The Smart Sewer Glossary: Every Term You Need to Know

Smart sewer technology sits at the intersection of civil engineering, computer science, environmental science, and public policy — which means it comes with a lot of specialized vocabulary. This guide explains every key term in plain language.

For the complete, always-updated glossary with 30+ terms, see our full Glossary page.

Overflow Types

CSO (Combined Sewer Overflow) — When combined sewer systems (carrying both sewage and stormwater) overflow during heavy rain. The overflow is discharged into waterways. CSOs are regulated under EPA's 1994 CSO Policy.

SSO (Sanitary Sewer Overflow) — Overflow from sanitary-only sewers, caused by blockages, breaks, or infiltration. Unlike CSOs, SSOs are never permitted and are always a violation. The overflow is undiluted raw sewage.

Technology Terms

RTC (Real-Time Control) — Automated systems that adjust gates, valves, and pumps based on live sensor data. The core technology behind most smart sewer cost savings.

SCADA (Supervisory Control and Data Acquisition) — Industrial control systems used to monitor and control infrastructure. Most utilities already have SCADA; smart sewers extend or complement these systems.

IoT (Internet of Things) — The network of sensors and devices embedded in infrastructure that transmit data wirelessly. In sewers: flow meters, level sensors, quality monitors, gas detectors.

RTDSS (Real-Time Decision Support System) — Software that integrates live data, models, and AI to recommend operator actions. The "brain" of a smart sewer system.

Digital Twin — A virtual replica of the physical sewer system that runs real-time simulations. Enables "what-if" scenario testing and predictive analysis.

CMAC (Continuous Monitoring and Adaptive Control) — Technology combining sensor data with weather forecasts to proactively adjust controls before storms arrive.

Infrastructure Terms

I&I (Inflow and Infiltration) — Stormwater entering sanitary sewers through cracks (infiltration) or direct connections like downspouts (inflow). A major cause of SSOs and unnecessary treatment costs.

Green Infrastructure — Nature-based stormwater management: rain gardens, permeable pavement, bioswales, green roofs. Reduces runoff volume and improves water quality.

Gray Infrastructure — Traditional engineered systems: pipes, tunnels, tanks, treatment plants. Smart technology adds intelligence to gray infrastructure.

Lift Station — A pumping station that moves wastewater uphill. Smart monitoring optimizes pump cycling and detects failures.

Force Main — A pressurized sewer pipe using pumps. Smart monitoring detects pressure anomalies indicating problems.

Regulatory Terms

NPDES (National Pollutant Discharge Elimination System) — EPA's permit program regulating wastewater discharges under the Clean Water Act.

Consent Decree — A court-ordered agreement requiring specific actions to address Clean Water Act violations. Often mandates expensive infrastructure — but smart technology can reduce these costs by 50-95%.

LTCP (Long-Term Control Plan) — A municipality's plan to reduce CSOs, typically required by a consent decree.

CWA (Clean Water Act) — The primary federal law governing water pollution, enacted in 1972.

Sensor and Communication Terms

LPWAN (Low-Power Wide-Area Network) — Wireless technologies (LoRaWAN, NB-IoT) used by sewer sensors. Long range, low power, years of battery life.

RTU (Remote Terminal Unit) — Field devices that collect sensor data and execute control commands at remote locations.

PLC (Programmable Logic Controller) — Industrial computer controlling equipment like pumps and gates at field sites.

Measurement Terms

Surcharge — When a pipe fills completely and becomes pressurized — a sign the system is overwhelmed.

Wet Weather Flow — Increased sewer flow during rain, the primary challenge smart sewers address.

Dry Weather Flow — Normal non-rain sewage flow. Anomalies in dry weather flow can indicate I&I or blockages.

FOG (Fats, Oils, and Grease) — Common cause of sewer blockages that smart monitoring can detect early.