The Impact of Severe Weather on Municipal Wastewater Treatment Systems

Severe weather events, such as storms with heavy rainfall and tropical cyclones, have resulted in significant damage over the past 40 years. In fact, according to the National Centers for Environmental Information, the United States has faced 400 weather and climate disasters since 1980, where damages reached or exceeded $1 billion.

Furthermore, hurricanes and severe storms with significant rainfall, such as this year’s Hurricane Helene, have a considerable impact on municipal wastewater systems, especially when these systems aren’t prepared to handle large influxes of rainwater. Still, these weather events will continue to happen, so wastewater treatment facilities must be prepared, especially considering the damaging impact of hurricanes and other severe storms in the U.S. is expected to increase year after year.

So, how exactly does severe weather affect municipal wastewater systems, and what are some preventative measures plants can take to prepare for disastrous weather? Let’s take a look.

Stormwater Surges/Combined Sewer Overflows

When heavy rainfall occurs during a severe storm, the added volume of stormwater (and potential flooding) can quickly overwhelm water treatment facilities. Stormwater sewers and treatment plants are only equipped to handle so much water at once, so when stormwater exceeds that capacity, the system can’t process the incoming flow effectively, leading to surges and sewer overflows.

This is particularly bad because when systems are overwhelmed, especially in areas with combined sewer systems, stormwater and untreated sewage (containing pathogens, hazardous chemicals, and other contaminants) are directly discharged into rivers and lakes to prevent the plant from flooding.

Physical Damage to Infrastructure

High winds, flooding, and other conditions can also physically damage water tanks, pumps, lift stations, and other equipment with very little notice. And, while facilities may have contingency plans in place for some damaged equipment, severe storms can bring entire treatment processes to a halt.

Untreated Wastewater

Hurricanes and other severe storms lead to widespread power outages, which can be devastating to municipal wastewater treatment facilities. This is especially true in facilities where reliable generators are not available (or where generators are not robust enough to power all equipment needed to treat wastewater effectively). The result can be the dangerous discharge of untreated wastewater, which could expose citizens to pathogens and bacteria.

Even when storms do not cause total power outages, heavy rainfall can impact the effectiveness of wastewater treatment. As previously mentioned, overwhelmed systems can cause overflows, contaminating public water supplies and possibly harming public health.

Preventative Measures for Wastewater Treatment Plants

Although severe weather can be extremely detrimental to municipal wastewater treatment facilities, there are several practical measures that plants can implement to reduce the negative impact of severe weather and protect populations from contaminated water supplies during wet weather treatment.

Use Overflow Screens & Coarse Screens

One of the simplest yet most effective steps wastewater treatment facilities can take to mitigate the risk of severe weather and heavy rainfall is installing overflow screens and coarse screens, such as JWC Environmental’s Mechanical Bar Screen Monster and Chain & Rake Monster.

Coarse screens are the first line of defense for treatment systems. They are designed to filter out large debris and solids from incoming wastewater, preventing clogging and damage to downstream equipment. By removing these large solids and debris early on, coarse screens help ensure a manageable water flow and protect downstream equipment, even during high inflow periods.

Comparatively, overflow screens provide an additional layer of filtration when inflows exceed the plant’s capacity. These screens capture debris and solids in combined sewer overflows, reducing the amount of untreated contaminants that could pollute nearby water.

Upgrade Outdated Equipment

Municipalities face (relatively) newer challenges. Some of these challenges include larger volumes of wastewater and solids due to population growth, more industrial discharge, and tougher materials like rags, wipes, and other non-biodegradable items being irresponsibly flushed. This means that grinders installed years ago may not be able to withstand the increased flow rate and volume of solids or efficiently shred challenging solids like rags.  

Plant supervisors must analyze and evaluate whether their grinders are sized for the plant’s normal flow rate and volume of solids and if they’re well-equipped to withstand stormwater filtration from increasingly powerful and more frequent storms. If the equipment isn’t performing optimally, supervisors should invest in more powerful equipment, such as a Muffin Monster. Available in multiple sizes, these grinders are designed to process larger volumes of wastewater and solids more effectively and feature optional Wipes Ready® cutter technology that can efficiently shred rags and wipes.

Implement Generators or Equipment With Bypass Weirs

Unfortunately, power outages do occur as a result of severe storms, and the impacts on municipal wastewater treatment facilities can be devastating. This is why plants need to have generators in place to provide backup power in the event of an outage.

Likewise, adding bypass weirs to existing equipment can also reduce the impact of an outage. When inflows exceed equipment capacity, the weir diverts excess water into alternate pathways, like storage basins, overflow areas, or outfalls, which help prevent damage to equipment and potential contamination of public water supplies.

Learn More From JWC Environmental

JWC Environmental has been engineering innovative municipal wastewater treatment equipment for over five decades. You can visit our website to learn more about our positive impact on wastewater treatment facilities across the United States, or browse our blog for more municipal wastewater news.