To become a Civil Engineer its very important to have a balance Theoretical Knowledge as well as Practical Knowledge. Eventually with the same concept our visit was organized to WATER TREATMENT PLANT at Nigdi.
The visit was plan with the intention to enhance our theoretical knowledge with practical experience.
The Water Treatment Plant is operated by Pimpri-Chinchwad Municipal Corporation (PCMC). Water is treated here and then supplied to the entire twin city.
The Water Treatment Plant works with basic aim to make water more acceptable for a specific end-use. The end use may be drinking, industrial water supply, irrigation, river flow maintenance, water recreation or many other uses, including being safely returned to the environment.
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| Water treatment plant Procedure |
The Operation Cycle of Water Treatment Plant.
The Water Treatment Plant work is distributed in 6 parts.
1) Intake source management to get fullfill amount of water every day.
2) Sampling Unit.
3) Processing Unit.
4) Storage unit.
5) Supervision & Control Unit.
6) Maintenance Unit.
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| Pavana Dam |
The Intake Source
The intake source of Water Treatment Plant plays a very important role as the intake source should be sufficient to provide every day water requirement of Plant so as to avoid shortage of water.
The Intake Source of Water treatment Plant Nigadi is Pawna dam situated nearly 4km away from the plant. The plant treats 420 MLD ( ie Milions Litres Per Day).
PCMC is planning to build fourth water treatment plant in Chikhali.The new plant will enable the PCMC to treat water that will be drawn in future from Andra and Bhama Askhed dams to meet the growing needs of Pimpri Chinchwad.
The city's population is expected to rise to 25 lakh by 2025, which means the water supplied through Pavana dam will prove inadequate. As per the plan, the areas in Pavana and Mula river basins will get water drawn from Pavana dam while the areas in the Indrayani river basin will get water from Bhama Askhed and Andra dams, located around 20 kms away. From reports for Pimpri Chinchwad, the state government has sanctioned 167 MLD water from Bhama Askhed and 100 MLD water from Andra dam.
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| Laboratory Tests in WTP LAB |
Laboratory Treatments
The water sample from source is been treated to examine the amount of contaminants and the selection of the suitable procedure of treatment.
The is managed by Mr. Sanket Mote and he guided us with the procedure conducted at the plant.
The test conducted are:
•)Turbidity
•)pH
•)Hardness
•)Heavy metals concentration
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| Equipments in Lab |
Turbidity test is conducted to determine the amount of mud silt and other containments in water which cant be seen through naked eyes.
Turbidity is generally high in Rainy season as compared to other season therefore extra efforts are taken at the time of Rainy season.
Turbidity can be measured using either by an electronic turbidity meter or a turbidity tube. Turbidity is usually measured in Nephelometric turbidity units (NTU) or Jackson turbidity units (JTLJ),
depending on the method used for measurement. The two units are roughly equal. At Water treatment Plant the Turbidity is measured by Turbidity Meter
HACK2100QT.
Drinking water should have a turbidity of 5 NTU/JTU or less. Turbidity of more than 5 NTU/JTU would be noticed by users and may cause rejection of the supply. Where water is chlorinated, turbidity should be less than 5 NTU/JTU and preferably less than 1 NTU/JTU for chlorination to be effective
The dosage for alum to form coagulant is determined and added after aeration to for proper sedimentation. However if the amount of coagulant is more then it affects the filtration process.
Bacterial Test
The bacterial test is conducted to determine the Pathogenic bacteria's present in the sample.
There are some types of bacterial test like
1. MPN method.
2. Radicals.
3. Single path method.
The Equipment used to conduct Bacterial test at Water treatment Plant Nigdi was Single path kit for the 3rd method.
The aim of conducting the bacterial tests determine the Pathogenic bacteria's present in the sample so as to determine the amount of Chlorine dosage for bacterial degradation of water is designed.
Residual Chlorine Test.
The Residual Chlorine test is to determine the quantity of residual chlorine in the sample to preserve the quality of water supplied
Orthotolidine Test
In this test, 10 ml of chlorinated sample of water is taken after the required contact period, in a glass tube. To this 0.1 ml of orthotolidine solution is added. The color formed is observed after 5 minutes. The formation of yellow color normally indicates the presence of chlorine (either combined or free) in the water. The more yellow the color, the greater, is the chlorine residual. The amount of residual chlorine can be ascertained by comparing the colour developed in the glass tube with the standard colors already kept in the laboratory. This test, is therefore, very simple and does not require much technique or time. Under normal conditions, a lemon yellow color is satisfactory for public water supply. The orthotolidine test will normally gives the total residual chlorine present in water. However, it may be adjusted so as to give separately the quantities of free residual as well as combined residual of chlorine.
The free residual chlorine forms the yellow color during the first 5 seconds of the addition of orthotolidine, while the combined residual chlorine goes on forming the colour for about 5 minutes. Hence, the colour after 5 seconds will give the quantity of free residual chlorine, and the colour after 5 minutes will give the free and combined chlorine. The difference in value between the two values is the combined chlorine.
The orthotolidine test, however, is not accurate, because the impurities such as iron, manganese, nitrate etc., are likely to cause a false yellow colour, and indicating wrong and increased chlorine residual.
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| Cascaded Areator |
Aeriation unit
This is the starting unit of the water treatment procedure. Once the sample is tested the water coming from Ravet is pumped through this cascaded aerator. The purpose of having an aerator is to improve the amount of dissolved oxygen in the water and to release the other gases, also a few metals get oxidized during this procedure.
This procedure is important to make the water odorless as there is transmission of gases during this process. Water is allowed to freely fall on the cascaded steps and which each fall the water particles are exposed to the fresh air from the surrounding. This process promotes the exchange of gases like CO2, etc.
Clariflocculator
This is the second unit placed after Aeration unit.
flocculation is the central portion of the tank which consist of a mixer that is rotating at a low speed to facilitate the collision of the charged particles and their conversion into sludge which are settled down.
The water contains negatively charged particles whose amount is been analyzed and the same quantity of positive charged particles are supplied in so as the positive charged particles and negative charged particles gets attracted to each other and as the size of this particles increases they settled down in Sedimentation zone.
Sedimentation zone is the outer zone which is curved in nature and there is depression at the center.
The water is having a detention time of 0.5hr in the flocculation and 3hr in the sedimentation zone.
Chlorination Unit
Chlorine is used to destroy disease-causing organisms in water, an essential step in delivering safe
drinking water and protecting public health. Chlorine is by far the most commonly used disinfectant
in all regions of the world. Where widely adopted, chlorine has helped to virtually eliminate water-
borne diseases such as cholera, typhoid and dysentery. Chlorine also eliminates slime bacteria, molds
and algae that commonly grow in water supply reservoirs, on the walls of water mains and in storage
tanks. Only chlorine-based disinfectants leave a beneficial “residual” level that remains in treated
water, helping to protect it during distribution and storage.
Chlorine is a versatile and low-cost disinfectant appropriate for any size water system, whether it
serves a remote rural village or a large modern city. Where piped water supplies are not available,
chlorine can also be used for treating water in individual households. Specially-packaged chlorine
bleach can disinfect household water.
However there are other disinfectants too like UV, Ozone, Boiling, Potassium Permaganet. But the main objective of adding disinfectant to water is to provide safe drinking water till it reach large span consumers. Therefore chlorine is the best option which satisfy all the requirements.
Storage unit and pumping
In this unit the treated water is allowed to stay for sometime and them pumped to the distribution network by using mechanically operated pumps. The plant is powered by electricity from the MSEDCL
Filtration unit
This is a big unit comprising of a number of filter pits. The filter used in this tank was rapid sand filter in which the water is allowed to pass through the sand and it gets filtered as it passes down under the action of gravity. The sand is having small pores which allows water to pass through it preventing the suspended matter.
During filtration the water enters the filter through upper valve, moves down towards the filter bed, flows through the filter bed, passes the underdrainage system (filter bottom)and flows out through lower valve. The unit used to measure filtration rate is actually the approach velocity, which is the inflow rate (m^3/h) divided by the filtration area (m^2).
When, after a period of operation, the filter rate controller is fully opened, further
clogging of the filter bed cannot be further compensated and the filtration rate will fall.
The filter is then taken out of service for backwashing.
For this, the upper and lower valves closed, and upper back wash valve is opened to drain the remaining raw water out of the filter. A few minutes later lower backwash valve is opened to admit the wash water.
The backwash rate should be high enough to expand the filter bed by about 20% so that the filter grains can be scoured, and the accumulated deposits carried away with the wash water. The wash water is collected in the wash water troughs from where it drains to waste. When the backwashing is completed, backwash valves are closed and upper valve is re-opened, admitting raw water to begin a new filter run.
Use of Supervisory Control and Data acquisition (SCADA)
This plant employs one of the most advanced techniques for its daily operations. SCADA is a cloud based tool that is developed for the plant and helps the plant management to monitor and control the daily activities at the plant in the supply network.
Diagram Explaination
Level 0 contains the field devices such as flow and temperature sensors, and final control elements, such as control valves.
Level 1 contains the industrialised input/output (I/O) modules, and their associated distributed electronic processors.
Level 2 contains the supervisory computers, which collate information from processor nodes on the system, and provide the operator control screens.
Level 3 is the production control level, which does not directly control the process, but is concerned with monitoring production and targets.
Level 4 is the production scheduling level.
I would like to thank Civil Department of Trinity College of Engineering for conducting the visit to Water Treatment Plant Nigadi. Especially Meenakshi Khapre mam & Harshal sir for conducting the visit.
I would also like to thank
Mr. Praveen Ladkat Executive Engineer, PCMC for allowing us to visit the plant and to grab the pratical experience.
