UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D.C. 20460 JUN -9 2009 OFFICE OF MEMORANDUM SUBJECT: Definitions of Conventional Filtration Treatment and Direct Filtration FROM: Ronald Bergman, Chief ------- Regulation and Supporting Guidance The preamble for the Long Term 2 Enhanced Surface Water Treatment Rule (LT2) (71 FR 654, January 5, 2006) addressed the issue of what constitutes conventional filtration treatment. Conventional Filtration Treatment (p. 675 Table IV B-2 footnote 1) is said to "apply to a treatment train using separate, sequential, unit processes for coagulation/flocculation, clarification, and granular media filtration. Clarification includes any solid/liquid separation process following coagulation/flocculation where accumulated solids are removed during this separate component of the treatment system." The preamble for LT2 also clarifies what EPA means by designation of conventional filtration treatment through the review of clarification process performance studies. Specifically, these studies indicate that plants using clarification processes other than sedimentation that are located after coagulation and prior to filtration can achieve performance equivalent to conventional filtration treatment plants. Based on these studies, any treatment train that includes coagulation/flocculation, clarification and granular media filtration (e.g., sand-ballasted clarification or dissolved air floatation) may be regarded as conventional filtration treatment and awarded treatment credit as conventional filtration treatment. EPA guidance for the filtration and disinfection requirements, The Guidance Manual for Compliance with the Filtration and Disinfection Requirements for Public Water Systems Using Surface Water Sources (March 1991 Edition, Section 4.3.3), includes a reference to the Ten State Standards1 which states - The minimum criteria in the Ten State Standards for conventional filtration treatment are considered sufficient for the purposes of complying with the SWTR with the following addition: The criteria for sedimentation should be expanded to include other methods of solids removal including dissolved air floatation. Plate separation and upflow-solids contact clarifiers included in the 1987 Ten State Standards should also be considered. In addition, EPA's guidance in Section 4.2.1(e), footnote 1, summarizes that package plants, depending upon the type of treatment units in place, could be categorized as conventional filtration treatment, direct filtration, slow sand filtration, diatomaceous earth filtration or alternate technology at the discretion of the state. Implementation Recommendations For alternative filtration technologies, existing regulatory provisions require a removal demonstration under 40 CFR 141.73(d) for Giardia, and 40 CFR 141.173(b) for Cryptosporidium, The alternative technologies have to satisfy removal requirements at the regulatory turbidity limit (or alternative performance criteria) over an expected range of source water conditions. Examples of other alternative performance criteria include, but are not limited to, removal/inactivation of viruses and Giardia lamblia. Systems must demonstrate to the state how the alternative technologies are operated and that they will routinely meet state specified criteria to be awarded treatment credit. 2 1 Ten State Standards are public water supply standards established by GLUMRB, a water board often Midwest states. 'This guidance is highly respected and widely used by state regulatory agencies. The standards can be accessed from this website: http://IOstatcsstandards.com/waterstandards.html ------- Conventional filtration treatment plants without the capacity to meet enhanced coagulation TOC (Step I) removal requirements due to water quality parameters or operational constraints may qualify for alternative compliance criteria or may apply for TOC (Step 2) removal requirements. Conventional filtration treatment plants must apply for alternative minimum TOC removal (Step 2) requirements within three months of failure to achieve TOC removals required by 40 CFR 141.135(b)(2). The state may make those requirements retroactive for the purposes of determining compliance. A Step 2 removal application at a minimum must include results of bench- or pilot-scale testing conducted under 40 CFR 141.135(b)(4)(i). These results must be used in determining the alternate enhanced coagulation TOC removal requirement. Conclusion States must be consistent in applying the provisions associated with conventional, direct, and alternative filtration technologies. States must designate the technology to be implemented by the water system, specify all associated treatment and performance criteria (e.g., turbidity limits, flow rates, etc.), assign the appropriate filtration credit and require compliance with precursor removal requirements in 40 CFR 141.135 as appropriate. If you have additional questions about conventional filtration treatment and direct filtration, please contact Ed Moriarty, of my staff, at 202-564-3864. cc: Jim Taft, ASDWA MDBP Workgroup ------- |