Rule 3745-81-79 | Filter backwash recycling.
A surface water system that uses conventional filtration treatment or direct filtration treatment and that recycles spent filter backwash water, thickener supernatant, or liquid from a dewatering process shall meet the following:
(A) Surface water systems shall notify the director in writing if spent filter backwash water, thickener supernatant, or liquid from a dewatering process is recycled prior to initiation of recycling if the notification requirements of this paragraph have not been completed previously. This notification must include at least the following information:
(1) A plant schematic showing the origin of all flows which are recycled that may include, but are not limited to:
(a) Spent filter backwash water.
(b) Thickener supernatant.
(c) Liquid from a dewatering process.
(d) Filter to waste.
(e) The hydraulic conveyance used to transport them.
(f) The location where they are mixed in the water treatment process.
(2) The typical recycle flow, the highest observed plant flow during the previous twelve months and the state approved design capacity. All flows shall be reported in gallons per minute.
(B) Surface water systems which recycle spent filter backwash water, thickener supernatant, or a liquid from a dewatering process shall return these flows through the existing conventional filtration treatment or direct filtration treatment, or through an alternative location that is approved by the director. Failure to comply with this paragraph is a treatment technique violation.
(C) Surface water systems which recycle spent filter backwash water, thickener supernatant, or liquid from a dewatering process shall collect and retain on file the following recycle flow information for review and evaluation:
(1) A copy of the recycle notification and information that was submitted to the director in accordance to paragraph (A)(1) of this rule.
(2) A list of all recycle flows and the frequency with which they are returned.
(3) The average and maximum backwash flow rates through the filters and the average and maximum durations of the filter backwash in minutes.
(4) The typical filter run length and a written summary of how filter run length is determined.
(5) The type of treatment provided for the recycle flow.
(6) Data on the physical dimensions of the equalization and treatment units, typical and maximum hydraulic loading rates, type of treatment chemicals used and average dose and frequency of use, and, if applicable, frequency that solids are removed.