February 20, 2024

What Is a Wastewater Bar Screen and Why Is It Important?

By
Jane Cooper

America has 14,778 wastewater treatment plants and they all work to purify the water that plants, animals, and humans drink every day.

One of the most crucial pieces of equipment for these facilities is a wastewater bar screen. It's the first step in the process because it filters out large solids. Without it, hazardous materials would remain in public drinking water and clog up the rest of the plant’s equipment.

Read our guide to learn about a bar screen’s place in the wastewater treatment process and how to find the best one for your needs.

What Is Wastewater Treatment?

Wastewater contains contaminants such as feces, urine, sticks, and debris. 35% of it contains solid objects.

Wastewater treatment helps clean this water. It's also used to return it to the ecosystem without harming the environment. The entire process takes about 24 to 36 hours from start to finish.

The stages of wastewater treatment include pre-treatment, primary treatment, secondary treatment, disinfection, and effluent release.

Pre-Treatment

Pre-treatment begins when wastewater arrives at a treatment plant. It flows through a bar screen, and any large solids get sent to landfills. The water then moves to a grit chamber that lowers its velocity and removes smaller particles.

Primary Treatment

Primary treatment begins when sediment settles in the grim chambers. The water moves to a primary clarifier. Heavier solids settle at the bottom and become sludge, while lighter material floats to the top and becomes scum. This makes the water effluent, meaning that it's slightly treated and free of solids and organic materials.

Secondary Treatment

Secondary treatment begins when the effluent water flows into an aeration basin. It artificially adds air in a process known as aerobic digestion that removes any leftover solids and organic matter. The water then goes to a secondary clarifier to remove the sludge. After that, it returns to the aeration basin.

Disinfection

When disinfection begins, 85% of organic matter has already been removed from the water. Water treatment plants use chlorine, ozone, or UV disinfection to remove the rest.

Chlorine disinfection puts chemicals into the water and then removes them before discharging them into a stream or lake.

Ozone disinfection pumps an electrical current through the effluent water to separate oxygen molecules. It removes 99.99% of bacteria.

UV disinfection sterilizes water using ultraviolet light to kill any remaining microorganisms.

Effluent Release

Effluent release is the last step in the process. It involves sending the treated wastewater back into local waterways or discharging them into another treatment plant.

What is a Wastewater Bar Screen?

A wastewater bar screen is a coarse screen made of vertical steel bars spaced 1-3 inches apart. It filters out large solid objects such as rags, plastic, paper, and metal from flowing water.

The most basic wastewater bar screen uses nothing but vertical bars that allow water to pass through but stop larger objects. They're effective but not as efficient as other types. Objects can build up on them, preventing flow and elevating backwater levels.

Many plants use a conveyor system where bars or wires pick up solids that build up on the screen and take them to a separate container. This is a type of mechanical bar screen.

Manual bar screens require little maintenance, but need frequent cleaning. The process is time-intensive and dangerous because it can cause overflows or flow surges. Only old plants use them as a primary screening system. They're best utilized as a backup option or for small facilities or bypass channels.

Mechanical bar screens automate removing debris. They reduce labor costs and the risk of overflows, but are more expensive to purchase and maintain.

There are 4 types of mechanical bar screens; chain-drive, reciprocating rake, catenary, and continuous belt screens.

Chain-drive screens use a rake that can go up or down to help keep themselves clean.

Reciprocating rake or climber screens use one rake that moves to the base and pulls waste to the top where it's disposed of. They're efficient, but not the best option for heavy screening.

Catenary screens have a rake that goes against the bars and travels up to deposit waste into a chamber.

A continuous belt screen uses a large number of rakes to maintain cleanliness.

Why Do I Need a Bar Screen for Wastewater Treatment?

Emptying improperly treated water into lakes and rivers can devastate local plants and wildlife. It can also negatively affect public health.

As the first step in the wastewater treatment process, the importance of a wastewater bar screen cannot be overstated.

A wastewater bar screen prevents damage and wear and tear, reducing the need for maintenance for the whole system. It minimizes interference during the treatment process while also preventing clogging and contamination of waterways.

How Do I Choose the Best Wastewater Bar Screen?

There are several factors to consider when choosing a wastewater screen.

Consider the size and volume of the material that needs to be removed. You may need larger screens to filter out heavy material.

You should also consider the minimum and maximum water levels in the area. You'll need a larger screen system to filter out more water, even if it's clean.

Look into the screen's maintenance requirements and reliability. For example, manual bar screens require less maintenance, but aren't as reliable because they get covered in built-up material more often.

Consider the characteristics of your plant. Ensure that the screen meets your needs.

You must also determine who is the best supplier in your area to purchase the wastewater bar screen from. You must do your research to find the most reliable, highly-rated company possible.

Where Can I Find a Wastewater Bar Screen?

Wastewater treatment provides the world with healthy drinking water by removing large contaminants and those that are too small to see. There are thousands of plants dedicated to achieving this purpose.

A wastewater bar screen stops and removes large solids. It purifies the rest of the water that moves on to other purification processes.

Choosing the right wastewater bar screen begins with examining your needs. If you're aware of how much water needs to be processed, what it contains, and what equipment you already have, you can choose the right type and size of screen to manage it.

Franklin Miller is a trusted provider of wastewater treatment equipment. Browse our wastewater screening equipment today.

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