tart of transcript. Skip to the end. Wherever you get your drinking water from, the tap,a bottle or a source; your water will not just contain pure H2O. But what is in your water?And, more importantly, what should definitely not be in there? Welcome to the Drinking Water Treatment lecture about Wate

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1.2 - Water quality aspects

tart of transcript. Skip to the end. Wherever you get your drinking water from, the tap,
a bottle or a source; your water will not just contain pure H2O. But what is in your water?
And, more importantly, what should definitely not be in there?

Welcome to the Drinking Water Treatment lecture about Water Quality Aspects.
My name is Doris van Halem and I'm an Assistant Professor in Drinking Water.
Today I'm your lecturer and I will introduce you to five groups of water quality parameters that are used to assure safe drinking water supply: first, organisms in drinking water,
Health-related, chemical parameters, Aesthetics of drinking water and Operational parameters.
well the first group of key compounds in water consists of living creatures,
which you most often cannot see with the naked eye.
In nature, water contains all kinds of organisms and
they are present in large numbers.

Also in drinking water many different organisms are found. Generally speaking, these organisms can be divided, based on their size, into four groups: higher organisms,
protozoa, bacteria, and viruses.
Higher organisms have a size between 0.05 and 10mm.
And just to give you an idea, a kubic meter of water may contain over 50,000
of these organisms, which gives the impression of a large zoo
and seems unsuitable for drinking and to be avoided by vegetarians.
However, fortunately a characteristic of most of these higher
organisms is that they are harmless to human health.
Their presence in drinking water is only aggravating if they are detectable by the naked eye.
An overview of higher organisms as typically found in drinking water is depicted in the slide.
Also smaller micro-organisms, such as bacteria, can be abundantly found in water - and the majority of them does not effect your health.
However, there are also micro-organisms that are harmful to human health, the so called pathogenic micro-organisms.
Pathogenic micro-organisms, or pathogens in short, are not present in water by nature, but they enter the water through feces and urine from humans and animals.
Pathogens have difficulty to survive in natural water, because the temperature of water is lower than body temperature.
An important source of pathogens in surface water is the continuous supply of un-treated
or not fully treated wastewater from domestic and bio-industry.
Pathogenic micro-organisms can cause different diseases, which may become epidemic rather quickly in water.
They can be divided into three main groups, each with their own individual characteristics:
protozoa, which are single cell animals and can cause diarrhea and stomach complaints;
bacteria, responsible for typhoid fever and cholera; And virusses, the smallest organism of the three groups, and responsible for hepatitis and polio.
The size of bacteria, viruses and different particulate matter in water determines to a great extend their removal potential by treatment processes.
There are analytical techniques to determine what pathogens are in your water, but for safety reasons, it is preferred to measure indicator organisms and not the real disease-causing organisms.
For bacteria, coliforms or E.coli are used as indicator organisms, they can also be found in human and animal feaces, but can be more safely cultured and counted as colony forming units per volume.
For virus indicators, mostly bacteriophages are used which form plaque forming units per volume.
This picture shows an example of a plated sample for E.coli counts, each dot represents a colony forming unit.
In the guidelines of the World Health Organisation it is stated that when testing a 100mL sample no E.coli may be found.
Well, lets get to the second group of parameters important for safe drinking water which consists of dissolved compounds, both inorganic and organic.

A subdivision can also be made based on the concentrations present in the water, as macro-pollutants for concentrations over 1 mg/L and micropollutants for concentrations below 1 mg/L.
The long list of health related, chemical constituents can be divided roughly into: Metals and related substances (such as, lead, mercury, arsenic) Organic micro-pollutants (for example, pesticides and hormones)Disinfection byproducts (such as, bromate or trihalomethanes)And other compounds (which include nitrate and fluoride)
Guidelines for the maximum allowable concentration exist for these substances based on considerations,
such as, health impact,
detection limit of measuring device or the available removal technologies.
The impact of a substance on human health depends strongly on the specific constituent,
making dose-response and epidemiological studies crucial.
Most countries have their own guidelines for these parameters,
there are also international guidelines, for example of the World Health Organization
and the European Union.
In EU guidelines a maximum allowable health risk of 10-5 is used for the formulation
of the guidelines.
In other words, it is accepted that no more than 1 in 100,000
persons can develop an illness for each contaminant.
well let's briefly go through the different chemical contaminants that can threat safe drinking
water supply.
Metals and related substances include well-known heavy metals,
such as mercury and lead, but also the metalloid arsenic.
These contaminants originate from different sources,
including natural release into the water from sediments,
through mining activities, and industrial or domestic discharges.
These metals and related substances pose a serious threat to human health as they are
often carcinogenic and may cause illnesses to the bladder,
lungs and other organs.
Another group of chemical compounds that may be present in source water are organic micro-pollutants,
shortly called OMPs.
This group includes contaminants such as pesticides pharmaceuticals human care products drugs
and gasoline.
Depending on the dose these compounds may be genotoxic and endocrine disrupting.
A particular concern is the potential mixture of many different of these organic micropollutants,
such a cocktail of substances, as it is difficult to detect and to remove.
Disinfection by-products are originally not present in the source water,
but enter the water during a treatment process for disinfection.
Disinfectants react with natural organic matter or bromide in the water,
resulting in carcinogenic by-products.
Trihalomethanes, NDMA and bromate are examples of DBPs
which are produced by chlorine, chloramine and ozone, respectively.
In the group "other compounds" I want to mention nitrate and fluoride specifically.
Nitrate enters the water in areas with agriculture and is particularly of concern for babies
and pregnant women, as nitrate is transformed to nitrite in the body.
Fluoride can be naturally present in groundwater and at elevated levels is also threat to human
health, as it may cause brittle bones are tooth decay.
Now you have been introduced to the most important parameters that can have an impact on human health.
These microbial and chemical parameters are crucial for the safety of drinking water.
However, also the consumer comfort and perception is
a key component to take into account.
Therefore the third group of water quality parameters is "aesthetics of drinking water".
The water should not only be safe, but also be perceived as safe.
Odour and taste are subjective parameters which cannot be detected by any device.
The acceptable taste and odour of water are determined by using consumer panels,
which determine whether they detect any unpleasant flavor or smell to the water.
Colour and turbidity can be measured in the water.
As well as the constituents influencing the aesthetics of drinking water,
such as iron and sulphate.
Also, undissolved matter or suspended solids can
cause discoloration or turbidity to the water.
Undissolved matter consists of large or small particles which have not been dissolved in
the water.
This is a different group of contaminants than the earlier mentioned chemical substances,
as these are generally dissolved in water.
A distinction based on size is made between suspended and colloidal matter.
The diameter and specific gravity of particles are important for removing them from the water.
Colloidal particles have are very small and have a specific gravity similar to water.
Colloidal particles generally have a negative electric charge and their electrostatic repulsion
makes them difficult to remove.
Operational water quality parameters are very important for drinking water supply companies.
The objective of these parameters is to assure that the water quality in maintained post-treatment.
So, the water quality should not change because
of storage in reservoirs, or distribution and use within households,
such as heating.
A distribution network can be an important source of contaminants,
as organisms may grow in it.
Important parameters contributing to growth in the distribution network are the organisms
themselves, but also nutrients,
temperature, bicarbonate for buffer capacity and dissolved oxygen.
Apart from growth during distribution, also dissolution of pipelines should be prevented,
so aggressive water should be prevented.
For this reason saturation index, hardness,
and pH.
but also, hardness of water,
as calcium and magnesium ions, is important as it may cause scaling in heating installations,
a film on tea, and less effective use of detergents.
Now you know the main water quality parameters that you need to pay attention to when designing
a water treatment plant.
Also, you have learned about their effect on human health, consumer demands and operation.
The next step will be to learn more about how you can remove these constituents from
the water.
We have come to the end of this lecture, so I want to thank you for watching.
And please use the discussion board for your questions.

 


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