MANUAL: METHODS FOR PURYFING DRINKING WATER

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MANUAL: METHODS FOR

PURYFING DRINKING WATER

AUTHORS: FABIAN GALLI & NIKITA SMIYANOV

ENGINEERS WITHOUT

BORDERS SWEDEN

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Background

WHO Criteria

There are a variety of pollutants that can be transported with water, which poses a great danger to humans in search of drinking water.

Pollutants are usually divided into pathogens, inorganic substances, organic substances and waste. Bacteria, viruses and protozoans are common pathogens that have varying effects on human health when consumed (Alo, B.T., 2018). There are many different types of technologies that purify water from these contaminants and the World Health Organization (WHO) has compiled a number of criteria for how effective a method should purify water.

Table 1. Criteria for water purification techniques effeciency, created by WHO.

A 2 log10 reduction means a 99% reduction and a 3 log10 reduction means a 99.9% reduction (World Health Organization, 2016)

Water is a very important substance that humnas need to survive and even though 70 % of the earths surfaces is covered by water, the availability of clean water is a major problem in many places around the world. Of the earth’s approximately 7 billion inhabitants, 2.1 billion are living in lack of access to clean drinking water (United Nations, n.d.) and with the world's growing population it is increasingly necessary to take drastic measures to meet the big and growing need. Lack of access to clean water provides the potential for increased infection risk and results in spreading of many different diseases, such as cholera, diarrhea and hepatitis A.

Each year, 842 000 people are expected to die from diarrhea due to this lack of access, of which 361 000 of these are children under 5 years old. Lack of clean water also affects hospital hygiene globally and causes 15% of patients to receive some type of infection during their hos- pital stay (World Health Organization, 2018).

The need for clean water is great and it is of great importance for the improvement of many peoples lives. Today there are many non-governmental organisations working to improve the situation of many people by providing, developing and making technologies available and eco- nomically affordable. There are many solutions for solving problems related to contaminated drinking water, and today many methods of water purification are used, but they have different efficiencies and costs, and it is necessary that the correct method reaches the right places in the world.

Bacteria Virus Protozoa Reduction requirement ≥ 2 log₁₀ ≥ 3 log₁₀ ≥ 2 log₁₀

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Indicators

FUNCTIONALITY

Functionality describes how efficient a technique removes impurities from water. Efficiency is measured in how well the technology reduces the presence of viruses, bacteria, protozoa, chemicals and heavy metals, as well how it manages turbidity in the water. The methods ability of reducing viruses, bacteria and protozoa is graded on a scale between 1 and 4. Where 1 means that the method does not purify the specific impurity, 2 that the reductions is under 90%, 3 that the reduction is over 90% but does not meet the WHO criteria and 4 that the WHO criteria are met.

The efficiency in reducing chemicals, metals and turbidity in the water is not graded, but only answered with a ”yes” or ”no”.

COST

This indicator includes all associated costs for a technique. This means the first cost of the product, installation costs and possible costs for electricity consumption. The cost per liter cleaned water is also calculated and presented which is used in the grading of this indicator.

If the cost per liter is low, a higher score is given to the method. If the cost per liter is called X, the methods are scored as follows: X ≤0,0005 (5-points); 0.0005 ≤ X ≤0.001 (4 points); 0.001 ≤ X ≤0.005 (3 points); 0.005≤X ≤0.01 (2 points); 0.01≤X (1-point)

USE OF CHEMICALS AND ELECTRICITY

The indicators are answered with a simple yes or no and describe whether they require electricity or chemicals in the purification process. The methods usage of chemicals and electricity is graded by giving a “No” 1 points and “Yes” 0 points.

AVAILABILITY

How well this indicator is deemed to be met is based on the state of the art of advanced technology, it is a large system or just a PET bottle that needs to be acquired.

The grading of availability is an estimate based on information presented in the result. The estimate is a highly subjective assessment made by the authors based on a self-designed scale.

Availability is graded on a scale between 1 and 5, where 5 is most available and 1 is least avai- lable

USER FRIENDLINESS

This indicator refers to how simple or advanced a method is to use, if it is several steps to get clean water or if it only requires water to be poured into the system, but also if it requires a com-

plicated assembly or continuous maintenance.

The grading of user friendliness is an estimate based on information presented in the result. The estimate is a highly subjective assessment made by the authors based on a self-designed scale.

User friendliness is graded on a scale between 1 and 7, where 7 is most user-friendly and 1 is least user-friendly.

SCALABILITY

The evaluation of the methods scalability is done by looking at the methods ability to provide people daily with water. In the calculations, flow and user frequency are taken into account.

For the smaller techniques an estimate was made about the user frequency, though it is not li- kely that they will be used every hour of the day. A user frequency of 8 hours per day was there- fore estimated. When calculating how many people can be provided with water, it is estimated that people require 2 liter water per day. The grading of scalability is given depending on how many people can be provided with water per day, as follows: 1-10 people/day (1 point); 11-50 people/day (2 points); 51-500 people/day (3 points); 501-5000 people/day (4 points); < 5001 people/day (5 points).

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Table 2. Functionality in reducing impurities

Bacteria Protozoa Virus Metals Chemicals Turbidity Total score

Moringa Oleifera

seeds 3.5 3 3.5 Yes No Yes 3

Bleach 4 3.5 4 No No No 2.5

Aquatabs 4 3.5 4 No No No 2.5

SODIS 4 4 3 No No No 2

WADI 4 4 3 No No No 2

Solvatten 4 4 4 No No Yes 4

Lifestraw Commu-

nity 4 4 4 No data No data Yes 4

Lifestraw Family

2.0 4 4 4 No data No data Yes 4

Ceramic Pot Filter 4 4 3 No No Yes 3

Tata Swach 4 4 4 Yes No data Yes 5

Slow Sand Filter 3.5 4 3.5 Yes Yes Yes 5

Sawyer filter Poin-

tOne 4 4 1 No No No 3

Sawyer filter Zero-

PointTwo 4 4 4 No No No 4

Gift of Water 4 No data 4 Yes Yes Yes 5

SunSpring Hybrid 4 No data 4 No No Yes 3

Method overview

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Method overview

Table 3. Evaluation of the methods based on the indicators.

EUR per cleaned

liter

Use of Chemicals

Electricity

use Availability User Friend- liness

Scalability (persons per unit and liter)

Total score Moringa

Oleifera seeds 1 (0,02-0,08 €) 1 (No) 1 (No) 4 7 3 (50–200) 17

Bleach 5 (0,0004 €) 0 (Yes) 1 (No) 5 6 3 (500) 20

Aquatabs 1 (0,027 €) 0 (Yes) 1 (No) 4 7 2 (30) 15

SODIS 3 (0,0016 €) 1 (No) 1 (No) 5 7 1 (1) 18

WADI 3 (0,0021-

0,00574 €) 1 (No) 1 (No) 4 7 5

(Unlimited) 21 Solvatten 4 (0,00068-

0,00098 €) 1 (No) 1 (No) 3 6 2 (20) 17

Lifestraw Com- munity

3 (0,003-

0,0043 €) 1 (No) 1 (No) 3 5 2 (48) 15

Lifestraw Fa-

mily 2.0 3 (0,0023 €) 1 (No) 1 (No) 3 5 2 (20) 15

Ceramic Pot Fil- ter

4 (0,00045 or

0,0022 €) 1 (No) 1 (No) 3 6 1 (10) 16

Tata Swach 1 (0,013 €) 1 (No) 1 (No) 3 5 2 (16) 13

Slow Sand Filter 1,5 (0,0055-

0,055 €) 1 (No) 1 (No) 1.5 3 1 (1 - 6) 9

Sawyer filter

PointOne 5 (0,00014 €) 1 (No) 1 (No) 4 5 3 (294) 19

Sawyer filter

ZeroPointTwo 5 (0,00038 €) 1 (No) 1 (No) 4 5 3 (54) 19

Gift of Water 0 (No data) 0 (Yes) 1 (No) 2 0 (No data) 0 (No data) 3 SunSpring Hy-

brid

4,5 (0,00024-

0,00087 €) 0 (Yes) 0 (Yes*) 1 5 4,5 (3167–

9500) 15

* Self-sufficient.

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Moringa Oleifera seeds

TECHNICAL INFORMATION

The seeds of the Moringa oleifera tree can be used for water purification. The Moring tree is also called "miracle tree" because it is possible to get both food and oil from the tree. Seeds can also be used for water purification. The properties of the protein in the seeds are the microscopic structure of the coagulated small particals formed by protein. It turns out that the coagulated particles formed are very dense, which is an advantage for the purification of water. The purification proceeds so that protein from decayed moraine seeds connects to particles in water and causes them to coagulate.

Impurity Reduction

Bakterier 3.5 /4

Protozoer 3/4

Virus 3.5 /4

Chemicals No

Metalls Yes

Turbidity Yes

DESCRIPTION SCORE

COST

• The cost per purified liter is calculated at 0.08 EUR (1 seed / liter), 0.04 EUR (1 seed / 2 liter), 0.03 EUR (1 seed / 3 liter), 0.02 EUR (1 seed / 4 liter).

• The cost varies depending on turbidity in water.

1/5

CHEMICAL USE ^• Water treatment with Moringa Oleifera seeds does not

use chemicals, only natural substances found in seeds. 1/1

ELECTRICITY USE • No use of electricity is required. 1/1

AVAILABILITY ^• Moringa Oleifera seeds should be bought in stores, on-

line or picked where they grow. 4/5

USER FRIENDLINESS ^• The method is easy to use, crush seeds and mix them in

water. The seeds should be stored in a dry environment. 7/7

SCALABILITY

• Depending on turbidity in water, roughly 1 seed per 1 liter of water.

• A pack of 100 seeds will be able to give water to 50 people a day.

3/5 FUNCTIONALITY

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Bleach (Sodium Hypochlorite)

A common method of purifying water is to use different types of chlorine. It is a chemical process that eliminates various contaminants by directly attacking the cells in the compounds. Ble- ach contains a certain type of chlorine in liquid form and by using the correct dosage of the agent in the right amount of water, water can be effectively purified from a variety of contaminants.

Bakterier 4/4

Protozoer 3.5 /4

Virus 4/4

Chemicals No

Metalls No

Turbidity No

COST

• A bottle costs between 0.09-0.43 EUR

• The price per purified liter is 0.0004 EUR (assuming the price is 0.43 EUR for a bottle)

5/5

CHEMICAL USE • The purification process uses chemicals 0/1

ELECTRICITY USE ^• The method requires no electricity or batteries to work 1/1

AVAILABILITY ^• The technique requires a small bottle that can be found in

many stores 5/5

USER

FRIENDLINESS

• Sodium hypochlorite is very toxic and causes serious damage in contact with skin and eyes.

• It has serious consequences for marine life if released in the sea

6/7

SCALABILITY

• A bottle of sodium hypochlorite can clean up to 1000 liters of water

• A bottle can supply 500 people with water per day 3/5 FUNCTIONALITY

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Aquatabs

Aquatabs is a chlorine-based water purification method that comes in the form of tablets as opposed to sodium hypochlorite that is in liquid form.

Bakterier 4/4

Protozoer 3.5 /4

Virus 4/4

Chemicals No

Metalls No

Turbidity No

COST ^• The cost of a pack of 30 tablets is 16.5 EUR

• The cost per purified liter is 0.0267 EUR 1/5

CHEMICAL USE ^• The purification process uses chemicals 0/1

ELECTRICITY USE ^• The technology requires no electricity or batteries to

function 1/1

AVAILABILITY ^• A small product 4/5

USER

FRIENDLINESS

• The method is simple just applying a tablet to contamina-

ted water 7/7

SCALABILITY

• An Aquatab tablet cleans 20 liters of water and can supply 10 people with water per day

• In a box there are 30 tablets. With theses 600 liters of water can be purified and can supply 300 people with water per day

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SODIS

SODIS stands for Solar Water Disinfection and is a method of purifying water using the sun's UV radiation by filling a PET bottle with water and placing it out in sunlight. The method requires that the bottle used is relatively new, that is, a bottle that is not too scratched and dented. When the bottle is placed out in sunlight, the sun's UV radiation is used to purify the water from bacteria and viruses, thus rendering the water cleaned.

Bakterier 4/4

Protozoer 4/4

Virus 3/4

Chemicals No

Metalls No

Turbidity No

COST

• The price for a bottle is approximately 0.6 EUR

• The cost per cleaned liter of water is 0.00164 EUR.

3/5

CHEMICAL USE ^• The method does not require chemicals in the purificat-

ion process 1/1

ELECTRICITY USE ^• The method does not require any electricity in the purifi-

cation process 1/1

AVAILABILITY ^• A PET-bottle is a small product and can be found

anywhere 5/5

USER

FRIENDLINESS

• The purification process is only consisting of filling up a

bottle with water and placing it in the sun 7/7

SCALABILITY

• The Petbottle used in the purification process can have the maxiumum size of 3 liters

• The number of people that it can provide for per day is 1.5 people

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WADI

WADI is a product used with SODIS and is used as an indicator to ensure that the water is drinkable. The product consists of a small device put in the sun together with the PET bottles, contai- ning the water that is desired to be purified. When the water has been exposed to enough radiation, the WADI device shows a happy mouth indicating that the water is drinkable

Bakterier 4/4

Protozoer 4/4

Virus 3/4

Chemicals No

Metalls No

Turbidity No

COST

• The cost of the product is 15 EUR

• If WADI (with a lifespan of 5 years) is used with 1 PET bottle the price is 0.00574 EUR per cleaned. If WADI is used with 100 PET bottle the price is 0.00205 EUR per cleaned liter

3/5

CHEMICAL USE ^• The method does not require chemicals 1/1

ELECTRICITY USE ^• The method does not require any electricity since it is

powered by solar power with its own solar panel 1/1

AVAILABILITY • The product is a small product 4/5

USER

FRIENDLINESS

• When purifying water, WADI is put out in the sun and the water is clean when the indicator on the product shows a smiling face.

7/7

SCALABILITY ^• WADI can be used with an almost unlimited amount of

bottles 5/5

FUNCTIONALITY

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Solvatten

Solar water is a technique that uses the sun's UV light to purify water. It is also equipped with a filter that purifies the water furt- her. When the water is clean, an indicator shows a green guy saying that the cleaning process is complete. Once the water is cleaned, it has a temperature of 55 degrees, but can also reach a maximum temperature of 75 degrees. This means that Solvatten can also be used for preheating water for cooking or for hygiene purposes.

Bakterier 4/4

Protozoer 4/4

Virus 4/4

Chemicals No

Metalls No

Turbidity Yes

COST

• The cost of a unit is 97 EUR

• Optimally the technique can purify up to 40 liters a day and with a lifespan of 7-10 years the cost is 0,00068 - 0,00098 EUR per cleaned liter

4/5

CHEMICAL USE • The method does not require chemicals 1/1

ELECTRICITY USE • The method does not require any electricity 1/1

AVAILABILITY • The product is a medium sized product 3/5

USER

FRIENDLINESS

• Purifying water is done by pouring water into the product

• The maintenance of the product is to rinse it once a week 6/7

SCALABILITY ^• The technology cleans up to 40 liters per day, it can pro-

vide up to 20 people per day with water 2/5 FUNCTIONALITY

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Lifestraw Community

Lifestraw is a product that uses a filter to purify water from various contaminants. There are many different versions of the product that vary in price and efficiency when cleaning water.

Lifestraw community uses a prefilter and a finer filter to reduce turbidity and clean water from bacteria, viruses and protozoans.

The device cleans 12 liters of water per hour and a total of 70,000 - 100,000 liters of water and can store up to 25 liters of pure water. The device has a lifespan of 5 years.

Bakterier 4/4

Protozoer 4/4

Virus 4/4

Chemicals No

Metalls No

Turbidity Yes

COST

• Lifestraw Community has a cost of 308 EUR

• The price per purified liter is 0.003 - 0.00429 EUR per liter

/5

CHEMICAL USE ^• The method does not require chemicals /1

ELECTRICITY USE • The method does not require any electricity /1

AVAILABILITY • It is a medium sized product /5

USER

FRIENDLINESS

• The device needs to be installed before first use

• Daily cleaning of all filters is recommended /7

SCALABILITY ^• The device can provide up to 48 people per day with

purifyed water /5

FUNCTIONALITY

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Lifestraw Family 2.0

Lifestraw is a product that uses a filter to purify water from various contaminants. There are many different versions of the product that vary in price and efficiency when cleaning water.

Lifestraw family 2.0 uses a prefilter and a finer filter to reduce turbidity and clean water from bacteria, viruses and protozoans.

The device cleans 2.5 liters of water per hour and a total of 30,000 liters of water and can store up to 5 liters of pure water.

The device has a lifespan of 5 years.

Bakterier 4/4

Protozoer 4/4

Virus 4/4

Chemicals No

Metalls No

Turbidity Yes

COST ^• Lifestraw Family 2.0 has a cost of 71 EUR

• The price per purified liter is 0,00233 EUR per liter 3/5

AVAILABILITY • It is a medium sized product 3/5

USER

FRIENDLINESS

• The device needs to be installed before first use

• Daily cleaning of all filters is recommended 5/7

SCALABILITY ^• The device can provide up to 20 people per day with

purifyed water 2/5

FUNCTIONALITY

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Ceramic Pot Filter

Ceramic Pot Filter is a water purification technique that uses a clay pot for filtering and removing contaminants. In the manufacture of the pot, a small amount of silver is added, which also allows for the reduction of bacteria and protozoa. The pot can be used by filtering water into a regular plastic bucket, but there are also some more customized systems with container for clean water with a tap. The flow through the filter is 1-3 liters of water per hour and it has a lifespan of 2 years.

Bakterier 4/4

Protozoer 4/4

Virus 3/4

Chemicals No

Metalls No

Turbidity Yes

COST

• The price for a pot is between 6 - 6.5 EUR and 20-32 EUR for the whole system

• Purchasing a system results in a cost of 0.00219 EUR per liter

• Purchasing only one pot results in a cost of 0.000445 EUR per liter

4/5

ELECTRICITY USE ^• The method does not require any electricity 1/1

AVAILABILITY • The product consist of a small system 3/5

USER

FRIENDLINESS

• The method only requires the user to pour water into the filter

• To maintain a good flow of water it is necessary to clean the filter and associated containers regularly

5/7

SCALABILITY ^• The method can provide up to 10 people per day with

purifyed water 2/5

FUNCTIONALITY

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Tata Swach

The method purifies water with an MF membrane (MicroFilter membrane) to make water microbiologically safe from viruses, bacteria and parasites, thus ensuring a treatment against algae, fungi, rust, metal particles and turbidity. The method works by adding water into the upper container and infiltrated through a microfilm membrane using the gravity where the particles and parasites remove, finally clean water flows into the lower reservoir that collects the purified water. The lifetime capacity of the filter is 3000 liters.

Bakterier 4/4

Protozoer 4/4

Virus 4/4

Chemicals No data

Metalls Yes

Turbidity Yes

COST

• The cost of a standard fully equipped system is 40 EUR.

• The cost per purified liter is estimated at 0.013 EUR over the lifetime of 3000 liters.

1/5

CHEMICAL USE ^•The method uses a membrane, no chemicals are involved in the

purification process. 1/1

ELECTRICITY USE ^•There is no need of electricity in the purification process. 1/1

AVAILABILITY ^•In size, the product is large.

• Can buy online. 3/5

USER FRIENDLI- NESS

• Easy cleaning of water tank, due to turbidity.

• Need to be assembled when delivered. 5/7

SCALABILITY ^•Tata purifies water with a flow of 4-5 liters of water per hour, re-

sulting in a unit potentially being used by 16 people per day. 2/5 FUNCTIONALITY

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Slow Sand Filter

Slow Sand Filtration is a technique that filters water through an approximately 1-1.25 meter thick sand cover and purifies water from many different pollutants. The purification takes place through a biological process that works in such a way that a layer of mucus is formed in the upper centimeters of the sand, a so-called "schmutzdecke", where harmful particles and microorganisms get stuck. The system requires a regular replacement and cleaning of the upper sand layer to work. The flow of water is 0.05-0.5 liters per hour and per square meter through the sand filter. The lifespan of a Slow Sand Filter is at least 10 years.

Bakterier 3.5 /4

Protozoer 4/4

Virus 3.5 /4

Chemicals Yes

Metalls Yes

Turbidity Yes

COST

• The cost of a Slow Sand Filters system varies between 82-246 EUR per square meter

• The price per purified liter is 0,00548–0,0548 EUR

1.5 /5

AVAILABILITY ^• The method consists of a big system 1.5 /5

USER

FRIENDLINESS

• Usage demands knowledge

• It requires regualar and demanding maintenance

• The system needs to be installed before first use

3/7

SCALABILITY ^• The system can provide water to 1.67–6 people per day

and square meter 1/5

FUNCTIONALITY

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Sawyer Filter PointONE

Sawyer filter PointONE Bucket Adaption is purifying water using a 0.1 micron pore size filter that cleans water from bacteria and protozoa. Bucket adaption is the Sawyer filter, attached to a 3 foot hose, which is mounted on a bucket. The bucket must be purchased separately. The filter has a flow of 73.5 liters per hour and has the ability to clean a total of 370,000 liters of water

Bakterier 4/4

Protozoer 4/4

Virus 1/4

Chemicals No

Metalls No

Turbidity Yes

COST ^• Sawyer Filter PointONE has a cost of 50 EUR

• The price per purified liter is 0,000135 EUR 5/5

AVAILABILITY • The filter is a small product 4/5

USER

FRIENDLINESS

• Before first use, place the filter on the bucket

• The filter requires regular cleaning 5/7

SCALABILITY ^• The filter can provide up to 294 people per day with

purifyed water 3/5

FUNCTIONALITY

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Sawyer Filter ZeroPointTwo

Sawyer filter ZeroPointTwo Bucket Adaption is purifying water using a 0.02 micron pore size filter that cleans water from bacteria, virus and protozoa. Bucket adaption is the Sawyer filter, attached to a 3 foot hose, which is mounted on a bucket. The bucket must be purchased separately. The filter has a flow of 13.6 liters per hour and has the ability to clean a total of 370,000 liters of water

Bakterier 4/4

Protozoer 4/4

Virus 4/4

Chemicals No

Metalls No

Turbidity Yes

COST ^• Sawyer Filter ZeroPointTwo has a cost of 115 EUR

• The price per purified liter is 0,000378 EUR 5/5

AVAILABILITY • The filter is a small product 4/5

USER

FRIENDLINESS

• Before first use, place the filter on the bucket

• The filter requires regular cleaning 5/7

SCALABILITY ^• The filter can provide up to 54 people per day with

purifyed water 3/5

FUNCTIONALITY

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Gift of Water Purifier

Gift of Water Purifier is a technique that uses several processes to purify water from contaminants. The unit is divided into two buckets. In one of the buckets the water is poured together with a chlorine tablet and after 30 minutes the full bucket is placed on top of the other, which starts flowing through a prefilter and activated charcoal filter. This technique effectively removes viruses, bacteria, protozoans, metals and chemicals from drinking water. The flow through the product is about 20 liters per hour.

Bakterier 4/4

Protozoer No data

Virus 4/4

Chemicals Yes

Metalls Yes

Turbidity Yes

COST ^• No data 0/5

CHEMICAL USE • Chlorine is used in the pruification process 0/1

AVAILABILITY • The method consists of a big system 2/5

USER

FRIENDLINESS ^• Not enough data 0/7

SCALABILITY • No data 0/5

FUNCTIONALITY

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SunSpring Hybrid

This type of technology can clean up to 19 cubic meters of water per day and is powered only on batteries recharged from renewable energy coming from integrated components. The system works by pumping water from a nearby water reservoir, lake, river, pool or well and allowing water to pass through a thin UF membrane that does not allow microbiological contaminants to penetrate it. Furthermore, water is treated with a chlorine treatment and stored in a water tank.

Bakterier 4/4

Protozoer No data

Virus 4/4

Chemicals No

Metalls No

Turbidity Yes

COST

• The cost of a standard fully equipped system is 16500 EUR.

• The cost per purified liter is estimated at 0.00024 EUR throughout the lifetime of 10 years.

4,5 /5

CHEMICAL USE ^•Water is treated with a chlorine treatment and stored in a

water tank to eliminate bacterial growth 0/1

ELECTRICITY USE ^•The system is self-sufficient during daytime (wind propellers

and solar cells), but also night time (wind propellers). 0/1

AVAILABILITY ^•In size, the product is large.

• Can buy online or through contact with the company. 1/5

USER FRIENDLINESS ^•The method has automatic and self-cleaning properties that

do not require maintenance. 5/7

SCALABILITY ^•3167 people can use SunSpring, 8 h per day

• 9500 persones can use method, 24 h per day 4,5 /5 FUNCTIONALITY

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References

Alo, B.T., 2018. List of Water Pollutants. [Online] Sciencing. Available at: https://

sciencing.com/list-water-pollutants-6309497.html. [Accessed 21 March 2018]

United Nations, n.d. Water. [Online]

Available at: http://www.un.org/en/sections/issues-depth/water/. [Accessed 25 April 2018]

World Health Organisation, 2016. Results of round I of the WHO international scheme to evaluate household water treatment technologies. [Online] World Health Organisation. Available at: http://apps.who.int/iris/bitstream/

handle/10665/204284/9789241509947_eng.pdf?sequence=1. [Accessed 21 March 2018]

World Health Organisation, 2018. Drinking-Water. [Online] (Updated 7 February 2018)

Available at: http://www.who.int/en/news-room/fact-sheets/detail/drinking-water.

[Accessed 25 April 2018]

For more information concering the methods please refer to the report ”Comparision of Different Alternatives for Drinking Water Purification in Development Countries”, made by Nikita Smiyanov and Fabian Galli, 2018.

MANUAL: METHODS FOR PURYFING DRINKING WATER