Introduction
Textile effluent is considered the most polluting element released from the textile industry. They are contaminated with pollutants like dyes, suspended solids, dissolved solids, and toxic metals. It acts as an important source of environmental pollution. Textile effluent pollutes air, soil, subsurface, and surface water. Textile wastewater contains total dissolved solids (TDS) due to the use of Glauber salt and common salt for textile processes.
Total dissolved solids (TDS) concentration in surface water and groundwater increases due to textile effluent discharge and causes an osmotic imbalance in aquatic organisms. The toxic chemicals in textile wastewater contaminate the environment and cause health hazards to living organisms. Cytotoxicity and genotoxicity associated with textile effluent are studied using an Allium assay.
What Is Textile Effluent?
Textile industries produce large quantities of wastewater containing complex chemicals released into the environment. The discharged water causes harmful effects on the environment and affects ecological status. Textile effluents contain various substances like dyes, soaps of metals, acids, alkalis, starch, print pigments, surfactants, and hydrogen peroxide. These chemicals are responsible for environmental pollution and adverse health effects. Pollutants present in textile effluent are classified based on their bio-degradation.
It includes the following types:
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Harmless Inorganic Contaminants - These include neutral salts like chlorides, phosphates, silicates, sulfates, mineral acids, and oxidizing agents like chloride, chlorine, and peroxides.
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Moderate to High Bio-Degradation - It is classified into two types. Substances like starch, fats and waxes, organic acids, vegetable oils, and surfactants in textile wastewater have moderate to high bio-degradation but are easily degradable. Mineral oil, starch ethers, wool grease, and softeners (ionic and non-ionic) are challenging to degrade even though they have moderate bio-degradation values.
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Difficult to Biodegrade - Dyes, polymeric impurities, silicones, fluorescent brighteners, synthetic polymer finishes, and polyacrylate sizes in textile effluent are difficult to biodegrade.
What Are the Harmful Effects of Textile Effluent?
The textile industry is one of the most important anthropogenic causes of polluting water bodies. Waste water from textile industries contains harmful chemicals that can cause environmental pollution and toxic health effects. Textile dyes in wastewater pollute the water bodies and increase chemical and biochemical oxygen demand (COD and BOD). They may also inhibit plant growth, impair photosynthesis and enter the food chain. After reaching living cells, they can produce toxicity, carcinogenicity, and mutagenicity.
Chemicals in the textile wastewater will combine with other industrial pollutants and cause environmental degradation and harmful diseases in plants and animals. Acute exposure to textile dyes causes allergic responses like rhinitis, skin rashes, eye irritation, and occupational lung diseases. Genotoxic assessment of textile effluents using Allium cepa root cells has shown chromosomal abbreviations. The toxic chemicals in textile effluents cause cytotoxicity by inhibiting intracellular enzymes of the nervous system.
What Is an Allium Bioassay?
Allium cepa bioassay is used for assessing toxicity and its harmful effects on the environment and human health. Allium consists of bulbous plants like onion, leek, garlic, and chives. Plant bioassays are inexpensive, rapid, and comparatively easier than others. Plant species are sensitive to changes in water quality and show responses detectable as early signs. Plants and animals have similar chromosomal morphology and response to mutagens. Thus plant assays offer several advantages over microbial and mammalian systems in assessing genotoxicity and cytotoxicity. Allium cepa (onion plant group) is widely used as a phytoindicator to identify disturbances in the mitotic cycle, chromosomal aberrations, and DNA damage. Allium cepa contains large chromosomes in good chromosome conditions in reduced numbers (2n=16).
How Is Cytotoxic and Genotoxic Assessment of Textile Effluent Done Using Allium Assay?
Cytotoxic and genotoxic assessment study of textile effluent using Allium assay is conducted to identify the chromosomal abnormalities in root tip cells of the Allium cepa plant (Wijeyaratne and Wadasinghe method). Allium cepa plants are exposed to textile effluents present in the aquatic environment. This study details genotoxic and cytotoxic substances in textile effluents and their effects on inducing abnormalities in the environment and biological organisms.
It includes the following procedures:
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Allium cepa (common onion) determines genotoxicity, cytotoxicity, and mutagenicity. Healthy, equal size onion bulbs are selected, and outer scales are removed carefully to expose the root primordia. Scraped onion bulbs are kept in a glass test tube with distilled water for 24 hours for germination under dark lighting.
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The rooted bulbs are then exposed to water samples (containing textile effluent) from selected sites. Ten onion bulbs are selected and placed on test tubes containing water samples. Aged tap water is used as the control medium (ten onion bulbs are used for control also).
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Allium bioassay is conducted in a dark room at 25 to 26 degrees Celsius, and the control and exposure mediums are changed daily.
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After two days of exposure, ten onion bulbs with roots are selected randomly from the control and exposure media for microscopic examination.
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Root tips are fixed using ethanol: glacial acetic acid solution stored at a temperature of four degrees Celsius for one night.
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Root tips are then transferred to 70 percent alcohol at four degrees celsius temperature until analysis.
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Root tips are placed in hydrochloric acid for five minutes during processing and later washed with distilled water.
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Five percent acetocarmine stain is used to stain root tips and observed under a light microscope (400x magnification).
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From each slide, a minimum of 1000 meristematic cells were scored randomly. It is then used to score chromosomal aberrations, interphase cells, and mitotic stage cells in the dividing cells.
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The mitotic index, phase index, and percentage of chromosomal abnormalities are then calculated using specific formulas.
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These parameters can be used for further studies to confirm textile effluents' genotoxic and cytotoxic effects.
Conclusion
Textile effluent contains wastewater with harmful chemicals released from textile industries. Once released into the environment, they pollute water bodies and cause harmful effects on living cells. Cytotoxic and genotoxic effects of textile effluent are studied using an Allium root assay. Appropriate effluent treatment processes must be done to the textile wastewater before releasing it into the natural environment to reduce toxicity and adverse environmental effects.
