After high flow conditions, why might the effluent chlorine residual be too low?

In wastewater treatment, particularly in the chlorine disinfection process, the contact chamber is crucial for allowing sufficient contact time between chlorine and the pathogens in the effluent. Under high flow conditions, the flow rate through the contact chamber may increase, which can reduce the time the chlorine has to react with the microorganisms. If there is also an accumulation of solids in that chamber, it can inhibit the mixing and contact of chlorine with the water, leading to insufficient disinfection and consequently a low effluent chlorine residual.

Solid accumulation can create channeling or areas where the flow is not adequately treated, meaning that not all of the effluent receives the proper amount of chlorine. This results in lower than expected chlorine levels in the discharged effluent, affecting the overall disinfection process.

While other factors, like a faulty chlorine meter or low chlorine concentration, can also contribute to low chlorine residuals, the specific scenario of solids accumulation during high flow conditions directly impacts the efficiency of the disinfection process, making it a significant concern in maintaining proper chlorine levels in the effluent.