Reuse of Textile ETP Sludge from Tirupur Region as Construction Material An Experimental Investigation

As per Tamil Nadu State Pollution Control Board (TNPCB) records, there are about 830 large units engaged in textile industrial processes in Tirupur alone. These industries have established eight Common Effluent Treatment Plants (CETPs) and many individual Effluent Treatment Plants (ETP), which are subjected to treat about 75,000 m3 of effluent per day genereated by textile industries. On the other hand, the sludge that retained due to the solids separation process in the treatment plants create lot of environmental problems due to lack of disposal methods. The practicing method of disposal of sludge in the Tirupur region is the Land filling method. Except engineered landfills, the rest of the sludge is disposed off by dumping it on the earth surface which may lead to ground water contamination and thereby results in socio-economic impacts. Many studies have been conducted in those areas and it needs for an alternative sludge management. The industrial solid waste of different nature is effectively utilized in Building materials as light weight cement.

Textile sludge has been collected from (CETP), Tirupur and studied its chemical, physical and engineering properties. The collected sludge was dried to reduce its moisture content and then sieved to remove the dusts present in that. The sieved sludge was then mixed with the concrete cubes and mortar cubes in 4%, 8% and 12%. The cast specimens were then cured for 7 days, 14 days and 28 days. The cured specimens were tested for its compressive strength. Then hollow blocks, pavement blocks and mortar bricks were cast and cured for 7, 14 and 28 days. The cured specimens were tested for its compressive strength. The strength of the specimens was compared with the reference specimens. The strength of the specimens was found to decrease with increase in the percentage of textile ETP sludge. From the experimental study, it was found that 4% sludge mixed and 28 days cured building specimens were found to have more or less equal strength to that of reference specimens.

N. Rajkumar, Lecturer, S. Hema, Lecturer, Department of Civil Engineering, Kongu Engg, College, Perundurai, Erode

Introduction

Textile industry is one of the oldest and largest industrial sectors in India. Textile industries involves processing or converting of raw materials in to finished cloth materials by employing various processes, operations and consumes large quality of water and produces extremely polluting waste effluents. While treating the wastewater released from textile industries huge volume of sludge is produced. In Tirupur region alone, around 200 tonnes of sludge is produced every day. Due to lack of disposal methods and yards, this sludge is causing lot of environmental problems. Indian construction industries are running short of construction materials. In the present investigation, an attempt is made to study the strength characteristics of sludge mixed concrete and mortar.

Literature Review
Textile Industrial Scenario

India has several industrial sectors. Among that textile industrial process is the oldest and has traditional values. There are more than 700 large textile mills mainly concentrated in Ahmedabad, Bombay, Tirupur, Erode, Coimbatore, kanpur and Delhi. Out of 21,076 units in India, Tamilnadu alone has 5285 units (A.S.Bal, 1999) where as Maharashtra has the next highest number of units. Most of the textile units involved in processing cotton in India stands third in the export of cotton fabrics, producing about 400 million metres of clothes and approximately 1000 million kg of yarn (J.Karthikeyan and S.Venkatamohan, 1999) and provides employment to 20 million workers.

In Tirupur, there are 800 large units engaged in textile related industrial processes. The knit wear industry in Tirupur has grown by leaps and bounds in recent years and its annual export earning exceeds `2500 crores. Tirupur produces 90% of knitwear made in India (C.Thomson Jacob et.al, 1999). Over three thousand industries operate in Tirupur of which about 750 are engaged in bleaching and dyeing works (R.Sivakumar, 2001). The present market size for environmental management technology equipments in the textile industries in India is approximately $43 million, and the US share is $9 million.

Raw materials for the textile industries are mainly cotton, wool and synthetic fibres. Natural fibres are wool, silk, hemp (animal), flax, hemp (vegetable) and synthetic fibres are rayon, soyabeans, casein (regenerated) and polyamide, polyacrylic, polyester (J.Karthikeyan and S.Venkatamohan, 1999).

Chemicals and Dyes

The processing chemicals used viz., starch, carboxymethyl cellulose, sodium hydroxide, detergents, peroxides, hypochlorides, dyes and pigments, sodium gums, dextrin, wanes, sulfate, soap, chromium, acids etc., (A.S.Bal, 1999). In recent years, most of the dyes used in the textile processing are prepared from hydrocarbons such as benzene, naphthalene, anthrocene, toluene and xylene.

Effluent from the Industry

The industry releases the effluent from the manufacturing process. These effluents are colored, alkaline, high in suspended solids and temperature and contains BOD, COD, Nitrogen, Phosphate, Toxic chemicals, oil and grease etc., (J.Kartikeyan and S.Venkatamohan, 1999). In Tirupur region, the treated effluents from the textile processing industries are discharged in to natural river streams, particularly in to Noyyal River (R.Ilangovan and P.Krishnaraj, 2001).

Environmental pollution, due to textile industrial activities (in Tirupur)

The entire Tirupur environment was found to be polluted in the state of water, land and air due to the industrial process of the textile industries. Due to the disposal of sludge in the non engineered landfills the ground water as well as the soil was found to be polluted. So, disposal of sludge in Tirupur region is a major problem existing today. River Noyyal which emerges from the Vellingiri hills and flowing through Tirupur region was completely polluted which affected the irrigation of around 16,000 acres of land (C.Thomson Jacob et.al, 1999). The surface water was also found to be much affected and the drinking water for Tirupur region is pumped from river Cauvery, which is flowing through Erode district.

Water Pollution at River Noyyal

The river Noyyal has its origin in the Vellingiri hills, passing enrooted the industrial town of Tirupur. The effluent from the industries and the treatment plants of about 75,000 m3 is being released in to this river everyday. Several studies has been conducted on river Noyyal and riverside ground water quality and reported that the concentrations of chlorides, sulphates, electrical conductivity, COD, BOD, pH, Total hardness, sodium and alkalinity were exceeding the standards (C.Thomson Jacob et al, 1999). The Orathupalayam check dam is constructed on River Noyyal, which irrigates about 16,000 acres of land. However, the farmers decline to use the water for irrigation because of the pollutants mainly from dyeing industries. Depending on the soil characteristics, the effluents percolate down to the aquifer and foul it. The soil in Tirupur is light and medium textured loamy sand. This type of soil is comparatively poor to remove pollutants from the percolating water (P.A.Azeez, 2001).

The dewatered sludge in the effluent treatment plants is currently stored in the treatment unit premises. It creates leachate with toxic metals and organic impurities and cause pollution of ground water and land. It is very essential to manage the sludge generated from the treatment (K.Chandrase- karan, 2001). The sheer volume of the sludge generated by the Tirupur based dyeing and bleaching units, which was estimated at around 200 tonnes per day and their disposal will prove a knotty issue for the local dyers, especially when there is no viable technology available for recovery or reusing the salty sediments found in the treated effluents discharged from the units.

Sludge is generated during the treatment process consisting of coagulation (by addition of Aluminium/iron salts), flocculation and liquid/solid separation. The sludge contains heavy metals and inorganic salts and classified as hazardous waste (Management and Handling Rules of our country). The recent amended rule of January 2000 also classifies the sludge as Hazardous (schedule U.S. No 22) (K.Palanivelu and R.Raj kumar, 2001).

Construction Material Requirement

There is an urgent need for the identification of new construction materials in India. The depleting natural resources are demanding for the new building materials. In fact, only small percentage of architects is actually involved in research and development of alternative technology and building materials today (Arun Laul, 2002). With the increase in the industrial activities, the amount of wastes generated will increase manifold. Scientists, technologists, environmentalist and organizations like National Council for cement and Building materials (NCB) have to play their due role in managing such waste for the good of the society (K.M.Sharma and S.Laxmi, 2002).

Manjit Singh et.al. (2002) carried out a study on value added products from industrial waste of phospho-Gypsum (by product of gypsum) in a pilot plant, at CBRI, Roorkee. He reported that the waste phospho-Gypsum is beneficiated by pressing the mining Gypsum-water slurry through 30 microns sieve fitted in the vibratory screen where by coarser fraction below 10% the richer in fractions is discarded. The finer fraction is centrifuged and dried at 110oC to 120oC to get dried beneficiated phospho - Gypsum as per IS: 12679-1989.

Mohini Saxena et.al. (2002) carried out an experimental study on innovating building materials. They reported that the copper tailings added with clay for the brick manufacturing exhibits good results by reducing shrinking properly. Even though the adsorption of water increasing slightly it conforming to IS: 2117-1991.

Chaudhary.S.K, (2002) carried out an experimental study on utilization of industrial waste product fly ash in the following building materials. Fly ash sand lime gypsum bricks, flyash clay bricks, flyash concrete, Portland pozzolona cement, ready mix flyash concrete and sintered flyash light weight aggregate which are cost effective and eco-friendly innovation building materials.

A. Ravichandran and S.K. Sekar (2000) carried out an experimental investigation on effect of flyash on strength of cement mortar and concrete. In their report, they concluded that above 20% of cement in mortar could be replaced by flyash and further replacement will affect the strength of mortar.

K.Chandrasekaran (2001) has carried out the studies on management of sludge from hosiery knitwear dyeing wastewater treatment plants and reported that the bricks made from 10% sludge and 90% clay soil is suitable for use in construction of load bearing walls. The bricks with 30% sludge and 70% clay soil as well as 20% sludge and 80% clay soil, having strength of 2.8 N/mm2 and 4.5 N/mm2 respectively are ideal for construction of partition walls. Further burning of bricks also reduces the leaching of color from it. The option of mixing small quantities of sludge, up to 15% for load bearing bricks and up to 30% for partition bricks is also a promising techno-economic alternative.

Materials and Methods

The cement used in the present investigation was 43 Grade with fineness of 5%. The standard consistency of the cement was found to be 29% and specific gravity of 3.15. The size of the coarse aggregate used in the present investigation was of 20mm and with fineness modulus of 7.3. The specific gravity and water absorption of the coarse aggregate were 2.62 and 0.50%. Naturally occurring river sand was used as fine aggregates with size of 2mm. the fineness modulus of the sand was 3.5 and the specific gravity was found to be 2.6 with water absorption 1.0%. The mix proportion used in the present investigation is 1:2:4 with water cement ratio of 0.5.

Textile ETP Sludge

The textile ETP sludge used in the present investigation was taken from CETP, Tirupur. The wet sludge was collected from the CETP and then dried. The dried sludge was then sieved for removal of dusts. Then the sludge was mixed along with the cement concrete and mortar to test its characteristic strength. The sludge was found to have very high concentration of pollutants like sulfate, chloride, color etc., the sludge was also found to be highly corrosive.

Quarry Dust

Quarry dust taken directly from the quarries was used as a binding material in the manufacture of hollow blocks. These materials were found to have very good binding properties. The color of the dust was grey and size was found to vary from 90 microns to 2mm.

Coarse Aggregate in Hollow Blocks

The coarse aggregate used in casting the hollow block was of size passing through 10mm and retained at 6mm sieve. The specific gravity of the aggregates was found to be 2.61.

Experimental Investigation

Experimental investigation was carried out by casting cement concrete cube specimens, mortar cube specimens, hollow blocks, pavement blocks, mortar bricks with 4%, 8% and 12% of textile ETP sludge along with it. The mixing proportions of the for sludge was on weight basis. The required amount of sludge was weighed and mixed with the concrete still a uniform homogeneous mix was obtained. The concrete cubes, mortar cubes were cast in the concrete laboratory and compacted well using table vibrator. The hollow blocks, pavement blocks and mortar bricks were cast in their respective manufacturing industries. Three specimens were cast in each proportion of 4%, 8% and 12% of sludge with it. The cast specimens were named as S1 for 4% sludge, S2 for 8% sludge and S3 for 12% sludge mixed. Reference specimens were cast in all aspects to compare the strength characteristics. The cast specimens were then cured for 7 days, 14 days and 28 days. The cured specimens were then subjected to compression testing in the Universal Testing machine of 40 tonnes capacity.

Results and Discussions

The test results of the various specimen cast with textile ETP sludge are discussed. The compressive strength of the building specimens are given below.

Concrete Cubes

SpecimenAverage Compressive Strength N/mm2
After 7 DaysAfter 14 DaysAfter 28 Days
S1 (4%)11.6016.6617.33
S2 (8%)11.1115.1115.55
S3 (12%)8.6614.6014.66
Reference15.1116.1118.00
Table - 01 Average Compressive Strength of Concrete Cubes
Reuse of Textile ETP Sludge as Construction Material
Fig - 01 Ultimate Load Carrying Capacity for Sludge Mixed Concrete Cube
Cement concrete cube of standard size 150mm x 150mm x 150mm were cast with 4, 8 and 12% of sludge. Three specimens were cast in each mix percentage and the specimens were cured for 7, 14 and 28 days. The mix ratio adopted was 1:2:4. The average compre- ssive strength of the concrete cubes is given in the Table – 01.

After 28 days curing, the 4% textile ETP sludge mixed concrete cube was found to take about 96% of the load taken by the reference concrete cubes after 28 days. The average compressive strength of the concrete cube was found to decrease as the percentage of textile ETP sludge increased. The compressive strength of the concrete mixed with 4% textile ETP sludge was found to take more or less equal load as reference concrete after 28 days curing. So, this type of material can be used in structures of less importance.

The comparison of the ultimate load carrying capacity of the textile ETP sludge mixed concrete cubes is shown in the Fig - 01.

Hollow Blocks

SpecimenAverage Compressive Strength N/mm2
After 7 DaysAfter 14 DaysAfter 28 Days
S1 (4%)0.650.850.92
S2 (8%)0.590.850.78
S3 (12%)0.460.650.78
Reference1.750.860.98
Table - 02 Average Compressive Strength of Hollow Blocks
Reuse of Textile ETP Sludge as Construction Material
Fig - 02 Ultimate Load Carrying Capacity of Sludge Mixed Hollow Blocks
Hollow blocks of size 400mm x 200mm x 200mm (16" x 8" x 8") were cast by mixing sludge with it. The surface area of the hollow blocks was found to be 76,000 mm2. The mix ratio adopted for manufacturing hollow blocks were 1: 1: 2: 7 (Flyash: Quarry Dust: Sand: Coarse Aggregate). Textile ETP sludge was mixed with hollow block in a mix percentage of 4, 8 and 12% on weight basis. Hollow blocks with 4% sludge, with 14 and 28 days curing was found to have more or less equal compressive strength. The average compressive strength of the hollow blocks with 4% sludge was found to be 0.85 N/mm2 and 0.92 N/mm2 after 14 and 28 days respectively. The average compressive strength of the textile ETP sludge mixed hollow blocks is given in the Table - 02.

Fig – 02 shows the comparison of ultimate load carrying capacity of the textile sludge mixed hollow blocks with reference blocks for various curing days.

Pavement Blocks

SpecimenAverage Compressive Strength N/mm2
After 7 DaysAfter 14 DaysAfter 28 Days
S1 (4%)30.6334.4836.58
S2 (8%)21.2733.1834.03
S3 (12%)12.0028.9330.63
Reference34.3736.4148.50
Table - 03 Average Compressive Strength of Pavement Blocks
Reuse of Textile ETP Sludge as Construction Material
Fig - 03 Ultimate Load Carrying Capacity of Sludge Mixed Pavement Blocks
The pavement block specimens of zig-zag type with textile ETP sludge was cast in the manufacturing site. The surface area of the cast individual pavement block was found to be 5876 mm2. The mix ratio adopted for manufacturing pavement blocks was 1: 1: 2: 7 (Flyash: Dust: Sand: Coarse Aggregate). Textile ETP sludge was mixed in the earlier said percentages. The cast specimens were cured and tested for its compressive strength. The results of the tested specimens are given in Table - 03. After 28 days curing, the compressive strength of the 4% sludge mixed pavement blocks were found to take 75% of the load when compared with the reference blocks.

The comparison of ultimate load carrying capacity of the sludge mixed pavement blocks with the reference blocks for various days of curing is shown in Fig – 03.

Mortar Cubes

SpecimenAverage Compressive Strength N/mm2
After 7 DaysAfter 14 DaysAfter 28 Days
S1 (4%)11.0316.0519.06
S2 (8%)6.0115.0416.05
S3 (12%)4.0111.0312.03
Reference11.2317.8525.28
Table – 04 Average compressive Strength of Mortar Cubes
Reuse of Textile ETP Sludge as Construction Material
Fig - 04 Ultimate Loads for Sludge Mixed Mortar Cubes
Cement mortar cubes of size 70.6mm x 70.6mm x 70.6mm were cast by mixing textile ETP sludge along with it. The mix ratio adopted was 1:3 (cement: sand). The sludge was mixed in the above said percentages and the cast specimens were cured and then tested for its compressive strength. The average compressive strength of the textile ETP sludge mixed mortar cubes are given in the Table – 04. The compressive strength of the sludge mixed mortar cubes was found to be less than the reference cubes.

The comparison of the ultimate load carrying capacity of the sludge mixed mortar cubes are shown in the Fig – 04. The figure also shows the comparison of ultimate loads for 4, 8 and 12% sludge mixed mortar cubes cured for 7 days, 14 days and 28 days with the respective reference mortar cubes.

Mortar Bricks

SpecimenAverage Compressive Strength N/mm2
After 7 DaysAfter 14 DaysAfter 28 Days
S1 (4%)6.356.346.77
S2 (8%)5.715.926.56
S3 (12%)5.505.505.62
Reference6.517.237.61
Table - 05 Average Compressive Strength of Mortar Bricks
Reuse of Textile ETP Sludge as Construction Material
Fig - 05 Ultimate Load Carrying Capacity of Sludge Mixed Mortar Brick
Mortar bricks of size 225mm x 105mm x 75mm were cast by mixing textile ETP sludge along with it. The cast specimens were cured for 7, 14 and 28 days and then tested for its compressive strength. The mix ratio adopted for casting the mortar bricks was 1:5 (cement:sand). The strength of the mortar bricks were found to decrease as the sludge content increased. Maximum strength was obtained for 4% sludge mixing. When compared with the reference mortar cube the strength for the sludge mixed mortar bricks were less. The compressive strength of the textile ETP sludge mixed mortar bricks after various curing period are given in the Table - 05.

The comparison of ultimate loads for various percentages of sludge mixed mortar bricks for various curing period are shown in the Fig - 05. The ultimate loads of the reference bricks were found to be more when compared with the sludge mixed mortar bricks. The average compressive strength of the 4% sludge mixed mortar bricks after a curing period of 7 days were found to take 97% of the load when compared with the reference mortar bricks.

Conclusion

From the experimental study conducted, the textile ETP sludge was found to be better when used in the non structural elements. Particularly, the 4% sludge mixed specimens after 28 days curing were found to have good strength when compared with other mix percentages. Even though the 8% and 12% sludge mixed concrete and mortar specimens were found to take good loads, but when compared with the reference specimens the load carrying capacities were considerably less. This study reveals that textile ETP sludge can be mixed with the plain cement concrete specimens. This may be one of the ways for safe disposal of sludge.

The use of textile ETP sludge in reinforced cement concrete will corrode the reinforcements due to its corrosive properties. So, sludge can only be used in plain cement concrete specimens. The sludge mixed building specimens like mortar bricks and hollow blocks can be used in construction of partition walls and compound walls. The textile ETP sludge mixed pavement blocks can be used in footpaths where the expected load is less. These methods of using sludge in building materials will not only be a new building material but also reduces the environmental degradation due to improper disposal of sludge.

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NBMCW October 2011