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A Complete Guide to the Water Treatment Process

Riley Kooh   |   June 10, 2022

As Earth’s most valuable natural resource, water is constantly being utilized for drinking, bathing, food production, industry, energy, waste management, and more. Worldwide, humans currently use 10 billion tons of freshwater every day. Managing and treating water on that scale can sound like an insurmountable task, however effective internal practices can assist water treatment plants to meet these needs.

What is a Water Treatment Plant?

“Water Treatment” is an umbrella term used to describe the process of improving water quality for safe use for a specific task like drinking, industry, or irrigation. Modern practice dictates that water treatment takes place in official Water Treatment Plants to standardize safe procedures. Depending on the initial water source being drawn from and the end use-case, facilities can be categorized. These categories are Water Treatment Plants, Wastewater Treatment Plants, and Industrial Water Treatment Facilities.

Water Treatment Plant

Water Treatment Plants refer to facilities that harvest groundwater or rainwater to purify for drinking water. This clean water is then transferred directly to communities or stored in potable water tanks. Plant sizes are generally smaller than wastewater plants due to the higher initial water quality requiring less overall treatment for safe use.

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Wastewater Treatment Plant

As the name dictates, Wastewater Treatment Plants draw sewage from communities for cleaning and sanitation. Rather than repurposing for potable drinking water, a wastewater plant’s goal is to purify wastewater to a safe level for redistribution into natural environments. These plants are generally larger and more complex due to the more extensive treatment required on wastewater.

Industrial Wastewater Treatment Facility

While some industrial wastewater can be treated within a standard wastewater plant, certain industrial processes like battery manufacturing or electric power plants handle dangerous chemicals or compounds. Due to the potentially hazardous nature, these instances require specific treatments to ensure wastewater is completely safe before redistribution.

Steps to the Water Treatment Process

There are a lot of variables that can affect the steps in the water treatment process. These include but are not limited to: country, municipality, quality of water being treated, and desired end-use. Regardless, all plants end-goal is to cleanse water to meet the legal standards of their respective location. These are the common steps which all treatment plants base their practices on.

Step 1: Screening

As the first stage of water purification, a general screening process is required to remove larger debris from the water. This not only removes large contaminants from the water, but also ensures the equipment is safe from jams or damage from solids. Screens can be classified as coarse or fine depending on the width of their filtering bars/pores.


A coarse or ‘bar’ screen spaces steel bars at 5-15cm intervals to catch the largest of solids like logs or animals. Water will first travel through the coarse screens and into the fine screens which space their bars at 5-20mm intervals. All sediment and organics will then fall to the bottom of a collection area and be pumped out for processing and disposal.

Step 2: Aeration

Introducing oxygen into the water encourages the natural breakdown of organic materials, kills off bacteria, and removes iron or manganese which can affect taste. Oxygen will also help expel carbon dioxide and hydrogen sulfide to lower the corrosion level of the water. Staff will consistently monitor dissolved oxygen, ammonia, and nitrate levels to ensure bacteria is effectively being converted.

Step 3: Coagulation and Flocculation

Coagulation refers to the introduction of a coagulant into the water. This chemical holds a positive electrical charge and neutralizes the water’s fine particles to allow them to group and form ‘flocs’.

The water is then stirred by mechanical paddles to force contact between the flocs and compound into larger particles. To avoid the flocs from breaking apart, the water travels through different compartments within a basin with progressively slower mixing speeds. This process is called flocculation.

Step 4: Sedimentation

Once the work of coagulation and flocculation is complete, water is left in a basin to settle. After several hours, the flocs will sink to the bottom for removal.

Step 5: Filtration

Nearing the end of the treatment process, the water is now ready for filtration. Any remaining solids after sedimentation will be removed after passing through a filtration system. The most common materials used for this process are sand, gravel, or granular activated carbon beds. These filters not only remove remaining particulate matter, but also cleanse the water of remaining organics that can cause unpleasant tastes.

Step 6: Disinfection

As a final measure of security for safe water use, chlorine (or another disinfectant) is added to the water to eliminate the last remaining microorganisms. In order to abide by World Health Organization guidelines, residual chlorine levels should be at a maximum residual chlorine of 5 mg l–1 of water. The minimum residual chlorine level should be 0.5 mg l–1 of water after 30 minutes of contact time for safe consumption.

Depending on the scenario, additional treatment measures may be beneficial to implement. A common additive to drinking water is fluoride to assist in oral health and prevent dental decay.

Step 7: Storage/Distribution

Once the water has passed through all the above stages of treatment and adequate testing, it is now ready to distribute or store. Water will either be transferred to potable water tanks or released safely into local waterways.

The Importance of Water Treatment Plants and Water Quality

Maintaining rigorous health standards for water quality is integral to the overall health of communities, economies, and environments. Allowing contaminated water to be used for drinking, household activities, agriculture, industry, or be reintroduced into the environment can cause a variety of serious issues. An estimated 245,000km² of marine ecosystems are negatively affected by inadequately treated wastewater, and poor water quality results in more annual deaths than all wars and other violence combined. LAKE INVADERS_intext A solution to these problems lies in the global development and implementation of standardized water treatment. In its current state, nearly 80% of the world’s wastewater is dumped back into environments at a “largely untreated” state. Dedicated facility development, combined with thorough testing, inspection, and maintenance of existing facilities can help alleviate this environmental and humanitarian impact.

How Water Treatment Plants Maintain Good Water Quality


Every country abides by their own internal regulations for water quality. In the United States, EPA created the National Primary Drinking Water Regulations (NPDWR) as a legally enforceable standard for water contaminant levels. In order to abide by these regulations, water treatment plants must be constantly monitored and tested. Every facility should have a designated testing area at the end of the treatment process where water can be tested multiple times a day.

Additionally, testing should also be conducted of the waterway in which water is being drawn and deposited for quality assurance. For quick and effective sampling throughout different water levels and locations, ROVs with water sampling attachments or environmental sensors are an invaluable tool.


Although the screening process assists in removing large debris that can cause damage to equipment, degradation is an ever-persistent issue. With constant exposure to water, facility components should be consistently monitored for rust, marine growth, and general functionality. Additionally, working with exposure to potentially dangerous chemicals increases the need for strict safety precautions and functional assets.

Submerged inspections of basins, filter systems, paddles, etc., can be difficult and/or dangerous for divers to perform without downtime. ROVs can be an effective tool for safely conducting and recording underwater inspections, as well as retrieving or manipulating physical debris. Identifying areas of concern and scheduling cleaning or maintenance helps alleviate potential issues in the future. droplets-fountain-water-bird

The Canadian city of Regina's water treatment plant at Buffalo Pound Lake serves as an excellent example of how an ROV could assist in consistent inspections. High levels of algae in the water have slowed the filtration process to half the regular capacity (CTV Regina 2015). Citizens were asked to lower their water consumption by 25% for days until the facility could resolve the issue.


Maintenance and cleaning of water treatment plants is integral for smooth operation of such a vital piece of infrastructure. Once an issue such as rust or marine growth is identified in an inspection, preventive maintenance is traditionally conducted by divers or during a partial shutdown. It’s advised that the plant is cleaned and emptied 1-2 times annually to avoid compounding build up.

Sludge and sediment is also intentionally occurring during the treatment process which should be routinely removed. There are various types of systems in place to remove the majority of this build up, however ROVs or Utility Crawlers can effectively be deployed to assist in sludge removal.

Make routine inspection affordable and easy with ROVs

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How Deep Trekker can Improve Inspection of Water Treatment Facilities

Deep Trekker offers a variety of comprehensive robotic solutions designed to streamline the inspection and cleaning processes within water treatment facilities.


The DTG3 is Deep Trekker’s most portable and compact ROV in its lineup. It’s simple yet durable design weighs in at just 19lbs, and the entire system travels in a single Pelican case. This enables a single operator to easily transport and deploy the ROV for effective inspections.

Its small form factor is also capable of operating in areas as narrow as 16”, making it adept for working in confined spaces. Coming standard with a 270 degree panning HD camera, vertical precision thruster, and recording capabilities, the DTG3 performs admirably as an all-in-one inspection tool. droplets-fountain-water-bird

Beyond visual inspections, the DTG3 can be equipped with physical manipulator claws, samplers, environmental sensors, gauges, and more for improved monitoring of submerged assets. Building an in-depth portfolio of status reports using an ROV is an effective way to catch defects quickly. A report history also helps forecast future maintenance without the cost, risk, or scheduling associated with divers.


The DT640 VAC Crawler is Deep Trekker’s innovative solution to remote tank cleanings. Coming in two different sizes, this utility crawler allows an operator to quickly and easily remove sediment from the bottom of tanks and basins. Consistent removal is the key to preventing build up.

If left unchecked, sludge that has been missed by removal systems will cause operational or contamination issues, and will need to be removed manually. The safest and most cost-effective method of this is to deploy the DT640 VAC. droplets-fountain-water-bird

A-200 Pipe Crawler

Deep Trekker’s latest A-200 Pipe Crawlerprovides immediate and effective inspections of pipelines. Being battery operated and fully submersible up to 50 meters allows for a portable solution across the entire facility. The elevating arm allows for the camera to center itself in pipes between 8” to 36” for NASSCO certified inspections. For water treatment plants, the A-200 is a powerful tool for remote inspections of transfer pipes. droplets-fountain-water-bird As always, our team of experts is available to answer any questions you may have. If you’re looking to upgrade your inspections and avoid plant downtime, reach out to get your customized quote today.

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