Experimental Studies on Disposal of Various Industrial Solid Wastes

In the present study, solid waste from various industries has been collected and characterized. Based on the nature and composition of solid waste, the possible chemical composition is evaluated and value added products are prepared. Methods for conversion of solid wastes into building materials such as bricks and concrete blocks have been described. Mixing of solid waste in various proportions with red soil also carried out as pot experiment. From the results of various tests on final product, it is concluded that solid waste can be used suitably to produce bricks with 25-30% of sludge, for concrete blocks with 45-50% of sludge. By applying this type of alternative, solid waste could be disposed off in a better way without affecting the existing environment.


Introduction
Based on the quality of liquid effluent, textile house is one of the leading and most polluting industrial sectors in India.To treat this waste water, adsorption and coagulation techniques are used by the most of textile effluent treatment plants.The textile solid waste, brownish in color, contains mainly iron, chloride, sulphate and a few traces of other substances, all coming from different sections and type of dyes used in the textile industries.The solid waste form the glass industries will be grey in color.In general, sludge generation and accumulation are the most serious problems faced by the treatment plants.Due to its chemical and mineral content, these industrial solid wastes are found to be hazardous in the view of environmental consideration (Khan 1994).Unsafe disposal of the solid waste may cause harmful effects on the environment & human beings (Giri andBhattacharya, 1991, Raviprasath et al, 2003).Hence, solid waste management should be given primary importance before things becomes too convoluted (Kumaravelan and Anandan, 2004).The conventional techniques for sludge disposal like compositing, land filling, agricultural utility, open dumping and thermal techniques are found to have some drawbacks such as land losing its fertility, possible contamination of under ground water, requirement large surface area for storage and high cost of disposal.
To overcome the drawbacks of the existing sludge disposal methods, an attempt has been made to dispose the solid sludge waste from textile house, glass industry and thermal industries (all are located at Erode, India).The employment of waste sludge to produce valuable products is considered to be the most advanced trend in solid waste management for the environmental damages can be reduced or overcome and the cost is can be considerably reduced without necessitating heavy establishments.The present work analyses the feasibility of producing building materials like bricks and concrete blocks.The experimental work was carried out at our college (Erode Sengunthar Engg.College, Erode, India).The solid wastes collected are subjected to chemical analysis to get the nature and chemical composition of the sludge.An attempt has been made to study the possibility of mixing the solid wastes in various proportions with red soil or other conventional raw materials to produce the building materials.Mixing solid wastes in various proportions with red soil was carried out as pot experiments.To obtain the quality of bricks compressive strength, water holding capacity and efflorescence test were carried out.

Materials
Sludge after the solar evaporation was taken from textile house, glass and thermal industry.All the reagents used for finding the characteristics of the sludge are of A.R.Grade.

Analysis of Sludge
The solid waste was evaluated based on its various characteristics of loss of ignition and insoluble residue; iron, sulphate, calcium, aluminium and silica were analyzed as per the standard methods (Vogel, 1961, APHA, 1991, Arnold et. al, 1992).

Manufacture of bricks
The most common bricks are one of the oldest building materials and it is extensively used at present as a leading material of construction because of its durability, strength, low cost and easy availability of raw materials.The conventional bricks are manufactured by four distinct operations like preparation of clay, molding, drying and burning.The sludge was dried in order to remove the moisture.Then it was mixed with various binding materials and water in the ratio 1:0.25.Fly ash was used as binding materials.In preparation of brick, the composition of textile house sludge, glass industry sludge, thermal industry waste (fly ash) and red soil were made in various proportions.The sludge was mixed in various proportions with the red soil forming a murrite.The mixture was then made in to brick shape using a brick mold made of cast iron having the dimensions 22 cm x 10 cm x 6 cm.The wet brick was put in the open air for atmospheric drying for about 8 days.Then the bricks were arranged and burnt in a lime kiln at a temperature around 950-1200 0 C.The burnt bricks were then subjected to various tests.

Manufacture of concrete blocks
Normally 8 kg of coarse aggregates, 4 kg of sand, 2 kg of cement and sufficient amount of water were mixed with water -cement ratio of 0.45 and 0.5.The concrete mixture was filled in the mould in layers approximately 5 cm deep.The mixture was tamped with the help of a standard rod.The specimens were kept in cold water for 24 hours.After the mould is removed, the specimen is subjected to curing for about 3-7 days.In the present study, 4 kg of aggregates was replaced by waste concrete aggregates, 2 kg of sand was replaced by glass industry waste and 1 kg of cement was replaced by fly ash and powder solid glass waste.

Tests on Burnt Bricks
Various properties of burnt bricks like compressive strength, water holding capacity, efflorescence test, flexural strength and compacting factor test for concrete blocks were carried out as per the standard procedures (Rangola, 2002, BIS-1077-1957).

Recovery of Iron Oxide
Since, in the textile waste sludge, the amount of Iron Oxide present is 30.18%, an attempt has been made to recover this.0.250 kg of the textile solid sludge was taken in 1000 ml beaker and 1:1 Hydrochloric acid (HCl) was added in such a way that the level of the acid was 0.05 m above the solid.The contents were boiled for 10-15 minutes and allowed to settle.The supernatant liquid was filtered.The above procedure was repeated 5 to 6 times to leach the iron completely and Iron was precipitated in the filtrate by Hydroxide Method (Vogel, 1961).The precipitate was dried and ignited.This iron may be used in paint industry.

Results and Discussion
For bricks manufactured from individual and combination of various industrial sludge, various tests like compressive strength, water holding capacity, flexural strength; efflorescence test and for concrete blocks compacting factor test were conducted and results have given in Table 2, 3, 4, and 5. Maximum allowable values for the bricks are given in Table 6.From the analysis results of various solid wastes (given in Table 1), it found that these sludge is considered to be suitable for the production of building materials such as bricks and concrete bocks.The work mainly focused on using sludge to replace red soil/clay in the manufacture of bricks and sand/ aggregates/cement in the manufacture of concrete blocks.From the tabulated results it is clear that sludge can be replaced up to 25-30% in the manufacture of bricks that does not affect physical and chemical properties of bricks.But in the manufacture of concrete blocks, compaction factor test results (Flexural strength of concrete blocks: Breaking point of concrete block =0.22 m) and flexural strength of concrete blocks shows that 45-50% of sludge can be replaced.

Conclusion
Solid waste from various industries (textile house, glass and thermal industry) has been collected and characterized.These solid waste were obtained can be utilized in the production of building materials.From the results, it is concluded that solid waste sludge can be replaced up to 25-30% to produce bricks and 45-50% to produce concrete blocks.The bricks produced with 25-30 % sludge were observed to have good compressive strength and water holding capacity, which meets the specifications recommended.As the present disposal methods are found to be hazardous, a highly eco-friendly method has been formulated for the conversion of solid wastes into value-added products like building bricks and concrete blocks.This promising alternate disposal method thus paves a better way to dispose the solid wastes from various industries on one side and provides a means to utilize the solid wastes for useful purpose, on the other.

Table 1 .
Composition of the various industrial sludge ( wt %)

Table 2 .
Analysis of textile house waste-red soil blended bricks (wt.%)

Table 3 .
Compaction factor and flexural strength test on concrete blocks

Table 4 .
Analysis of textile house sludge-glass industry sludge-red soil blended bricks

Table 5 .
Analysis of industrial wastes of textile-glass -thermal-red soil blended bricks

Table 6 .
Maximum allowable values for the bricks