Let’s do a small experiment. Would you rather drink
this water, or this water? Well, of course you would
choose the water on the left. Unfortunately, some people
in other parts of the world have no choice at all. Did you know that small floating
particles in drinking water can make you sick? Imagine we have a super
powerful microscope and we can zoom into the water. Zoom. What will we find? What are these small
floating particles, and how do they float? These particles
are of two types. Inorganic, like clay,
silt and mineral oxides. And organic, such as algae,
protozoa, and bacteria. The bacteria, once ingested by
humans, can sometimes be fatal. All of these small
particles are able to float because they are not heavy
enough to settle to the bottom by gravity. Suspended particles that are
too light and small to settle are called colloids. When looked at
together, these colloids cause a state of cloudiness, or
haziness, known as turbidity. The more cloudy a fluid
looks, the more turbid it is. Here. we see four
beakers of water with increasing levels of
turbidity from left to right. There is a relation
between turbidity and the risk of
getting a disease. Science shows that
the more turbid the drinking water is, the
higher the risk of getting sick is. Now, why is this? This is because toxic
compounds can adsorb, that is stick to, the surface
of the suspended colloids. The more colloids there
are, the more toxic the water can become. These toxic materials
and bacteria can cause cholera,
salmonellosis, hepatitis A, dysentery, and E coli infection. These illnesses affect and
kill millions of people a year, and are especially dangerous
to children whose weak immune systems cannot provide
an adequate defense. Fortunately, we can do
something about this. One of the very practical ways
to clean this turbid water is called flocculation. Flocculation is the process
in which colloids aggregate, or come together, to form
larger particles called flocs by the addition of a
chemical called a flocculant. Typical flocculants units
include alum and ferrix, because they work well with
high turbidity fluid mixtures. Now, let’s demonstrate
how flocculation works. First, we’ll need to go out
and collect some muddy water from the Charles River. Here are two beakers
filled with the same amount of muddy Charles River water. On the left is our control,
which will remain untouched, and on the right we’ll
add three milliliters of prepared flocculant solution. Then we’ll stir for
two minutes and wait. [MUSIC PLAYING] Wow, what just happened? The colloids in the turbid water
on the left may never settle. Whereas, with the addition
of just a little bit of flocculant, the water
on the right became clear. In order to make
this water potable, it will require skimming
and filtration, and maybe some additional treatment. If you’re wondering
what’s going on, let’s explain how this
flocculant business works. Almost all colloids have
negatively charged surfaces. This means that positive ions,
or charged particles in water, will attract to the colloid
surface, forming a first layer. Recall how like
poles of a magnet will repel, while opposite
poles will attract. The same occurs with
colloids in water. A diffuse layer, made up of a
mix of positive and negative ions, will then
surround the first, forming what is
called a double layer. This double layer
provides a repulsive force that prevents two colloids
from sticking to each other. Once the flocculant
is added, it adheres to the surfaces
of the particles, compressing the double layer,
and allowing the colloids to stick to each
other and form flocs. These flocs are now heavy
enough to settle to the bottom by gravity. Given how effective
flocculation is, many countries around
the world use this method for cleaning their
water supplies. Did you know that
Singapore, for instance, produces drinking
water from sewer water, using a number of methods
including flocculation. As the global population
increases, and fresh water resources become
more and more scarce, flocculation is
one tool that can supply clean, healthy, and
tasty drinking water worldwide. [MUSIC PLAYING]

100 thoughts on “Flocculation

  1. That was a great explanation.  I work in water treatment and will share this with others having to give educational presentations. 

  2. Very helpful.  It does help me to see why flocculation is important in cleaning water, the mechanics of how it works and why mining companies would use this process in the tail end.  

  3. i tried flocculation once but my mom caught me and said i would go blind if i continue.  needless  to say i stoped when i needed glasses. 

  4. Great vid, thank you! We just bought a Lovibond flocculator today in work, I set it up and we will be using it over the next few wks. Great to get a simple overview as to what's it all about.

  5. Alum and Ferric are cationic coagulants, not flocculants.  Cationic coagulants neutralize the net negative charges on the suspended solids which allows the colloidal particles to naturally join together as you demonstrate.  Flocculation, if necessary, follows coagulation and is done with very high molecular weight, long chain polymers.

  6. wow its an amazing. Can u tell us that how much amount of alum would be added in a liters. or if we would like to use in reserve tank then how we can use. another thing is, Is that flocculation process helps to reduce the iron and ammonia from the water? [email protected]

  7. When you add flocculent to precipitate out iron from a pool how much aluminum is left in the pool? How dangerous is it to ingest aluminum if you swallow pool water with leftover aluminum?

  8. If they don’t have clean water, R.O. Filters, distillation apparatus, or… think going to have flocculants? I’ll just head on down to local empty shop, get bottled water, antibiotics, and flocculants, which one? 🤔 💭 “All your flocculants, shop keep!” Sanctions, because of Zionist/proxy american cuckoldry agreement, forgot, just hurts children and poor, wealthy untouched At least we have no water and power, hospital, food, medicine, luxury goods! Greater Israel plan, yeah! How many wars, and 4 million middle easterners dead and mounting, US servicemen, getting a few more according to plan, and un winnable too, evil people not central banking debt slaves! We are, maybe could use on Detroit on lead, nah! Sorry good information, bullets and bombs bumming us out! English language, well thanks for explanation though! Fun learning! Hope don’t get captured and sold into bondage, that’s still real, not just water, Libya was nice once, too NOBODY went without!

  9. How Does Water Get to You?

    Hello! I am Samantha, a chemical engineering student at Universitas Indonesia. My team and I would like to ask for your participation to help us to win the AIChE Video Competition 2018 with the topic "Chemical Engineering in Water Treatment".

    Please watch and like our video through this link: https://youtu.be/nYHRepVAp4E

    Your likes will be extremely helpful to us. Thank you and have a good day!😁

  10. a very good explanation, i was wondering what it meant. I got past the term by a yeast for beer, became curious and used the search term on youtube and got a clear explanation. my beer will be much clearer now, hope my mind stays clear too 😉

  11. Why do colloids have negatively charged ions? Are all substances mixed in with water ionic? If not, how do they remove them?

  12. So about how many mg of Alum did you put into the beaker. The volume of the solution was mentioned but not the concentration of the solution or mass of alum.

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