When a hospital loses power, patients are at risk. When a data center goes dark, businesses lose money. But when a wastewater treatment plant loses power, raw sewage flows into rivers, bays, and neighborhoods — and the consequences persist for months. Backup power at water and wastewater facilities is not about convenience or business continuity. It is about preventing public health emergencies.
The regulatory framework for water and wastewater backup power is less prescriptive than healthcare or high-rise building codes, which creates a dangerous ambiguity. Federal law requires planning, but does not mandate a specific generator size or fuel supply. Some states have stepped in with stronger requirements. Many facilities remain underprepared. And the real-world failures — measured in billions of gallons of untreated sewage — demonstrate exactly what happens when backup power systems are inadequate.
This guide covers the federal and state requirements, critical load prioritization, generator sizing, and the documented failures that should inform every water and wastewater utility’s emergency power strategy.
What Federal Law Requires for Water and Wastewater Backup Power
The primary federal authority for water system emergency preparedness is the America’s Water Infrastructure Act (AWIA) of 2018, specifically Section 2013. This law requires all Community Water Systems (CWS) serving more than 3,300 people to conduct a Risk and Resilience Assessment (RRA) and develop an Emergency Response Plan (ERP).
The RRA must address the resilience of pipes, physical barriers, source water, treatment operations, storage, and distribution systems. Backup power must be specifically addressed as part of both the RRA and the ERP. These assessments must be reviewed and updated at least once every 5 years, with initial certifications submitted to the EPA in 2020-2021.
Here is what AWIA does not do: it does not mandate a specific generator size, fuel supply volume, or minimum runtime. Unlike healthcare regulations (which specify 96 hours of fuel planning) or high-rise building codes (which specify 10-second transfer times), AWIA takes an assessment-based approach. It requires water systems to identify risks and develop countermeasures, but leaves the specifics to the utility.
The EPA’s Power Resilience Guide for Water and Wastewater Utilities (updated 2023) fills some of this gap with design guidance. The EPA recommends systems be designed for 24 to 48 hours of full operation at minimum, with plans addressing extended runtime during prolonged outages. Diesel generators with automatic transfer switches (ATS) are the standard recommendation. Facilities treating over 10,000 gallons per day often require standby power to comply with state and federal operational regulations.
The Safe Drinking Water Act (SDWA) provides the broader framework, and the NEC applies to all electrical installations at treatment facilities, including backup power systems. But the gap between “you must plan for power loss” and “here is exactly what you must have” remains a significant vulnerability in the regulatory landscape.
The American Water Works Association (AWWA) recommends that every public water supply and wastewater utility assess the likelihood and consequences of power supply disruption, identify critical vulnerabilities, and set uninterrupted service as a high-priority operating goal.
State Mandates: Texas SB 3 and the Push for Stronger Requirements
While federal law leaves specific requirements to the utility, some states have enacted more prescriptive mandates — most notably Texas, following the catastrophic failures of Winter Storm Uri in February 2021.
Texas Senate Bill 3: The Strongest State Mandate
Winter Storm Uri exposed the fragility of Texas water infrastructure. When the power grid failed across much of the state, wastewater treatment plants lost power, lift stations went offline, and sewage systems backed up into homes and waterways. The legislative response was Senate Bill 3 (SB 3), which established the most clearly defined state-level backup power requirements for wastewater facilities in the country.
SB 3 mandates that wastewater treatment facilities must:
- Treat and maintain disinfection practices during all power outages, including extended ones — not just short-term interruptions
- Operate return-activated sludge pumps at full capacity during outages
- Submit emergency preparedness plans (deadline was July 1, 2022)
- Document the use of portable generators or pumps in the facility’s engineering report, if applicable
- Conduct monthly inspection, testing, and verification of electrical transfer switches (grid to generator)
Texas also maintains the TXWARN mutual aid program, which enables utilities to share equipment — including pumps and generators — during emergencies. This provides a supplemental layer of resilience, but SB 3 is clear that individual facilities must have their own backup power capabilities.
Other States
Florida embeds backup power requirements within broader permitting and operational standards under the Florida Department of Environmental Protection (DEP), without a standalone generator mandate. California’s requirements are governed by the State Water Resources Control Board and local regulatory agencies, with specific mandates varying by region and facility type. Most other states rely on the federal AWIA framework supplemented by state environmental agency guidance.
The trend, driven by the increasing frequency and severity of extreme weather events, is toward more prescriptive state requirements. Texas SB 3 is likely a model for future legislation in other states — particularly those that experience their own major backup power failures.
Critical Loads: What Must Stay Running at a Treatment Plant
Not all systems at a water or wastewater treatment plant carry equal criticality. Understanding the priority hierarchy is essential for generator sizing, load shedding configuration, and emergency response planning.
The following table ranks critical systems by the severity of consequences when they lose power:
Highest Criticality
Lift station pumps: These pumps move sewage through the collection system. When they fail, sewage overflows into streets, homes, and waterways. Every major hurricane-related sewage disaster traces back, at least in part, to lift station failures. These must be the first priority for backup power.
Distribution system pumps (water utilities): Loss of pumping pressure in a drinking water distribution system does more than stop water flow — it allows contamination. Negative pressure in the distribution pipes can draw groundwater, soil, and contaminants into the system through cracks and joints, creating a direct public health threat.
High Criticality
- UV disinfection systems: Without UV treatment, untreated or partially treated water enters the distribution system (drinking water) or discharge waterway (wastewater). Pathogen contamination follows immediately.
- Chemical dosing systems (chlorination): Similar to UV — loss of chemical dosing means pathogens are not neutralized. This is particularly dangerous because chlorine residual in the distribution system drops to zero within hours.
- SCADA systems: The Supervisory Control and Data Acquisition system monitors and controls the entire plant. Loss of SCADA means operators lose visibility into flow rates, chemical levels, equipment status, and alarm conditions — they are effectively operating blind.
- Filtration systems: Inadequate filtration allows suspended solids and contaminants to pass through treatment. Water quality degrades immediately.
- Aeration and blower systems: Biological treatment processes (activated sludge, trickling filters) depend on continuous aeration. Without oxygen, the microbial populations that break down organic matter die off. Rebuilding a healthy biological process after a collapse can take days to weeks.
- Return-activated sludge (RAS) pumps: These recirculate settled biological solids back to the aeration basin. Texas SB 3 specifically requires these to operate at full capacity during outages — their failure causes treatment process breakdown.
Medium Criticality
- Security systems: Treatment plants are critical infrastructure and potential targets. Loss of security monitoring creates vulnerability during the exact conditions (widespread outages, emergency response strain) when threats may be elevated.
- Facility lighting: Operators must continue working during outages — often performing manual operations that are more hazardous than normal. Adequate lighting is a safety requirement, not a convenience.
Case Studies: When Backup Power Failed
The consequences of inadequate backup power at water and wastewater facilities are not theoretical. Every major hurricane in the past two decades has produced documented, large-scale sewage failures directly attributable to power loss. The numbers are staggering.
Hurricane Sandy (2012) — New York and New Jersey
Hurricane Sandy caused an estimated 11 billion gallons of sewage overflow across the New York and New Jersey region. Two facilities illustrate the scale of failure:
The Bay Park facility on Long Island was knocked out for 44 hours. During that initial outage, 100 million gallons of completely untreated sewage flowed into Hewlett Bay. But the damage extended far beyond those 44 hours — over the following 44 days, another 2.2 billion gallons of partially treated wastewater was discharged as the facility slowly recovered.
The Passaic Valley Sewerage Commission plant in Newark lost power and discharged 840 million gallons of untreated sewage into Newark Bay in a single week. Over the following two weeks, another 3 billion gallons of partially treated wastewater entered the bay.
The financial toll was enormous: nearly $2 billion for sewage plant repairs in New York alone, plus $1 billion for New Jersey recovery and $1.7 billion in resilience investments to prevent a recurrence.
Hurricane Irma (2017) — Florida
Hurricane Irma caused 88 million gallons of sewage releases across Florida. Brevard County alone discharged 30 million gallons into the Indian River Lagoon — an already-stressed ecosystem. Waste also flowed into Biscayne Bay, Tampa Bay, and the St. Johns River. The state recorded 3,452 wastewater spills in 2017, nearly triple the 1,282 recorded in 2007, illustrating the accelerating trend.
Hurricane Milton (2024) — Florida
Hurricane Milton, a Category 3 storm, caused multiple sewage overflows across Florida. Palm Bay reported 467,400 gallons spilled across five locations. Clearwater’s Marshall Street facility discharged 25.4 million gallons of partially treated wastewater into Stevenson Creek. Across the Tampa Bay area, tens of millions of gallons entered waterways — seven years after Irma demonstrated the same vulnerabilities.
Hurricane Katrina (2005) — Gulf Coast
Two weeks after Hurricane Katrina, only 30% of affected drinking water facilities and 40% of affected wastewater facilities were operating. In Harrison County, Mississippi, one-third of sewage treatment facilities were destroyed or severely damaged. More than 1 million customers in New Orleans experienced severely disrupted water and sewage service. Lift stations across the region failed without power, causing sewage to overflow into houses and streets throughout the affected area.
Hopewell, Virginia — A Non-Hurricane Reminder
Backup power failures are not limited to hurricanes. In Hopewell, Virginia, faulty wiring caused a power outage at the wastewater treatment plant. The result: 1 million gallons of raw sewage discharged into the James River, affecting Gravely Run Creek and sections of the river downstream. No storm, no disaster — just an electrical fault at a facility without adequate backup power.
Generator Sizing for Water and Wastewater Treatment Plants
Generator sizing for treatment plants is driven by plant capacity, measured in millions of gallons per day (MGD). The following table provides general benchmarks:
Sizing by Plant Capacity
- Small plants (under 1 MGD): 15-50 kW typical power demand. A single generator is often sufficient, though redundancy should still be considered for critical systems.
- Medium plants (1-10 MGD): 50-500 kW typical power demand. Multiple generators may be needed for load segregation and redundancy.
- Large plants (10-50 MGD): 500 kW to 5 MW typical power demand. A redundant generator plant is required, typically with N+1 configuration.
- Very large plants (over 50 MGD): 5-20+ MW typical power demand. Multiple large generator sets with paralleling switchgear are necessary to manage the load and provide redundancy.
As a rough benchmark, the median energy use intensity for wastewater treatment is approximately 10 kBtu per gallon per day (with a wide range of 3-36 kBtu/gallon/day depending on treatment processes and efficiency). For planning purposes, each MGD processed requires approximately 27 kW of electricity.
The Pump Starting Problem
One of the most common generator sizing errors at treatment plants involves pump starting loads. Large pumps draw significantly more power during startup than during steady-state operation — the starting kVA can be 5 to 7 times the running load. If the generator is sized only for the running load, starting a single large pump can cause voltage collapse that trips other equipment offline.
Two technologies help manage starting loads. Soft starters ramp up voltage gradually, reducing the starting current surge, though they can cause voltage distortion on the generator bus. Variable-frequency drives (VFDs) allow motors to start at reduced speed and ramp up gradually, significantly reducing starting loads and enabling operation at various speeds for process optimization.
Generator sizing must account for the worst-case starting scenario — typically the simultaneous restart of multiple pumps after a power restoration — not just the steady-state running load. Use our fuel consumption calculator to estimate fuel requirements once the generator size is determined.
Planning for Extended Outages: Fuel, Maintenance, and Dual-Source Power
The case studies above share a common theme: extended outages of days or weeks, not hours. Planning for a 4-hour outage is fundamentally different from planning for a 4-day or 4-week outage. Several factors become critical during extended operations.
Fuel Logistics
The EPA recommends a minimum of 24 to 48 hours of on-site fuel for full-load operation. But as Katrina and Sandy demonstrated, grid restoration can take weeks. On-site fuel storage should be supplemented with reliable fuel delivery agreements — and “reliable” must account for the reality that roads may be impassable, fuel suppliers may be overwhelmed, and regional fuel stocks may be depleted during a major event.
NFPA 110 Section 5.5.3 requires that fuel storage include a 133% safety buffer — the tank must hold 133% of the fuel needed at full rated load for the required runtime. This buffer accounts for fuel quality variations, consumption fluctuations, and generator efficiency losses. Our 96-hour fuel rule calculator can help determine the storage requirement including this buffer.
Generator Maintenance During Extended Runs
Diesel generators are designed for backup duty — intermittent operation with regular rest periods. Running a generator continuously for days or weeks introduces maintenance requirements that many facilities are not prepared for: oil level monitoring and possible oil changes, coolant system checks, fuel filter inspection (especially if fuel quality is marginal), battery charging system verification, and exhaust system monitoring for leaks or backpressure issues.
Staff must be trained for these extended-run maintenance procedures, and spare parts (oil, filters, belts, coolant) must be stocked on-site before an event, not ordered during one.
Dual-Source Power and Redundancy
CISA’s Resilient Power Best Practices for Critical Facilities and Sites recommends maintaining at least two backup generation sources for critical infrastructure. For treatment plants, this might mean multiple generators in an N+1 configuration, a combination of fixed and portable generators, dual utility feeds from separate substations, or agreements with the TXWARN mutual aid program (in Texas) or equivalent regional mutual aid networks.
The structural vulnerability of wastewater plants compounds the challenge. These facilities are typically built in low-lying areas near discharge waterways, making them inherently vulnerable to flooding during storms — precisely when backup power is most needed. Generator placement must account for potential flood elevation, not just convenience of installation.
The Health and Environmental Stakes
The consequences of wastewater treatment plant power failures extend far beyond the immediate discharge event. Understanding the full scope of impact is essential for making the case for adequate backup power investment.
Pathogen Contamination
Untreated sewage carries E. coli, toxic chemicals, heavy metals, and pharmaceutical residues. A University of South Florida study found vancomycin-resistant bacteria in wastewater — vancomycin is a last-resort antibiotic, and the discharge of resistant organisms into waterways accelerates the spread of antibiotic resistance, a growing public health crisis. When lift stations fail and sewage backs up into homes, residents face direct exposure to these pathogens through contaminated standing water.
Long-Term Environmental Damage
Beach and river closures persist long after storms pass. The nutrient load from sewage discharges — nitrogen and phosphorus — feeds algal blooms that can devastate aquatic ecosystems. The Indian River Lagoon in Florida experienced severe algal blooms following Hurricane Irma’s 30-million-gallon sewage discharge into the system. These blooms kill fish, smother seagrass beds, and can produce toxins harmful to both marine life and humans.
Drinking Water Contamination
When distribution system pumps lose power, the resulting pressure loss creates the potential for contamination throughout the drinking water system. Negative pressure draws groundwater, soil, and surface contaminants into pipes through cracks and joints. The contamination can be widespread and difficult to identify without comprehensive water quality testing across the distribution system. Boil-water advisories may persist for days or weeks after power is restored while the system is flushed and tested.
Frequently Asked Questions
Does federal law require a specific generator size for water treatment plants?
No. The America’s Water Infrastructure Act (AWIA, Section 2013) requires community water systems serving more than 3,300 people to assess their risks and plan for power loss, but it does not prescribe a specific generator capacity, fuel supply, or runtime duration. The EPA recommends designing for 24-48 hours of full operation, but this is guidance, not a mandate. State requirements vary — Texas SB 3 is the most prescriptive, requiring wastewater facilities to maintain treatment and disinfection during all outages. The NEC applies to the electrical installation of any backup power system, regardless of the absence of a federal generator mandate.
How long should a treatment plant be able to run on backup power?
The EPA recommends a minimum of 24-48 hours, but real-world events consistently demonstrate that extended outages — measured in days or weeks — are not uncommon during major storms. After Hurricane Sandy, the Bay Park facility on Long Island needed 44 days to return to full operation. After Katrina, 60% of affected wastewater facilities were still offline two weeks after the storm. Facilities in hurricane-prone or extreme-weather regions should plan for significantly longer runtimes than the 24-48 hour minimum, supplemented by fuel delivery agreements and mutual aid programs.
What is the NFPA 110 133% fuel buffer, and does it apply to treatment plants?
NFPA 110 Section 5.5.3 requires that fuel storage hold 133% of the fuel needed at full rated load for the required runtime duration. This 33% safety margin accounts for fuel quality variations, consumption fluctuations, and generator efficiency changes. The requirement applies to any Emergency Power Supply System (EPSS) classified under NFPA 110, including those at treatment plants. If your generator consumes 10 gallons per hour and you need 48 hours of runtime, the raw fuel need is 480 gallons, but the compliant storage requirement is 638 gallons.
What happens to the biological treatment process during an extended power outage?
Activated sludge and other biological treatment processes depend on continuous aeration to keep microbial populations alive and active. Without aeration, dissolved oxygen drops to zero within minutes, and the beneficial bacteria begin to die. If power is not restored within hours, the biological process can collapse entirely. Rebuilding a healthy microbial community — known as re-seeding — can take days to weeks, during which treatment performance is severely compromised. This is why aeration and blower systems are classified as high-criticality loads for backup power.
Can portable generators serve as the primary backup for a treatment plant?
Portable generators can supplement fixed generators and are commonly used for smaller lift stations and remote facilities. Texas SB 3 permits the use of portable generators but requires that their use be documented in the facility’s engineering report. However, relying on portable generators as the sole backup strategy introduces significant risks: deployment time (someone must transport and connect them), availability during regional events (when every facility needs them simultaneously), and the logistical challenge of fueling multiple portable units across distributed locations. Fixed, permanently installed generators with automatic transfer switches provide far more reliable protection for primary treatment facilities.
How should generators be placed at flood-prone treatment plants?
Wastewater plants are inherently flood-prone because they are typically sited in low-lying areas near discharge waterways. Generator placement must account for the facility’s flood elevation, not just electrical convenience. Best practices include elevating generators above the 500-year flood level (not just the 100-year level), protecting electrical switchgear and transfer switches in flood-resistant enclosures, ensuring fuel tanks are anchored to prevent flotation during flooding, and routing fuel lines and electrical connections above expected flood depths. After Hurricane Sandy, billions of dollars in resilience investments went to exactly these types of hardening measures.
Related Resources
- Fuel Consumption Calculator — Estimate your generator’s fuel consumption with derating factors for altitude, temperature, and equipment age.
- 96-Hour Fuel Rule Calculator — Calculate fuel storage requirements including the NFPA 110 133% safety buffer.
- Critical Buildings Backup Power Hub — Compliance guides and tools for commercial, institutional, and infrastructure facilities.
Need help with generator fuel systems? FuelCare provides emergency fuel delivery and generator fuel system maintenance for water and wastewater facilities across the western United States. Contact us for a consultation.