EPA Approves Final Filter Backwash Rule

The recently published Filter Backwash Recycling Rule will apply to more than 4600 systems which serve nearly 35 million Americans. Fewer than 400 systems are expected to require capital improvements as a result of the rule, which will have an annualized cost of about $6 million a year, EPA predicted.

EPA published the filter backwash rule on June 8 to meet a statutory requirement of the 1996 Safe Drinking Water Act (SDWA) Amendments. The rule requires public water systems to review their recycle practices and, where appropriate, work with their state Primacy Agency to make any necessary changes to recycle practices that could compromise microbial control.

The rule applies to all public water systems that:

• Use surface water or ground water under the direct influence of surface water (GWUDI)
• Use direct or conventional filtration processes
• Recycle spent filter backwash water, sludge thickener supernatant, or liquids from dewatering processes

The rule requires that recycled filter backwash water, sludge thickener supernatant, and liquids from dewatering processes be returned upstream of all conventional or direct filtration treatment systems, including coagulation, flocculation, sedimentation (conventional filtration only) and filtration. Systems may apply to the state for approval to recycle at an alternate location.

The rule also requires that systems notify their state in writing that they practice recycle. Systems must provide the following information:

• 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 (gpm), highest observed plant flow experienced in the previous year (gpm), design flow for the treatment plant (gpm), and the state-approved operating capacity for the plant where the state has made such determinations.

Systems also must collect and maintain the following information for review by the state, which may, after evaluating the information, require a system to modify their recycle location or recycle practices:

• Copy of the recycle notification and information submitted to the state;
• List of all recycle flows and the frequency with which they are returned;
• Average and maximum backwash flow rate through the filters and the average and maximum duration of the filter backwash process in minutes;
• Typical filter run length and a written summary of how the filter run length is determined (headloss, turbidity, time etc.);
• The type of treatment provided for the recycle flow; and
• Data on the physical dimensions of the equalization and/or treatment units, typical and maximum hydraulic loading rates, type of treatment chemicals used and average dose and frequency of use, and frequency at which solids are removed where such units are used.

Systems must notify the state with the appropriate information no later than 30 months after the June 8 promulgation of the rule. Systems must comply with the recycle return location requirements of the rule within 36 months. If a system requires capital improvements to modify the location of its recycle return, it must complete all improvements no later than 60 months after promulgation.

The practice of filter backwash recycling has not previously been addressed in drinking water rules promulgated by EPA. The 1996 Amendments to the SDWA required EPA to promulgate a regulation governing the recycling of filter backwash water within the treatment process of a public water system no later than four years after the date of the enactment of the Amendments.

The Agency believes that establishing such a regulation will improve performance at conventional and direct filtration plants by reducing the opportunity for recycle practices to adversely affect plant performance in a way that would allow microbes such as cryptosporidium to pass through into finished drinking water.

The rule ensures that the 2-log Cryptosporidium removal requirement established in the Interim Enhanced Surface Water Treatment Rule and proposed in the Long Term 1 Enhanced Surface Water Treatment Rule is not jeopardized by recycle practices.

The rule also ensures that systems and states will have the recycle flow information necessary to evaluate whether site-specific recycle practices may adversely affect the ability of systems to achieve 2-log Cryptosporidium removal. Surges of recycle flow returned to the treatment plant may adversely affect treatment systems by creating hydraulically overloaded conditions (when plants exceed design capacity or state-approved operating capacity) that can lower performance of individual units within a treatment plant resulting in lowered cryptosporidium removal efficiency.

EPA estimates that the annualized cost of the Filter Backwash Recycling Rule will be $5.84 million. Capital costs associated with modifications to recycle locations at an estimated 371 systems represent $5.5 million. The recycle return provision of the rule accounts for 95 percent of total annualized costs. Public Water System expenditures for all provisions are greater than 99 percent ($5.8 million) of total annualized costs; State expenditures make up less than 1 percent ($0.07 million).

EPA estimates the rule's mean annual cost per household is $0.20 and the total annual cost per household is less than $1.70 for 99 percent of the 31.4 million households potentially affected by the rule. The remaining one percent of households will experience a range of costs between $1.70 and approximately $100 per year. Only 321 of the 31.4 million households potentially affected by the FBRR (.00005 percent) are expected to incur costs of approximately $100 per year.

The agency worked with American Water Works Association (AWWA), the American Water Works Service Company (AWWSCo.), and Cincinnati Water Works to develop 12 issue papers on commonly generated recycle flows. EPA began outreach efforts to develop the filter backwash rule in the summer of 1998. EPA held several formal and informal meetings with stakeholders, trade associations, and environmental groups.

For general information on the Filter Backwash Recycling Rule, contact the Safe Drinking Water Hotline, at (800) 426-4791, or visit the EPA Safewater website at http://www.epa.gov/safewater/filterbackwash.html.