National Drinking Water Clearinghouse
West Virginia University
PO Box 6893
Morgantown, WV

Filter Backwash Rule
Set to Take Effect

By Kathy JerspersonOn Tap Associate Editor

Virtually every drinking water safety discussion since 1993 has included the cryptosporidiosis outbreak that struck Milwaukee, Wisconsin. It was the largest waterborne disease eruption ever to occur in the U.S., with an estimated 400,000 people affected. Fifty died.

Glossary of Filter Backwash Recycling

Recycle—The act of returning recycle streams
to a plant’s primary treatment process.

Recycle flow or stream—Any water, solid, or semi-solid, that a plant’s treatment, operational, or residual processes generate and that is returned to the plant’s primary treatment process.

Spent filter backwash water—A stream containing particles dislodged from filter media when water is forced back through a filter (backwashed) to clean the filter. Spent filter backwash water can contain particles, including coagulants, metals, and microbes, such as Cryptosporidium.

Thickener supernatant—A stream containing liquid from a sedimentation basin, clarifier, or other unit used to treat water, solids, or semisolids from the primary treatment processes. The “clear water” that exits the units after the particles have been allowed to settle out is thickener supernatant (or sludge thickener supernatant).

Liquids from dewatering processes—A stream containing liquids generated from a unit used to concentrate solids for disposal. Processes may consist of centrifuges, filter passages, belt presses,
vacuum filters, monofills, or other sludge concentrating equipment. Such equipment may be used to dewater sludge from treatment units used in recycling processes or sludge from units found in the primary processes.

Source: U.S. Environmental Protection Agency

The U.S. Environmental Protection Agency (EPA) considers microbiological contaminants a health concern. If finished water supplies contain microbiological contaminants, illnesses and disease outbreaks may result. Twelve waterborne cryptosporidiosis outbreaks have occurred at drinking water systems since 1984. Researchers linked three of these to contaminated drinking water from water utilities with questionable recycling practices.

In the backwash process, water is forced back through the filter media (e.g., gravel, sand) to clean the filter. This backwashed liquid contains particles dislodged from the filter that can contain microbes, metals, and coagulants, such as ferric chloride or alum.

The Filter Backwash Recycling Rule (FBRR) addresses a statutory requirement of the 1996 Safe Drinking Water Act (SDWA) Amendments to regulate filter backwash water recycling. The purpose of the FBRR is to require public water systems (PWSs) to review their recycling practices and, where appropriate, work with the state primacy agency to change recycling practices that may compromise public health by allowing microbes to slip through.

The primary benefits of this rule come from reduced risk of illness from microbial pathogens in drinking water. In particular, FBRR focuses on reducing the risk associated with pathogens, such as Cryptosporidium, that chlorine and other standard disinfectants don’t kill.

The provisions of this rule will likely reduce exposure to disinfection-resistant pathogenic protozoa, such as Giardia, or other waterborne bacterial or viral pathogens. In addition to preventing illnesses, this rule is expected to have other benefits, such as avoiding non-health related costs associated with waterborne disease outbreaks.The FBRR applies to all public water systems that:
• use surface water or groundwater under the direct influence of surface water (GWUDI);
• use direct or conventional filtration processes; and
• recycle spent filter backwash water, sludge thickener supernatant, or liquids from dewatering processes.

The FBRR requires that recycled filter backwash water, sludge thickener supernatant, and liquids from dewatering processes be returned to a system’s conventional treatment process, including coagulation, flocculation, sedimentation (conventional filtration only), and filtration, are employed. Systems may apply to the state for approval to recycle at an alternate location.

EPA expects the final rule to apply to 4,650 systems serving nearly 35 million people and estimates that fewer than 400 systems will require capital improvements as a result of the requirements. The final rule was published June 8, 2001. Small systems must submit recycle notification to their state’s primacy agency by December 2003 and have the approved process in place by June 2004.

Systems Must Provide Data
The FBRR also requires that systems notify the state in writing that they recycle. When notifying the state, systems must also provide the following information by December 8, 2003:
• A plant schematic showing the origin of all recycle flows, the hydraulic conveyance used to transport them, and the location where they are recycled back into the plant; and
• Typical recycle flow in gallons per minute (gpm), highest obser-ved plant flow experienced in the previous year (expressed in gpm), design flow for the treatment plant (in gpm), and the state-approved operating capacity for the plant if the state has determined one.

Finally, systems must collect and maintain the following information for the state to review, including:
• Copy of the recycle notification and information submitted to the state;
• List of all recycle flows and how often they are returned;
• Average and maximum backwash flow rate through the filters and
the average and maximum duration of the filter backwash process in gpm;
• Typical filter run length and a written summary of how filter run length is determined (headloss, turbidity, time, etc.);
• The type of treatment the recycle flow receives; and
• Data about the physical dimensions of the equalization and/or treatment units, typical and maximum hydraulic loading rates, treatment chemicals used, their average dose and frequency, and the frequency at which solids are removed where such units are used.

After evaluating the information, the state may require a system to modify its recycle location or recycle practices.Systems must notify the state with the appropriate information no later than 30 months after the rule is promulgated. Systems must comply with the recycle return location requirements of the FBRR no later than 36 months after promulgation. If a system requires capital improvements to modify the location of its recycle return, it must complete all improvements within 60 months of promulgation.

About the Photos: The Filter Backwash Rule requires recycled filter backwash water, sludge thickener supernatant, and liquids from dewatering processes to be treated to reduce the possibility of microbial contamination in finished water.

The FBRR addresses filter backwash water and two additional recycle streams: sludge thickener supernatant and liquids from the dewatering processes. EPA believes that establishing such a regulation will reduce the opportunity for microbes, such as Cryptosporidium, to pass into finished drinking water.

This rule ensures that recycle practices do not jeopardize the 2-log (99 percent) Cryptosporidium removal requirement the Interim Enhanced Surface Water Treatment Rule established and proposed in the Long Term 1 Enhanced Surface Water Treatment Rule.

The rule requires that recycle be returned through the processes of a system’s existing conventional or direct filtration process that the agency has recognized capable of achieving 2-log Cryptosporidium removal. This rule also ensures that systems and states will have the recycle-flow information necessary to evaluate whether site-specific recycle practices may adversely affect a system’s ability to achieve 2-log Cryptosporidium removal. Recycle flow surges may create conditions where plants exceed design capacity or state-approved operating capacity. Hydraulically overloaded situations can lower the performance of individual units within a treatment plant resulting in Cryptosporidium contamination.

EPA Calculates Cost
EPA estimates that the annualized cost of this final rule will be $5.8 million. The agency suggests that systems seek assistance from the drinking water state revolving loan fund. Other federal funds for infrastructure financing are available through the Housing and Urban Development’s Community Development Block Grant Pro-gram, and the U.S. Department of Agriculture’s Rural Utilities Service. EPA also provides program management funding to states that have primary enforcement responsibility for their drinking water programs through the PWSs grants program.

For more information about the FBRR, contact the Safe Drinking Water Hotline, at (800) 426-4791, or visit the EPA Safewater Web site at An EPA fact sheet titled “Technical Fact Sheet: Final Filter Backwash Recycling Rule is available at