Is Water Leaving The Treatment Plant Clean Enough To Drin
What Are H2o Treatment Procedure Steps?
The Water Treatment Process includes the handling of h2o supplied to the household for drinking and other utility purposes and also the wastewater to be tending of into the h2o sources.
The Water Treatment Processes involved in both the supply of water and wastewater differ in many ways. Here, we volition be discussing the processes included in the drinking water supply.
Drinking Water Handling
The journey of drinking water starts from the source. It can exist anything- a lake, river, or other streams of water except seawater. Handling of seawater costs too much to make information technology viable for drinking, hence information technology is avoided.
Drinking water treatment means the removal of the pollutants present in the h2o and the inactivation of the microbes that may cause harm.
Drinking Water Quality Standards
Every country has decided to potable water quality standards. It includes the lower and upper limits of various ions and elements nowadays in water.
Also, information technology sets the limitations up to which sure contaminants similar turbidity, odour, colour, and other physical characteristics tin be tolerated.
Objectives of Water Treatment Process
- To remove colour and odor from water
- To remove the hardness of water
- To remove the harmful microbes that cause diseases from water
- To remove murkiness and turbidity of the water
- To remove dissolved gases present in water
- To brand the water suitable for various purposes like drinking, industrial and many others as per the demand
Types of Drinking Water Treatment Process
Drinking water treatment is treated in a water treatment constitute and supplied to the household via a conveyance organization. Care should be exercised that the drinking water is not contaminated again during its conveyance. For this, precautions are taken at the handling establish itself from the start.
The Processes involved in Water Treatment
Following are the types of processes involved in the water handling,
1. Physical Water Handling Process
- Sedimentation
- Filtration
- Dissolved Air Floatation
2. Chemical Water Treatment Process:
- Pre-chlorination
- Aeration
- Disinfection
3. Physio-Chemical (Conventional) Water Treatment Process:
- Coagulation
- Flocculation
iv. Biological Water Treatment Process:
- Boring Sand Filtration
Drinking Water Treatment Process
Let us see the drinking water treatment process in particular here and the various processes involved in the same. The h2o handling process starts with the collection itself.
There are two types of sources of water. One is the surface water source like river, reservoir, etc. the other 1 is footing water source like bore well. The water treatment procedure differs for these systems considerably.
The impurities present in both the sources belong to a different category and hence the treatment process is different too. Surface water has a large number of suspended particles and other concrete impurities while groundwater has the presence of ions.
These ions make groundwater- hard. However, the ions are defective in surface water. So, the groundwater required chemical treatment more than the physical one.
1. Collection of Water
The water is nerveless from the sources like a lake, river, or reservoir. The water is to be transported from this source to the water treatment establish for the water treatment process. This is included in the collection of water.
Generally, water treatment plants are built near the h2o source itself.
2. Screening
Screening is done to remove the floating matter from the water during the water treatment process. Surface water contains a large number of suspended particles that increment the unnecessary load on the treatment plant units.
Screening is mostly washed at the intake point itself. The large-sized suspended particles like dried leaves, fallen twigs, and other floating debris.
Two types of screens are used for screening:
1. Coarse Screens/ Bar screens
Bar grills are installed and water is allowed to pass through them in this process. 25 mm bars are installed at 75 to 100 mm middle to centre distance. This traps particles of big size every bit the water flows through them.
Mostly the bars are kept in an inclined position so that they can be cleaned hands with racks to remove the trapped particles.
2. Fine Screens/ Automated Strainers
An automatic device is fitted in the screens so that the trapped materials tin can be removed on their ain. Such type of screens is called automated strainers.
3. Microstainers
A stainless steel wire is used to make the cloth designed specially and information technology is mounted on t periphery of the revolving drum afterward. Information technology has an organization for backwashing too. This ensures that it does non get clogged.
3. Sedimentation
The sedimentation process removes the heavy particles that can settle down under gravity. The weights of the particles increase as they aggregate so settle down.
A sedimentation tank is then designed that the velocity of the flowing h2o is reduced. As the h2o is discharged into the sedimentation tank, the cantankerous-section expanse of the water flow is in the case and therefore, velocity reduces.
Sedimentation is likewise of two types: One is Plain sedimentation without the addition of chemicals while the other is sedimentation with coagulation in which chemicals are added.
The efficiency of the sedimentation tank depends upon the post-obit factors:
- Design considerations for the tank
- Shape and size of the sedimentation tank
- Detention period
- Size of suspended particles
- Characteristics of suspended particles
- The menses velocity of water
i. Plain Sedimentation
In this blazon of sedimentation, the particles aggregate on their own nature and settle down under the forcefulness of gravity.
two. Sedimentation with Coagulation
To speed upwards the procedure of sedimentation and to increase efficiency also, sometimes, chemicals are added to the water. These chemicals are chosen coagulants.
Coagulants help in the aggregation of the particles, which increases the size of aggregated particles and hastens their settling in the water treatment process.
Types of Sedimentation/ Settling Tank
At that place are two types of sedimentation or settling tanks equally described below:
1. Fill up and Describe Type
The water is filled in the fill and depict-type starting time and so immune to remain for a detail duration. Detention fourth dimension is normally kept 24 hours for the fill up and describe-blazon tank. The suspended particles settle downwards to the tank bottom in this detention catamenia.
The above-mentioned tank is also known as Quiescent Tank.
Equally the retention period is over, the clear h2o from above is taken out past opening the outlet valve, and the tank is cleared for the suspended particles settled downward earlier. To clean the tank, 6-12 hours' fourth dimension is required.
Thus, ane operation cycle to obtain clear water takes effectually 30 to 36 hours for the fill and draw-type tank.
2. Continuous Flow Type Tank
The fill and describe-type tank take upwardly too much fourth dimension to get i batch of filtered water. This is non feasible when a large population is to be supplied with water.
Taking a look at the factors mentioned above-affecting sedimentation, the velocity of incoming water can be managed without all-encompassing efforts.
Hence, in a continuous flow type tank, the water is allowed to movement continuously under much less velocity. The suspended particles settle downwardly as the water flows and attain the outlet at the bottom of the tank.
Continuous menstruation type tanks can exist further constructed of ii types based on the flow direction of h2o as follows:
Horizontal flow tank- A rectangular tank is used and length is generally kept twice its width. The flow of water is in the horizontal management. Maximum permissible velocity = 0.3 seconds.
Vertical flow tank- A circular or rectangular tank with a hopper bottom. The dimension of these tanks is generally more in the depth. The flow of h2o is in the vertical management. Water enters into the tank through a centrally located inlet pipe and and then it is deflected downwards.
four. Clarification or Sedimentation with Coagulation
The sedimentation with coagulation is termed every bit clarification. It is required to increment the efficiency of sedimentation equally stated to a higher place during the water treatment process. Patently sedimentation consumed too much time.
How does description work?
The colloidal particles suspended in the water accept a negative or positive charge effectually them. Coagulants neutralize this charge and allow these particles to coalesce.
Steps in Clarification in H2o Treatment Procedure-
- Addition of measured amount of chemicals to the water
- Thorough mixing of water
- Formation of precipitates in h2o
- Formation of flocs which is formed by coagulation initiated by the precipitates
- Sedimentation
Types of Coagulants used in H2o Treatment Process-
- Alum
- Ferrous sulphate and lime
- Magnesium carbonate
- Polyelectrolytes
- Sodium aluminate
Alum is near normally used as a coagulant.
Devices used for Carrying out Mixing of Coagulants-
- Centrifugal pump
- Compressed air agitation
- Mixing basin
five. Filtration
Filtration is ane of the well-nigh crucial steps of the water treatment process.
The flocs formed during flocculation are not removed entirely past sedimentation. Hence, to remove the finely sized particles and flocs, filtration is required. And the particulate matter which was retained in the sedimentation tank previously is removed, specially the not-settleable particles.
Types of Filters
The following type of filters are available based on the time taken for filtration:
i. Tiresome Sand Filter
These filters were introduced as early equally the 1800s. Slow sand filters are named so because they have taken likewise much fourth dimension for filtration. The filtration fourth dimension is one-twentieth as compared to that of the rapid filters.
The components of a boring sand filter comprise an enclosure tank, fitter media, base material, an under-drainage organisation, and goods.
Enclosure tank is an open up bowl tank with a bed slope of 1 in 100 or 1 in 200. The surface area varies from 50 to yard cubic meters. Filter media is formed of sand which should be free from loam and suspended or organic matter.it is laid in 90 to 110-centimeter thickness.
The base of operations fabric is formed of gravels laid in a xxx to 75-centimeter thick layer. Under drainage system is formed of a number of lateral drains. Some appurtenances are also installed for diverse purposes, like to mensurate head loss through filter media, to control depth of water above filter media, etc.
2. Gravity Type Rapid Sand Filter
The components of a rapid sand filter incorporate an enclosure tank, fitter media, base fabric, an nether-drainage system, and appurtenances.
The enclosure tank is smaller in size equally compared to that of the ho-hum sand filter. Other components are similar in characteristics to that of the slow sand filter. However, the appurtenances consist of wash water troughs, air compressors, and rate control devices.
Rapid sand filters may be logged frequently, which is why the sand has to be cleaned at frequent intervals. For this, backwashing and surface wash methods are practical.
iii. Pressure Filters
The pressure filter is also a rapid sand filter, however, instead of an open basin, the closed container is used for this, and water is allowed to pass through the filter in force per unit area. The force per unit area may exist about iii to 7 kg/cmiii
These filters are either horizontal or vertical blazon based on the direction of water flow.
Automatic pressure filters are also available at present. In this type of filter, backwashing is washed automatically.
Issues in Filters
Because of poor design or lack of proper operation of the filter, many filtration problems arise in sue course of time.
Some of the problems in filters include:
i. Cracking and Clogging of Filter Bed in Filters used in H2o Treatment Process
This mostly occurs when the solids accumulate in the superlative surface of the filter media. The coating on sand grains cracks and the head loss is observed to have been increased. This results in the penetration of dirty water into the filtered media up to the gravel layer. This decreases the efficiency of the filter.
2. Mud Balls Formation
Conglomerates of floc sand and other binders are termed as mud assurance. Mud balls are formed near the top of filter media and are resulted from the insufficient washing of filter sand grains. Mud accumulates on the sand surface forming a dense mat and reduces the effectivity of the filter. This can exist avoided past backwashing the sand at regular intervals.
three. Binding of Air
When dissolved gases of water are released in the course of air bubbles, air binding occurs. These air bubbles clog the voids of the filter media and the water may non be able to flow every bit earlier. This condition of air bounden tin can exist avoided by preventing the warming of water before it is allowed to laissez passer the filter media, control of algae or avoiding supersaturation of h2o with air.
4. Sand Boils
When the water follows the path of least resistance during backwashing, sand balls may be formed. The sand may boil like quicksand, lifts up sand, and fifty-fifty gravel to the surface. Surface launder or air scour before backwashing tin can eliminate the fluidity.
5. Sand Leakage
When the layer of fine gravel is displaced during backwashing, sand leakage may take place. Sand leakage is the downward migration of the fines. With the proper proportions of the level of sand and gravel, sand leakage may be prevented.
vi. Disinfection
Subsequently filtration, the side by side pace of the water treatment process is disinfection. Disinfection includes the inactivation of pathogenic bacteria and other microorganisms that can cause diseases. This stride is essential to control water-borne diseases.
A disinfectant is added in this footstep to filtered water. Skilled operators are required to carry out the process of disinfection so every bit to maintain the appropriate dosage.
Some of the Important Characteristics of A Disinfectant
- Information technology should be constructive in killing the microorganisms in the contact fourth dimension provided
- It should be hands available in the market
- Information technology should not be expensive
- It should non make the water toxic
- Its awarding should not exist complicated involving a series of processes
- It should not impart any objectionable colour to the water
- It should take the ability to remain in the water in a remainder amount so that the water is not contaminated once again
Types of Disinfectants used in H2o Treatment Process
- Physical treatment- Application of ultrasonic waves, heat or other physical agents
- Radiation- Application of gamma radiation
- Metallic ions- copper, argent
- Alkalis and acids
- Oxidants- Add-on of chlorine, bromine, iodine, ozone, chlorine dioxide, etc
The well-nigh commonly used disinfection method is chlorination.
Chlorination- About widely used Disinfection Method
The chlorination process for disinfection has go the most popular method because it is inexpensive, easily available, and easy to handle.
Chlorine is dissolved in water at a temperature of 49-212 °F. Chlorine gives hypochlorous and hypochlorous acid by the hydrolysis process. Ionization takes place and hypochlorous acid dissociates into hydrogen and hypochlorite ions. These compounds- hypochlorous acrid and hypochlorite ions aid in disinfection.
Forms of Chlorine Application to Water
As bleaching powder ie in hypochlorite form: It was used when chlorination was first introduced, notwithstanding, it is non stable and its ability of disinfection is lost when stored or exposed to air.
Every bit chloramines: These are compounds of chlorine and amino acids. Chloramines were discovered to be disinfectants post-obit the instability of bleaching pulverization. The residuum of chloramines is more stable than the chlorine residual. These besides reduced the objectionable gustation in h2o. Ammonia is added to water before the add-on of chlorine.
As Costless Chlorine: It can be applied in liquid, gaseous or even solid course. It is the virtually popular class of chlorine tablets that are also available.
As Chlorine Dioxide: Chlorine dioxide is more effective in leaving the microorganisms inactive as compared to gratis chlorine. Nevertheless, information technology is simply used in special water treatment processes.
i. Pre-chlorination
It is washed earlier the water enters the treatment units especially the filter unit. In pre-chlorination, a piddling amount of chlorine is applied so that the organic thing can be oxidised and a less amount of coagulant is required.
ii. Postal service chlorination
Mail service chlorination is the corporeality of chlorine added after the water is completely treated and ready to be distributed. Postal service chlorination prevents the contamination of h2o in the route and besides ensures no harmful microbes are introduced to the drinking water.
seven. Water Softening
Water softening is done to make the hard water soft. Surface water usually does not contain much hardness. However, the water taken from hole-and-corner sources similar bore well contains hardness due to the presence of ions.
The hardness of water prevents the h2o from forming lather and too causes problems in the plumbing system. It even affects the taste of water and fifty-fifty nutrient cooked with hard h2o tastes tough or rubbery.
There are ii types of the hardness of water and their handling methods also vary with it.
Types of Hardness and their Removal
i. Temporary Hardness
Crusade: calcium bicarbonate and magnesium bicarbonate ions
Methods of Removal of Temporary Hardness:
- past boiling
- by the addition of lime
two. Permanent Hardness
Cause: calcium sulphate, magnesium sulphate, calcium chloride and magnesium chloride ions
Methods of Removal of Permanent Hardness:
- Past Lime Soda process
- Zeolite process
- Demineralization or Deionization process
eight. Other Treatment Methods
There are a few other characteristics of water to be adjusted as per the quality standards set up by the guidelines.
Some of these characteristics of water to be brought under the limit are:
To Remove Colour, Odor, and Taste:
This is necessary when objectionable color, odour, or gustation is imparted to the water, which may be because of i of the following reasons:
- Organic and vegetable thing
- Dissolved gases beyond a sure limit
- Dissolved mineral affair
- Industrial waste
- Microbes like moulds, bacteria, etc.
Some of the methods used to remove this objectionable colour, aroma, and taste are:
1. Aeration
In aeration, air and h2o are mixed intimately.
It mostly removes the taste considering of dissolved gases. It as well increases the content of dissolved oxygen in the h2o.
Gratuitous Autumn Aerators
There are three types of aerators equally follows:
1. Cascade Aerators
Information technology is the simplest type of free fall aerator. A series of steps are constructed and h2o is immune to fall through a height of 1 to 3 metres.
ii. Slat Tray Aerators
These are non commonly used. Information technology has a serial of closely stacked wooden slats in a closed room. Information technology is either circular or square in shape. Water period is from top to bottom.
iii. Gravel Bed Aerators or Trickling Beds:
In this type of free fall aerator, h2o is supplied to the top and allowed to autumn downward while air is blown upwards. The water trickles downwards from the beds of gravel of thickness one to ane.v meters.
4. Spray Aerators
Water is divided into fine streams and droplets in case of spray aerators and it is allowed to come in intimate contact with the air. Water is sprinkled in the form of a jet with the help of nozzles.
5. Air Diffusion
A perforated pipe network is present in the lesser of the aeration tank through which compressed air is blown. The water travels up in this case and the memory time is about 15 minutes.
6. Copper Sulphate Application
Besides removing color, odour and taste, it also removes algal growth if present in water.
It is available in pulverisation or crystal form and is directly applied in the water when it enters the distribution system.
seven. Desalination
It is required when the water contains excessive saline concentration. Very less water on the surface of the world is fresh h2o and if freshwater is not bachelor, and saline water is to be used, then this step is necessary.
Desalination methods are costly. Some of them are listed below:
- Distillation
- Reverse Osmosis
- Electrodialysis
- Solar evaporation
H2o Treatment Process at a Glance
The water handling process includes various treatments of water so that information technology meets the quality standards as specified. In that location are various types of processes involved in the water handling process and each process plays a meaning function.
Information technology starts with the collection of water from the source. Then it is screened for larger-sized articles. Later that, it is allowed to flow through the sedimentation tank where the heavier particles settle down nether gravity.
If the particles have a relatively large size, then an appropriate coagulant is added and then sedimentation is carried out which is chosen clarification.
Later on that, water is filtered and disinfected as well. For hard water, the water softening procedure is too carried out depending upon the type of hardness.
U.S. Safe Drinking Water Human action
U.Due south. Eastward.P.A. Environmental Protection Agency has set standards for drinking water quality under the U.S. Safe Drinking Water Human activity for public water systems.
State health agencies lookout man that the standards are implemented in the region.
Around 90 contaminants are listed and divided into 6 groups by EPA. These six groups are as follows:
- Microorganisms
- Disinfectants
- Disinfection by-products
- Inorganic chemicals
- Organic chemicals
- Radionuclides
All the countries accept their own drinking h2o quality standards. In India, IS: 10500 describes the standards for drinking water quality.
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