Design an ETP for Garments or Clothing Industry houses
The Garments/Clothing Industry is one of the major industries in the world, and it generates a significant amount of wastewater containing different types of pollutants such as dyes, chemicals, oils, and suspended solids. It is necessary to treat this wastewater before discharging it into the environment to protect the water bodies and public health.
In here, we will discuss the design of an Effluent Treatment Plant (ETP) for Garments/Clothing Industry/Clothing Export houses in detail with a process flow diagram and working function.
What is an ETP?
An ETP is a system that treats the wastewater generated from various processes in the textile and garment industries, such as sizing, desizing, scouring, bleaching, mercerizing, dyeing, printing, and finishing. The wastewater contains different kinds of pollutants, such as dyes, chemicals, starches, acids, heavy metals, and organic matter. These pollutants can harm the environment and human health if they are discharged into water bodies without proper treatment.
An ETP helps to solve this problem by removing or reducing the pollutants from the wastewater using various physical, chemical, and biological methods. An ETP also helps to save water and energy by recycling the treated water for reuse in the industry or for irrigation. An ETP also helps to comply with the environmental regulations and standards for wastewater discharge.
Process Flow Diagram:
The design of an ETP depends on the type and quantity of wastewater, the quality of inlet and outlet water, the available space and budget, and the specific requirements of the industry. However, a general flow diagram of an ETP for garments industry can be given as follows:
Design of Effluent Treatment Plant (ETP):
1. Wastewater Characterization:
The first step in designing an ETP is to determine the characteristics of the wastewater generated by the garments/clothing industry. The wastewater from this industry contains a high level of Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), Total Suspended Solids (TSS), and Color.
The pre-treatment process is necessary to remove the large suspended solids such as fibers, threads, and cloth pieces. The pre-treatment process consists of a screen chamber, grit chamber, and oil and grease trap. The screen chamber removes the large suspended solids, while the grit chamber removes the sand and other heavy particles. The oil and grease trap remove oil and grease present in the wastewater.
3. Equalization Tank:
After pre-treatment, the wastewater is stored in an equalization tank. This tank is used to provide a uniform flow of wastewater to the ETP, which helps to achieve consistent treatment performance.
4. Primary Treatment:
The primary treatment process involves the removal of suspended solids and the separation of oil and grease. The primary treatment process consists of a sedimentation tank, where suspended solids settle down to the bottom of the tank, and an oil and grease trap, where oil and grease are separated from the wastewater.
5. Secondary Treatment:
The secondary treatment process involves the removal of organic matter from the wastewater. The secondary treatment process consists of an activated sludge process or a trickling filter. In the activated sludge process, the wastewater is mixed with a microbial culture in an aeration tank, where the organic matter is biologically degraded. The trickling filter consists of a bed of rock or plastic media, which provides a surface area for microbial growth. The wastewater is trickled over the media, and the organic matter is biologically degraded.
6. Tertiary Treatment:
The tertiary treatment process is the final stage of treatment, which involves the removal of residual suspended solids, color, and odor. The tertiary treatment process consists of a sand filter, activated carbon filter, and ultraviolet disinfection. The sand filter removes any remaining suspended solids, while the activated carbon filter removes color and odor. The ultraviolet disinfection provides a final disinfection step, which kills any remaining bacteria and viruses.
Equipment list in garment ETP of Garment Indusrty:
The following table shows a sample equipment list of an ETP for garments industry:
The design of an ETP for Garments/Clothing Industry/Clothing Export houses depends on several parameters, such as wastewater flow rate, wastewater characteristics, and treatment objectives. The following are the design parameters for an ETP:
1. Wastewater Flow Rate:
The wastewater flow rate is the volume of wastewater generated by the Garments/Clothing Industry/Clothing Export houses in a given time. The wastewater flow rate is used to determine the size of the treatment units, such as equalization tank, sedimentation tank, and aeration tank.
2. Wastewater Characteristics:
The wastewater characteristics such as COD, BOD, TSS, and color are used to determine the treatment process and the size of treatment units. The design parameters for each treatment unit are as follows:
a. Screen chamber: Size of the screen, spacing between bars, and angle of inclination.
b. Grit chamber: Size of the chamber, velocity of wastewater, detention time, and angle of inclination.
c. Oil and grease trap: Size of the trap, type of media, and detention time.
d. Equalization tank: Size of the tank, detention time, and mixing system.
e. Sedimentation tank: Size of the tank, overflow rate, and detention time.
f. Aeration tank: Size of the tank, hydraulic retention time, and air flow rate.
g. Trickling filter: Size of the filter bed, depth of media, and recirculation rate.
h. Sand filter: Size of the filter bed, depth of media, and backwash rate.
i. Activated carbon filter: Size of the filter bed, type of carbon, and contact time.
j. Ultraviolet disinfection: Size of the reactor, intensity of UV, and contact time.
3. Treatment Objectives:
The treatment objectives are the effluent quality standards that the ETP should achieve before discharging the treated wastewater into the environment. The effluent quality standards are set by the local regulatory bodies, and they vary depending on the type of receiving water body. The following are the effluent quality standards for an ETP for Garments/Clothing Industry/Clothing Export houses:
COD: < 250 mg/l
BOD: < 30 mg/l
TSS: < 30 mg/l
Color: < 20 units
The working function of an ETP for Garments/Clothing Industry/Clothing Export houses is as follows:
· The wastewater from the garments/clothing industry/clothing export houses is collected in a screen chamber, where large debris and solids are removed by a mechanical screen.
· The wastewater then enters a grit chamber, where sand, grit, and other heavy particles settle down by gravity.
· The wastewater then flows into an oil and grease trap, where oil and grease are separated from the wastewater by gravity.
· The wastewater then enters an equalization tank, where the flow rate and composition of the wastewater are equalized to prevent shock loads on downstream treatment units.
· The wastewater then flows into a sedimentation tank, where suspended solids settle down by gravity and are removed by a scraper mechanism.
· The wastewater then enters an aeration tank, where microorganisms break down organic matter in the wastewater by using oxygen.
· The wastewater then flows into a trickling filter, where microorganisms attached to the media remove organic matter in the wastewater by aerobic digestion.
· The wastewater then flows into a sand filter, where remaining suspended solids are removed by filtration through sand media.
· The wastewater then enters an activated carbon filter, where remaining organic matter and odorous compounds are removed by adsorption on activated carbon media.
· The final step is disinfection, where the treated wastewater is disinfected by ultraviolet (UV) radiation to kill any remaining microorganisms.
· The treated wastewater is then discharged into the environment, where it meets the effluent quality standards set by the local regulatory bodies.
The design of an Effluent Treatment Plant (ETP) for Garments/Clothing Industry/Clothing Export houses involves the selection of appropriate treatment units and their sizing based on the flow rate and characteristics of the wastewater. The design parameters for each treatment unit are determined by using formulae that are based on the detention time, hydraulic retention time, surface overflow rate, and other relevant parameters. The PFD and working function of the ETP show the step-by-step treatment process, starting from the collection of wastewater to the discharge of treated wastewater into the environment. The effluent quality standards set by the local regulatory bodies are achieved by the ETP, thus protecting the environment and public health.
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