5 Common Wastewater Challenges and How To Mitigate Them

Wastewater treatment utilities are constantly battling aging infrastructure and rising demand — all while contending with tighter budgets and fewer staff. Yet, many of the most persistent operational headaches stem from familiar sources: rags, grit, surges, odors, and cost pressures. Fortunately, there are proven strategies and technologies that can help utilities address these issues while maintaining optimal plant performance.

Challenge 1: Ragging and Clogging

Even though manufacturers are now clearly labeling wipes as non-flushable, people’s bad habits remain. Clogs from wipes and other rags cause sewage backups that can flood basements, resulting in high cleanup costs, public upset, environmental hazards, and sometimes regulatory penalties. At the plant level, these materials can overwhelm pumps, blanket aeration systems, and more.

To address this, utilities must take a two-stage approach. First, in the sewer lines and pump stations, where removal is impractical because stations are unmanned, grinders are key. They break the rags and wipes down, keeping the material moving to prevent them from clogging transportation pumps. Second, once the flow reaches the wastewater treatment plant (WWTP), screening becomes critical. High capture rate efficiency screens are needed to remove trash.

Challenge 2: Solids and Grit

An increasing presence of solids and grit is most often attributed to aging infrastructure. Inflow and Infiltration (I&I) occurs when cracked or broken pipes allow extraneous stormwater and surrounding earth into the system. This abrasive material causes significant damage to treatment equipment. Grit can wear down grinder teeth and pump impellers. Meanwhile, screens are designed to pass grit, not remove it. Therefore, WWTPs should implement a specialized grit collection system as part of the headworks design. Investment in such systems, along with high capture rate efficiency (CRE) screens can mitigate the damaging effects of I&I and associated grit.

Challenge 3: Variable Flows

The increasing frequency of major storms (combined with I&I from aging infrastructure) is causing extreme variability in flows. Plants designed for 5 MGD can sometimes see peak flows that are three or four times as much during storm events. The need to bypass or store after the initial first flush of heavy solids is a must. However, it is also critical to have screens with high turndown ratios —ideally as much as 10:1. This allows them to effectively handle both very high and very low flows.

Challenge 4: Odor Control

Many WWTPs, built 40 or 50 years ago in isolation, are now surrounded by residential properties. Despite residents knowingly moving in near the plant, the smells can be a significant nuisance for them. A major contributor to odor is the biological material present in the removed screenings. To mitigate this, the screenings should be run through a washer compactor. This will rinse the microbial material off the screenings and reintroduce it back into the plant to help feed the biological treatment process, thereby controlling odors. As a bonus, washing and dewatering results in an 80% to 90% reduction in volume and a 70% to 90% reduction in weight of the screenings, translating into massive savings in transportation costs.

Challenge 5: Balancing Cost And Function

When selecting headworks equipment, the primary challenge is balancing budget constraints with the real performance requirements. The most important factor is CRE. High CRE (closer to 100%) makes downstream operations easier. However, CRE is directly related to head loss. For example, fine screens used for membrane bioreactors (MBR) require screening down to 1mm or 2mm, which results in very high head loss and necessitate larger or more numerous units.

As such, operators must aim for a blend of high efficiency and reliability, such as with a channel rotary screen. This technology offers the high CRE of a drum screen with the versatility of a channel screen. In addition, washer compactors can be oversized to handle a large turndown rate. They sit patiently, dewatering the solids until enough material accumulates, before initiating the washing and compacting phase.

Finally, operators should avoid the mindset that if equipment is running, it’s fine. Machinery like grinders, washer-compactors, and screens can benefit from regular maintenance. These small actions, performed one or twice a year, can significantly extend equipment lifespan, ensure consistent performance over the long-term, and increase overall ROI.

While the challenges of ragging, grit, variable flows, odors, or cost constraints can never be eliminated, they can be managed effectively with smart design, reliable equipment, and disciplined maintenance. By investing in the right headworks and collection system solutions, utilities can safeguard performance, reduce downtime, and deliver cleaner, more efficient wastewater treatment for years to come.