CHAPTER ONE: 1.0     INTRODUCTION:          The effluent treatment plant is designed to treat the effluent coming from different areas of the plants. The treatment of different effluent varies with the type of effluents.

          Water is recycled from effluent coming from textile and chemical industries using series of operations i.e coagulations, flocculation, aeration and filtration technique. The effluent produce has high BOD, COD, PH, TSS, TDS and colour materials. This study includes characterization of effluents and making of process flow sheet of effluent treatment plant after visit to various location in industrial areas.

          However, the application of nanotechnology has been employed in recent advances to water treatment. These technique extends from the fabrication of membranes from nano-materials to the use of catalyst for the decomposition of noxious compounds in water. At the nanoscale level, materials are characterized by different physical, chemical and biological properties than their normal size equivalent. For instance, materials as metals, metal oxides, polymer and ceramics and carbon derivatives (carbon nanotubes and fullerenes) have a level. In other words, the surface area of particle size increases with decreasing particle size and as such, nanoscale particle exhibits different optical, electrical and magnetic properties from the properties exhibited by macroscopic particles (Shelly, 2005). These remarkable characterizations of particles at the nanoscale level possibly originated from the increase in the number of surface atoms with the decreasing particles size.

          Nanotechnology can easily merge with other technologies and modify, endorse or clarify any existing scientific concept which is why it is called a platform technology (Shmidt, 2007).

          The use of nanotechnology in the future is expected to expand into numerous industrial applications and help decrease production cost by reducing energy consumption, alternatives environmental pollution and increase the production efficiencies in developed countries. Moreover, nanotechnology maybe a useful tool to address different social problems of developing countries such as the need for clean water and the treatment of epidemic diseases (Fleischer and Grunwall, 2008).

          Many potential benefits of nanotechnology have already been identified by many researchers in the environment and water sector, medicine and in several industrial applications. Major potential environmental benefits of nanotechnology were reported in the draft nanomatrial research strategy by Savage et.al. (2008) including      

  • Early environmental treatment and remediation
  • Stronger and lighter nanomaterials
  • Smaller, more accurate and more sensitive sensing and monitoring devices.

Additional benefits lay in the cost-effective use of renewable energy, low energy requirement and low waste generation devices, early disease detectors for preventive treatment, pollution control, and the prevention and remediation using improved systems.

1.1     EFFLUENTS

          Effluent is a wastewater (treated or untreated) that flows out of a treatment plant, sewer or industrial outfall. It is generally referred to liquid wastes discharged into surface waters.

          Effluent considered to be water pollution, such as the outflow from a sewage treatment facility or wastewater discharged from industrial facilities. A effluent sump pump, for instance, pumps waste from toilets installed below a main sewage line.

          In the context of waste water treatment plants, effluents that has been treated is sometimes called secondary effluent or treated effluents. This cleaner effluent is then used to feed the bacteria in biofillers.

          In the context of a thermal power station, the outpour of the cooling system maybe referred to as the effluent cooling water, which is noticeably warmer than the environment. Effluent only refer to a liquid discharge.

          In sugar beet processing, effluent is often settled in water tanks that allow the mud-contamination water to settle. The mud sinks to the bottom, leaving the top section of water clear, free to be pumped back into the river or be reused in the process again.

  • Agricultural effluent
  • Industrial effluents

1.1.1   Agricultural Effluents

Agricultural effluent, any liquid generated by agricultural activities such as:

Organic wastes – animal wastes typically called manure slurries arable wastes (such as sugar cane and vegetable lactated and winery wastes.       

  • Processing wastes – cannery, winery and diary.
  • Mechanical and chemical wastes – fuels and lubricants from crop processing and crop protection chemicals.
  • Human wastes – septic tank and pit latrines.
  • Catering wastes – canteen kitchens, communal food preparation etc unlike most other industries farm seldom have charge access to municipal systems, so the farmer has to ensure that all his effluents is catered for.

1.1.2   INDUSTRIAL EFFLUENTS

          These are effluent generated from the industries. Industrial waste consists of both organic and inorganic substances. Organic wastes include pesticide residues, solvents and cleaning fluids, dissolved residues from fruits and vegetables and lignin from pulp and paper it also contains inorganic wastes such as brine salts and metals. The clean water act has standards for the permitted release of a limited amount of contaminants into waterways. This is an incentive for industry to pretreat their water by neutralizing the chemically active components, recycling dilution or extraction and collection for proper diposal. More than 200,000 sources of waste water are regulated by the national pollutant discharge elimination system (NPDES) permit program.

          Industries which use large amounts of water in their processes include chemical manufacturers, steel plants, metal processors, textile manufactures and the following.

  • Fruit and vegetable processing: Waste water contains high concentrations of dissolved organic matter and may be highly and maybe highly alkaline from the use of lye.
  • Petroleum refining: Oil is mixed with water in the refining process to remove salts and other impurities. It is then separate and collected most of these water is then recycled.
  • Pulp and paper: The use of bisulfate and sulfurous acid or sulphur dioxide in the pulp processing yields a waste sulfite containing various wood by products. There is presently a concern over the release of dioxins into waterways by the pulp and paper industry.

These practices pose a threat to drinking water, aquatic lives and the environment at large.

TEXTILE EFFLUENT   

Textile effluent can be defined as a stream of excess chemical liquor from the textile industry after being used in original operation. It is defined by the English dictionary as liquid waste or sewage discharged into a river or in the sea.

Textile effluents is considered to be the most polluting elements emitted from the textile industry it includes dyes and chemicals affects the environment very badly. In developing countries like Bangladesh, this condition is eye catching. The effluent becomes the source of pollution of the environment. It pollutes the surface and subsurface water, soil and air. Generally, surface water is used for irrigation, bathing, household usage etc. Thus textile effluents makes the surface water unsuitable for drinking, cooking, irrigation etc.

Besides polluting the ground and surface water, textile effluents pollutes the soil algae. Soil is the most important medium for growing plants, crops, etc. the quality of crops depends on the quality of soil so, when the quality of soil decreases due to textile effluent, the amount and quality of crops also decreases. It is also seen that the lower lands becomes more polluted than the higher liquids because the effluents ultimately deposited in the lower lands.

Textile effluents also put effect on air. Textile effluents pollutes the air by mixing bad odour in air.

Generally, textile effluents includes dyes and chemicals which is the major case of polluting the environment. Main pollution is effluents comes from dyeing and finishing process. The main pollutants in effluents are high suspended solids, chemical oxygen demand, heat, colour, acidity and other soluble substances.

The colloidal matter present along with colours and only seen increases the turbidity and gives the water a bad appearance. It prevents the penetration of sunlight necessary for the process of photosynthesis. This interfers with the oxygen transfer mechanism at air water interface. Depletion of dissolved oxygen is very essential for marine life. This also hinders self purification of water process.

When this effluent is allowed to flow into fields, it clogs the pores of the soil resulting in loss of soil productivity. The texture of the soil gets hardern and penetration of root is prevented when it flows into drains it corrodes and incrassates the sewerage pipes.

A textile effluent is a cause of significant amount of environmental degradation and human illness. All organic materials present in wastewater from textile industries are of great concern in water treatment because they react with many disinfectants especially chlorine. Chemicals evaporates into the air we breathe or are absorbed through our skin and show up as allergic reactions and may cause harm to children even before birth.

 1.2    EFFLUENT GENERATION AND CHARACTERISTICS

          Wet processing of textiles involves, in addition to extensive amount of water and dyes, a number of inorganic and organic chemicals, detergents, soaps and finishing chemicals to aid in the dyeing process to impart the desired properties to dyed textile products. Residual chemicals often remain in the effluents from these processes. In addition, natural impurities such as waxes, proteins and pigments, and other impurities used in processing such as spinning oils, sizing chemicals and oil stains present in cotton textiles, are removed during desizing, scouring and bleaching operations. This results in an effluent of poor quality, which is high in BOD and COD load.

Most organic industrial wastewaters are produced by the following industries and plants.

  • Factories manufacturing pharmaceuticals, cosmetics, organic dye-stuffs, glue and adhesives, soaps, synthetic detergents, pesticides and herbicides.
  • Tanneries and leather factories
  • Metal industries
  • Brewery and fermentation factories
  • Factories of the oil refining industry
  • Textile factories  

1.3     WATER TREATMENT

Water purification using nanofiltration technology or through adsorption and catalytic degradation process was made possible by the advances achieved and mysteries revealed in the Quantum world. Worldwide, the need for clean water is increasing because of population increase, drought and the contamination of conventional water sources. WHO (2004) reported that 1 billion people are at risk because they do not have access to portable water and another 2.6 billion people are at risk because they do not have clean water. The innovation of new technologies to increase the availability of clean water commenced 40daysago with the establishment of three membrane separation processes viz:

  1. Reverse Osmosis (RO)
  2. Ultra Filtration (UF)
  3. Micro Filtration (MF)

          During the 1970s and 1980s, nano filtration membranes (loose RO) were developed as an intermediate filtration material between ultrafiltration and reverse osmosis (Eriksson 1988). Membrane processes using different types of membrane are becoming increasingly popular for the waste water, surface water and ground water (Ventresque et. al; 2000).

The table below shows membrane types and characteristics

Membrane TypePore size   (nm)Pressure (bar)Product water
Reserve osmosis<0.630-70Pure water (PW)
Nanofiltration0-6-510-40Pure and low molecular solutes
Ultrafiltration5-500-8-10All above and macro-molecules
Microfiltration50-5000-5-2All above and colloids

          The impact of nanotechnology on the development of tools and techniques for water treatment will be more pronounced in the near future. As scarcity of natural water threatens the advancement and the social security of many countries around the world, it is expected that the solution will emerge from the exploitation of nanoparticles to make water recycling, seawater desalination and water remediation more efficient and cost effective. For instance, the use of nanofiltration membranes for treaty water in natal areas of South Africa to provide drinking water was described by Smith (2006). The advantages of using nanofiltration relied in the direct humanitarian benefit from using nanotechnology and in the production of economical viabilities in rural communities. Therefore, the production of nanostructures, nanocomposites and modified nanostructures for water remediation will increase because of the need for producing clean water in fast and low energy consumption ways. Nanotechnology should be regarded as the tool to ensure sustainability of social communities in different places. This is possible through the use of advanced filtration nanomaterials that enable desalination of seawater, recycling of contaminated water and the reuse of waste-water (Theron et.al., 2008).

1.4     WASTE WATER TREATMENT

          Waste water is any water that has been adversely contaminated by organic pollutants, bacteria and microorganisms, industrial effluents or any compound that has decolorated its initial quality. It can be sub-divided into

  1. Municipal waste water (liquid waste discharged by domestic residences and commercial properties)
  2. Industrial waste water (liquid waste discharged by industries and agricultural activities). Some of the factors that might affect the composition of waste water are: land uses, ground water levels, and the degree of separation between storm water and sanitary wastes. The composition of municipal waste is usually less variable that industrial waste water, the latter being highly affected by the type of industrial activity involved in the discharge of effluent water. In general, the organic composition of wastewater is estimated to consist of proteins (50%), carbohydrates (40%), fats and oils (10%), and trace amounts (e.g Ng/l or less) of priority pollutants, surfactants, and emerging contaminants. On the other hand, wastewater often contains 105-108 colony forming units (CFU)/ML of coliform organisms, 103 – 104 CFU/ML fecal streptococci, 101 – 103 protozoa cysts, and 101 – 102 virus particles (Ellis, 2004).

Treatment of municipal wastewater has to take into consideration all the aspects related to water contamination and has to ensure that the product waster is free from any substance that might adversely affect the health of human and the environment. The treatment process in wastewater treatment plants is directly related to the composition of wastewater. Generally, conventional sewage treatment includes the following stages (Shon et.al.2007):

  1. Preliminary Treatment: To remove coarse and readily settleable inorganic slides with the size range of more than 0.01mm.
  2. Primary Treatment: To remove the buck of suspended solids including both organic and inorganic matter (0.1mm to 35Nm).
  3. Secondary Biological Treatment: To degrade the biodegradable binding organic matter and treatment.
  4. Tertiary Treatment: To remove a portion of the remaining organic and inorganic solids and pathogenic microorganisms through a filtration step. This treatment is followed by chemical disinfection.

Industrial wastewater could be designated as the effluent produced from any industrial activity such as agriculture, food industry, iron and steel industry, mines and quarries etc. the composition of industrial effluents can vary according to the activity in question. Therefore, the treatment is selective to ensure high Quality filtered water with consideration of the cost involved in the filtration process. Wastewater from agricultural activities is high in organic compounds of animal and vegetable sources, microorganisms, and different chemicals used for the control of pest and diseases. It is not common to find agriculture effluent contamination with heavy metals or petroleum derivatives. Treaty industrial wastewater could follow the same styles described for municipal wastewater treatment with modification that might be integrated to ensure low concentrations of specific pollutants.

Additionally, the use of nanomaterials and nanoparticles to bio-remediate and disinfect wastewater is gaining popularity (Hu et.al, 2005). (Mohan and Pittman, 2007). For instance, metals oxide nanoparticles such as T102 are among the promising nanocatalyst were test successfully for their antimicrobial activity. Moreover, fullerenes, (C60) as pollutant tracers are being used to provide contaminant-fate information to assist in developing water remediation strategies. Magnetic nanoparticles are being developed to absorb metals and organic compounds; and nanocatalyst are being explored to reduce pollution of oxidized contaminants (Hillie et.al, 2006). Metal processing wastewater often contains hexavalent chromium species Cr(VI) which are toxic and can act as carcinogens, miltagens and teratogens in biological systems (Duporit and Gullon, 2003). Metal industries are required to reduce the amount of chromium in their effluent to around 0-1mg/L (Ayuso et.al,2003) before discharging it into the sewer system. Industrial pollutants such as phthalates, alkylphenols, bisphenol – A, pharmaceuticals and many others could be removed from industrial wastewater by nanofiltration. Nanofiltration is being integrated on many industrial effluent treatment plants to produce effluent with low concentrations of industrial pollutants (Brugeen et.al, 2008). The use of nanotechnology to remove contaminants in water is widespread and many advances have already been achieved. A summary of recent advances in nanomaterial research for industrial wastewater treatment includes. The nanofiltration of biologically treated effluents from the pulp and paper industry (Manttari et.al,2006); the degradation of organic dyes using manganese-doped Zno nanoparticles (Ullah and Dutta, 2008); the treatment of wastewater from molasses distilleries using nanosize pore membrane (Satyawali and Balakrishnan, 2008).