Effluent Treatment Plant (ETP) is a wastewater treatment system designed to remove harmful contaminants from industrial wastewater. The sugar industry generates a significant amount of wastewater that needs to be treated before it can be discharged into the environment.
Now we will discuss the process of designing an Effluent Treatment Plant for the sugar industry.
Waste generation from Sugar factories:
There are three types of waste generated from sugar manufacturing industries:
· Liquid waste
· Solid waste
· Gaseous waste
Out of these, we are interested in only liquid waste. Liquid effluent is generated from following processes:
1. Mill house – Cleaning and Washing, Juice leakages, Spillages of mill bearing water.
2. Boiling house – Chemical boiling and tube cleaning of evaporator and pans, Excess condensate water, pump leakages, Daily and periodical cleanings and washings, laboratory and domestic water usage
3. Spray pond over – Blow down of spray pond water
4. Boiler blow down
5. Power plant cooling tower blow down.
How to Design an ETP Plant for Sugar Industries?
Designing an ETP for the sugar industry involves the following steps:
· Step 1: Characterization of Wastewater:
The first step in designing an ETP is to characterize the wastewater generated by the sugar industry. This involves analyzing the composition of the wastewater to determine the types and amounts of contaminants present. The characteristics of the wastewater will vary depending on the specific processes involved in the sugar industry, but typically include high levels of organic matter, suspended solids, and nutrients such as nitrogen and phosphorus.
Generally, Waste water from sugar manufacturing units have following parameters:
pH – 4.0. to 6.5
Chemical Oxygen Demand ( COD) – 2000 to 3000 mg /lt.
Biochemical Oxygen demand (BOD ) – 1000 to 1200 mg /lt.
Total Suspended solids (TSS) – 500 to 600 mg/lt.
Total Dissolved Solids ( TDS) – 5000 to 6000 mg/lt.
Oil and grease – 10 to 50 mg/lt.
· Step 2: Selection of Treatment Technologies:
The second step is to select the treatment technologies that will be used to treat the wastewater. There are several treatment technologies available for treating sugar industry wastewater, including physical, chemical, and biological treatments. The selection of treatment technologies will depend on the characteristics of the wastewater and the discharge requirements.
· Step 3: Design of Treatment Process:
Once the treatment technologies have been selected, the treatment process can be designed. The treatment process typically includes several stages of treatment, including primary treatment, secondary treatment, and tertiary treatment. The primary treatment stage involves the removal of large solids and grit from the wastewater. The secondary treatment stage involves the removal of dissolved and suspended organic matter through biological processes such as activated sludge. The tertiary treatment stage involves the removal of remaining contaminants, including nutrients, through processes such as filtration, disinfection, and chemical precipitation.
· Step 4: Design of Treatment Units:
The next step is to design the treatment units required for each stage of the treatment process. This involves determining the size and configuration of the treatment units, including the reactors, clarifiers, filters, and disinfection systems. The design of each unit will depend on the treatment technologies selected and the flow rate and volume of the wastewater.
· Step 5: Preparation of Detailed Drawings and Calculations:
The final step in designing an ETP for the sugar industry is to prepare detailed drawings and calculations for the treatment system. This includes preparing process flow diagrams, equipment layouts, and piping diagrams. It also involves calculating the hydraulic and process parameters for each unit, including the flow rate, detention time, and loading rates.
Working process for Sugar Unit Effluent Treatment Plant:
The following process shows a typical treatment process for sugar industry wastewater which can be also seen in Figure 1:
1. Pretreatment: The pretreatment stage involves the removal of large particles and other insoluble impurities from the wastewater. This stage includes the following processes:
a. Screening: In this process, the wastewater is passed through a screen to remove large solids such as stones, leaves, and other debris.
b. Grit Removal: Grit chambers are used to remove grit, sand, and other heavy materials that settle at the bottom of the chamber.
c. Oil and Grease Removal: Oil and grease are removed from the wastewater by skimming or using coagulants.Equalization: The screened wastewater is then collected in a equalization tank to balance the flow rate and composition of the wastewater.
2. Equalization: The screened wastewater is then collected in a equalization tank to balance the flow rate and composition of the wastewater.
3. Primary Treatment: In the primary treatment stage, the organic matter in the wastewater is removed through physical and chemical processes. This stage includes the following processes:
a. Sedimentation: In this process, the wastewater is allowed to settle in a sedimentation tank, and the settled solids are removed as sludge.
b. Chemical Coagulation: Coagulants such as alum, ferric chloride, or lime are added to the wastewater to remove suspended solids.
4. Secondary Treatment: In the secondary treatment stage, biological processes are used to treat the wastewater. This stage includes the following processes:
a. Aeration: In this process, air is supplied to the wastewater to promote the growth of aerobic bacteria, which break down organic matter.
b. Activated Sludge Process: The activated sludge process involves the use of microorganisms to break down organic matter in the wastewater. The microorganisms are grown in a biological reactor, and the treated water is then separated from the sludge.
5. Tertiary Treatment: The tertiary treatment stage involves the removal of any remaining impurities from the wastewater. This stage includes the following processes:
a. Filtration: In this process, the water is passed through sand filters to remove any remaining suspended solids.
b. Disinfection: Disinfectants such as chlorine or ozone are added to the water to kill any remaining bacteria. UV Light can also be used for this step.
6. Discharge: The treated wastewater is finally discharged into the environment, meeting the discharge standards set by the regulatory authorities.
Conclusion:
Designing an Effluent Treatment Plant for the sugar industry requires a detailed understanding of the wastewater characteristics and the treatment technologies available. The treatment process typically involves several stages of treatment, including primary, secondary, and tertiary treatment, and the design of each unit will depend on the treatment technologies selected and the flow rate and volume of effluent.
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