is the likely hood of a direct contact between individuals, however converse may not be true.

4. Fabric type: Loosley knit or woven fabric or new fabric shed more fibers.

Source 12


Now that you've finished reading this post, what are you going to do? You should join the Forum.

A Note on Medical Textiles

Textiles act as an interface between man and treament. Depending upon the area of application, the medical textiles are categorises as Non-implantable, implantable and healthcare and hygiene products.

Non implantable material are external to the body, with or without skin contact. It includes absorbant pad, bandages and plasters among others. These material should have good padding characteristics and should be non sticking to the wound. Air and vapor permeability is requrired so that the material is comfortable to the patient. They should have high absorbancy and should be soft and pliable.

Implantable materials are used in place of defective body parts. It includes sutures and soft tissue implants. These materials should have compatibility with the natural body systems. They should be durable and resistant to alkali and acidic media. Of course, they should have functionality for the purpose for which they are applied.

Healthcare and hygine products are not directly used in medical treatment, rather they are used for good hygiene application and healthcare. It includes surgical clothing and surgical covers. They should have high bacterial and viral resistance. They should be hygienic and should have softness and breathablitity. They should have required strength.

Source of image: 1

Now that you've finished reading this post, what are you going to do? You should join the Forum.