Exact Stormwater Management

A stormwater quality filter is a type of infrastructure used in stormwater management systems to remove pollutants from stormwater runoff before they are discharged into natural water bodies or groundwater. These pollutants can include sediment, debris, heavy metals, and even nutrients like phosphorus and nitrogen that cause big problems when they enter natural waterways.

Water quality filters typically consist of several components including an inlet, an optional pre-treatment sediment chamber, filtration media (often in the form of a removeable cartridge), and an outlet structure. The inlet structure is where stormwater enters the system. Some inlets include areas where floatable materials like oil and grease get trapped. Inlets may include a mechanism to alter the direction or speed of the flow of runoff to help settle out heavier particles in the pre-treatment sediment chamber.

After that, runoff passes through the filtration media where most of the work happens. Most cartridges are designed to physically trap tiny particles within the cartridge, so that things like sediment and micro-plastics can’t escape. Some cartridges include a filter media designed to chemically attract dissolved pollutants like nitrogen and phosphorus, causing them to “stick” within the cartridge.

The Outlet is where cleaned stormwater exits the filter, which may include additional features to control flow rates and prevent re-suspension of filtered pollutants.

Water quality filters are an important tool in urban stormwater management, as the filter media contained inside can target the pollutants coming from the local area that cause the biggest problems. There are many different types of water quality filters, and they each filter water a little differently. If you need help understanding your filtration system and the regular maintenance it needs to continue protecting downstream waters, Exact can help identify what system you have and how it works, along with what type of inspection and maintenance schedule is necessary to ensure your system continues to protect receiving water bodies to mitigate the impacts of urbanization on aquatic ecosystems.

Inspecting a stormwater quality filter is crucial to ensure it functions effectively in removing pollutants from stormwater runoff. Inspections of newer systems should be done quarterly through the first year of use, and then at least annually thereafter. It's also a good idea to check on your filter after any major storm events to ensure its working properly and no large objects are jamming up water flow through the unit. 

The first step of any inspection is to check for any signs of damage or deterioration to the structure itself, including cracks, corrosion, or leaks. Ensure that all lids, access ladders, and other components can be safely utilized. 

Next, inspect the inlet and outlet structures for blockages, debris buildup, or erosion around the edges. Check all screens or flow control devices to make sure they are clear, with no obstructions. Look for signs of sediment accumulation in the pre-treatment. If your filter is functioning properly, it's very likely you'll see sediment inside the unit. That doesn't necessarily mean it's time for maintenance, though. However, you definitely want to take action before your cartridges are buried and become inundated with sediment.

Be sure to keep good records of your inspection findings, including any observations, maintenance needs, or corrective actions taken. Keep your notes in a log that includes inspection dates, findings, and maintenance activities for regulatory compliance and future reference.

If all of this sounds entirely too messy, or if you have concerns about your filter, consider hiring qualified professionals  like Exact for a more comprehensive inspection.

Regular inspections are an essential first step to ensure that your stormwater quality filter continues to operate effectively and comply with regulatory requirements.

Maintaining a stormwater quality filter is essential to ensure its continued effectiveness in removing pollutants from stormwater runoff. Filters can trap (literally) tons of sediment and debris, and keeping them clean not only keeps the system working properly, but also prevents the system from clogging, which puts it in bypass mode, sending all the nasty pollutants straight into the downstream water bodies.

Different types of filters require different processes to perform maintenance, and some even require confined space entry which can be pretty hazardous. You will almost always need professional help to maintain your filter, and here's what you should expect from them: 

Maintenance should always be triggered by an inspection that documents what needs to be done. While any structural deficiencies noted in the inspection should always be handled first to ensure the rest of the process is completed safely. Typical maintenance for water quality filters begins with removing the collected sediment and debris from the optional sediment chamber (if present). Some of that may be done by hand, but most systems are designed to be cleaned out with standard jet-vac equipment to avoid the hazards (and cost) of confined space entry.  

Next, the cartridges need to be maintained. Depending on their age and the type of cartridge, they may be able to be backflushed and re-used, but at some point all cartridges will need to be replaced. Old cartridges should be cleaned out and recycled with the system manufacturer, who will recharge the cartridge for reuse.  

Maintenance activities should also include the outlet structures. Clear any obstructions and ensure proper flow out of the filter. Remove debris, vegetation, and any other materials that may impede flow, and, if the treated water outlets to a drainage swale or natural waterway, check the outfall to ensure there's no erosion or blockages which could create problems. 

Keep detailed records of all maintenance activities, including pictures and descriptions of what was done. If you're using professional help, they should provide a full photo-documented report for your records. Keep the report in your inspection/maintenance log.  

By performing regular maintenance you can ensure that your stormwater quality filter remains effective in protecting water quality, meet your regulatory requirements obligations for stormwater quality, and avoid dumping polluted water on your downstream neighbors. 

Installation of a stormwater quality filter can be a pretty big task and is usually handled by a professional contractor. The process involves excavating the area and installing the (typically) very large, concrete structure using cranes or large equipment to move the components. Setting the structure at precisely the correct elevation is critically important to ensure water flows through the system properly. All water quality filters work on gravity, so being off - even by a few inches - can have drastic impacts on performance.

Once the system is installed, the inlet and outlet connections are made, and the system can be backfilled. Pavements or various surface treatments can be placed over the filter, and the access hatches can be installed, which allow the system to be inspected and maintained later on. Getting all of this work done properly is no small task, so be sure to get a professional stormwater contractor like Exact on your team to work through the details of a successful installation.