As winter gives way to spring, wastewater treatment plants (WWTPs) across Canada face a wave of seasonal challenges. Rising temperatures and snowmelt bring significant shifts in hydraulic load and biological processes, particularly in outdoor systems like lagoons, aerated ponds, and constructed wetlands, but they also impact other biological treatment systems.
While warmer temperatures increase microbial activity and improve treatment efficiency, the rapid influx of meltwater dilutes wastewater, shortens retention times, and disrupts biological stability. In outdoor treatment systems, thermal inversion in settling ponds can resuspend solids and release stored nutrients, affecting effluent quality. To maintain stable operations, operators must monitor conditions closely and adjust processes accordingly.
Springtime Effects on Biological Treatment
According to the Arrhenius Law (link here), biological processes speed up as temperatures rise. While this boosts microbial activity, the transition from winter dormancy to peak efficiency can be disruptive, requiring careful adjustments.
During winter, cold temperatures slow microbial metabolism, reducing the breakdown of organic matter and nitrogen removal efficiency. As spring temperatures climb:
Although this increase in microbial activity is beneficial, sudden shifts in metabolism can throw treatment processes off balance if adjustments aren’t made in time.
The abrupt shift from winter dormancy to peak microbial activity can overload biological treatment processes, leading to:
To stabilize biological treatment, operators should adjust aeration rates, manage sludge retention times (SRTs), and optimize nutrient dosing gradually as microbial activity increases.
Nitrification, the biological process that converts ammonia into nitrates, relies on temperature-sensitive bacteria that recover slowly from cold winter conditions. In early spring:
Optimizing aeration, pH levels, and microbial acclimatization is essential for ensuring effective nitrogen removal as temperatures rise.
Impact of Snowmelt on Hydraulic Loading in Outdoor Biological Systems
Beyond biological challenges, spring snowmelt brings an influx of water that can overwhelm treatment facilities, particularly those using outdoor biological systems.
As snow melts, excess water flows into wastewater systems, increasing hydraulic loading and diluting wastewater, leading to:
Operators can mitigate these challenges by using flow equalization strategies, optimizing retention times, and closely monitoring influent quality.
A less obvious but equally disruptive springtime challenge is thermal inversion in outdoor settling ponds and lagoons. This occurs when surface water warms faster than deeper layers, disrupting stratification and causing resuspended solids.
Consequences of thermal inversion:
To reduce these risks, operators can:
Conclusion
Spring presents both opportunities and challenges for wastewater treatment plants. While rising temperatures boost microbial activity and improve treatment efficiency, the season also introduces risks, including shock loads, ammonia removal inefficiencies, hydraulic overload, and thermal inversion in outdoor systems.
By monitoring conditions closely, making gradual process adjustments, and managing hydraulic loads effectively, WWTPs can navigate seasonal disruptions while maintaining compliance and treatment efficiency.
Trust AQUASAN’s technical team. We have extensive technical expertise in all types of water treatment. With extensive training and technical know-how, and we bring creative solutions that ensure treated water quality is preserved.