INTRODUCTION
Hardness is an indication of the amount of calcium and magnesium in the water. Hard water is due to the presence of calcium and magnesium and is formed when water passes through or over limestone or chalk areas and calcium and magnesium ions dissolve into the water. Hardness is given in terms of the equivalent quantity of calcium carbonate (CaCO3) in milligrams per liter (mg/L) or parts per million (PPM).Calcium and Magnesium are essential elements for plant growth that are reported in parts of element per million parts water (ppm) on a weight basis. Calcium in the range of 40 – 100 ppm, and magnesium in the range of 30 – 50 ppm are considered desirable for irrigation water.
Total Dissolved Solids (TDS) is a measure of the dissolved combined content of all inorganic and organic substances present in a liquid in Atomic, ionized or micro-granular (colloidal sol) suspended form. Total dissolved solids are normally discussed only for freshwater systems, as salinity includes some of the ions constituting the definition of TDS. The principal application of TDS is in the study of water quality for streams, rivers and lakes, although TDS is not generally considered a primary pollutant (e.g. it is not deemed to be associated with health effects) it is used as an indication of aesthetic characteristics of drinking water and as an aggregate indicator of the presence of a broad array of chemical contaminants.
Lime softening, also known as Clark’s process, is a type of water treatment used for water softening which uses the addition of limewater (calcium hydroxide) to remove hardness(calcium and magnesium) ions by precipitation.
Lime softening was first used in 1841 to treat Thames River water. The process expanded in use as the bactericidal effect of the process was discovered. Lime softening greatly expanded in use during the early 1900s as industrial water use expanded. Lime softening provides soft water that can, in some cases, be used more effectively for heat transfer and various other industrial uses.
As lime in the form of limewater is added to raw water, the pH is raised and the equilibrium of carbonate species in the water is shifted. Dissolved carbon dioxide (CO2) is changed into bicarbonate and then carbonate. This action causes calcium carbonate to precipitate due to exceeding the solubility product. Additionally, magnesium can be precipitated as magnesium hydroxide in a double displacement reaction.
In the process both the calcium (and to an extent magnesium) in the raw water as well as the calcium added with the lime are precipitated. This is in contrast to ion exchange softening where sodium is exchanged for calcium and magnesium ions. In lime softening, there is a substantial reduction in total dissolved solids (TDS) whereas in ion exchange softening, there is no significant change in the level of TDS .Lime softening can also be used to remove iron, manganese, radium and arsenic from water.
OBJECTIVE:
- To convert hard water into soft water of the Pabal village and make it drinkable.
- To reduce the clogging problem in drip irrigation system.
PROBLEM DEFINITION
In the Pabal village the TDS of the drinking water is about 450 ppm which is high than WHO guidelines. Abnormally high TDS in water is a problem, drinking of which will cause health issues. It becomes harmful only when it exceeds certain acceptable limit which was seen in that case. In fact, the TDS concentration is more of an aesthetic hazard as compared to a health hazard because it is secondary drinking water standard.
High concentration of TDS can cause water to become corrosive, salty or develop a brackish taste. This result in formation of scales in pipes, appliances like water heater and washing machines thereby reduce their efficiency. Because of all of this we need to reduce the level of TDS from water. IDEA
There are a number of methods to remove the hardness present in water. One those methods are being followed; the hard water gets converted to soft water. Some of the methods to remove hardness from water are,
- Chemical process of boiling hard water.
- Adding slaked lime (Clark’s Process).
- Adding washing soda.
- Reverse osmosis.
- Calgon process.
- Ion exchange process using ion exchange resins.
In this among reverse osmosis is one of common procedure which were used for reducing TDS level in water but it is very costly. The Lime Softening is one of the cheapest methods to reduce the TDS of water and make it drinkable.
METHODOLOGY
Effect of Hardness in Water:
- The health effects of hard water are mainly due to the effects of the salts dissolved in it, primarily calcium and magnesium.
- It will cause build up of lime scale in pipes causing reduced flow and cause pipes to need to be replaced.
- Calcium salts, particularly calcium carbonates, precipitate out as a white film or plating in the system which was seen in the boiler.
Methodology Followed:
- Decided to vary the sample size for experimentation starting from 1 liter to 100 liters.
- Variation of amount of calcium hydroxide was 2nd parameter in experimental plan
Two different methods manual and automated were tried. - The various parameters such as TDS, salt & pH electric conductivity were checked to verify effectiveness of process applied.
- The precipitate formed was removed by either filtration or sedimentation.
- Calcium oxide was tried in order to get cost beefiness.
Some Chemical Reactions:
The reactions involved in lime treatment process are as follows:
CaCO3 —-Heat——-> CaO + CO2
CaO + H2O ———> Ca(OH)2
CO2 + Ca(OH)2 ———> CaCO3 + 2H2O
Ca(HCO3)2 + Ca(OH)2 ———-> 2CaCO3 + 2H2O
Observations:
1] Firstly I take the various sample of water from vigyan ashram and measure its different parameters such as TDS, Salt, pH and Electrical Conductivity are as follows:
| Water Samples | Salt (ppm) | pH (Nagarjun) | TDS (ppm) | EC (MicroSimens) |
| Filter water from kitchen | 333 | 7.45 | 452 | 636 |
| Tap water from kitchen | 336 | 7.96 | 452 | 636 |
| Tap water from hostel | 269 | 8.26 | 365 | 514 |
| Dreamhouse | 272 | 8.16 | 377 | 523 |
2] LOD of calcium hydroxide is calculated observation and result are as follows:
Weight of Calcium hyroxide = 1.002 gm
Weight of petridish = 11.636 gm
For calculation of LOD wt. of samples are taken for different timing until wt. reduction stops.
| Wt. of petridish + Wt. of Ca(OH)2 | Timing | Wt. of Ca(OH)2 |
| 12.636 | 11.46 am | 1.002 |
| 12.042 | 12.16 pm | 0.406 |
| 12.031 | 12.31 pm | 0.395 |
| 12.028 | 12.36 pm | 0.392 |
| 12.030 | 12.41 pm | 0.394 |
From this we can conclude that in 1 gm of Ca(OH)2 their is 60% water and 40% solid matter.
Then I decided that for carrying out project the water with high TDS are use which are filter water from kitchen.
Then I decided that for carrying out project the water with high TDS are use which are filter water from kitchen.
SOME CHEMICAL REACTIONS :
The reactions involved in lime treatment process are as follows:
CaCO3 —-Heat——-> CaO + CO2
CaO + H2O ———> Ca(OH)2
CO2 + Ca(OH)2 ———> CaCO3 + 2H2O
Ca(HCO3)2 + Ca(OH)2 ———-> 2CaCO3 + 2H2O
After adding 1 gm of Ca(OH)2 in 1 litre of water and shaking it properly on shaker for one night result are as follows:
| TDS | Salt | pH |
| 365 | 272 | 10 |
After adding 0.5 gm of Ca(OH)2 in 1 litre of water and shaking it properly on shaker for one night result are as follows:
| TDS | Salt | pH |
| 272 | 205 | 9 |
Below table giving information of the various amount of Ca(OH)2 adding in 1 litre of water sample by shaking and by stable water.
On 12/2/2019 at 4.30 pm Ca(OH)2 added in water and placed on shaker for the time period of 17 hrs i.e at 9.30 am in next morning. After that it keep stable for 7 hrs i.e at 4.30 pm on same day and following observations are obtain.
| Shaking | TDS | Salt | pH |
| 0.3 gm | 329 | 254 | 7 |
| 0.7 gm | 352 | 260 | 9 |
| 1 gm | 740 | 562 | 11 |
| Stable | |||
| 0.3 gm | 415 | 310 | 8 |
| 0.5 gm | 410 | 304 | 8 |
| 0.7 gm | 460 | 338 | 8 |
| 1 gm | 378 | 278 | 8 |
On 13/2/2019 0.5 gm Ca(OH)2 added in 1 litre of water and three samples are taken after 12 hr shaking and 7 hr stabling observation are as follows:
| TDS | Salt | pH |
| 8 to 9 | 271 | 200 |
| 8 | 264 | 195 |
| 8 | 264 | 196 |
Adding 5 gm of Ca(OH)2 in 10 liter of water on 17/2/2019.
At 11 am shaking approx 5 min and on same day 4.30 pm shaking approx 5 min the results obtain on 19/2/2019 at 9.30 pm are as follows :
| TDS | Salt | pH |
| 246 | 182 | 8 to 9 |
Adding 10 gm of Ca(OH)2 in 20 liter of water which are taken in bucket on 20/2/2019.
Mixing by pump for 5 min and TDS was found 300 ppm on 21/2/2019 at 10 am.
On 22/2/2019 again test of 20 litre water was taken with 10 gm of Ca(OH)2
In this scenario 200 ml of water was taken in 1 liter capacity of water and 10 gm of Ca(OH)2 added in it and mix it for 5 min by using pump, milky solution was formed and then it pour in 20 liter water sample and on same day at 8.30 pm result was check, TDS was found to be 208 ppm which was accepted.
After that I took 2 -3 stones of alum and deep it in that same water having TDS of 208 ppm for the 30 min and I was found that whitish layer on the upper layer of the water. I again measure its TDS and that was 430 ppm, which are same as before adding Ca(OH)2 in water.
On 5/3/2019 again test of 100 litre water was taken with 50 gm of Ca(OH)2.The TDS and Salt of that water sample was 340 ppm and 240 ppm respectively.
In this scenario 750 ml of water was taken in 1 liter capacity of water and 50 gm of Ca(OH)2 added in it and mix it for 5 min,milky solution was formed and then it pour in 100 liter water sample.The results obtain are as follows.
| Time | TDS | Salt |
| 5 pm | 540 | 415 |
| 6 pm | 565 | 414 |
| 7 pm | 565 | 415 |
| 8 pm | 545 | 422 |
| 10 pm | 555 | 406 |
| 12 pm | 540 | 410 |
| 11.30 am | 510 | 390 |
| 5.30 pm | 485 | 370 |
| 10 pm | 475 | 370 |
On 11/3/2019 at 11 am the TDS was found to be 250 pm of 100 liter sample of water took on 5/3/2019
On 12/3/2019 again test of 100 liter water was taken with 25 gm of Ca(OH)2.The TDS and Salt of that water sample was 233 ppm and 171 ppm respectively
In this case 750 ml of water was taken in 1 liter capacity of water and 25 gm of Ca(OH)2 added in it and mix it for 5 min,milky solution was formed and then it pour in 100 liter water sample. In this case for mixing of water pump is used. At starting for period of 5 min mixing of water is done and then after some time period is increasing.The results obtain are as follows.
| Time | Shaking period( minute) | TDS | Salt |
| 12.30 pm | 5 | 400 | 290 |
| 1.30 pm | 5 | 218 | 150 |
| 5.00 pm | 5 | 195 | 150 |
| 6.00 pm | 5 | 200 | 145 |
| 7.00 pm | 5 | 185 | 138 |
| 8.00 pm | 20 | 186 | 137 |
| 9.00 pm | 20 | 197 | 137 |
| 10.00 pm | 30 | ||
| 9.00 am (13/3/2019) | 30 | 163 | 124 |
| 1.00 pm | 30 | 156 | 114 |
| 4.00 pm | 30 | 145 | 113 |
| 9.00 am (14/3/2019) | 134 | 134 |
On 21/3/2019 again test of 100 liter water was taken with 75 gm of Ca(OH)2.The TDS and Salt of that water sample before adding Ca(OH)2 was 660 ppm and 500 ppm respectively.Here two pumps was used for mixing. At 21.30 pm the test was start with 30 min of shaking time.At 22.30 pm TDS and Salt was found to be 526 ppm and 388 pm respectively. After that shaking time is increases that is 45 min. On 22/3/2019 at 9.30 am the TDS and Salt Was found to be 512 ppm and 384 ppm respectively. At 9.30 am shaking start that will end at 10.30 am. At 1.00 pm the TDS and Salt contains was check and found to be 507 ppm and 375 ppm respectively. On 23/3/2019 without doing any thing at 10.00 am TDS and Salt was found to be 460 pm and 360 pm respectively.
On 26/3/2019 test of 50 liter water was taken with 40 gm of Ca(OH)2.The TDS and Salt of that water sample before adding Ca(OH)2 was 754 ppm and 560 ppm respectively. Here also at starting two umps was used. At 10.30 am the Ca(OH)2 added in water sample. At 11.20 am to the 12.20 pm shaking was done and on 1.00 pm TDS and Salt was found to be 585 ppm and 440 ppm respectively. Then after that up to 1.30 pm shaking was done. At 3.30 pm TDS and Salt was found to be 570 ppm and 435 ppm respectively. At 17.30 pm again mixing was start but here three pumps are used that will up to 19.00 pm. At 21.00 pm TDS and Salt was found to be 565 ppm and 430 ppm respectively. At 21.00 pm again shaking was start and end at 22.00 pm. I observed that their is no change in TDS and Salt of water then I decided to add some amount of Ca(OH)2 in it.On 27/3/2019 at 10.00 am 25 gm Ca(OH)2 added in that water and shaking started and ended at 11.30 am. Here I found that their is increase in values of TDS and Salt.
On 29/3/2019 I check TDS of water after filtration through Whatman filter paper and it was found to be same as before that is 500 ppm.
On 31/3/2019 again test of 100 liter water was taken with 50 gm of Ca(OH)2.The TDS and Salt of that water sample before adding Ca(OH)2 was 467 ppm and 346 ppm respectively. At 2.00 pm shaking was start by using two pumps and ended at 3.00 pm. At 4.30 pm TDS and salt was found to be 273 ppm and 201 ppm respectively. At 4.30 pm again shaking was start and ended at 6.30 pm but their is no change in TDS and Salt. On 1/4/2019 at 5.00 pm 10 gm Ca(OH)2 added in same water and shaked up to 6.30 pm but their is no change in TDS ans Salt.
On 07/4/2019 again test of 1 liter water was taken with 0.16 gm of CaO.The TDS and Salt of that water sample before adding Ca(OH)2 was 467 ppm and 346 ppm respectively. Shaking it properly on shaker for one night.After that TDS and Salt are found to be 270 and 220 respectively.
SUMMARY AND CONCLUSIONS
SUMMARY
TDS is refer to "Total Dissolved Salts" and it comprises of inorganic as well as organic salt. The principal constituents that comprise TDS are calcium, magnesium, potassium, sodium, bicarbonate, sulphates, chlorides and nitrate ions. In this among calcium is in major quantity.
According to the Bureau of Indian Standards (BIS), the upper level of TDS level in water is 500mg/liter (500 ppm); however, TDS level in the range of 300 ppm is considered excellent per WHO Guidelines. Lime softening is one of the easy and cheapest method than the Reverse Osmosis which we can use to reduce the TDS of water.
In this project, to find out actual amount of calcium hydroxide or calcium oxide need to add in high TDS water and make it soft, is calculated by taking various samples. A different trial was done on number of water samples in small as well as large quantity. For the proper mixing of water, pumps are use but patterns are form in water and mixing was not properly done. To solve this problem two pumps was used which kept opposite to each other gave opposite flows, in this scenario there is uniform mixing of water. In this way the TDS of water is successfully reduced and make it soft. CONCLUSIONS
It was conclude that in case of small quantity of water such as 1 liter, 10 liter and 20 liter manually mixing is sufficient to reduce TDS level in water but as we go up to 100 liter water there was no effect of manually mixing of water. In this scenario mixing by using pump is needed to reduce the level of TDS. Instead of paste of Ca(OH)2 if we made milky solution of it before poured in the water then TDS level decrease rapidly.
If we used one pump for the mixing of water then time required to reduce TDS was more as compare to when we used two pumps. In case of the one pump patterns was formed during mixing of water and which will cause ineffective mixing. If we kept two pumps having opposite flow to each other then mixing was properly done. If we mix water at starting up to 1 hr. then instead of different time intervals like 10 min the TDS reduces rapidly.
Instead of Ca(OH)2 we can used CaO because quantity requirement of it for one liter was less as compared to Ca(OH)2. As solid matter in case of CaO was 100 % and in case of Ca(OH)2 it was 40%. For one liter of water amount of CaO required was 0.16 g and Ca(OH)2 was 0.5 g. Price of Ca(OH)2 in market was Rs 40 / kg so 2 paise is required for one liter .Price of CaO in market was Rs 20 / kg so 0.32 paise is required for one liter. From this we seen that CaO was cost effective than Ca(OH)2 gave same effect as Ca(OH)2.
CALCULATIONS :
How much amount of calcium hydroxide or calcium oxide needed to add in high TDS water to reduced its TDS ?
Firstly we need to know molecular weight of calcium bicarbonate and calcium hydroxide or calcium oxide. They are as follows:
Molecular weight of calcium = 40
Molecular weight of oxygen = 16
Molecular weight of hydrogen = 1
Molecular weight of carbon = 12
therefore,
molecular weight of calcium hydroxide i.e. Ca(OH)2 = 74
molecular weight of calcium bicarbonate i.e. Ca(HCO3)2 = 163
molecular weight of calcium oxide i.e. CaO = 56
If the TDS of water is 467 ppm then,
Ca(OH)2 Ca(HCO3)2
74 163
? 467
then by using cross multiplication, i.e. 74 X 467 = 163 X ?
? = 213.3
In 100 gm of Ca(OH)2 there is 60 % water and 40 % solid material
therefore, 213.3 / 0.4 = 578.25
From this we conclude that approx 0.5 gm Ca(OH)2 need to add in 1 liter of water sample having TDS 467 ppm .
By the same way we can do calculation for the calcium oxide but in that case there is 100 % solid material.
