Reuse of Textile ETP Sludge as Construction Material

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. l, 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. 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. . 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 hrough 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.