CSO screening, treatment & flow control

Protect the environment by removing trash, solids and other damaging pollutants from combined sewer overflows.

Combined sewers transport both wastewater and surface water runoff to wastewater treatment plants (WWTPs). Heavy, intense or prolonged rainfall can overload these combined sewers, which can overwhelm downstream treatment facilities. A combined sewer overflow, or CSO - also known as a stormwater regulator - is designed to act as a kind of safety valve for the WWTP that diverts excess wet weather flow, enabling the plant to continue operating and preventing upstream flooding.

Our CSO screening and treatment technologies catch gross solids and floatables during these excess flow events, protecting the environment from damaging overflow pollution. They can also be used to protect sanitary sewer overflows (SSOs).

CSO Treatment Solutions

Screens and separators

CSO screens provide a physical barrier to prevent trash, litter and other gross pollutants from passing through the sewer network and reaching a wastewater treatment plant, while separators use hydrodynamic forces to separate solids from water to remove pollutants such as total suspended solids (TSS) and biochemical oxygen demand (BOD). These technologies are typically small-footprint, non-powered and self-activating.

Storm King®

  • An advanced hydrodynamic vortex separator and screen that removes 100% of solids, floatables and neutrally buoyant material larger than 6 mm and meets primary treatment equivalency for TSS and BOD. It can also be used as a contact vessel for disinfection. View product


  • A compact CSO and wet weather screening system that captures trash, gross solids and floatables with high efficiency under high flow, surcharged and submerged conditions. View product

Hydro-Jet® Screen

  • A high-capacity screen that uses corrugated panels to increase capacity without increasing footprint, making it perfectly suited to small and medium-size CSO sites. View product

Hydro-Static® Screen

  • An economically sustainable screen for sites with infrequent overflows, providing effective gross solids and floatables capture at sites with smaller flows. View product


Wet Weather Flow Control 

Hydro-Brake® Drop

  • Allows safely dropping water from virtually any distance to eliminate water hammer and protect infrastructure from damage, vibration, noise, and odor. View product

CSO Monitoring

Find out more about why and how you should monitor CSOs