Water Quality Module

Part 1. Water Treatment and Purification

Section Overview
  1. What is water treatment?
  2. What is water purification?
  3. What does the word process mean? What is an SOP?
  4. Who decides if water should be treated?
  5. What is meant by pre-treatment?
  6. What is meant by coagulation?
  7. What is meant by flocculation?
  8. What is meant by sedimentation?
  9. What is a clarifier?
  10. What is meant by filtration?
  11. What is meant by disinfection?

A. Water Treatment

Water Treatment is a process used to make water safer to drink. The goals of water treatment processes are to:

  1. Remove existing contaminants (things that pollute) in water, improving it for later use,
  2. Allow treated water to discharge (go) into the natural environment, such as rivers, lakes and the sea, without harming the environment in some cases.

There are several stages or steps in the water treatment process. We'll take a very quick look now at the common ones for larger centres.

Stages of the Water Treatment Process
  1. Pre-Treatment – in this stage of the water treatment process large objects like sticks, fish and leaves are removed from raw water coming into the water treatment plant. Pre-treatment of the raw water prepares the water for the next stages of the process. Pre-treatment of the water supply depends on the condition or quality of the raw water. It may include removal of turbidity (suspended and dissolved solids). It may also include pH adjustment, water condition to prevent scale build up. Pre-disinfection in this stage may be done to prevent biological growth and to kill disease-causing microorganisms (pathogens).
  2. Coagulation – in this stage of the treatment process chemicals called coagulants are added. They are gently mixed with the raw water coming from the pre-treatment stage. The coagulants remove the electric charge of very small particles. Before the coagulant is added the particles repel or push away from each other. After the coagulant is added the particles begin to move together.
  3. Flocculation – in this stage the very small particles that are now moving together become larger particles called floc. Gentle mixing of the water and coagulants makes the particles come together. The particles then attach to each other and become bigger. These bigger particles of floc become heavy. They sink to the bottom of the tank. Some of the particles stay light. They float on the surface of the tank.
  4. Sedimentation – in this stage the larger particles that came together and became heavy sink or settle out in the tank. These tanks are called clarifiers. Once the floc settles to the bottom of the tank it is called sludge. The sludge is removed. It is dealt with in a side process. The floc that stayed light and floated on the top of the clarifier is removed. It is removed by skimming it off the water using arms called skimmers or flights. This floc is added to the sludge from the bottom. It is dealt with in a side process.
  5. Filtration – in this stage of the water treatment process any particles that did not float to the top or settle to the bottom are removed. These particles still in the water are called suspended particles. Suspended means that the particles are still floating somewhere in the water. These suspended particles are now removed when the water runs through a filter. The filter traps these particles. It holds onto them so that the particles cannot go any further. Periodically these particles stuck in the filter are removed by a process called backwashing. The backwashed particles may be returned to the start of the water treatment plant.
  6. Disinfection – There are many methods of disinfection. One is where chlorine is added to the now treated water. This is done to kill any remaining disease-causing organisms. Enough chlorine is added so that there will be chlorine residual in the water going to the water distribution system.
  7. Clear Well – in this area of the water treatment plant, water is given time to react with the chlorine that was added. The clear well is a large tank that stores the treated and disinfected water to be used in the water distribution system.

B. Water Purification

Water purification is the process of removing contaminants (things that pollute) and other harmful microorganisms (tiny organisms such as a virus that can only be seen under a microscope) from a raw (untreated) water source. The goal is to produce water for a specific purpose.  Most water is purified for human consumption (drinking water).

Water purification may also be done for other purposes, including: Medical, pharmacology, chemical and industrial use. Water purification may remove many undesirable elements.

Water treatment and purification are done in a Treatment facility. The work is done by Water Treatment Operators.

C. Meet a Water Treatment Facility Operator

Terry is a Water Treatment facility Operator for a small community of 2,500 people. Terry started working for Smallville 8 years ago as a public works labourer.

At the Start

Before working for Smallville Terry had different kinds of jobs. He was a grocery store clerk, a construction labourer and a maintenance person at a local hotel. Terry likes working with people. He also likes to build and maintain things. Most of all Terry likes variety in his work.

Career Possibilities

Terry's experiences helped him get the job as a labourer in Smallville 8 years ago. At first, Terry helped other public works employees install traffic signs, repair water and sewer lines, and operate heavy equipment. He started work at the Wastewater Treatment facility. Terry liked the variety of jobs at the Wastewater Treatment facility.

Smallville decided to build a Water Treatment facility. Terry jumped at the chance to work there as a labourer. Terry's past job as a maintenance person at the hotel helped him get this job. His experience with hotel maintenance and swimming pool water treatment made Terry the right person for the job.

What does Terry do?

For 2 years Terry has worked at Smallville's Water Treatment facility. Terry has a variety of Operator duties. These include:

Certification

Terry has worked hard to prove himself. In return, the community of Smallville has given Terry the opportunity to become a Water Treatment facility Operator. To become an Operator, Terry had to write a level 1 Water Treatment Operators' exam. Because of Terry's hard work, willingness to learn and his reliability, Terry has passed the exam. He has been awarded with a Water Treatment Operators Level 1 position in Smallville.

The Future

Terry enjoys his job as a Water Treatment Operator. Terry is now taking new Water Treatment courses. He is working towards writing his level 2 Operator's certification exam. Terry likes the variety of his work. He is given the chance to learn new skills, such as pump repair, welding and computer skills. Terry says, 「Every day is different. I've learned a lot of new skills. I get to use these skills each day. I can't wait until tomorrow!」

Opportunities in Water Treatment

We saw how Terry started in the Water Industry. It was a little different than how Sarah started. But just like Sarah, because he worked hard and was interested in learning he was rewarded. He has a Water Treatment Operator's position. This is another kind of opportunity in the Water Industry. Find out about yours!

Part 2. Water Quality Information

Section Overview

It's not enough to get water to people's homes or businesses. It has to be safe and be water that people want to drink or use! When we talk about water quality this is mainly what we are talking about. In this chapter we look at some of the things that make water unsafe. We begin with contaminants that are the mysterious sounding 「microorganisms」 and then we look at something called 「turbidity」.

A. Contaminants and Microorganisms

  1. What are contaminants?
  2. What contaminants are we looking for?

Contaminants are things in water that make it unsafe or water we don't want to use. These include something called microorganisms (bugs). There are 3 main classes of microorganisms that are of concern in drinking water:

  1. Virus
  2. Bacteria
  3. Prorozoa

Under certain conditions distribution water can be an ideal breeding ground. It can contain many types of bugs and other disease causing Pathogens (tiny organisms that can cause a disease).

Without a disinfectant like chlorine, one microbe (bug) can multiply. It can become an amazing 4,000,000,000,000,000,000,000. That is a lot of undesirable pathogens!

It's not practical to look for every single kind of microbe in water that could threaten public health. So we usually test for the most common microbes. Bacteria can multiply quickly. Testing must be done often. This way we become aware of a change, or contamination, as soon as possible.

Water System Operators are responsible to get safe drinking water to customers. At the plant Operators do the required tests for pathogens. They report the results to a public health official when the results are of concern.

Another test that Water Treatment Operators must do is a test for turbidity. This is a very important concept. We'll look at turbidity in the next section.

B. Understanding Turbidity

As you read through the information on turbidity answer the following questions:

  1. What is turbidity?
  2. What water sources are most affected by turbidity?
  3. How is turbidity measured and reported?
  4. How often is water typically tested and for what purpose?
  5. How should an elevated or higher level of turbidity be reported?
  6. What is turbidity an imporant water quality indicator?

1. What is Turbidity?

When you see water that is cloudy, or looks brown, we say it has high levels of turbidity. Water Operators work to keep turbidity at an accepted level.

Turbidity is a water quality term or word. It means all kinds of particles (tiny amount) in water like clay and silt. There are 2 kinds:

Turbidity levels are much higher in water from surface water sources (e.g. streams, rivers, and lakes) than from groundwater sources (e.g. aquifers). When it rains hard or snow melts in the spring run off, this water often carries lots of organic and inorganic particles into the water sources. So turbidity levels can be very high especially at that time.

Turbidity is measured and reported in nephelometric turbidity units. But almost everyone uses the shorter term, NTU. Turbidity levels can range from less than 1 NTU to more than 1,000 NTU.

Tip: At 5 NTU water is visibly couldy; at 25 NTU it is murky.

2. Standards for Levels of Turbidity

Water for drinking is measured against standards found in the federal, 「Guidelines for Canadian Drinking Water Quality」. To meet these standards, water is tested regularly for bad things we do not want in our drinking water. This includes viruses, bacteria (e.g. E-coli), parasites (e.g. Giardia and Cryptosporidium), and turbidity.

The Guidelines recommend that water used for drinking have a turbidity level less than 1 NTU. You see this written as <1 NTU (「<」 is a symbol for less than and 「>」 is the symbol for more than).

Many utilities monitor turbidity with computers 24 hours a day, 7 days a week. At some utilities Operators also collect samples daily. This is used as a second check of the turbidity levels.

Following the Guidelines for Canadian Drinking Water Quality and provincial Drinking Water Protection Regulations, water suppliers notify customers when turbidity levels are over 1 NTU. A Turbidity Index on a supplier's website shows if the water is 『Good' (<1 NTU), 『Fair' (1-5 NTU), or 『Poor' (>5 NTU). They provide recommendations for each. 『Fair' and 『Poor' ratings are also publicized through the media.

3. Turbidity & Contaminants

Bacteria, viruses, and parasites, such as Giardia and Cryptosporidium, can attach themselves to the suspended particles in turbid water. These particles can get in the way of disinfection (used as a means to clean something so as to destroy disease-carrying microorganisms). They shield contaminants from the disinfectant (e.g. chlorine). Note: Chlorine is not effective in deactivating (preventing something that is active or live from operating) Cryptosporidium.

Water Utilities may use more than one way to deactivate these contaminants. For example, the City of Kelowna has Ultra Violet (UV) reactors at 3 lake intakes to help with the chlorine disinfection. Ultraviolet light treatment is effective in inactivating (killing) certain parasites such as Giardia and Cryptosporidium that can be present in source water.

You can find lots more information about health issues and turbidity. A good place to look would be the Health Authority website.

Once you're familiar enough with the material presented, take the Online Quiz