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Working of an Effluent Treatment Plant (ETP)

  • Effluent treatment in pharmaceutical industries has a lengthy process that includes four levels of water treatment. After these four levels of purification water become safe for the environment.
  • Water is an essential part of manufacturing industry processes and domestic use. Water is used as a coolant, solvent, or in many other chemical-based reactions in companies.
  • After the manufacturing process is completed, wastewater is produced as a by-product. This wastewater is then called effluent. It contains both toxic and non-toxic materials. Effluent cannot just be disposed to the environment because of the harmful material it contains.
  • Therefore, an effluent treatment plant comes into play. This is simply a procedure put in place to purify industrial wastewater to recycle it or dispose of it safely. Different companies have different wastewater compositions and require slightly different effluent treatment plants.

Designing of Effluent Treatment Plant
As discussed above, each company has a different composition of wastewater which means that each company will have slightly different designs of ETP depending on the following characteristics of wastewater;

1. Physical Parameters of the Wastewater:
  • Physical properties of wastewater include - Suspended solids (soil, plant fibers, etc)
  • Turbidity - Ability to absorb sunlight which is determined by the presence of the suspended material.
  • The temperature of wastewater - High temperatures suggests a higher level of toxicity
  • Color - It is determined by the dissolved or suspended matter.

2. Chemical Parameters
  • Total dissolved solids- mainly dissolved salts
  • Inorganic substances present
  • Waste-water alkalinity
  • The hardness of water - composition of calcium and magnesium ions
  • Nutrients available
  • Organic matter
  • Metals- heavy metals are toxic
  • Fluorides- Toxic in high levels
  • Chloride presence in the wastewater
  • Dissolved oxygen and nitrogen- This varies with the number of salts dissolved in the wastewater. The higher the amounts of dissolved salts, the lower the percentage of oxygen and nitrogen.
  • Pesticides and other agricultural chemicals- Highly toxic to the environment.

3. Biological Parameters
  • This is the presence of microbial pathogens in the wastewater. Consists of microscopic flora and fauna. Some species of microbial organisms can survive in wastewater. These pathogens can transmit dangerous diseases such as typhoid, cholera and dysentery.
  1. Bacteria - Can be harmful bacteria or safe to the environment.
  2. Viruses- Wastewater may contain dangerous waterborne viruses such as the yellow jaundice virus and the polio virus.
  3. Protozoa- More complex in their metabolic activity than most microbial organisms.

  • An ETP is therefore designed to remove the physical, chemical and biological materials present in the effluent. Depending on the level of treatment the wastewater requires, an ETP is divided into four different levels each designed to remove a certain type of material in the effluent.
  • There are four levels in wastewater treatment each level designed in a way that by the time the process is complete, the water to be disposed to the environment is as friendly as possible. These levels are;

Preliminary Level:
  • This aims at the removal of physical waste present in the effluent. This level involves physical processes such as sedimentation, filtration, aeration, flow equalization, clarification, and screening.

Primary Level:
  • Aims at the removal of large solids and organic matter. It involves both physical and chemical processes. The same physical processes mentioned in the first level are utilized. The chemical process involves the addition of certain chemicals to improve the quality of the wastewater. These chemical processes include chemical coagulation, pH control by the addition of HCl or sodium carbonate, chemical precipitation, flocculation, and dissolved air flotation.

Secondary Level:
  • Involves the removal of biodegradable organic materials and suspended matter. This level uses biological and chemical processes. The chemical processes are similar to level 2.
  • The biological processes involved are the suspended-growth process and the attached growth/fixed-film process. The two biological processes can be used together or either one can be chosen.

Tertiary Level:
  • This level entails the removal of suspended and dissolved materials using the physical, chemical and biological processes utilized together. The processes are as discussed in previous levels.
  • Effluent treatment plants are a critical part of the manufacturing industries and other wastewater treatment plants. They keep the environment safe from hazardous materials through strict treatment protocols.

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