Industrial Water And Wastewater Treatment: Overview And Challenges

Describe the Industrial Water and Wastewater Treatment. 

Treatment of Water in Chemical Industry

The chemical industry has seen an economic growth extensively over the last few years thereby, contributing to the national economy of the country. The chemical industry contributes largely to the economy of various countries. The expected growth of the chemical industry is $4.1 trillion in 2013 to $5.1 trillion by 2020. Chain is the main driver for growth of the chemical industry and is expected to grow 8% by 2020. The huge growth in the chemical industry is due to continuous innovation in energy transformation, automobile industry, electronics and construction(Consultancy.uk, 2017).

Water is one of the significant requirements of the chemical industry as it is used for mixing with the raw materials, used as solvents, product washing and cleaning of equipment. Moreover, a significant amount of water is used for heating and cooling in the chemical industry. Globally, the countries are well aware of the adverse effect of such extensive use of water and taking taking measures to reduce the consumption in chemical industry. Increased use of water in the chemical industry results in increased effluent productionthat adversely affects the natural water system (Forstner and Wittmann 2012). The wastewaters released from the chemical industry are highly organic and consists of reactive residues along with particulates that are not dissolved. Therefore, the effluents released neither can be disposed nor can be reused in natural water system and requires treatment.

This report emphasises on the wastewater treatment technology used in chemical industry by critically analysing it. Recommendations are suggested for modifying the current wastewater treatment in this report.

Large volume of water is consumed by the chemical industry for purposes such as mixing with the raw materials, used as solvents, product washing and cleaning of equipment. The table below addresses the total amount of water consumed by the different processes in the chemical industry.

Table 1: Water consumption in Chemical Industry

However, the naturally available waters cannot be used directly by the chemical industry therefore; the water needs to be treated before use in order to achieve desired characteristics of water.

Table 2: Desired Water Characteristics

The process of water treatment can be challenging at times due to factors such as:

• Presence of increased amount of organic salts and metal ions in raw water
• The quality of natural and municipality water are comparatively low
• Bacterial growth on the equipment used in chemical industry due to presence of traces of water
• High concentration of water hardness results in decreased enzyme activities and solubility of chemical agents

In the case of chemical industry, high variability and permits of stringent effluent define the wastewater treatment (Gupta et al. 2012). Therefore, the water treatment technology for chemical industry needs to be selected appropriately based on the size of the molecules and the biodegradabilityof the pollutants. As commented by Eckenfelder and O’Connor (2013), biological oxidation methodconsists of activated sludge, lagoons and trickling filters that are most widely used water treatment technology in chemical industry. In the case of the pollutants with particulate size more than 10,000-20,000, it can be treated by coagulation method followed by flotation or sedimentation. According to Moore and Ramamoorthy(2012), prevention of waste during the production of chemicals is the first and foremost priority for the chemical industries.

A recommended water treatment involves exchange of ions thereby, reducing the number of ions present in the water. As a result, the turbidity of the water will be minimised thereby, enhancing the water quality.

Water Treatment Issues

The chemical industry for different industrial processes consume large amount of water. The main main water consuming factors for the chemical industry are listed in the table below. As commented by Ali (2012), these factors result in generation of higher amount of waste in the water. Due to the constituents of the wastewater, it is inappropriate to discharge the wastewater directly in the natural water. Moreover, the water cannot be also usedby the chemical industry due to presence of various contaminants. The table below also demonstrates the parameters of the wastewaterthat requires treatment for disposal in the natural system (Dhal etal. 2013).

Table 3: Wastewater Treatment in Chemical Industry

The chemical industry adds huge amount of impurities in the water that decreases the quality of the water. As commented by Warner et al. (2013), large volume of inorganic chemicals are present in the wastewater that is required to be treated before releasing in the wastewater.

Table 4: General Wastewater Impurities

In spite of the technological advancements, treating wastewater due to chemical industry is challenging (Mutamim et al. 2012). The main challenges encountered while treating chemical wastewater are:

• Dyes are the main issue in the chemical industry that is produced while manufacturing of paints. As asserted by Crittenden et al. (2012), traces of dye present in the water results in aesthetic issues while wastewater treatment.
• The strict governmental rules and regulations is making the wastewater disposal process more difficult.
• The chemical industry includes wide range of chemicals in terms of composition. As commented by Thurman (2012), the chemicals are generally inorganic, organic and long complex polymers. Therefore, processes for treating wide range of chemicals needs to be used for wastewater treatment.
• When exposed to water, light and chemicals for treatment, the complexity of the chemical structures makes it resistant to fading.
• In the case of using biological method of treatment, the effluent present in the chemicals possess harmful effect on the microorganisms thereby, killing them before the treatment process initiates.

The treatment procedure in the chemical industry is supposed to be conducted in the following way:

• Removal of the suspended and large particulates: In order to remove the large and suspended solid particulates in the water, coarse screening is the most significant way. As commented by Kunii and Levenspiel(2013), coarse screening is the best way to remove the large particulates in water at the initial process. However, filtration and grit are some other suggested methods of solid removal. If the size of the solid particulates ranges between 7-155 mm, the present coarse screening method is the most effective one.
• Equalization tank: As commented by Vlyssides et al. (2012), equalization tank helps in maintaining the pH of the effluent of the chemical discharge. As the microorganisms used for biological treatment of the chemicals, equalization tank helps in stabilising the pH.Addition of Sulphrric acid and nitric acid obtains the desired pH during the process. However, as suggested by Naik, Desai and Desai (2013), post equalization the pH cannot be altered therefore, it needs to be performed before conducting the biological treatment.
• Removal of small solid particulates: As commented by Feigin, Ravina and Shalhevet (2012), sedimentation is used for removing small solid particulates present in the effluent. The process of sedimentation uses the gravitational force to separate the particles. However, the other methods of removing small solid particulates from the effluent of the chemical wastewater arefloatation and flocculation.
• Floatation uses chemical agents that form flocks thereby, settling down and floatation forms froth and forces the solid particulate to move on the top
• As recommended by Zhong, Wang and Xu (2012), sedimentation is a comparatively slow process thereby, making floatation move effectively for chemical wastewater treatment. Forces such as hydrostatic force, buoyancy are used in this process. As altered pH will not affect the biological treatment, this process is more effective if conducted before equalization.
• Biological wastewater treatment: The most effective way of removing organic pollutants from the effluent is by the activated sludge process. As the BOD and COD of the chemical industry are comparatively low, it is considered to be effective for treating organic effluents. On the contrary, more cost-effective treatment processes are available to reduce organic pollutants.
• More cost-effective treatment procedures such as aerobic treatment, physiochemical and anaerobic treatment can also be used for treating wastewater from chemical industry. For example, aerobic treatment utilises oxygen for treating the organic effluents of the chemical wastewater. On the contrary, the same process is carried out in the presence of carbon dioxide in the case of anaerobic treatment. However, in the case of the physiochemical process, both biological and chemical are simultaneously carried out to remove to suspended organic matters in the wastewater form the chemical industry.
• Therefore, physiochemical treatment can be used because of its increased capability of removing organic matters from the effluent. The effectiveness of the process is basically determined by the dual action of the physiochemical treatment.
• Chemical treatment: The process of ozonisation is also one of effective chemical treatment as the UV rays helps in breaking the organic bonds of the pollutants (Xu et al. 2012). However, as argued by Padhi(2012), carcinogenic amines are released during the treatment process that is severely harmful. However, ozonisation can be replaced with other methods that can be used before the biological treatment process as maintaining the pH is necessary.
• Advanced treatment for reuse of the wastewater: Advancement treatments can also be used as methods for treating wastewater from the chemical industry as th removal efficiency of the advanced treatment is <95% based on the optimal working conditions. According to Miralles-Cuevas et al. (2013), the different types of advanced treatments are micro, ultra, Nano filtration and reverse osmosis. The Nano filtration has the capacity of removing particles sized 0.01-0.0001. Similarly, micro filtration and ultra-filtration has the capability of removing particles sized 10-0.1 and 0.1-0.01 respectively. However, the most effective advanced treatment for wastewater is reverse osmosis it can remove particles sized 0.001-0.0001 efficiently.
• Sludge treatment and Disposal: Before disposal of the wastewater in the natural system, the generated sludge due to various processes needs to be treated appropriately. Recycling of sludge is an effective way of reducing cost of the sludge treatment facility.

The socio-economic and the environmental impacts of the wastewater and the water treatment are furnished below:

Socio-Economic influence: As mentioned previously, the chemical industry greatly influences the overall economy of the country. In different countries, chemical industry contribute extensively for the overall growth in the country’s economy. The treatment of wastewater from the chemical industry is an expensive process. However, the margin of the profit generated by the chemical industry is distinctively significant. The chemical industry individually contributes to both unskilled and skilled employees in countries with considerable low economy.

Environmental influence: Due to high consumption of water by the chemical industry, it is considered as the major source of pollution in water. According to reports, approximately 25% of the industrial water pollution globally is caused due to the chemical industry due to lack of proper treatment and disposal. The chemical industries dispose huge number of hazardous chemicals in the water without proper treatment. Therefore, these reports indicates that treatment of wastewater from the chemical industry is of utmost significance as this will comparatively reduce the pollutants entering the natural water system. An essential way of effluent management can be achieved by treating the wastewater by implementing reusable standards. Using reusable standards reduces the concentration of pollution entering the natural system drastically along with reducing the annual consumption of the water by the chemical industry thereby, contributing to the conservation of water in various regions that encounters water scarcity.

Conclusion

In this report it can be concluded, chemical industry contributes extensively to the economic growth of the country. However, the amount of pollution released by the chemical industry in the natural water system has also increased over the years. This report conducts a detailed study about different features of the chemical industry followed by evaluating the present condition of the chemical industry and the wastewater treatment used for reducing pollution. The report also critically evaluates the various methods or treatment processes for wastewater treatment along with providing suitable recommendations for improvement. The report also discusses the socio-economic and environmental influences of wastewater from the chemical industries. Though chemical industry plays a significant role for the economic growth of the country, improper management of wastewater will adversely affect the country and the environment in the long run. As a result, the wastewater effluent needs to be managed appropriately. Reusing the wastewater after removal of the pollutants thereby, reduces the overall annual consumption of water by the chemical industry and conserves water efficiently. Therefore, wastewater treatment from the chemical industry is a significant aspect in order to promote healthy economy and safe environment.

References

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