How City Water Purification Works: Drinking and Wastewater

Summary

This script offers an insightful overview of the water purification process, from sourcing to treatment and return to nature. It details the steps in both drinking water and wastewater treatment, including coagulation, flocculation, ozonation, filtration, and UV disinfection. The script highlights the role of microorganisms in secondary treatment and the importance of environmental considerations in releasing treated wastewater.

Takeaways

• 💧 Drinking water originates from surface sources like rivers, lakes, and reservoirs, or from underground wells and springs.
• 🌀 Water treatment plants use a variety of processes, starting with coagulation and flocculation to remove suspended particles.
• 🔬 Coagulants neutralize the charge of particles in water, causing them to clump together into 'floc', which is then made heavier with micro-sand and polymer.
• 🛁 Settling tanks with baffles help floc particles settle out, while scraper blades remove the sludge, leaving clarified water.
• 🌪 Ozonation is used to treat taste and odor causing agents, including harmful bacteria and viruses, by oxidizing contaminants.
• 🌀 Ozone, with three oxygen atoms, bonds with contaminants, making them easier to filter out, and then reverts to normal oxygen, leaving no byproducts.
• 🌿 Filtration through activated carbon and microsand removes oxidized particles and other contaminants, with the carbon layer filtering biological and chemical elements.
• 🌞 UV light in the final disinfection stage destroys or disrupts the DNA or cellular structure of pathogens, ensuring water safety.
• 🏞️ Wastewater from homes is collected and treated in a wastewater treatment plant before being released back into the environment.
• 🚱 The headworks in a wastewater treatment plant removes large debris and heavier inorganic particles from the incoming flow.
• 🌀 Grit chambers separate heavier inorganic particles from the wastewater, allowing lighter organic material to pass through for further treatment.
• 🦠 Secondary treatment in an aeration tank involves microorganisms that consume biodegradable waste products, requiring oxygen for the process.
• 🌊 Final clarification and UV disinfection ensure that the treated wastewater is safe to be released back into natural water systems.

Q & A

What is the primary source of drinking water mentioned in the script?

Drinking water primarily comes from surface sources like rivers, lakes, and reservoirs, or from underground wells or springs.

What is the purpose of coagulation and flocculation in water treatment?

Coagulation and flocculation are processes used to neutralize the inherent electric charge of suspended particles in water, encouraging them to stick together into clumps called 'floc', making them easier to settle out.

What role does micro-sand play in the water purification process?

Micro-sand is added to make floc particles heavier, which helps them settle out more easily during the purification process.

How does the water flow through the settling process in the script?

The flocculated water flows through a set of baffles to slow its turbulence, allowing heavy floc particles to settle to the bottom of the tank, while remaining particles collide with angled plates and slide down to the settling zone.

What is ozonation and how does it contribute to water purification?

Ozonation is a process where ozone gas, which consists of three oxygen atoms, is injected into the water. It oxidizes contaminants, making metals easier to extract and disrupting the function of bacteria and viruses, without leaving any byproducts.

What is the function of activated carbon in the filtration stage?

Activated carbon, made from materials like wood, coal, or coconut husks, has a large surface area with many pores, providing ample opportunity for contaminants to adhere to its surface as water passes through, filtering out biological and chemical elements.

How does UV light disinfection work in the final stages of water purification?

UV light at various wavelengths can destroy or disrupt the DNA or cellular structure of viruses, bacteria, and other pathogens, effectively killing them and ensuring the water is safe for public consumption.

What happens to the wastewater after it leaves our homes?

Wastewater flows through the municipal collection system or city sewer pipes to a wastewater treatment plant, where it is processed before being released into a natural water source.

What is the purpose of the headworks in a wastewater treatment plant?

The headworks is a group of processes designed to remove large debris and heavier inorganic particles from the incoming wastewater flow, preparing it for further treatment.

How does the primary clarification process in wastewater treatment work?

In primary clarification, water flows into sedimentation tanks where floatable solids like grease and oil drift to the top and settleable solids sink to form a sludge, which is then removed for further processing.

What is the role of microorganisms in the secondary treatment of wastewater?

In the secondary treatment, microorganisms such as bacteria and protozoa consume biodegradable waste products and require oxygen. They form clumps called floc, which helps in the settling process and eventual purification of the wastewater.

Outlines

00:00

💧 Water Purification Process Overview

Jake O'Neal introduces the water purification process, detailing how water is sourced from rivers, lakes, reservoirs, or underground wells and springs. The script explains the general components and processes involved in treating water at treatment plants, including coagulation and flocculation to remove suspended particles. Coagulants neutralize the charge of particles, encouraging them to form 'floc' clumps, which are made heavier with the addition of micro-sand and polymer. The flocculated water then moves through a series of baffles, settling tanks, and angled plates to separate the sludge from the clarified water. The purified water is then subjected to ozonation and filtration to eliminate microscopic contaminants, including harmful bacteria and viruses, using ozone's oxidizing properties without leaving any byproducts. The water finally passes through an activated carbon and microsand filter to remove oxidized particles and other contaminants, resulting in clean, drinkable water.

05:01

🌿 Wastewater Treatment and Environmental Release

The script describes the journey of wastewater from homes to a wastewater treatment plant, where it undergoes a series of processes before being released back into the environment. The headworks phase removes large debris and heavier inorganic particles through the use of screw pumps and bar screens. A grit chamber follows, where heavier particles are separated from the wastewater, allowing lighter organic material to continue through the process. Primary clarification separates organic matter from the wastewater in sedimentation tanks, where floatable solids are skimmed off and settleable solids form a sludge at the bottom. The sludge is then processed for potential use as fertilizer. The water moves to secondary treatment in an aeration tank, where microorganisms consume biodegradable waste products and oxygen is supplied to support their life processes. The resulting floc is collected for reuse, and the processed water undergoes final disinfection with UV light before being released back into nature through a specially designed outfall pipe that minimizes environmental disruption.

10:04

🔬 Secondary Treatment and Microorganism Role

This paragraph delves into the secondary treatment of wastewater, focusing on the aeration tank where beneficial microorganisms such as bacteria and protozoa are introduced. These microorganisms consume biodegradable waste, including human waste, food waste, and cleaning products. Oxygen is pumped into the mixture to support the microorganisms, which either absorb soluble particles directly or emit enzymes to break down solid particles. Over time, these microorganisms form floc clumps, which are then separated in the final clarification stage. Some of the settled floc is collected for reuse in the aeration process, while the processed water moves on to final disinfection using UV light. Once disinfected, the water is prepared for release back into the natural environment, ensuring that treated wastewater does not contaminate drinking water sources.

Keywords

💡Animagraffs

Animagraffs is the creation of Jake O'Neal and represents a visual teaching tool used to explain complex processes in a simplified and engaging manner. In the script, Animagraffs is used to illustrate the intricate process of city water purification, making it accessible and understandable to viewers.

💡Water Treatment Plants

Water treatment plants are facilities designed to remove contaminants from water to make it safe for human consumption. They are central to the video's theme of water purification, as the script describes their general working model and the various processes involved in turning raw water into drinking water.

💡Coagulation and Flocculation

Coagulation and flocculation are chemical and physical processes used in water treatment to remove suspended particles. In the script, these processes are explained as the initial steps in purifying water, where coagulants neutralize the charge of particles, causing them to clump together into 'floc'.

💡Ozonation

Ozonation is a water treatment process that involves the use of ozone, a molecule composed of three oxygen atoms, to oxidize contaminants. The script highlights its role in eliminating taste and odor causing agents, as well as harmful bacteria and viruses, without leaving any byproducts in the water.

💡Activated Carbon

Activated carbon is a form of carbon processed to have small, low-volume pores that increase its surface area for adsorption. In the context of the video, it is used in the filtration stage to remove oxidized particles and other contaminants, playing a crucial role in ensuring water purity.

💡UV Disinfection

UV disinfection is a process that uses ultraviolet (UV) light to destroy or inactivate microorganisms in water by damaging their DNA or cellular structures. The script describes this as the final step in both drinking water and wastewater treatment, ensuring the safety of the water for consumption or release into the environment.

💡Wastewater Treatment Plant

A wastewater treatment plant is a facility that processes used water before it is released back into the environment. The script details the steps involved in treating wastewater, emphasizing the importance of this process in maintaining clean water sources.

💡Headworks

Headworks refers to the initial processes in wastewater treatment that remove large debris and heavier inorganic particles. The script describes the role of headworks in the treatment plant, including the use of screw pumps and bar screens to manage the coarse incoming mixture.

💡Primary Clarification

Primary clarification is a step in wastewater treatment where organic matter is separated from the water. The script explains how water flows into sedimentation tanks, where floatable solids and settleable solids are separated, contributing to the purification process.

💡Aeration Tank

An aeration tank is used in secondary treatment of wastewater to facilitate the growth of microorganisms that consume biodegradable waste. The script describes how air is pumped into the tank to provide oxygen for these microorganisms, which help break down waste products.

💡Floc

Floc refers to the clumps of particles that form during the coagulation and flocculation process in water treatment. In the script, floc is mentioned as a result of particles sticking together, which becomes heavier and easier to settle out of the water, aiding in the purification process.

💡Clearwell

A clearwell is a storage tank used in water treatment to hold water after it has been treated and is ready for distribution. The script mentions the clearwell as the final destination for treated water before it enters the municipal system for public use.

Highlights

Drinking water originates from surface sources like rivers, lakes, and reservoirs, or from underground wells or springs.

Water treatment plants vary in design, but the general model includes coagulation and flocculation as the initial purification process.

Coagulants neutralize the inherent electric charge of suspended particles, causing them to form clumps known as 'floc'.

Micro-sand and polymers are added to increase the weight of floc particles, facilitating their settling.

Baffles in the settling tank slow turbulence, allowing heavy floc particles to settle quickly.

Angled plates in the settling tank help remove remaining suspended particles.

Clarified water is collected in troughs after the settling process.

Ozonation is used to treat microscopic taste and odor causing agents, including harmful bacteria and viruses.

Ozone gas molecules, with three oxygen atoms, can oxidize contaminants, making them easier to extract.

Ozone leaves no byproducts in the water, unlike chlorination, as it reverts to normal oxygen after treatment.

Filtration stage uses activated carbon and microsand to remove oxidized particles and other contaminants.

Activated carbon granules have a large surface area for trapping biological and chemical contaminants.

UV light in the final disinfection stage destroys pathogens by disrupting their DNA or cellular structure.

Treated water is stored in a clearwell or distributed through the municipal system for public use.

Wastewater treatment involves a series of processes to remove large debris and inorganic particles.

Primary clarification in sedimentation tanks separates organic matter from wastewater.

Secondary treatment in the aeration tank involves microorganisms that consume biodegradable waste.

Air is pumped into the aeration tank to provide oxygen for the microorganisms.

Final clarification allows floc to settle, and some is collected for re-use in the aeration process.

Treated wastewater is released back into nature through a specially designed outfall pipe.

Treated wastewater and untreated drinking water are kept separate to prevent contamination.

Transcripts

I'm Jake O'Neal, creator of Animagraffs. And  this is how city water purification works:  

from drinking water to wastewater  to nature and back again. 

Let's start with drinking water, which comes  from surface sources like rivers, lakes, and  

reservoirs, or from underground wells or springs. Water treatment plants have near endless  

variations in design,  

so I've chosen major components and  processes to create a general working model. 

Cylindrical intake screens are  placed in a reservoir in such a way  

to best avoid ingesting silt from the reservoir  bottom, or floating material from the surface. 

A lift house with vertical pumps draws water  from a well and into the treatment plant. 

The purification process starts  with coagulation and flocculation. 

Particles suspended in water, like clay,  sand, and some larger organic particles  

such as algae, have an inherent electric  charge that causes them to repel each other.  

Coagulants are substances  with opposite electric charge  

that neutralize these particles and encourage  them to stick together into clumps called "floc". 

The coagulant and water is vigorously  mixed, and floc clumps start to form. 

To make floc particles heavier and therefore  even easier to eventually settle out,  

micro-sand is added as the water is  drawn through a special mixing tube,  

with a polymer to help the sand stick. The now flocculated water flows  

through a set of baffles to slow its  turbulence for the settling process.  

As the water travels upwards, heavy floc particles  quickly settle to the bottom of the tank. 

Any remaining suspended particles  collide with an array of angled plates,  

and slide down to the settling zone. 

Slowly rotating scraper blades continuously  remove the combined sludge and sand layer  

from the bottom of the tank while clarified  water flows upwards into collection troughs. 

At this stage the water already looks clear,  and a lot less cloudy. Now it's on to ozonation  

and filtration to treat microscopic taste  and odor causing agents. These can include  

inorganic elements such as iron or  sulfur, or harmful bacteria and viruses. 

In the ozone tank, ozone gas bubbles are injected  into the flowing water through diffusers.  

The tank is divided, which slows the  flow and gives the water a longer  

path with more time for ozone to do its job. An ozone gas molecule is made up of 3 oxygen  

atoms. The normal oxygen we breathe has just  2 oxygen atoms. When ozone is injected into  

the stream, the extra oxygen molecule can  bond with contaminants, or "oxidize" them,  

with various desirable results. For example,  oxidized metals have a weaker bond with water, and  

are therefore easier to extract. Oxygen also bonds  with elements in virus or bacteria cell walls,  

disrupting their function, and altering their  surface charge for easier filtration downstream. 

When ozone gives up its extra oxygen  molecule it just becomes normal oxygen,  

leaving no byproducts in the treated water, unlike  other purification methods such as chlorination. 

The water flows to the filtration  stage to remove the oxidized particles,  

and any other remaining contaminants. 

Water travels through a dense layered bed  of activated carbon granules and microsand. 

It's called "activated" carbon because  the resulting engineered granules,  

which are processed from  common materials like wood,  

coal, or even coconut husks, have a relatively  huge surface area with many features and pores,  

giving ample opportunity for contaminants to catch  or stick to the surface as water passes through. 

Generally speaking, the activated carbon layer  filters biological and chemical elements,  

while the sand layer filters inorganic  elements like unwanted metals. 

Passing particles stick to a  carbon or sand granule's surface  

due to naturally occurring attractive  forces, called Van Der Waal's forces. 

The filtered water flows to final disinfection  in the UV tank. Water passes through banks of  

ultraviolet lights. UV light at various  wavelengths can destroy or disrupt viral,  

bacterial, and other pathogen's DNA or cellular  structure, effectively destroying them. 

The water is now ready for public consumption.  

It flows into a what's called a clearwell for  storage, or into the municipal system for use. 

Now let's look at what happens  to water after we use it!

Wastewater flows from our homes through the  municipal collection system or city sewer pipes to  

a wastewater treatment plant, where it's processed  before being released into a natural water source. 

The headworks is a group of processes that removes  

large debris and heavier inorganic  particles from the incoming wastewater flow. 

Water arrives at the plant mostly by gravity.  Depending on local geography, it may need to be  

pumped or lifted into the wastewater plant. Screw pumps are a rugged, mechanically  

simple design built to handle  this coarse incoming mixture. 

Bar screens trap debris, including literal tons  of items that really shouldn't be flushed or sent  

down the drain, such as baby wipes, q-tips,  diapers, paper towels, medication, and so on. 

A moving platform called a “rake”  scrapes the bars, removing the  

debris for separate processing and disposal. The water then travels to the grit chamber  

to remove heavier, inorganic gritty particles  like sand, silt, clay, coffee grounds, eggshells,  

and so forth, while allowing lighter  organic material to pass through. 

A spinning plate with fins,  

called an impeller, creates an axial vortex  which is a sort of vertical spiral force  

along its spin axis, at a specific speed so as  to catch particles in a defined weight range.  

These heavier grit particles are forced  down chamber walls and out at the bottom. 

The grit is collected to undergo its own  separate dewatering and washing process. 

The wastewater leaves the headworks  towards primary clarification. 

Primary clarification separates  organic matter from the wastewater. 

Water flows in at the center of large circular  basins, called sedimentation tanks. A baffle slows  

down the flow rate to aid the settling process. Floatable solids like grease and oil drift to the  

top of the tank. A rotating skimmer continually  pushes this material into a collection trough. 

Settleable solids sink to the angled bottom  of the tank and form a sludge. Scraper arms  

push the sludge out of the tank into a sludge pit. This organic matter has its own purification  

process, and can eventually be  used, for example, as fertilizer. 

A baffle at the edge keeps floating material  from mixing with outgoing processed water  

as it flows over a lip at the  edge of the tank called a weir. 

At this point, the water is starting  to look a lot cleaner and clearer. 

The water flows to secondary treatment,  which in our model, is an aeration tank. 

In the aeration tank, helpful microorganisms  are mixed in with wastewater. These are  

special bacteria and protozoa that consume  biodegradable waste products, such as human waste,  

food waste, soaps and detergents. These helpful microorganisms also  

need oxygen to live, so air is vigorously pumped  through the mixture. They either directly absorb  

soluble particles as food, or emit enzymes that  eventually allow solid particles to be digested. 

The microorganisms naturally stick together  over time, forming clumps called floc. 

The water and floc mixture  travels to final clarification.  

Here, the floc sinks to the bottom of  the tank. Some of this settled floc is  

collected for re-use in the aeration process  as the helpful organisms are still active. 

Processed water flows over the edge of the tank  

en route to final disinfection  in a UV light exposure tank. 

After final disinfection, the water is  ready to be released back into nature.  

A specially designed outfall  pipe with diffuser nozzles  

mixes treated water evenly while causing minimal  disruption to existing environmental conditions. 

Treated wastewater and untreated drinking water  almost never share the same immediate natural  

water system, though some rare places  in the world are challenging that model.