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Effluent Treatment Plant

Choosing an Effluent Treatment Plants (ETP)

  1. Factors to consider while choosing an ETP

    Industrial undertakings those wish and are needed to install an ETP have to consider several factors. They include information and parameters (quality and quantity) of their wastewater that are discharged from their factory.This information can be derived by getting a sample of the effluent water tested and analysed at an authorized laboratory.

    Some of the factors to be considered while choosing an ETP are as follows:

    1. Knowledge of law of the land (national and international rules and regulations) in regards to water and wastewater treatment that you have to comply with.

    2. What quantity of effluent is produced in your entity on daily basis?

    3. The chemical contents and their concentration in the effluent. For instance, 30m3/hour with COD of 500ppm, and pH of 11.5.

    4. What is your budget for installing and running the ETP?

    5. Can you spend on its maintenance once it is installed?

    6. Do you have enough and suitable land area for the desired construction and installation?

    7. Choosing the right vendor is one of the critical factors to consider. An expert in the filed who provides excellent aftersales service should be considered.

    8. As there are many types to consider, choose the ETP that best suits your company requirements.

    9. Better recruitment and training to the personnel responsible for operation and maintenance of the plant.

    The answers to the above questions will assist in the choice of best suited ETP for your premise.

  2. Treatment Methods used by us for treating Effluent

    • a. Physical Unit Process

      Some of the common physical unit operations include among processes such as screening, flow equalisation, sedimentation, clarification and aeration.

      Screening

      Screening process includes the use of a screen with uniform sized openings to remove larger solid particlesthatcan damage the equipment, reduce theeffectiveness of the ETP or pollute the waterways.

      Flow Equalisation

      Equalization tanks are used to collect and store the wastes that allows to mix and become a regular quality before it is pumped to thetreatment units at a constant rate.ETPs are designed to treat wastewater that normally has a constantflow and a quality that fluctuates only within a narrow range. Theequalization tank overcomes this. The hourly variation of flow needs to be determined so that the required volume of the tank is determined.

      Sedimentation

      Sedimentation is used to remove grit and suspended solids, toproduce clarified effluent, and to thicken the sludge produced inbiological treatment. A sedimentation tank (settling tank or clarifier) is used for this process.Flocculation and sedimentation should remove most of the suspendedsolids and a portion of the BOD.

      Aeration

      This involves aerating the wastewater. The water is aerated (or shaken up) to release dissolved gases such as hydrogen sulfide. Aeration also replenishes oxygen, which is consumed by decaying organic matter found in wastewater. Bacteria are also used at this stage to consume nutrients and organic materials. Aeration at times can remove up to 90 percent of all solids and organic material.Two mainmethods are used for this, either mechanical agitation of the water sothat air from the atmosphere enters the water, or by introducing air intothe tank through diffusers.

    • b. Chemical Unit Processes

      Chemical unit processes areused with physical operations andmay also be used with biological treatment processes. Chemical processes use the addition of chemicals to thewastewater to bring about changes in its parameters/quality. They include pHcontrol, coagulation, chemical precipitation and oxidation.

      pH Control

      It is necessary toadjust the pH in the treatment process to make the wastewater pHneutral. A neutral pH is required particularly when biological treatment is being used, as the microorganisms used in biological treatment need a pHwithin the range of 6-8 and will be destroyed by highly acidic or alkali wastewater.Various chemicals are used for pH control. For acidic wastes (with low pH),sodium hydroxide, sodium carbonate, calcium carbonate or calciumhydroxide, may be used. For alkali wastes (with highpH), sulphuric acid or hydrochloric acid may be used. Acids can causecorrosion of equipment and care must be taken in choosing which acidto use. Hydrochloric acid is probably better from an environment’s point f view but can corrode stainless steel. Therefore, plastic orappropriately coated pumps and pipes must be used.

      Chemical Coagulation and Flocculation

      Chemical coagulation is an important unit process in water treatment for the removal of turbidity. Chemicalcoagulants such as aluminium sulphate (alum) or ferrous sulphate may beadded to wastewater to improve the attraction of fine particles so thatthey attach to form larger particles called flocs. Flocculation is aided by gentle mixing of flocculant chemical which causes theparticles to collide.The floc may then float to the top of the liquid (creaming), settle to the bottom of the liquid (sedimentation), or be readily filtered from the liquid.

    • c. Biological Unit Processes

      Biological treatment process generally aims at removal or reduction of the concentration of organic and inorganic compounds from the industrial wastewater.Biological treatment process can take many forms but all are based around microorganisms, mainly bacteria. Thesemicroorganisms consume the effluent componentsfor their survival and indoing so break them down to less complex and less hazardouscompounds. In this process the microorganisms increase in number.

      There are two main types of processes, these involve suspendedmicrobial growth (e.g. activated sludge) and attached microbial growth(e.g. fixed film). With both approaches large populations ofmicroorganisms are brought into contact with effluent in the presence ofan excess oxygen. In both systems the microbial population has to beretained in a tank referred to as the reactor.

      With suspended growth systems microbes grow in small aggregates or“flocs” (this is known as activated sludge). Activated sludge (AS) leavesthe reactor with the treated effluent but is settled out in a clarifier andreturned to the aeration unit to recycle the bacteria. If the amount of ASis excessive some may be disposed off rather than being recycled.


    Effluent can be treated in a numerous way depending on the level of treatment required. These levels are known as preliminary, primary, secondary and tertiary (or advanced). The mechanisms for treatment can be divided into three broad categories: physical, chemical and biological, which all include a number of different processes (Table 3). Many of these processes will be used together in a single treatment plant. Descriptions of the most commonly used processes are given here.

    Wastewater Treatment Levels and Processes
    Treatment level Description Process
    Preliminary Removal of visible bigger solids that maydamage equipment or result in operational problems. Physical
    Primary Designed to remove large debris and solids or settleable materials such as suspended solids and organic matter from the water. Physical and chemical
    Secondary Involves aerating the wastewater. The water is aerated (or shaken up) to release dissolved gases such as hydrogen sulfide. Aeration also replenishes oxygen, which is consumed by decaying organic matter found in wastewater. Removal of biodegradable organic matter and suspended solids. Biological and chemical
    Tertiary/advanced Tertiary treatment may involve the use of chemicals to remove remaining nutrients (nitrogen and phosphorous). It may also include the use of filter beds or other types of treatment. Removal of residual suspendedsolids / dissolved solids. Physical, chemical and biological

Effluent treatment plant (ETP) in various industries

In a world of ever-shrinking resources, it has become imperative that industries use less and fewer resources (especially fresh water) and reduce their carbon imprints.

Kelvin’s Effluent (treated industrial wastewater) treatment plant has exponentially grown in significance, as its ETP treats the wastewater coming from various industries like:

  1. Food and processing industries

  2. Pharmaceutical industry

  3. Tannery & Paper industries

  4. Textile and dye industry

  5. Dairy and Beverage industries

  6. Paint Industry

  7. Chemical Industries

The list is indicative, not exhaustive as there can be applications in other industries as well.

Kelvin’s ETP purifies wastewater for its reuse and releases safe water into the environment. Kelvin’s ETP uses physical, chemical, biological, and membrane processes to treat the effluent. Each industry has a different type of wastewater;thus the process has to be customised for the client’s needs.

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