Discuss about the industrial water and wastewater treatment.
In the present assignment, the main steps that are involved in the water cycle along with the waste water cycle has been included by aligning it with the textile industry. The key qualities that are needed for the water in the textile industry has also been incorporated in this assignment. In addition to this, the current assignment has taken into account the main characteristics of the generated waste water in the textile industry with adherence to a wheel diagram depicting the quality of the water. The major technologies that are generally used for the treatment of the waste water has also been included in this current discussion.
Apart from that, this assignment has been able to explain the target areas of application of the AOP technology which is one of the major wastewater treatment process. In addition, the technical principles, main process designing parameters along with the advantages and disadvantages of this AOP technology has also been discussed here.
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2. Various aspects of wastewater treatment in textile industry
2.1 Process flow diagram of the waste water cycle and explanation of the steps involved
The water is extensively used in the textile industry all over the world and the wastewater is also generated in a large scale throughout the processes involved in the textile manufacturing. One of the main sector where fresh water is largely used is during the pretreatment and the dyeing process. This wastewater is reused after going through several steps which can be depicted by a flow diagram (Qasim, 2017).
After the steps like pretreatment, dyeing, printing, washing and drying, a mixed wastewater is generated in the textile plant. This mixed waste water is passed from the flocculants dosing system which is generally used for the clarification of the waste water from the processing related to the mineral washing. This wastewater is then passed through the biological treatment plant where the water is treated with the anoxic and oxic process. This is also known as the A/O process in which the hazardous contaminants such as the aromatic hydrocarbons are potentially removed. The anoxic reactor is generally of 5 litre volume in which the activated sludge content is poured. The activated sludge content should be maintained at 5g/L level. From this biological treatment plant, the surplus waste water and thye surplus sludge is rejected (Von Sperling & de Lemos Chernicharo, 2017).
After that, the prefiltration is done. This prefiltration is positively used for the recycling of the wastewater. In this process, a membrane filtration technique is used where the concentration or pressure gradients generally lead to the separation of the suspended solids by the application of a semipermeable membrane. The last viable step in this context is the AOP or advanced oxidation procedure. Hydroxyl radicals are generated in this process which is responsible for oxidising the unwanted suspended particles in a diffusion controlled manner. Thereafter, the water as generated is obviously reusable (Punzi et al. 2015).
2.2 Description of the major requirements regarding the water quality in textile industry
In the textile industry, there are various steps that should require the continuous supply of the freshwater. However, there are some requirements that should be maintained for perfect ongoing of the manufacturing process. For all the process, the freshwater quality that would be suitable should contain a pH in the range 6.5 to 7.5. Total hardness of the water should be 50 and chloride concentration should be 300 mg/L. Both the Iron and Copper content should be 0.05 mg/L. On the other hand, specifically in case of the washing process, the color of the water should be non-visible and COd has to be 200 mg/L. pH should be in the range 7-8. Total hardness of the water should be 100 ppm and the chlorine content has not to exceed over the range 500-2000 mg/L (Rezaei et al. 2016).
2.3 Description of the main characteristics of the wastewater generated in the textile industry
The pH is considered to be prime factor that governs the characteristics of the wastewater generated from the textile manufacturing plants. The pH is dependent highly on the type of the clothes produced in the plant. In general, the composite wastewater is generated from the manufacturing plant is observed to have a pH in the range of 7 to 9. In most of the cases the wastewater coming out of the textile industry is observed to be of alkaline nature due to the extensive use of the caustic soda. Electrical conductivity of the wastewater is another parameter that influences the characteristics of the wastewater. In general, the electrical conductivity is found to be ranging from 4430 ms to 8710 ms. On an average it can be recorded as 6709.17 ms. Apart from that, total amount of the dissolved solids in the wastewater from the textile industry is found to be varying in the range of 3210 mg/L to 5290 mg/l. In addition to this, the suspended solids is another important parameter that directs the quality of the waste water. As a matter of fact, the viscous nature of the wastewater arises due to the high level of concentrated suspended solids. In general, the suspended solid content of the wastewater is observed to varying from 830 mg/L to 158 mg/L. Apart from that, the total hardness, as observed, is ranged between 120 mg/L to 150 mg/l in case of the textile industries. Microbes found are basically resistance forms because of the dissolved chemicals.
2.4 Wheel diagram narrating the parameters of wastewater quality
Various parameters are relevant to the wastewater quality. A major one is the dissolved organic contents which is measured as the COD or the BOD. It is generally measured as the 100 mg/L. The biological toxicity is another parameter that is responsible for determining of the wastewater quality and it is generally measured as 10*6 pathogens. Additionally, the hardness of nthe wastewater quality is in the range of 100 mg/L. Chemical toxicity is measured as the 10 mmol/L toxicants.
2.5 Major wastewater treatment processes
Various steps are coherent with the wastewater treatment among which the biological treatment is an important one. In this case, the UASB technology can be effectively used. In this technique microorganisms are efficiently used for serving the purpose of the removal of the organic contents, proteins, dissolved sugars and fats from the wastewater generated from the textile plant. In general, the microorganisms are fed in a specific kind of reactor which is properly evacuated from the atmospheric oxygen. The pollutants and hazardous effluents present in the wastewater is potentially transformed by the application of the chemical forces into the biogas that can be further used in the plant as the energy sources.
Prefiltration is another useful step that is adhered to the wastewater treatment of the textile industry. In this context, the technology known as the membrane filtration can be exclusively used. The membrane here acts as the filtering tool that allows the wastewater to go through it. The suspended solids are potentially removed by the intervention of this membrane filtration technique. Pressure-driven membrane filtration is particularly useful in this regard in which membrane in the range of 100-500 daltons are used.
On the other hand, AOP or the advanced oxidation procedure is another relevant step in the wastewater treatment. Ozonation is definitely a useful technology from this perspective. Ozone generator is typically used in this technique that converts the oxygen into the ozone by the application of the UV radiation. This ozone in the reactor potentially oxidises organic materials, moulds, bacteria and other pollutants. Thus, this step can be regarded as the disinfectioning process.
3. Ozonation technology
3.1 Main area of application of ozonation technology
The main area of application of the ozonation technology is definitely the wastewater treatment coming out from the textile industries. Thus, it can be considered as the potential measure for serving the purpose of disinfection technique of the wastewater. The AOP or the advanced oxidation process is a prime step in the wastewater treatment where the hazardous effluents are potentially removed and the ozonation technique is extremely relevant in this context.
3.2 Scientific principles of the ozonation technology
In the AOP process, the ozone is exclusively used along with the application of the UV radiation, peroxide and the whole matter is processed under a high pH. Although hydrogen peroxide is a potential oxidant, however, UV is definitely not. But when this combination is used along with the ozone gas, the organics are broken down to carbon dioxide and water molecules. When the ozone as well as the UV radiation is present in the system, the hydrogen peroxide explicitly decomposed into hydroxyl radicals. Both the ozone molecules and the ozone radicals are in the high level of oxidative state. The free radicals after the decomposition has the high capacity to withdraw the hydrogen atoms from the substrate on which the process is applied. The hydrogen peroxide is responsible for making the pollutant more vulnerable for the attack by the ozone molecules. The UV radiation also facilitates this attack by breaking of the chemical bonds.
3.3 Main design parameters of the ozonation process
Wastewater treatment by the application of the ozonation is supposed to be a pilot technique. A ozone reactor is utilized in this process. The ozone dose as required in this process is largely influenced by the suspended solids as well as the organic content present in the wastewater. An increase in the overall contact time as well as the concentration of the residual ozone largely influences the removal of the bacteria and viruses. In particular, the Ct approach is beneficial in the ozonation process. In this case, ozone is transferred to the effluent chamber in which the residual ozone is generated and this is measured to find out the progress of the process.
3.4 Advantages and disadvantages of the ozonation process
Wastewater treatment by suitable application of the ozonation technique is associated with many advantages. For example, this technique kills bacteria efficiently. In addition to this, unwanted substances in the wastewater such as the iron and the sulphur is oxidised potentially followed by the filtration to remove those from the wastewater content. Apart from that, after the treatment by the ozonation process, it is observed that the wastewater is free from any ubiquitous odor or hazardous residues. Not only that, the ozonation is beneficial also from the viewpoint of quick conversion of the ozone molecules to oxygen and thus, no traces of ozone is left in the process.
However, some disadvantages are also pertinent in this context such as requirement of enormous energy in the form of the electrical mode which needs investment of lots of money. Apart from that, dissolved salts and minerals cannot be eliminated in this process staying of which isd hazardous for the quality of the water. Additionally, byproducts such as bromnmates are produced in ozonation process which are obviously harmful for the humankind if not controlled on an early basis.
Hence, it can be concluded that the textile industries are associated with the huge amount of the waste water. This waste water is used to hazardous for the mankind and hence requires the proper treatment. Various processes are significant for the wastewater treatment such as the biological treatment, prefiltration and the AOP process. The textile industries are using the latest technologies such as the ozonation process, membrane filtration technique and the UASB method which are believed to be extremely potential for the treatment of the wastewater.
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