Effluent Treatment Plant: The Waste Water Treatment Process
The abbreviation of ETP is Effluent Treatment plant. Effluent Treatment Plant includes mechanisms and processes used to treat water bodies that have been contaminated in some way by man-made industrial or commercial activities prior to discharge into the environment or reuse them.
The Purpose and Objective of ETP
ETP reinforces the water for the safe disposal of the water from the pharmaceutical plant. In the pharmaceutical plant, water is one of the major parameters for manufacturing, processing, and other requirements. The effluent from the different units of the plant contains several types of solids, toxins, antibiotics, hazards, various types of contamination, etc. That water obviously is not safe to dispose of freely into the environment. So, the main purpose and objective of ETP is to prepare the effluent water in this way so that it does no harm to human health, marine life, and the ecosystem.
Importance of ETP
1. Provides Clean, Safe Water
To clean industry deriving waste and reuse it for encourage use. Wastewater can actually be turned into reused water. The treatment handle dispenses with any contagions from the water and produces clean, secure water indeed. As it were around 3% of the Earth’s water is drinkable. It’s a renewable asset but it takes very a long time for dissipation and rain to channel out the toxic substances. Wastewater treatment prompts to prepare up and gives clear secure reusable water.
2. Saves Water
To cut consumption on water procurement, ETP is very important. Actually, ETP is helping to save water. If ETP was not there, a lot of water would be wasted due to its use in the industry. As ETP recycles old water, water is saved, not wasted. It ensues chemically treatment of water in an environment-friendly way.
3. Maintains the Proper Guideline
To meet the Guidelines for outflow or discharge of natural toxins from different Industries set by the Government and maintain a strategic distance from strong penalties.
4. A Proper Way to Minimize Waste
To protect the environment against contamination and subsidize in sustainable improvement.
Flow Chart for Effluent Treatment Plant
Design of ETP
The design and size of the ETP will depend on:
1. Quantity and quality of the industries discharge effluent.
2. Land availability.
3. Cash costs for construction, operation and maintenance.
4. Area dimension depends on:
a) Quality of wastewater to be treated,
b) Flow rate
c) Type of biological treatment to be used
5. In case of less available land
a) Common Effluent Treatment Plant (CETP) is preferred over ETP
Major Treatment Units in ETP
1. Sedimentation/ Settling tank
3. Equalization Tank
4. Neutralization Tank
1. Activated Sludge Process (ASP)
2. Trickling Filter
3. Aerated Lagoons
5. Multiple Evaporator (ME) Plant
6. Rotating Biological Contactors (RBC)
1. Sand/ Membrane Filters
2. Activated Carbon Filters
5. Nutrient Removal
Mechanism of ETP
Effluent treatment plant has three treatment levels;
1. Primary Treatment level
Here, both physical and chemical methods are employed. First, sedimenting particles such as suspended solids are settled, and then chemical treatment is applied to control the pH and aggregate.
2. Secondary Treatment level
This level includes biological treatment of wastewater that can be performed under both aerobic and anaerobic conditions.
3. Tertiary treatment level
In this level, final cleaning of wastewater takes place before releasing the water into the environment. Wastewater is treated with chlorine and alum to remove not only the remaining inorganic compounds, but also microorganisms such as bacteria, viruses and some parasites.
1. Primary Treatment Level
Removal of suspended solids and sediments such as suspended solids and organic matter.
Both physical and chemical methods are used during this stage of treatment.
Chemical Unit Processes
Chemical unit processes are always used with physical operations and may also be used with biological treatment processes. Chemical processes use the addition of chemicals to the wastewater to bring about changes in its quality. Example: pH control, coagulation, chemical precipitation and oxidation.
pH Control is needs to adjust the pH in the treatment process to make the pH of wastewater neutral.
a) For acidic wastes (low pH): NaOH, Na2CO3 , CaCO3 or Ca(OH)2 etc. are used.
b) For alkali wastes (high pH): H2SO4 , HCl etc. are used.
Chemical Coagulation and flocculation:
Coagulation refers to collecting the minute solid particles dispersed in a liquid into a larger mass. Chemical coagulants such as Al2(SO4)3 (also called alum) and Fe2(SO4)3 are added to the wastewater to improve the attractiveness between the fine particles so that the fine particles can gather to form larger particles called flocs.
Chemical flocculants (usually polyelectrolytes) enhance the flocculation process by aggregating particles into larger flocs that settle faster. Flocculation is aided by gentle mixing which causes the particles to collide.
2. Secondary Treatment Level
Biological and chemical processes are involved in this secondary level.
Biological Unit Process
Biological treatment process used to remove, or reduce the concentration of organic and inorganic compounds. It can take many forms but all are based around microorganisms, mainly bacteria.
Aerobic treatment processes take place in the presence of air (oxygen). Utilizes those microorganisms (aerobes), which use molecular/free oxygen to assimilate organic impurities i.e. Turn them into carbon dioxide, water and biomass.
The anaerobic treatment processes take place in the absence of air (oxygen). Utilizes microorganisms (anaerobes) which do not require air (molecular/free oxygen) to assimilate organic impurities. The final products are methane and biomass.
Sedimentation Tank (Clarifier)
Sedimentation Tank are designed to remove suspended particles that are heavier than water through gravitational force by reducing water velocity. So it’s a solid liquid separation process in which a suspension is separated into two phases;
a) Clarified supernatant leaving the top of the sedimentation tank (underflow).
b) Concentrated sludge leaving the bottom of the sedimentation tank (overflow).
An efficient sedimentation tank can remove about 90% of SS and 40% organic matter with two hour of detention time.
1. To remove coarse dispersed phase.
2. To remove coagulated and flocculated impurities.
3. To remove precipitated impurities after chemical treatment.
4. To settle the sludge (biomass) after activated sludge process / tricking filters.
Factors affecting sedimentation:
1. Characteristics of solid particles- size, shape, specific gravity, concentration, etc. Characteristics of fluid temperature, viscosity, specific gravity, etc.
2. Physical characteristics of clarifiers- detention period, shape and depth of basins, flow rate, etc.
Types of Sedimentation Tanks:
1. According to shape- Rectangular tank, circular tank
2. According to direction of flow- Longitudinal and radial flow, vertical flow.
3. According to nature of working- Fill and draw, Continuous flow
4. According to method of sludge collection- flat bottom tank with or without scrapper, hopper bottom tank.
The most common are horizontal flow sedimentation tank and centre-feed circular clarifiers
Sludge Thickening Unit
In this unit sludge is dried and discharged. A partial amount of sludge is returned back to the aeration tank from thickening unit through recycle tank called return sludge tank and disperse tank.
Function of disperse tank is to mix the sludge coming from recycle tank with waste water. It helps to proper aeration.
Function of aeration is oxidation by blowing air. Aerobic bacteria is used to stabilize and remove organic material presents in waste. About 200 kg aerobic bacteria is given to the plan for 5 years.
In this tank sludge is settled down partially. Sedimentation pack provides the advantage of fast sludge separation
3. Tertiary Treatment Level
Final cleaning process that improves wastewater quality before it is reused, recycled or discharged to the environment.
Removes remaining inorganic compounds, and substances, such as the nitrogen and phosphorus. Bacteria, viruses and parasites that are harmful to public health are also removed at this stage.
Alum used to remove additional phosphorus particles and group the remaining solids together for easy removal in the filters. Chlorine contact tank disinfects the tertiary treated wastewater by removing microorganisms in treated wastewater including bacteria, viruses and parasites. Remaining chlorine is removed by adding sodium bisulphate just before it’s discharged.
In this tank pH of the influent is corrected to meet the standard. Acid or alkali is added to the effluent by dozing to increase or decrease the pH of influent respectively. Multi-meter type pH meter is used in this process.
Pharmaceutical ETP Water Treatment Trends
Mechanical manufacturing forms in the pharmaceutical industry create wastewater that is by and large characterized as elevated quality organic effluent – waste streams that can be thought-provoking to oversee with accustomed wastewater treatment. The four primary constituents in pharmaceutical plant waste streams that supervisors are for the most part concerned with integrate oil, grease and lard, pH, suspended solids, and natural oxygen or chemical oxygen levels, dissolved oxygen concentration etc. But in expansion to these constituents, different countries and states are starting to centre on the mineral substance in pharmaceutical plant effluents. “This is relatively new to the pharmaceutical industry and represents an area of potential change,” Brittan (technical director for the pharmaceuticals and microelectronics markets with Siemens Water Technologies in Britain) said. Inorganic effluent mineral concentrations can vary, and can also be affected by raw water influent sources, depending on the pharmaceutical product manufactured. The plants need to maintain the discharge requirements for pH, mineral contents, microbial present etc.
The Process Flow in the ETP of Pharmaceutical Plant
It is the first stage of processing in ETP where all the effluents are passed into different units of pharmaceutical plant. By this filtration procedure, all the solid particles are removed from waste water.
Cooling and Mixing
All the effluents from different source are mixed and cooled in this stage.
Neutralization by Acid or Alkali
In this step, acid or alkali is mixed with effluent water to neutralize them and maintain a certain pH.
Chemical co-agulants are added with waste water in ETP.
Settling and Separation of the Sludge
After different treatment, the treated water is settled and separate into another place. The residue remains the sludge.
Secondary filtration may include different treatments like carbon filtration, anti-microbial treatment, pressure filtration etc. to remove the remaining wastes from the water.
After completion all the process, the water is discharged through certain drains to the disposal river or others.