INDUSTRIAL WASTEWATER TREATMENT TECHNOLOGY IN PETROLEUM AND CHEMICAL INDUSTRIES
Industrial wastewater treatment covers the mechanisms and process used to treat water that have been contaminated in some way by anthropogenic industrial or commercial activities prior to its release into the environment or its re-use.
Water is a natural and inorganic solvent with the composition of hydrogen and oxygen only (H20). When there is addition of other organic or inorganic, substances (high levels of nutrients, nitrogen and phosphorous) in water which may come as a result of weather change domestic, waste, industrial waste, lack of awareness and ignorance, then the water is known as waste water which cause a disease called water borne diseases.
Wastewater is very dangerous especially to human beings and should be treated to avoid these dangerous diseases.
There are many method of treating waste water and they include:
- Primary Method
The primary method involves many treatment process such as;- screening process, skimming process and sedimentation process.
The secondary method of treatment also involves such treatment process such as aerated lagoons process, trickling filters process etc.
The tertiary method is the final method that involves disinfections process. This process is used to polish and bring back the quality of water which include: PH value, hardness, flories, taste suspended solid, colour etc (Uche, 2011).
Water is essential for the survival of any form of life. On an average, a human being consumer about 2 litres of water everyday. Water accounts for about 70% of the weight of a human body. About 80% of the earth’s surface (ie 80% of the total 500 million hectares in area) is covered by water. Out of the estimated 1,11 million km3 of the total water present on earth, only 33,400m3 of water is available for drinking, agriculture domestic and industrial consumption. The rest of the water is locked up in oceans as salt water, polar ice caps and glaciers and underground. Owing to increased industrialization on one hand and exploding population on the other, the demands of water supply have been increasing tremendously.
However, consideration, part of this limited quality of water is contained by sewage, industrial waste and a wide array of synthetic chemicals. The menace of water-borne diseases and epidemics still threatens the well being of population, particularly in under-developed and developing countries.
Thus, the quality as well as the quantity of clean water supply is of importance for the welfare of mankind (cheremissinof 1981).
1.1 INDUSTRIAL WASTEWATER
An industry is a place or an establishment for the production or making of things (products) in factories or companies. Industry uses large volume of water in its manufacturing and supporting operations. Indeed, the chemical petroleum and other industries uses a large volume of water that fare exceeds the combined volume of other raw materials, finishing operation generally draw appreciable quantities of water. But it is not the water entering industrial works that actually becomes part of the manufactured product, a small fraction of the water is consumed or lost by evaporation while the larger fraction is not used or is employed non-consumptively.
The water that is employed non-consumptively becomes spent water and many contain mainly waste (Pollutants or contaminants) and that is the reason it is called wastewater. When untreated wastewater accumulates and is allowed to go septic, the decomposition of the organic matter it contains will lead to nuisance condition including the production of mal-odorous gases. It can also contain pathogenic micro organisms that dwell in the human intestinal tract and nutrients which can stimulate the growth of aquatic plant and toxic compounds that potential may be mutagenic and carcinogenic. For these reason, the immediate and nuisance free removal of wastewater from its source of generation, followed by treatment, reuse or disposal into the environment is necessary to protect public health and the environment.
1.2 DEFINITION OF WASTEWATER TREATMENT AND INDUSTRIAL WASTEWATER TREATMENT
wastewater treatment is the collection, processing, treating, recycling or disposal of waste material in water (usually waste produced by human activities) in order to reduce their effect on human health and the environment.
Industrial wastewater, treatment covers the mechanism and processes used to treat waters that have been contaminated in some way by anthropogenic industrial or commercial activities prior to its release into the environment or its re-uses.
It can also be defined as the application of scientific and advanced methods in the recycling or disposal of unwanted water or combination of liquid removed from factories or companies like chemical and petroleum industries (Bachok et al, 1967).
1.3 TO TREAT, REUSE AN DISPOSE WASTE WATER, IT IS NECESSARY TO HAVE KNOWLEDGE OF THE FOLLOWING
i. constituent of wastewater.
ii. Effect of these constituent when water is dispersed into the environment.
iii. The transformation and long-term fate of these constituents in the treatment processes.
iv. Treatment methods that can be used to remove the
constituent found in the wastewater.
v. Methods for beneficial use or disposal of the solid generated by the treatment system.
1.3.1 CONSTITUENT OF WASTEWATER FROM CHEMICAL AND PETROLEUM INDUSTRIES
Chemical industry comprise the companies that produce industrial chemicals while a petroleum industry is an industry or company that refines oils and petro-chemical products.
The component of their waste can be classified into the following:
i. Organic waste such as oxygen demanding waste, disease causing waste, synthetic organic compounds, and oil pollutant/ waste.
ii. Inorganic waste: this comprise of mineral acids, inorganic salts, finely divided metals, or metal compounds, trace elements, cyanides, sulphate, nitrates, etc.
iii. Suspended solids and sediments are mostly contributed by soil erosion by natural processes, agricultural development, strip mining and construction activities.
1.3.2 Effects of these constituents
Oxygen demanding waste causes depletion of dissolved oxygen (2.0) from the water and these is harmful to aquatic organisms.
Disease causing waste such pathogenic microorganism cause dangerous water borne disease like cholera, typhoid, dysentery and polio. Synthetic organic compounds such as peticides, insecticides and other chemicals are very toxic to plants and animals and humans. Some of them causes offensive, odours and tastes in water.
Oil waste cause reduction of light transmission through surface waters thereby reducing photo synthesis by marina plants. Also, it reduce the dissolved oxygen (D.O) in water and endangers water birds, coastal plants and animals.
In organic waste stimulate algal growths in water and metal toxicity in aquatic ecosystem.
It causes chromosome damage and interfere with the process of heredity in man.
1.4 WATER QUALITY
The three parameters for assessing water quality are: physical, chemical and biological characteristic of water (Uche, 2010).
1.4.1 PHYSICAL WATER QUALITY PARAMETER
Physical parameters analyze those characteristics of water that respond to the sense of sight, touch, taste, and smell. Suspended solids, turbidity, colour, odur and temperature are the main factors that asses the physical water quality.
1.4.2 CHEMCIAL WATER QUALITY
The chemical properties necessary for water quality management are; total dissolved solid (TDS), PH (alkalinity) hardness, fluorides, metals and organic compounds.
I. TOTAL DISSOLVED SOLIDS (TDS): Dissolved solids are the materials remaining after the filtration in which the suspended solids are separated and discarded. The dissolved materials results from the solvent action of water on solids, liquids and gases. Like suspended materials, dissolved substances may be organic or inorganic in nature. Inorganic substances which can dissolved in water are minerals, metal and gases. The sources of contact with these substances are in the atmosphere, on surfaces within the soil. Some of the common organic dissolved constituents of water are material from decay products of vegetation, organic chemicals and organic gases.
II. PH(Alkalinity): Alkalinity is described as the quantity of ions in water that will neutralize hydrogen ions. Alkalinity is simply the ability of water to neutralize acids.
The constituent of alkalinity in neutral water systems are C02-, 0H-, HSi03-2, H2B032-, HPo = HS etc. The presence of these compounds in water in through dissolution of mineral substances in the atmosphere and within the soil.
This is concerned with the concentration of multivalent metallic cations is solution. At supersaturated conditions, the hardness cations will react with anions in the water to form a solid precipitate.
IV. Fluorides: Flourides ions are among the few chemical substances that are needed to enhances the water at a small quantity. At large quantities, fluorides is toxic to men and animals. The floride concentration of approximately 1.0mg/L in drinking water help to prevent dental cavities in children.
V. Metals: The sources of metals in natural waters are through dissolution from natural deposits and discharges of domestic, industrial or agricultural wastewater. All metals are soluble to some extent in water. While excessive amounts of any metal may present health hazards, only those metals that are harmful in relatively small amount are commonly regarded as toxic.
VI. Organic: Most natural organics are the decay products of orgnics solids, while synthetic organics are usually the result of waste water discharge or agricultural practices. Dissolve organics in water are usually divided into two broad categories, biodegrade and non-biodegradable. Biodegradable material consists of organic that caneb utilized for food by naturally occurring micro-organisms within a reasonable length of time. They include: starches, fats proteins, esters and adelydes. Non biodegradable organic are materials that are resistant to biological degradation, they include; tonnic and liquid acid, cellulose and phenols which are most often found in water.
1.4.3 BIOLOGICAL WATER QUALITY
Water serves as a medium, in which most of the micro organisms reside. Aquatic organisms range in size and complexity from the smallest single cell micro –orgnism to the largest fish. All members of the biological community are to some extent serving as water quality assessment as the presence or absence may indicate in general term the characteristics of a given water body.
1.5 TREATMENT METHOD
The method of treating wastewater are classified into the following:
i. Primary Treatment
ii. Secondary Treatment
iii. Tertiary Treatment
This is a types of treatment that involves the removal of materials that can easily be collected from the raw wastewater and a physical operation usually sedimentation is used to remove the floating and settlable materials found in the wastewater. Examples of materials that can be removed during primary treatment include; large objects, rags, goit, fats, oil and grease and floating materials.
This involves the use of biological /chemical processes in removing most of the organic matter.
Tertiary (Advances) Treatment
This involves the use of physical and chemical process in removing residual suspended solids and constituents that are not reduced significantly by conventional secondary treatment. It is aimed at polishing the effluent from the secondary treatment process in order to improve the quality of the water.
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