9.1 Collection Systems, Lift Stations & SSO Reporting

9.1 Collection Systems, Lift Stations & SSO Reporting

Quick Answer: Collection systems convey wastewater to the plant by gravity sewers and, where grade fails, force mains fed by lift stations. Operators must control I/I, prevent SSOs from blockages, power loss, and capacity shortfalls, and meet Florida SSO reporting duties. FOG and roots are the most common dry-weather causes; response is stop the overflow, protect public health, document, and report.

Domestic wastewater never reaches the treatment plant by magic. A collection system—gravity mains, manholes, service laterals, lift stations, and force mains—moves wastewater under public health rules that Florida operators live every day. On FDEP wastewater Class C (and higher) exams, collection and SSO topics show up under system operation, safety, and regulatory reporting—not as civil-design trivia. Expect scenarios: wet-well high-level alarm at 02:00, grease blockage in a trunk main, or an SSO that reached a storm drain.

Gravity Sewers vs Force Mains

Gravity Collection

Gravity sewers slope so wastewater flows downhill without continuous pumping. Typical design features operators should recognize:

• Minimum slope and minimum velocity goals (often about 2 ft/s when flowing full enough) to keep solids moving and limit deposition.
• Manholes at junctions, grade changes, and intervals for inspection and cleaning.
• Service laterals from buildings to the public main—private laterals are a major I/I and FOG source even when the public main is sound.
• Surcharge risk: when flow exceeds pipe capacity or a downstream restriction backs up, manholes and laterals can pressurize and overflow.

Gravity systems are passive and energy-efficient, but they fail when solids settle (low flow, flat grades, debris), when roots invade joints, or when I/I (inflow and infiltration) floods capacity during Florida storms.

Force Mains and Pressure Sewers

Where elevation, flat terrain, or long distances make continuous gravity flow impossible, lift stations pump into force mains—pressurized pipelines that discharge to a higher gravity manhole or directly toward the plant.

Florida’s flat coastal topography means many small and large lift stations. Force-main discharges create turbulence and H2S release—a headworks odor and corrosion problem as well as a collection-system issue.

Inflow and Infiltration (I/I)

Infiltration is groundwater leaking into cracked pipes, poor joints, and manhole walls. Inflow is stormwater that enters through manhole lids, roof drains, catch-basin cross-connections, and flooded cleanouts. Together they are I/I.

Why I/I matters for operators and exams:

1. Hydraulic overload of interceptors, lift stations, and the plant—blowing out primary clarifiers, washing out secondary solids, and risking SSOs.
2. Dilution of BOD/TSS that confuses process control if you only watch concentrations, not mass loadings.
3. Energy cost—pumping rainwater is pure waste.
4. Florida reality—high water tables, tropical storms, and aging coastal sewers make wet-weather I/I a core design and O&M driver.

Operators support I/I control through night-flow monitoring, manhole inspections, smoke/dye testing coordination, known “hot spot” cleaning, and honest wet-weather incident documentation.

Lift Station Components

A standard wet-well lift station includes:

Wet Well

The wet well is the below-grade chamber that receives gravity flow and stores wastewater until pumps start. Level is controlled by floats, pressure transducers, or ultrasonic sensors. Operators watch:

• Normal lead/lag start-stop bands (avoid short-cycling pumps)
• High-level alarm (imminent SSO risk)
• Low-level / off setpoints (protect pumps from dry run)
• Grease mats, rags, grit buildup, and septic odors indicating long detention

Pumps

Most municipal stations use submersible centrifugal pumps (or dry-pit pumps in older designs) in duplex or triplex arrangements: lead, lag, and often a standby. Key operator checks:

• Amps, run hours, starts per hour
• Unusual noise/vibration (ragging, bearing failure, cavitation)
• Check valves that stick open (pump recirculates, wet well never draws down)
• Impeller wear from grit and sand—common in Florida coastal/sandy soils

Controls and Alarms

Control panels sequence pumps, alternate lead/lag, and annunciate alarms. SCADA telemetry is common for remote high-level, power fail, and intrusion alarms. Exam-relevant expectations:

• Test high-level alarms on a schedule
• Know local auto-dialer / SCADA notification chains
• After storms, verify stations returned to normal lead/lag (not stuck on lag or hand)

Backup Power and Valves

Portable or permanent generators, automatic transfer switches, and bypass pumping ports are the difference between a power outage and a neighborhood SSO. Isolation valves, check valves, and air-release valves on force mains complete the mechanical picture.

Sanitary Sewer Overflows (SSOs): Causes

An SSO is an untreated or partially treated wastewater release from the collection system (or plant hydraulics related to collection overload) to the environment, streets, buildings, or surface waters. Classic causes:

“Flushable” wipes and non-dispersibles combine with FOG to form fatbergs—dense blockages that exam questions love to pair with lift-station ragging.

Florida SSO Reporting Urgency and Public Health

Florida treats SSOs as public-health emergencies, not paperwork afterthoughts. Untreated sewage can carry pathogens (E. coli, viruses, parasites), create slip hazards, contaminate stormwater systems, and close recreational waters. Operator priorities in order:

1. Stop or minimize the overflow (clear blockage, restore power/pumping, bypass as authorized).
2. Protect the public—barricade, keep people and pets out, prevent entry to storm drains and surface water where possible.
3. Contain and recover spilled wastewater and solids when safe and feasible; disinfect hard surfaces per utility SOP.
4. Notify per utility emergency plan and FDEP / county health / local requirements—timelines are urgent (often measured in hours, not days). Know your plant’s written notification tree; exams test the urgency and public-health rationale, not a memorized phone script that changes by permit.
5. Document start/stop times, volume estimate method, receiving waters impacted, cause, and corrective actions.
6. Follow up with cleaning, CCTV if structural, and corrective maintenance to prevent recurrence.

Volume estimates (e.g., duration × estimated flow, or measured pump-down) appear in incident reports and must be honest and consistent with training. Never under-report to “look good”—that is a compliance and ethics failure.

FOG, Roots, and Operator Response Culture

Fats, oils, and grease (FOG) cool and solidify in pipes, especially downstream of food-service establishments without maintained grease interceptors. Roots seek moisture at pipe joints and create progressive blockages. Effective programs combine:

• Hot-spot cleaning schedules (hydro-jetting, root cutting)
• FOG ordinance / grease-trap inspection coordination with pretreatment staff
• Public education (“only toilet paper, not wipes”)
• Rapid response SOPs for customer backups and street overflows

When an alarm or call comes in, good operators respond, communicate, and leave a paper trail. Collection failures become plant failures if wastewater never arrives—or arrives as a flood after a blockage breaks free.

Exam Anchors for Section 9.1

Memorize the functional split (gravity vs force main), the wet-well/pump/control/alarm model of a lift station, I/I as wet-weather overload, FOG/roots/power as SSO drivers, and Florida’s expectation of immediate public-health protection plus prompt regulatory reporting. That cluster covers most collection/SSO items on wastewater operator exams.