Springs in the Central Parts of Vallentuna Municipality

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DEGREE PROJECT IN CHEMICAL ENGINEERING AND TECHNOLOGY, FIRST LEVEL

STOCKHOLM, SWEDEN 2017

Traditions and threats

Hannan Hadodo

A stream emerging from a spring horizon in Arkels tingstad, Vallentuna

KTH ROYAL INSTITUTE OF TECHNOLOGY

KTH CHEMICAL SCIENCE AND ENGINEERING

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Degree Project

Bachelor of Science in

Chemical Engineering and Technology

Title: Springs in the central parts of Vallentuna municipality traditions and threats

Swedish title: Källor i centrala Vallentuna traditioner och hot

Keywords: Spring, water quality, restoration

Workplace: KTH and Vallentuna

References in

Vallentuna: Anton Mankesjö, Vallentuna kommun

Staffan Rosander, Vallentuna Hembygdsförening

Anders Eriksson, Källakademin

Nicole Sundin, Vallentuna kommun

Supervisor: Olle Wahlberg

Student: Hannan Hadodo

Date: 2017-‐11-‐07

Examiner: Lars Kloo

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Abstract

Twenty springs in the central parts of Vallentuna municipality have been studied to determine their present water qualities and suggest actions that could be taken to improve the water quality and availability of the springs. The measured parameters are the water volume, the water flow, the water temperature, the pH-‐value, the electrical conductivity, the chloride concentration, the alkalinity and the CODMn. The sensory properties of the springs were also examined, which include odour, colour, clarity and precipitation.

Measurements of the water flows, the water temperatures, the pH-‐values and the electrical conductivities were performed during a field trip in Vallentuna. During this field trip, two water samples were taken from each spring. Thereafter, the alkalinity, the chloride concentration, the CODMn and the sensory properties were determined in the laboratory.

Four of the springs, which were wells, have water of high quality and can easily be restored.

Some of the twenty springs have not been cared for or have even disappeared.

The water from the spring horizon near Arkels tingstad is unfortunately mixed with stormwater, which runs off the nearby roads. This contamination is examined by measuring the chloride flows of the different streams. The roads also contribute with metal pollution, with metals such as cadmium. Therefore, metal speciations of cadmium were examined. A simple solution is suggested to remove the metal pollution. The measured water flows of all of the spring waters in Vallentuna were quite small.

The results of the measurements of the spring waters were compared with the values recommended by Livsmedelsverket and Socialstyrelsen. Most of the values were between the recommended limits for drinking water.

Suggestions are given to improve the springs concerning water quality and availability.

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Sammanfattning (Abstract in Swedish)

Tjugo källor i centrala Vallentuna studerades för att bestämma deras vattenkvalitet och för att föreslå åtgärder i avsikt att förbättra vattenkvaliteten och tillgängligheten av källorna. De mätta parametrarna är vattenvolym, flödeshastighet, vattentemperatur, pH-‐värde, elektrisk

konduktivitet, kloridkoncentration, alkalinitet och CODMn. Dessutom undersöktes källvattnens sensoriska egenskaper, vilka innefattar lukt, färg, klarhet och utfällning.

Mätningar av flödeshastigheterna, vattentemperaturerna, pH-‐värdena och elektriska

konduktiviteterna gjordes under en exkursion i Vallentuna. Två vattenprover togs från varje källa. Därefter undersöktes kloridkoncentrationen, alkaliniteten, CODMn och de sensoriska egenskaperna på laboratoriet.

Fyra av källorna, vilka var brunnar, har vatten av hög kvalitet och kan relativt enkelt restaureras.

En del av de tjugo källorna har inte vårdats under lång tid och har till och med försvunnit.

Vattnet från källhorisonten vid Arkels tingstad har olyckligtvis blandats med dagvatten, vilket rinner från de närliggande vägarna. Denna förorening analyseras genom att mäta kloridflödet i olika strömmar. Vägarna bidrar också med metallföroreningar, t.ex. kadmium. Därför har också metallförekomstformer för kadmium modellerats. En enkel metod föreslås för att avlägsna metallföroreningarna. Vattenflödena från källorna i centrala Vallentuna är relativt små.

Resultatet av mätningarna av källvattnen jämfördes med de rekommenderade värdena för dricksvatten enligt Livsmedelsverket och Socialstyrelsen. De flesta värdena låg inom gränserna för de rekommenderade värdena för dricksvatten.

Förslag ges till förbättring av källorna med avseende på vattenkvalitet och tillgänglighet.

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Preface

During my degree project, I have learnt to appreciate the value that springs have to us humans.

Exploring different locations in nature that are not commonly visited and finding clean spring water was a new experience for me. It shows how we tend to forget that clean water can be accessed not only from water taps, but also from other sources such as wells. Maintenance of spring water gives the opportunity for future generations to enjoy clean water from such sources.

I would like to express my sincere thanks to my supervisor at KTH Olle Wahlberg, who came up with my degree project about the springs in Vallentuna. Olle Wahlberg guided and helped me during the course of my degree project. I also wish to thank residents in Vallentuna who gave information about some of the springs, and Källakademin that has expressed interest in my work.

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1 Introduction

Vallentuna municipality is located 25 km north of Stockholm centre. Today it is a suburb of Stockholm. There are many springs in Vallentuna that were earlier used as water supplies. Most of these springs are now forgotten or have been contaminated. Some of them have even

disappeared. Most people in Vallentuna now use tap water from Mälaren. Some springs can still be restored and enjoyed by people who visit. The springs also have a cultural value, and every courtyard in Vallentuna once used to have its own spring or well.

Twenty springs in central Vallentuna are studied in this project. A few of the springs are well cared for, but most of them are forgotten and not maintained. However, the springs are an example of local traditions and the threat to this cultural heritage that the expansion of the modern society leads to.

In Vallentuna, the spring water mostly comes from small moraine hills, which is the reason why the water flow is usually small. The ground water influences the water quality of the springs and therefore, the springs have been used to survey the ground water quality by SGU (The Swedish Geological survey).

1.1 Problem

Many of the springs in the central parts of Vallentuna municipality are no longer in use. These springs have a potential to be used for drinking water if they meet the requirements for drinking water. The springs of interest will first be located to then determine their water quality. Their water quality can be measured with different measuring devices used directly on the springs and also analytical methods executed at the Department of Applied Physical Chemistry in KTH.

Their surrounding environment will also be examined in order to propose methods that can increase their water quality.

1.2 Goal

The goal with this degree project is to locate and determine the water quality of the studied springs in the central parts of Vallentuna municipality. The local history and threats to these springs will be reviewed. Solutions to increase the water quality of some of the springs will also be suggested.

Methods 1.2.1

Most of the springs will be located by interviewing local residents. Physical-‐chemical methods and sensory methods will be used to examine the water quality of the springs. Measurements of water flows, water temperatures, pH-‐values and electrical conductivities are to be performed in the field. The parameters that will be analysed in the laboratory are the alkalinity, the chloride concentration, the CODMn, the odour, the colour, the clarity and the precipitation of the studied springs. The surrounding environment of the springs and the history of some of the springs will also be examined.

1.3 Aim

The aim of this degree project is to give information about the springs in the central parts of Vallentuna municipality in order to make them available to the public.

1.4 Limitations

This degree project is limited to the springs that are located in the central parts of Vallentuna.

The measurements and analyses are limited to temperature, pH, electrical conductivity, water flow, chloride concentration, alkalinity, CODMn and sensory properties of the springs.

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The chemical analyses will be performed in the laboratories of the Department of Applied Physical Chemistry in KTH. It is advised that the spring waters are analysed by an accredited laboratory before the public are proposed to drink the spring water.

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2 Background

Groundwater and spring water are parts of the water cycle, which is run by sun energy and gravity. Precipitation in different forms gives the amount of water that is included in the water cycle. A spring is defined as a continuous flow of ground water from a low point in a terrain (see Figure 1). A stream may lead the water from the spring. [1]

Figure 1 The biogeochemical cycle of water (this image is used with permission from The Swedish Academy of springs) 1) evaporation from snow and ice, 2) rainfall, 3) humid airmasses, 4) condensation, 5) infiltration, 6) runoff, 7) percolation, 8) evaporation from vegetation, 9) groundwater surface, 10) evaporation, 11) lake, 12) spring, 13) river, 14) spring, 15) sea, 16) groundwater stream, 17) marginal zone: freshwater and saltwater [1]

In 2015, Niina Veuro studied the cold springs in Täby and Vallentuna in her degree project.

Fifteen springs were found in the databases SGU (The Swedish Geological Survey),

Skogsstyrelsen (the board of the Swedish Forest Survey) and Riksantikvarieämbetet (the board for the preservation of the Swedish cultural heritage). Niina Veuro provided the geological background of the springs in the area and also suggested how to preserve the springs. She described a spring in Säberg and also mentioned a spring horizon located in Arkels tingstad.

2.1 Traditions and importance of springs in Vallentuna

Vallentuna was a farmer’s land in the 19^th century. The local train was established in 1885, which was very important for the transportation of the farmer’s products to Stockholm city. Two brickyards and a mechanical industry were localised close to the railway station in Åby farmland during the 20^th century, but these industries are presently closed. Vallentuna is today a suburb of greater Stockholm and has a population that is growing rapidly, with more than 30 000 inhabitants in 2017.

Åby farm was located right in the centre of Vallentuna. A spring is shown in an old map of Åby village from the year 1775. The spring has disappeared and the area is presently used for parking cars close to the commuter train.

All of the farms had traditionally at least one spring or well. The water was used for different purposes such as food preparation, washing clothes, brewing of beer and as drinking water for inhabitants or cows and horses at the stables. Nowadays, most people use tap water originating from Mälaren. The countryside spring water is still used, but deep ground water resources via drilled wells are more often used. [2] [3] [4] [5]

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2.2 Threats to springs in Vallentuna

Many of the old springs have been forgotten. For example, very few people recognize a spring that is close to the church, which is heavily surrounded with overgrown bushes. The spring in Åby farm has been gone for a long time, but a well in Åbyholm (the outland of Åby farm) still remains. However, the well is covered with litter from a nearby construction site.

There is a spring horizon in Arkels tingstad, where spring water flows from a moraine hill down to Vallentunasjön (a lake in Vallentuna) in several small streams. Several springs in this area disappeared between 2015 and 2017 because new houses were built in the valley of Arkels tingstad. The spring water in Arkels tingstad is currently mixed with stormwater from the roads.

There is a small spring with a stream running down to Vallentunasjön that the Vallentuna municipality has restored recently.

There are still several springs in the farm Uthamra gård, which have been developed into

convenient wells. One of the wells is still in use for a stable. Cows and horses were formerly kept in the stable, but it is presently empty. The main farmhouse burnt down in 1961. One of the current owners is restoring a traditional well that belongs to the main farmhouse. There is a well nearby that was formerly used for a brewery house and washing clothes. A different well, which was also used for washing clothes, has been filled out by the present owner. Approximately 500 m north of the stable, there is a typical spring belonging to a crofter’s house, which contained water in June 2015 but was dry September 2017.

The outlaying land of Uthamra gård on the eastern side of Vallentunasjön, with the name Nyborg also belongs to Uthamra farm. The hydrology of Nyborg is interesting. There is artesian water in Nyborg, which means that the pressure of the ground water is very high, thus the water casually runs over the borders. It is a problem because the area is planned for new settlements.

Nowadays, people usually drill deep holes in the ground for the supply of safe water. [2] [3] [4]

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2.3 Water properties

The water properties studied in this degree project are the electrical conductivity, the chloride concentration, pH, the alkalinity and CODMn. There are regulations for these parameters so that the water quality is suitable for drinking. There are different regulations depending on the size of the water consumption from the source. Livsmedelsverket (National Futures Association) and Socialstyrelsen (National Board of Health) both have regulations for drinking water (see Table 1). The regulations of Livsmedelsverket apply to water consumption for more than 50 people or for water consumption over 10 m³ per day. [6] The regulations of Socialstyrelsen apply to drinking water from small waterworks and individual wells. [7]

Parameter Livsmedelsverket Socialstyrelsen

Electrical conductivity [mS/m] <250 Chloride concentration [mg/l] <100 <100 pH-‐value 7.5< pH <9.0 >6.5

CODMn [mg O2/l] <4.0

Table 1 Drinking water regulations from Livsmedelsverket and Socialstyrelsen

Electrical conductivity 2.3.1

The electrical conductivity is a measure of the water capacity to carry electric current. It is the sum of several conductivities of ions in the water, resulting from the present electrolytes. That is

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why electrical conductivity is directly proportional to the dissolved mineral matter of water. The electrical conductivity is dependant of the temperature. [8]

Chloride 2.3.2

Chloride is a common anion present in water. Chloride appears naturally in groundwater, and can be found in larger amounts when seawater or road salt makes its way into water. It usually forms different salts with cations of various elements such as calcium, magnesium or sodium.

High levels of chloride in water can damage plants if it is used for irrigation, and it can give an unpleasant taste of drinking water. [9]

pH 2.3.3

A small number of water molecules dissociate, which results in some ions forming hydroxide ions and others forming hydronium ions. Acidic water contains more hydronium ions than hydroxide ions, and basic water contains the opposite. The pH-‐value is a measure of how acidic or basic an aqueous solution is, ranging from 0 to 14. The pH of water affects the hardness of the water, which is a measure of metals such as calcium ions and magnesium ions. [10]

Pure water has a pH-‐value very close to 7, which is classified as neutral. Ground water usually has a pH-‐value between 6 and 8.5. Water that has a pH-‐value less than 6.5 is considered to be acidic. Acidic water is typically corrosive and soft. It can contain metal ions, such as copper, iron, lead, manganese and zinc. The metal ions can be toxic, result in a metallic taste of the water and cause corrosion of metal pipes. Water that has a pH-‐value greater than 8.5 is considered to be basic. This water is usually hard, has an alkaline taste and can form scale deposits in pipes. [11]

Alkalinity 2.3.4

Alkalinity is a measure of the capacity of water to react with hydrogen ions without a significant change in the pH of the water. This means that it gives information about the acidification sensitivity of the water. The pH-‐value of a solution that has an alkalinity greater than zero does not change proportionally with the addition of hydrogen to the solution until the alkalinity decreases to zero. [12] [13]

The alkalinity of water often depends on the content of bicarbonate, carbonate and hydroxide compounds of calcium, magnesium, sodium and potassium in the water. The alkalinity of water can also depend on the content of borates, phosphates and silicates in the water. Most ground water only contains carbonates and bicarbonates in significant amounts. The origin of

bicarbonate is mainly the weathering of rocks. [12]

COD 2.3.5

The Chemical Oxygen Demand (COD) is a water quality parameter. It is a measure of the amount of oxygen required to oxidize organic matter in water. It is an important measure because it shows the effect that wastewater can have on the surrounding environment. A high level of COD indicates that the water contains a high level of organic material. The organic material in natural waters oxidizes by dissolved oxygen, which is then consumed. [14] [15] Tap water in Stockholm County contains approximately 2.6 mg O2/l. [16] The oxidation of organic compounds in natural water is a microbiological process.

2.4 Solutions for problems with the water quality of springs and wells

The construction and the surrounding area of a spring or a well should be inspected if the water has poor quality. Water quality problems are often due to surface water that leaks into the well or surface activity that affects groundwater.

Field operations in the area near the spring or the well can pollute the water system. Relatively common sources of pollution are for example sewers, manure, oil tanks and road water. In some instances, spring water and well water can be contaminated even if there is no new source of

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pollution near them. Various kinds of field works, such as excavation and drilling, can cause pollutants that were previously stable in soil layers to come into contact with groundwater.

Therefore, it is essential that the area near the spring and the well is protected against different sorts of land degradation. It is important to identify the pollution source in order to restore the water quality of the spring water. The source may have to be repaired or removed. It can take a long time to see improvements of the water quality because of the long-‐term processes of groundwater.

Impact of surface activity on the spring water or the well water indicates that other

contaminants from the surface can come in contact with the water. It is important to check the places that have a high risk for leakage in wells. In many cases, it is possible to get rid of the problem through different types of sealing techniques. These techniques include replacing the well lid, sealing the joints in buried wells or mounting an extra plastic liner or a sealing cuff in mountain wells.

The only solution left if the waterbed is contaminated, and if the source of pollution has not been removed or sealing of the well has not helped, is to construct a new water supply upstream of the source. It is important that the previous spring or well is refilled with sealing material or secured so that the contamination pathway through the well to the groundwater waterbed is eliminated. The new water supply that is built will often have to be located outside of the affected area.

Springs or wells that have been contaminated with temporary pollutants of surface water or organic matter that have flowed directly into the well and lead to microbiological growth will often have to be sanitized. A common method is to disinfect these wells with chlorination. It is also advisable to rinse the well to remove any material that could cause bacterial infections in the future. [17]

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3 A survey of the studied springs

Twenty springs in the central parts of Vallentuna municipality were studied. These springs were located in the parish, which belongs to the old church in Vallentuna. The examined springs were located in four different areas (see Figure 2). These areas were named A, B, C and D. The springs from each area were numbered. All of the samples are shown in Figure 3, larger images of the samples are available in Appendix 1. The co-‐ordinates for most of the springs are included in Appendix 2.

Figure 2 Map showing the location of the springs that were studied

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Figure 3 Image of the water samples taken from the springs

3.1 Springs in area A

Springs near the church and in the centre of Vallentuna.

A1 Kyrkans källa 3.1.1

Kyrkans källa is a spring near the old church in Vallentuna. It is located in a small grove at the edge of a ridge not far from the church. It is overgrown by bushes and plants, there are also some scattered stones and mud around it. The well is currently in poor condition. The water level inside the well is 3 cm higher than the water level outside of the well. The spring water of this well slowly flows south towards a paddock nearby.

A2 Prästgårdens källa 3.1.2

Prästgårdens källa is a spring situated at the edge of a ridge behind a cow house in Prästgården. The well is filled with rocks, supposedly for safety reasons. There is currently no water present inside the well because it has been drained by a ditch, which was built to drain the cemetery nearby. This spring was used as a source of water supply for the cows in the house nearby in the twentieth century.

A3 Kullens källa

3.1.3

Kullens källa in Väsby gård is between an immense field and the bottom of an inclined forest behind a house. The depth of the water is 0.5 m. The forest ground and the muddy field can possibly affect the water inside the well. The water contained humus from the ground and clay from the field nearby.

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A4 Spring in Åby gård 3.1.4

The spring is only found on an old map of Åby gård from the year 1775. The spring is no longer visible because it has since disappeared. In the 20^th century, two brickyards and a

mechanical industry were built in this location. The land is presently used as a parking place for cars near the commuter train.

A5 Well in Åbyholm 3.1.5

The well in Åbyholm and was recently reported in a report by WSP, which is an analysis and technology consulting company. The well is now covered by leftover material from a nearby construction site, as seen in the upper image.

3.2 Springs in area B

Springs along the eastern shore of Vallentunasjön, near a spring horizon in Arkels tingstad.

B1 Well close to the spring horizon 3.2.1

The well obtains its water directly from the spring horizon in Arkels tingstad and is located in a garden near a road. There are many new houses being constructed near the well and part of the spring horizon has already disappeared. The diameter of the well is 1.0 m and the depth of the water in the well is 1.1 m. The well has a cover that protects the water from surface contamination.

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B2 Stormwater stream from Skadronvägen 3.2.2

The image shows a stormwater stream from a road surface, close to Arkels tingstad. The water flows slowly from a pipe with metal bars. The stormwater pipe is located 50 m away from a pond. Spring water also runs down to the pond.

B3 Stormwater stream 3.2.3

A stormwater ditch that is located close to B2. The water from B2 flows to B3 and then flows to the pond.

B4 Stream in Arkels tingstad 3.2.4

The stream in Arkels tingstad leads the water from the pond, containing both stormwater and spring water down to the lake Vallentunasjön.

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B5 Stream in Hasseludden 3.2.5

The water of this stream flows down to the lake in Hasseludden, which is about 200 m from Arkels tingstad.

The stream starts approximately 800 m south of Hasseludden near the road Uthamravägen and runs along the spring horizon. Several small streams from the spring horizon flow to this stream. It contains spring water and stormwater from roads.

B6 Spring near Uthamravägen 3.2.6

The image shows a small stream of spring water near Uthamravägen continues to Vallentunasjön. Vallentuna municipality cares for the place where it is located and the stream has been nicely restored.

3.3 Springs in area C

Springs located in the old farm village Uthamra gård.

C1 Well near the brewery house/ washhouse 3.3.1

The well near the brewery house/ washhouse is located not far from a moraine hill full of old graves, i.e. ancient relics. The well becomes dry by the end of summer.

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C2 Well near a cow stable of Uthamragård 3.3.2

The well is located close to a stable in a field of growing wheat. The diameter of the well is 1.0 m and the well is sealed with a lock. The depth of the water inside the well is 3.6 m. The water has been used for the cows and horses in the nearby stable, which is presently empty.

C3 Spring near the main building 3.3.3

The main well has been filled with sand and bricks to protect children from accidents. It has now been restored by one of the present owners, Peter

Kristiansson. The well is constructed with big natural stones. It was formerly covered with a millstone from a nearby windmill.

C4 Old basin used for washing clothes 3.3.4

A very old constructed basin used for washing clothes in the 20^th century and earlier. No picture could be taken of the basin because the present owner Bernt Bodin has filled it with soil.

C5 A crofter’s well 3.3.5

The well is very close to the remnants of a small house, which disappeared about 80 years ago. The spring was full of water in the beginning of the spring, but it became dry during the summer. There is a stone construction at the end of the pit where water was formerly collected.

3.4 Springs in area D

Springs located in Nyborg, the outland of Uthamra gård.

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D1 Well in a forest 3.4.1

This well is located in a forest. The diameter of the well is 0,7 m, and the depth of the water in the well is 1,9 m.

D2 Well in a garden

3.4.2

The well is located in a garden belonging to a house in Nyborg. The depth of the water in the well is 1,4 m.

D3 Old construction for washing clothes 3.4.3

A basin, which probably has been used for washing clothes, was found in Nyborg. It was filled with water in the beginning of the spring, but was dry during the summer. The water emerged from a small spring located 10 m away. The water was not suitable for drinking, but well enough for washing clothes. There is a two-‐story concrete house nearby.

D4 Spring found in the SGU database 3.4.4

No picture could be taken of this spring because it was located inside a locked house. The water was furnished from a nearby well 50 m away, which was also not accessible.

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D5 Deeply drilled well 3.4.5

The most common water supply to the population of Vallentuna is currently tap water from the lake Mälaren.

The second option most people use is water from a deeply drilled hole in a rock that is typically 100 m deep.

The picture shows a deeply drilled well in Nyborg.

Though most drilled wells are hidden, this one can easily be seen. The pump is drained at the bottom of the well.

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4 Laboratory Methods

The determination of the chloride concentration, alkalinity and CODMn can be done with analytical chemistry methods.

4.1 Determination of the chloride concentration

The chloride concentration of the water can be measured with a titration using silver nitrate (𝐴𝑔𝑁0_!). The silver nitrate is used as the titrant in this method because silver ions form insoluble salts with halide elements such as chloride. The salt that is formed from silver and chloride ions is silver chloride (𝐴𝑔𝐶𝑙).

An indicator that can be used for titrations with silver nitrate is potassium chromate (𝐾_!𝐶𝑟𝑂_!).

The solution containing chloride ions appears yellow once drops of potassium chromate are added to the liquid. Thereafter drops of the titrant are carefully added to the mixture, which results to the following reaction:

𝐴𝑔^!+ 𝐶𝑙^!⟶ 𝐴𝑔𝐶𝑙 (𝑠)

A white precipitate of silver chloride forms in the solution as long as the colour indication of the solution is yellow. The titrant is to be added to the mixture until there are no free chloride ions in the solution. A reddish colour change is visible once all of the chloride ions are consumed.

That is when the following reaction occurs:

2𝐴𝑔^!+ 𝐶𝑟𝑂_!^!!⟶ 𝐴𝑔_!𝐶𝑟𝑂_! (𝑠)

A red precipitate of silver chromate forms in the solution. Silver chromate only appears after all of the chloride ions are consumed because the momentum for silver and chloride ions to react is higher than that for silver and chromate ions. The titration is complete once there is a sign of red precipitation in the solution. [18]

The results from the titration can be calculated to determine the chloride concentration of the solution containing the sample. The formula that can be used to calculate the chloride

concentration is determined with the reaction formula for silver and chloride ions. The molar ratio of the reaction of silver and chloride ions is 1:1, which results to the following formula:

𝑉!"!#$%!×𝐶_!"^! = 𝑉!"!#$%&×𝐶_!"^! The definition for each parameter:

𝑉!"!#$%! The titrant volume 𝑉!"!#$%& The titrand volume

𝐶_!"^! The concentration of silver ions in the titrant 𝐶_!"^! The concentration of chloride in the titrand 4.2 Determination of the alkalinity

The alkalinity of water is due to the presence of hydroxide ions (𝑂𝐻^!), bicarbonate ions (𝐻𝐶𝑂_!^!) and carbonate ions (𝐶𝑂_!^!!). However, bicarbonate ions and hydroxide ions are in equilibrium state according to the reaction:

𝑂𝐻^!+ 𝐻𝐶𝑂_!^!⟶ 𝐶𝑂_!^!!+ 𝐻_!𝑂

The alkalinity of water can be determined by titrating the water with a standard acid solution, for example hydrochloric acid. An indicator that is suitable for this titration is a mixed indicator containing methyl red and bromcresol green. A sample that has an alkalinity value greater than zero will appear pink once drops of mixed indicator are added to it. The following reactions occur during the titration with the standard acid solution:

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𝑂𝐻^!+ 𝐻^!⟶ 𝐻_!𝑂 𝐶𝑂_!^!!+ 𝐻^!⟶ 𝐻𝐶𝑂_!^!

The alkalinity of the solution is zero once all of the hydroxide ions and carbonate ions are consumed. The solution has a faint greyish colour at this stage of the titration. The presence of the indicator results to a greyish appearance of the solution. It is pink in alkaline solutions. Two drops of the indicator are enough to distinguish the colour of the solution. [19]

The titration is complete once the pink colour in the titrand has disappeared. The alkalinity of the titrand can be calculated once the required amount of titrant to decrease the alkalinity to zero is known. The formula that can be used to calculate the alkalinity is determined with the reaction formulas for the titration. The molar ratio between the reactants in both of the reaction formulas is 1:1, which results to the following formula:

𝑉!"!#$%!×𝐶_!"# = 𝑉!"#$%&×𝐶_!"#

Where each parameter has the definition:

𝑉!"!#$%! Consumed titrant volume 𝑉!"#$%& Sample water volume

𝐶_!"# Hydrochloric acid concentration in the titrant 𝐶_!"# Alkalinity of the water sample

4.3 Determination of the CODMn

The COD of a solution can be determined with a titration of an oxidant to the solution. A suitable oxidant for this method is potassium permanganate (𝐾𝑀𝑛𝑂_!). Manganese has the oxidation state +7, and has a high redox value in low pH-‐values. The redox potential of potassium permanganate is strongly affected by the pH of the solution, where the oxidation state of manganese varies from +2 to +6 depending on the pH and reactant of the system. The reaction formula for the titration differs depending on the pH condition of the titrand. [20]

Strongly acidic solution:

𝑀𝑛𝑂_!^!+ 8𝐻^!+ 5𝑒^!⟶ 𝑀𝑛^!!+ 4𝐻_!0 Alkaline solution:

𝑀𝑛𝑂_!^!+ 2𝐻_!𝑂 + 3𝑒^!⟶ 𝑀𝑛𝑂_{! (!)}+ 4𝑂𝐻^! Neutral solution:

𝑀𝑛𝑂_!^!+ 4𝐻^!+ 3𝑒^!⟶ 𝑀𝑛𝑂_{! (!)}+ 2𝐻_!0

The solution can be acidified with sulphuric acid (𝐻_!𝑆𝑂_!) in order to achieve the first reaction for the titration with potassium permanganate.

The solution becomes pink when potassium permanganate is added to it because potassium permanganate has a pink/ purple colour. The solution should be heated in boiling water after a small amount of the titrant is added to it in order for the reaction to occur. The solution will turn clear once all of the permanganate is consumed in the reaction. If the solution stays pink after heating, then the permanganate will no longer react because all of the organic compounds in the solution have been oxidized.

A standard reference is needed in order to determine the CODMn of the solution in interest. A solution with a known amount of CODMn can be used as the standard reference, where the process for the titration with potassium permanganate is executed on the solution. If the CODMn of tap water is known then tap water can be used as a reference.

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The number of drops used for the titration of tap water can be compared to the amount

consumed by the solution with the unknown amount of organic material to calculate the CODMn of the solution. The following formula can be used to calculate the CODMn:

𝐶_!"#_!" =^!!"#$%&×!_!"#

!!"#

Where each parameter has the definition:

𝐶_!"#_!! CODMn of the sample

𝑁!"#$%& Number of potassium permanganate drops consumed by the sample 𝐶_!"# CODMn of the tap water (standard reference)

𝑁_!"# Number of potassium permanganate drops consumed by the tap water

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