Determination of permanent hardness of water

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The available methods for determination of permanent hardness of water are O’Heners method, EDTA method and Soap titration method. Initially we have to know; what is hardness? –Hardness is due to presence of bicarbonate, sulphates, chlorides and nitrates of calcium and magnesium. It is expressed in ppm (part per million) as calcium carbonate. There are two types of hardness:

  1. Temporary hardness
  2. Permanent hardness

Bicarbonate of calcium and magnesium is responsible for temporary hardness whereas sulphates, chlorides and nitrates of calcium and magnesium are responsible for permanent hardness. The salt of Na, K and NH4- do not reacts with soap; hence the presence of these salt do not creates hardness of water.

Determination of permanent hardness of water by O’hehners method
Theory: At first, the water is boiled to remove temporary hardness. When the water is boiled then, the Bicarbonate of calcium and magnesium are change into non-dissolve carbonate.
Ca(HCO3)2 → CaCO3 + H2O + CO2
Mg(HCO3)2 → MgCO3 + H2O + CO2

After that, added Na2CO3 solution. This chemical reacts with dissolved calcium and magnesium salts and converts them into insoluble carbonate.
CaCl2 + Na2CO3 → CaCO3 + 2NaCl
MgCl2 + Na2CO3 → MgCO3 + 2NaCl
The residue Na2CO3 is then determined by titrating against a standard acid. The reduction in the amount of soda added is equivalent to permanent hardness.
Burette for determination of permanent hardness of water

BrandTech 4761161 Borosilicate Glass 50mL Titrette Bottletop Burette, with Titration and Recirculation Valve

Apparatus

  • Beaker
  • Weighing Balance
  • Burette with stand
  • Pipette
  • Conical flask
  • Hot plate

Chemicals

  • N/10 Sodium carbonate solution
  • N/10 HCl acid

Indicator

  • Methyl orange

Procedure:

  1. Take 50ml of water sample into a 500ml beaker and boil for 15 min.
  2. Add 50ml of N/10 Na2CO3 solution into it with stare.
  3. Separate the precipitate with filter paper and wash the precipitate 3-4 times with a little distilled water. Take the filtrate and cool the solution to room temperature. Then, take it into a 250ml volumetric flask and dilute it up to the mark with distilled water.
  4. Take 50ml in a conical flask from volumetric flask with a pipette and titrate it against N/10 HCl using Methyl orange indicator. At the end point the color of the solution turns into reddish yellow.
  5. Take the burette reading. Let, it is v ml.
  6. For blank titration, take 50ml of N/10 Na2CO3 solution into a 250ml volumetric flask and dilute it up to the mark with distilled water. Take 50ml in a conical flask from it with a pipette and titrate it as same process against N/10 HCl using Methyl orange indicator.
  7. Determine the consumed N/10 Na2CO3 solution from the difference of this two reading.

1ml 0.1N HCl ≡ 0.005005g CaCO3

Calculation:
Volume of N/50 Na2CO3 used for removing permanent hardness in 50ml of water sample
=50 -43.5 = 6.5 ml
Normality of water due to permanent hardness:
N1V1 = N2V2
N1 × 50 = N/50 × (6.5)
N1 = 6.5 /50 × 50 = 0.0026
Amount/Lit = N × Eq.wt
= 0.0026 × 50 = 0.13 gm/lit
Mg/lit = 0.13 gm/lit × 1000mg/1gm = 130 mg/lit
As,
1mg/lit = 1ppm
Permanent hardness = 130 ppm
Result: the given sample of water contains 130ppm permanent hardness.

Determination of permanent hardness of water by EDTA method:
The temporary hardness can be removed by boiling. The permanent hardness is determined first by precipitating the bicarbonates of Ca2+ and Mg2+ by heating and filtering off.

Procedure:

  1. Take 100ml of water sample into a beaker and boil gently for 15-20 minutes.
  2. Cool the solution then filter and wash the precipitate several times. Collect both the filtrate into a 250ml volumetric flask and level upto the mark with distilled water. Then, shake well.
  3. Take 50ml of solution from volumetric flask with pipette and place into a conical flask.
  4. Add 1-5ml NH4OH/NH4Cl buffer solution. It increases the pH level and should be 10. Check the pH with standardize pH meter.
  5. Add 2-3 drops 0.1M Mg-EDTA solution and 3-4 drops Eriochrome Black T indicator. Then, shake well and the color becomes wine red.
  6. Fill up the burette with standardized 0.01M EDTA solution. Record the initial burette reading and titrate the water sample with this standard solution.
  7. At the end point the color of the solution turns into blue from wine red. Titrate carefully near the end point.
  8. Take the final burette reading. Let, it is V1 ml.
  9. Repeat the titration process at least three times.
  10. You can run a blank titration for more accurate result. Let, it is V2 ml.

Water sample Vs EDTA

Serial No Volume of water sample (ml) Burette readings (ml) Volume of EDTA solution (ml)
Initial Final
1
2
3

Permanent hardness calculation:
In case of blank titration, the calculate volume of EDTA required by sample water, V = (V1-V2)ml
The permanent hardness can be calculated by using the following formula.
1ml 0.01M EDTA ≡ 1.00mg CaCO3
∴ Vml 0.01M EDTA = V ᵡ 1.00mg CaCO3

The 100ml sample water is dilute into a 250ml volumetric flask
Hence, 50ml dilute water = 100 ᵡ 50/250 ml = 20ml sample water

Now, 20ml of sample water ≡ V ᵡ 1.00mg CaCO3
∴ 1000ml of sample water ≡ V ᵡ 1.00mg ᵡ 1000/20 CaCO3
≡ V ᵡ 1.00 ᵡ 50 ppm CaCO3

Result
Amount of permanent hardness present in the given water sample = ppm

Determination of total hardness of water

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To determine the Total Hardness of Water, EDTA is the easiest method. Reason, EDTA reacts with all metal without alkali metal and the proportion is 1:1. The main cause of water hardness is dissolved salts of calcium and magnesium. Moreover the other ions like Strontium, Iron, Barium and Manganese also contribute of water hardness. Traditional it is measured by the amount of soap that is required to produce leather. The EDTA method is more accurate and more rapid.

Mn+ + Na2H2EDTA → [M-EDTA](4-n)- + 2Na+ + 2H+

There are two types of hardness: (1) temporary hardness and (2) permanent hardness.
The temporary hardness is due to the presence of Ca(HCO3) or Mg(HCO3) or both. On the other hand, permanent hardness is due to the presence of sulphates, chlorides and nitrates of calcium and magnesium (as like CaCl2, CaSO4, MgCl2 and MgSO4) in water.

To determine the Total Hardness of Water with EDTA method initially an inorganic acid is added to convert temporary hardness into permanent hardness.
Ca(HCO3)2 + 2HCl → CaCl2 + H2O + 2CO2

At pH 10, EDTA forms colorless, water soluble stable complexes with calcium and magnesium ions. When the indicator Erichrome black T dye is added into the hard water, then the indicator forms unstable complex with calcium and magnesium ions and the solution turn into wine red. If there is no hardness the color becomes blue which is original color of indicator. Now, when this solution is titrated against EDTA, then the calcium and magnesium ions started to form a stable metal-EDTA complex. After all the free calcium and magnesium ions are consumed, the EBT is replaced by EDTA from the unstable complex and liberates the free Eriochrome Black-T. Then the water color change from wine red to blue that indicates the end point.

Apparatus:

  • Conical Flask
  • Funnel
  • Burette
  • Sand
  • Beaker
  • Pipette
  • Graduated cylinder
  • Hot plate stirrer
  • Wash bottle
  • Spatula

Chemicals:

  • Buffer solution
  • Inhibitor
  • Eriochrome black T indicator (blue color)
  • NaOH
  • Standard EDTA Solution 0.01M
  • Magnesium sulphate

Procedure:

  1. Take 50ml of water sample into a conical flask.
  2. Then add 2-3ml 1:1 HCl and boil for 2 min.
  3. Cool the solution and neutralized with the dil NaOH.
  4. Add 1-5ml NH4OH/NH4Cl buffer solution. The pH should be 10. Check the pH with standardize pH meter. (you can also add an Inhibitor, after the buffer solution)
  5. Add 2-3 drops 0.1M Mg-EDTA solution and 3-4 drops Eriochrome Black T indicator. Then, shake well and the color becomes wine red.
  6. Fill the burette with standardized 0.01M EDTA solution. Record the initial burette reading and titrate the water sample with this standard solution.
  7. At the end point the color of the solution turns into blue from wine red. Titrate carefully near the endpoint.
  8. Take the final burette reading. Let, it is V1 ml.
  9. You can run a blank titration for more accurate result. Let, it is V2 ml.

Total hardness calculation:

Serial No Volume of water sample (ml) Burette readings (ml) Volume of EDTA solution (ml)
Initial Final
1
2
3

In case of blank titration, the calculate volume of EDTA required by sample water, V = (V1-V2)ml
The total hardness (temporary + permanent) can be calculated by using the following formula.

1ml 0.01M EDTA ≡ 0.001001g CaCO3
∴ Vml 0.01M EDTA = V ᵡ 0.001001g CaCO3

Now, 50ml of water sample ≡ V ᵡ 1.001mg CaCO3
∴ 1000ml of water sample ≡ V ᵡ 1.001mg ᵡ 1000/50 CaCO3
≡ V ᵡ 1.001 ᵡ 20 ppm CaCO3

Determination of total amount of cations in water

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Different types of metal salt are dissolved in natural, industrial or any other water. Therefore, the water contains different type of cations. The cations in water can be determined by using cation exchange resin. They are electron donors and consequent positively charged. Some common cations are Na+, K+, Mg2+, Ca2+, Fe2+ or Fe3+, Mn2+, Al3+. On the other hand, cation exchange resin contains negatively charged group. The most common group is sulfonate group, -SO3–. If the water passes through a cation exchange resin in hydrogen form then the resin except the metal ion from the water and leave equivalent hydrogen ion. In other words leave an equivalent amount of acid. It is just a substitution reaction.

M+ + R-H → R-M + H+

This total amount of acid can be determined by titration with NaOH solution.
Determination of total amount of cations in water

Regeneration
Initially the cation exchanger resin may be regenerated to introduce hydrogen ion into the resin. To regenerate a column, you have to pass HCl through the cation exchange resin. Then the following reaction occurs which is revise process of previous reaction.
R-M + HCl → R-H + MCl
Additional acid and metal salt are removed from resin by passing cation free water (distilled water).

Apparatus Required:

  • Cation exchange resin column
  • 250ml volumetric flasks
  • 20ml, 25ml pipette
  • Beakers
  • Graduated cylinder
  • pH meter and pH electrode
  • Wash bottle

Chemicals:

  • 2N HCl
  • Methyl orange indicator
  • AgNO3 solution
  • distilled water
  • litmus paper

Procedure:

  1. Took a long glass tube (as like burette) with stopcock and make a 25-30 ml long column by keeping some glass wool at the end point of the glass tube.
  2. Pass 250 ml 2N HCl through the column so that 3-4 ml solution is passing per minutes.
  3. Then rinse the column with distilled water until the elution becomes neutral (no acidity or pH is greater than 5.8). You can cheek it by the methyl orange or pH meter. Moreover, you can also use AgNO3 solution to check for the presence of Cl– ion; it indicates the presence of HCl. It should be noticed that always some water exist on the column.
  4. Take about 40 ml sample water with the pipette and pass 3-4 ml water per minutes through the column. Exit the elution and mark the upper level of the resin column.
  5. Now take 20ml sample water, then pass it through the column at same rate and collect the elution in a conical flask. At the moment, it should be noticed that the upper level of the resin column remain equal.
  6. Collect two more at same process.
  7. This resulting H+ (the collected water) can be determined by titration with NaOH using methyl orange indicator. Then calculated the original concentration of cations in water using the formula.

You can direct use the sample water. It may require diluted the water in case of higher concentration of cations. To dilute take 25ml sample water in a 250ml volumetric flask and fill up to the mark with distilled water.

Calculation
Generally, the total amount of cation in water is expressed as equivalent mineral acidity (EMA). It is the amount of equivalent calcium carbonate of per liter solution. If the volume of sample water is V ml, normality of the NaOH is B and the volume of the NaOH is A ml, then
EMA = (AᵡBᵡ50ᵡ1000)/V

Problems of iron and copper in pool water

Tasrik 3 Comments

The presence of metal such as manganese, iron and copper in pool water can lead to discolor the water when chlorine or any other oxidizer is added. It does not affect on the clarity of the water too much. Magnesium and manganese can also increase the hardness of the water. The metal may enter in pool water through by chemicals, pool equipment and plumbing or poles, toys, and tools that are fall into the water. Moreover, fresh water is also an important source of metal in pool water. Higher level of metals can create stains on swimming pool.

Iron in pool water
Iron in pool water

Copper in pool water

Copper in pool water can be introducing in many ways. It can enter as one of the natural element through your local water source. Cheaper algaecides are another source. Moreover, it is also used in many equipment and plumbing of swimming pools. Copper may be dissolved into the pool water, if the water is imbalances at any how such as misuse of chemicals, lower pH, total alkalinity or calcium hardness.

Copper in pool water
Copper in pool water

High copper in pool water

Higher copper is not allowed for swimming pool. The maximum level for copper is 1.00 ppm, but it is better to keep below 0.2 ppm or zero. If the copper level is high, it can lead to green hair, fingernails, pool walls and water, as well as pool staining. Lower concentration of copper with proper direction usually does not cause a problem. It can be helpful for pool water. For example copper sulfate or chelated copper is useful in controlling common pool algae. Moreover, it will help to proper sanitation by reducing the consumption of chlorine. It is recommended not to use copper sulfate; it is not suitable for swimming pool. It is suitable for surface waters such as reservoirs, lakes and ponds algaecide. Instead of it you may use other algaecides.

Remove copper from pool water

To remove copper from pool water the following method can be applied:

  • Chelating agents: Copper staining can be protected by using chelating agents. This agents formation a bond with the metal ions and prevents them from oxidized with the chlorine and other oxidizers.
  • Using metal-trap filter: physically, copper and other heavy metal can remove by using metal-trap filter. Recirculation the pool water by submersible pump, through a metal-trap filter will reduce the possibility of staining and discoloration.
  • You can replace a portion of pool water with fresh water, but it would not a wise decision, it can imbalances the pool water.
copper in pool water removal

Complete Stain Removal Bundle Filter Size

Iron in pool water

Higher Iron is not allowed for swimming pool; it may alter the original pool water color into brown or green color. The maximum acceptable level of iron in pool water is 0.3ppm although iron-free water is wanted. High concentrations of iron can damage or discoloration of the pool surface. As like copper, corrosive water can lead to introducing iron in pool water. The water tends to be corrosive, if the pool water is lower pH, lower total alkalinity or lower calcium hardness level. As a result the “rusting” of metal parts of pool’s pump, pipe-network, heater, or other metal accessories can be dissolved into water.

You can remove iron from pool water as same process of copper removing.

copper in pool water removal

Pool Mate 1-2550 Mineral Out and Stain Remover for Swimming Pools, 1-Quart

Manganese in pool water

When chlorine or any other oxidizer is used in Manganese containing pool water then it discolor and the water turn into deep purple, blue or black. The water generally does not lose its clarity or become cloudy. It is difficult to identify. Super chlorination completely oxidized the manganese and allows precipitating to the bottom of the pool. It can stains on pool plaster and tile grouting.

Testing of iron or copper in pool water

You can know what metal along with quantity of the metal by testing the pool water. Primarily you can make a visual diagnosis with the help of water color. If the water is green then it may be copper whereas brown color indicates iron. Since the iron or copper in pool water does not change dramatically, hence it is enough to test once per month. It is recommended to test immediately if rapidly changes the color (as we mix various copper containing chemicals). You can test it, any time of the day.

Testing the copper and iron in pool water is very easy process with test strip kits. Just dip the test strip into the sample water for 5-60 seconds. Then remove the test strip from the water and shake once for removing extra water from the strip. Wait for while and compare the color on the test strip with the color chart that comes with the kit. This is the general instruction but you must read the package instructions and test the water sample according to their guide lines. You can use following kits to test copper, iron or other metal in pool water

1. AquaChek 661455 Iron Test Strip

AquaChek 661455 Iron Test Strip Measures the Total Iron. This strip allows a fast and accurate way to test for metal contaminates that can cause staining and water discoloration in pool and spa water. It measures the total iron from 0 to 5 ppm. It contains 25 strips per bottle.

2. Industrial Test Systems 481348 Copper 3 in 1 Pool Check

The Industrial Test Systems 481348 Copper 3 in 1 Pool Check strip is used for testing Copper, Total Alkalinity, and pH. These three tests combined into one strip, testing is super easy and efficient. It Contains 50 test strips. You can measure the copper level up to 0 to 2 ppm. The strip is made in the USA. You can easily read the colors. It provides you more accurate result than traditional test strips. Copper test strips can monitor copper ionizing systems and copper sulfate pentahydrate additives.

3. LaMotte 2994 Insta-Test Iron and Copper Multi-Factor Test Strip Kit

The LaMotte 2994 Insta-Test Iron and Copper Multi-Factor Test Strip Kit is colored paper pads. It can measure the iron level from 0 to 5 ppm and copper level from 0 to 3 ppm. It contains 25 test strips. They are easy to use, give accurate results and are way less expensive than using an outside lab.

4. 16 in 1 Drinking Water Test Kit Strips

Med Lab Diagnostic’s 16 in 1 drinking water test kit can measure 16 pool water parameters including Copper, Iron, Mercury, Lead, and Aluminum. It contains 200 test strips in two separate sealed pouches. Each of the pouches has 100 strips; so the strips will have a longer shelf life. The shelf life of the strips is 2 years when they are sealed. Once they are opened, the strips are generally good for approximately 90 days. These water testing strips provide accurate results very quickly and easily for testing your pool water. They are made from biodegradable material so Safe for the environment. These strips come with a full color instruction guide which has information about each of the 16 parameter tested. Although the Med Lab Diagnostics is a USA company its product is manufactured in China.

Water Summit for clean drinking water in Minnesota

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Governor’s Mark Dayton called his first Water Summit at the Intercontinental Saint Paul Riverfront Hotel, to focus public attention on how to clean drinking water and other supplies. The summit is held on Saturday, dated 27.02.2016. More than 800 individuals, including water quality experts, members of the public, local leaders, farmers, legislators, regulators, the business community, and a wide variety of other stakeholders were gather to talk to the serious challenges facing Minnesota’s water supplies – in both rural and urban areas of the state. Dayton arranges the water summit because of several reports indicated that a lot of southwest Minnesota water is not safe and sound for drinking or recreation. Moreover, the Minnesota Pollution Control Agency reported that 60 percent of groundwater wells in the central sands area have high nitrate concentrations. This water is not a safe drinking water.

All through the day, the Summit participants discussed water-quality challenges and brainstormed potential solutions, so that water crisis of this state should not turn into as bad as Flint and Michigan.

In the mean time, a small group of people joined him at stage in the ballroom, holding banners that said, “Love water not oil”. They also criticize Dayton not to invite tribes in the summit and for supporting oil pipelines across sensitive lands and wet lands in northern Minnesota. Although he invited the tribe leaders to attend the summit but they did not send representatives. The protesters (Environmentalists and some tribal groups) left the place quietly when Dayton agrees to meet with them after his speech. The pipeline would runs across the Lake Superior and the Mississippi River that are the great freshwater sources in the world.

In water summit, they discussed different Breakout Session topics such as aquatic invasive species, challenges facing Minnesota’s iconic waters, ensuring the state is resilient to extreme weather, sustaining clean water supplies, water in the urban and built environment, water and wastewater infrastructure, water in the rural environment, living cover and investing in clean water.

Some of the points that are discussed or suggested:

  • In this state agricultural runoff is the significant factor that impact on water quality. Different nitrogen and phosphorous fertilizers are used in farmlands; these chemicals are washout and go to water bodies and polluted the water.
  • Simple change to farming practices can have a big strength on using less fertilizer, pesticides and herbicides.
  • It needs to improve communications with farmers and others Minnesotans.
  • The farmers are well known that what to do better than anybody else on their own farmlands to Minnesota’s water.
  • As the soils are different across Minnesota, hence, to prevent pollution from chemicals farmers should to need different solutions.
  • Safe drinking water and other supplies water efforts need to be balanced so that farmers and the environment both benefit.
  • Conservation practices can decrease runoff.
  • The governor plans to ask lawmakers for funds for communities, chiefly small ones in rural areas, to make safe drinking water.
  • Potential solutions discussed included keeping more green cover plants on farm fields and other lands for more of the year instead of leaving the soil vulnerable to erosion.
  • How can manage stormwater runoff best way in urban areas where rooftops and pavement speed polluted water to lakes and rivers?

Clean drinking water challenges could not be solved with one water summit, it should be discussed effectively in many water summits. The governor already decided to set aside an April week to highlight safe drinking water needs to Minnesotans.

What is the reason for bubbles in bottled water

Tasrik 2 Comments

What is the reason for bubbles in bottled water? – The main reason for bubbles in water bottle is dissolved gases. There are many reasons for dissolving gases in the water. The amount of gases dissolved in water depends on pressure, temperature, types of dissolved gas, chemical composition of the bottled water. Atmospheric gases such as oxygen, carbon di-oxide, nitrogen and other gases can dissolve in water.

Pressure
Pressure is the important parameter for dissolving gases into the water. When the pressure is higher, then more gases are dissolved into the water. On the other hand, in lower pressure, there is less ability to dissolved gases into the water. When pressure is comes down from higher to lower then the water release some gases as bubbles. Therefore we see the bobbles in bottled water. Tap or pipes water is one of the example of high pressure water.
bubbles in bottled water
Temperature
Temperature is another factor for more bubbles in bottled water. When the temperature is lower, then it is extended possible to dissolve more gases into the water. Conversely, in higher temperature, it is less possible to dissolved gases into the water. As a result when the cold water allow to warms at room temperature then some gases such as nitrogen, oxygen and carbon di-oxide come out of solution as tiny bubbles which we are found side of the bottled.

Tap water
Different chlorine-based chemicals are added in two the water to kill bacteria. As a result chlorine gas may introduce in to the tap water. Normally, water is under high pressure inside the pipes compare to outside the pipes. Therefore many gases as like nitrogen, carbon di-oxide, oxygen, chlorine can dissolve into the water. When the bottled is filled with this tap water then it resides in your bottle and come out of water while the pressure is released.

When a bottle is filling with tap water sometimes it may looks cloudy. Reason, tap water remains under a high pressure, when the pressure is released then tiny air bubbles come out of solution. Moreover, at first the “air” inside the empty bottle may dissolve in water due to dynamic high pressure but eventually they also come out as tiny gas bubbles. Hence we see the cloudy water. After a few seconds the cloudiness will be cleared as the gases goes into the air above.

Soda water or soft drinks
We know that the gases dissolved in water greatly in lower temperature and high pressure. This technique is applied in soda water or soft drinks. Carbonated water is one of the main sources for manufacturing soft drinks and soda water. Carbonated water is produced by dissolving carbon di-oxide in water at high pressure and lower temperature. When a bottle is filling with this, then some pressure is released and temperature is slowly increases. Consequently, the gas comes out of water as thousands of tiny bubbles. They tend to appear on the sides of the bottle because the bottles surfaces are porous (or rough spots). Immediately this bobbles disappear and exists as free gas in free spaces inside the bottles and rest carbon di-oxide gas are exist in soda or soft drinks as dissolved gas. So, normally, we cannot see the bobbles when we buy soda water from market. When we de-cap the bottles then we again see the bobbles in water bottle because the pressure is released. Sparkling water is usually bottled or canned like same process as soft drinks. These are the reason for bubbles in bottled water.

Total dissolved solids in pool water

Tasrik 2 Comments

Generally the total dissolved solids in pool water are always rising. TDS is the measure of the total amount of the soluble substances that are dissolved in the water. The including soluble substances are calcium, manganese, sodium, copper, iron, other trace metals, chlorides, sulfates, rubber ducks, swimmer waste, every bit of dissolved dust, pollen, total alkalinity, conditioner, and all chemical treatment. Usually, low TDS levels are present in soft water. It can be measured by TDS test meter.

Table of Contents:

Pool TDS factors

The total dissolved solids in pool water can be affected in many ways. All the chemicals that we are added to balance pool water are increased the TDS level such as chlorine, pH increaser or reducer, algaecide, alkalinity, water hardness increaser or reducer, shock, clarifiers etc. Pool TDS may introduce by swimmers with the help of sweat, perfume, deodorant, hairspray and others substances that are coming from their bodies. Evaporation can also increase the TDS level. Water is evaporated from the swimming pool as pure level by leaving behind the dissolved solids. To maintaining pool water level fresh water are added which is containing certain amount of TDS. Therefore, it increases the total dissolved solids. Moreover, all things such as dust, dirt, animal wastes that are carried by the wind or rain into the pool water also contribute to TDS level.

Pool TDS Level
According to EPA water standards the maximum acceptable level of distilled or pure water is 0 ppm and for drinking water is 500 ppm. There are various opinions about the maximum tolerable level of TDS for swimming pool water. By consideration all opinions the maximum acceptable level is 1,500-2000 ppm. Conversely the minimum acceptable level is 300 ppm. The TDS level is not main issue; the main subject is what type of the solids that are dissolved. Therefore some pool can operate without problems at higher ppm.

How to Test TDS
There are two methods to test the total dissolved solids in pool water. The most common and accurate method is TDS test meter. This method is working basis on conductivity. To maintain accuracy this device needs calibration. The other test method is TDS test strip method which is inexpensive and less accurate. It is very simple method; anyone can determine the pool TDS level with the help of color chart. It is suggested to test the TDS twice per month during summer months due to high evaporation rate. During others season, it is enough to test at least once per month. If you are facing with TDS problems you can test more frequently. There is no exact time of day to test it.
Total dissolved solids in pool water
HM Digital COM-100 Waterproof Combo Meter for EC, TDS and Temperature, 1-Pack

Problems of High TDS
High TDS can lead to many problems such as cloudy pool water, stains on tile and plaster, scaling, hard water, salt taste and trouble to keep chlorine level. In fact sometimes excess of TDS, have no influence without on clarity. Reason, all solids will not create problems. The problematic dissolved solids are nitrates, phosphates, sulfates, chlorides and ammonia whereas calcium and some other salt are actually good TDS.

If the bad TDS level increases then it can decrease the effectiveness of chlorine. Moreover, it can irritate the skin and eye of swimmers. If the total dissolved solids in pool water is for higher levels of phosphates and nitrates then it can consume more chlorine and supply nutrients to algae. Therefore it will be allowing algae to bloom simply.

At higher pool TDS, sometimes; the pool water may detect an unpleasant salty taste. Reason, we use many sodium containing chemicals for pool maintenance such as sodium carbonate, sodium bicarbonate, sodium hypochlorite, sodium bisulfate. Due to increasing conductivity, at higher TDS level the metal corrosion of pool equipment may occur.

How to Fix TDS Problems in swimming Pool
There is no significant product to reduce the total dissolved solids in pool water. The most common and easiest solution is to drain a portion of pool water and fill up it with the fresh water. How amount of water should to be drain, it depends on the pool TDS level. It may be partially or totally. Always you have to concern about the fresh water TDS level. Moreover it will not affect significantly on your pool water balance. In one word, it will not affect the pH, alkalinity, chlorine level, hardness etc. A regular backwash will help you to prevent from raising the pool TDS too much. Although the common pool filters do not remove the dissolve materials.


Determination of chloride in water by mohr method

Tasrik 9 Comments

Mohr method is one of the significant methods for determination of chloride in water. It is also known as Argentometric method. Chloride ion is a negatively charged ion. This method is appropriate for neutral or slightly alkaline water. Water sample is titrating against standard AgNO3 solution by using potassium chromate indicator. It is a precipitation titration method.

Table of Contents:

Sources of chloride in water
Generally, chloride ions are present in water as a different form of salts. The most common salts are NaCl, KCl, MgCl2 and CaCl2. They are extremely soluble in water. The Sources of chloride in water may be natural or human beings. The natural sources are surrounding rock or soil or seawater intrusion in coastal areas. Whereas, various human sources are fertilizers, road salting, wastewater from industries, animal feeds, septic tank effluents etc.

Limitation
The Mohr method for determination of chloride in water is a pH sophisticated method. It must be perform between the pH levels 6.5-9.0. It is better to carry out between the pH ranges 7-8. At upper pH level, the silver ions react with hydroxide ions and precipitated as silver hydroxide. In contrast, at lower pH level, potassium chromate may be converted into potassium dichromate (K2Cr2O7) and mask the end point. Consequently, accurate result cannot be obtained. If the water sample is acidic, then gravimetric method or volhard’s method is appropriate.
Ag+(aq) + OH–(aq) → Ag(OH)(s)
CrO42-(aq) → Cr2O72-(aq)

Theory of determination of chloride in water
The amount of chloride in water can be simply determined by titrating the collected water sample with silver nitrate solution by using potassium chromate indicator. The reaction is quantitative. The AgNO3 reacts with chloride ion in a 1:1 ratio. The result is expressed as ppm.

When silver nitrate solution is gradually added into the flask, then silver ions react with chloride ions and forms silver chloride. It is precipitated in bottom of the flask. The precipitation is white in color.
Ag+(aq) + Cl–(aq) → AgCl(s)

The end point of the titration takes place when all the chloride ions reacts and precipitated. Then slightly extra silver ions react with the chromate ions and form a brownish-red precipitate of silver chromate. The solubility product of silver chromate exceeded in the presence of additional silver ions, and then the precipitation occurs.
2Ag+ + CrO42-(aq) → Ag2CrO4(s)
Determination of chloride in water

Apparatus:
Conical flask, burette with stand, pipette, measuring cylinder, volumetric flask, beakers, wash bottle.

Reagents:
Deionized water, water sample, standard N/50 silver nitrate solution, pH test paper, sodium hydroxide solution, nitric acid, Indicator potassium chromate solution.

Procedures:

  1. Measure the pH of the water sample. Adjust the pH with nitric acid or sodium hydroxide, if needed.
  2. Take a 25 ml collected water sample into a conical flask.
  3. Add 2-3 drops potassium chromate (K2CrO4) indicator. The color of the water sample is turn into light yellow.
  4. Add standard N/50 silver nitrate solution from the burette and shake well. Titrate until the light yellow color changes to permanent brownish-red color (bricks-red color) precipitate with white color precipitate.
  5. Note the volume of silver nitrate added.
  6. Repeat the titration for concordant values.
  7. Calculate chloride ion concentration

Chloride ion concentration (mg/l) = (VSN× NSN ×35.45) ×1000/Vw
Where: VSN = volume of titrant used, NSN is normality of silver nitrate, and Vw = volume of water sample used (ml)

NB: If the collected water contains massive amount of Chloride ions such as sea water. Then it needs to be dilute into a volumetric flask.

Observations and Calculations:

Serial No Volume of collected water sample (ml) Burette readings (ml) Volume of silver nitrate solution (ml)
Initial Final
1
2
3

Concordant Volume of silver nitrate solution, VSN = …. ml

Normality of standard silver nitrate solution, NSN = 0.02N
Volume of silver nitrate solution, VSN = ……… ml
Volume of collected water sample, Vw = ……. ml
Normality of collected water sample, Nw = ?
Now, Nw can be calculated from the following normality formula
Nw ×Vw = NSN × VSN
Or, Nw = NSN × VSN / Vw

Amount of Chloride ions = Nw × equivalent weight of chlorine
= Nw × 35.45 g/lit
= Nw × 35.45 × 1000 mg/lit or ppm

Result: The Amount of Chloride in water sample is ——- ppm

Swimming pool pH balance – maintaining pool water pH level

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The swimming pool pH level is one of the most significant factors in pool water balance. The pH is the determination of the acidity or alkalinity of the water. pH means hydrogen ions molar concentration in a solution. It is calculated by the formula –log[H+]. The pH level is measured from 0 to 14, whereas pH 7.0 is neutral. When the pH is below 7.0 then it is called acidic. Conversely, when the pH is above 7.0 it is called alkaline. There are various causes that can change pool water pH level such as heavy rain, chemicals, number of swimmers.

Table of Contents:

Swimming pool pH level

The best pool water pH level is 7.2. Always try to keep the swimming pool pH level minimum 7.0 and maximum 7.6. By keeping within the range you can avoid some problems. The pH of human eyes is varying from 7.2 to 7.4. Moreover pool pH level 7.4 also provides excellent chlorine disinfection.

How to test pool pH
As the high or low pool water pH level can causes many troubles to us. Hence it should be regular checking and adjust the pH according to the result. It is better to check at least every week. If it is not found in ideal ranges then it should be corrected.

TAYLOR TECHNOLOGIES INC K-2006 TEST KIT COMP CHLORINE FAS-DPD

Problems for high pH in pool
There are many problems for high pH in pool water. Some of them are discuss in below.

  • The calcium and carbonates in the pool water combines and form scale on pool surfaces, waterline and accessories. Therefore the sand filter and other elements can lose their efficiency.
  • The pool water turns into cloudy or murky.
  • It can be burning eyes and nose of the swimmers. Moreover, the skin may become dry and itchy.
  • If the swimming pool pH level becomes over 8.0 then the chlorine loses its disinfection potential. Therefore it may increases algae growth or requires more chlorine to act properly.

How to reduce pool pH
Normally, the tendency of pool water pH is increasing, due to chlorination, swimmer’s wastes such as sweat, urine. To reduce pool pH you can be used an acid. The most familiar pool acids are muriatic acid and sodium bisulphate. The muriatic acid means the liquid hydrochloric acid with 30-35% concentration. On the other hand, the sodium bisulphate is a dry acid; it is granule or powder type. You can also use sulfuric acid or nitric acid to reduce pool pH. But they have a drawback. Both of them are highly corrosive. Moreover, sulfuric acid will increases TDS level.
Not use acid directly into the pool water. It is better to use a plastic bucket to mix the acid into the water. It is recommended that never add water into acid, all the time add acid into water.
Swimming pool pH increaser
In The Swim Pool pH Reducer – 60 lb. Pail

Problems for low pH in pool water
The various problems of low pH in pool water are following.

  • The plaster or grouting of the pool can started to decay when the water becomes acidic. Therefore the surface becomes roughness which is suitable for pool algae growth.
  • The metal parts of pool equipment, pipe fittings, pump connections, etc are corrode. Sulphates are formed due to pool walls and metals corrode, which is responsible for ugly brown and black stains.
  • The chlorine is activated and rapid dissipation. Consequently, it loses its disinfectant activities and required multiple dosages.
  • burning eyes and nose
  • dry and itchy skin

Swimming Pool pH increaser
Low pool water pH means more amount of H+ ions. We can increase pH by using pool pH increaser. It is nothing but a base. Generally the active element of swimming pool pH increaser is soda ash (sodium carbonate). It reduces the H+ ions and increases OH– in pool water. Therefore, increases the pH of the water. To increase the pool water pH level 1.0 for a 10000 liters water is required approximately 400 gm of soda ash.
Swimming pool pH reducer balance
In The Swim Pool pH Increaser – 50 lb. Pail

Pool calcium hardness increaser and reducer

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The total mineral that contains in the pool water such as calcium, magnesium, iron, manganese and sodium are responsible for Total hardness. On the other hand, pool calcium hardness means the amount of calcium ions concentration in water express as CaCO3. Both high and low levels of calcium hardness create problems in swimming pool. The perfect level of calcium hardness in pool water is 150-350 ppm. This range is also true for the salt water pool system. The water condition at all state in USA is not same. The water of some areas is very soft whereas some areas are very hard. For example, the calcium hardness in Central Oregon is about 1ppm-5ppm; on the other hand, it is 200ppm-350ppm or higher in Arizona, Southern California, Florida, and Nevada.

Table of Contents:

How to test calcium hardness

It should be routine work to test pool calcium hardness for keeping it at proper levels. Then, you can able to keep your pool, pool water, equipment, even yourself risk free. To test you need a test kit or test strips. It is an occasional test not a regular, because it does not change dramatically. It is better to test twitch a month or one time in a month. If you add other chemicals that contain calcium or adding water into your pool, then it needs more frequent testing.

TAYLOR TECHNOLOGIES INC K-2006 TEST KIT COMP CHLORINE FAS-DPD

Problems for high calcium hardness in pool
If the pool calcium hardness is too high, then you have to face many problems. A scale will be formed on the pool surfaces. It will hamper the plumbing system; scales may form in pipes and filter and they become clogged. As a result the water flow and filtration effectiveness will be reduced. When the amount of hardness too much, then the water turns into dull and cloudy. High calcium levels will also causes sore eyes; irritate Skin and eyes of the swimmers.

Pool Calcium hardness reducer
It is very hard to reducing calcium hardness in pool water. You can reduce it by replacing some portion of pool water with fresh water. But in this case, you have to face others chemical problems as they also drain. So alkalinity, chlorine level, pH etc also affected. The other method is using Pool Calcium hardness reducer which is more effective seems to me. It solves the pool calcium hardness problems; same time does not effect on other chemicals. Prevent it from depositing out. You can also try to reduce calcium hardness in pool water by using zeolite in your sand filter. In addition any resin based water softening filter can also reduce calcium hardness. Otherwise you can consult with pool experts.
Pool Calcium hardness reducer
Doheny’s Calcium Hardness Reducer – 4 Quarts (4-1 Qt. Bottles)

Problems for low calcium hardness in pool water
If the pool calcium hardness is too low, it is also harmful to pool and its equipments. The pool water turns into corrosive. As a result the pool’s surface like plaster becomes pitting and etching. The metal equipment such as pipes, filter, pump will be oxidized and rust rapidly. It can create stains of the pool’s walls and floor.

Pool Calcium hardness increaser
Low calcium hardness can easily be increased by using pool Calcium hardness increaser. Calcium chloride is the popular Calcium hardness increaser. How much calcium chlorides will needs it can be calculated by the analysis of calcium hardness level and amount of water. It is recommended that Calcium Chloride should not mix in a bucket as it is rising temperature. Moreover, should not use all calculated amount of Calcium Chloride at a time. Add half or one third amount for 1st time and circulated the water for 3-4 hours. Test the water and add more if needed. At first it may makes the water cloudy; after for a while it will clear. It may take about four hours.
Pool Calcium hardness increaser
In The Swim Pool Calcium Hardness Increaser – 25 lb. Pail

Calcium hypochlorite is another solution of the pool calcium hardness but it can also increase the chlorine level. If the chlorine level of your pool is lower, then you can easily use it as Calcium hardness increaser.
increase calcium hardness in pool water
Leisure Time CB Calcium Booster, Quart