Oklahoma Administrative Code › Title 310 - Oklahoma State Department of Health › Chapter 315 - Public Bathing Place Facility Standards › Subchapter 7 - Construction and Operation › Section 310:315-7-15 - Filters

Current through Vol. 41, No. 20, July 1, 2024
(a)
General.
The filter plant
				shall be provided with influent and effluent pressure gauges for each tank,
				backwash sight glass, air relief valves, and rate-of-flow indicator, as
				provided in this chapter. All filters must be approved and listed by the
				National Sanitation Foundation. In vacuum filter installations where the
				circulating pump has a rating of two (2) horsepower or higher, an adjustable
				high vacuum automatic shutoff shall be provided to prevent damage to the pump
				by cavitation. A compound gauge shall be installed in the pump suction line,
				between the pump and hair catcher (see
				310:315-7-14
				for exception). The sight glass may be omitted if the backwash discharge can be
				clearly viewed from the backwash control valves. The filter plant shall be
				provided with fixed piping and valving to permit the functions of filtering to
				pool or backwashing to approved waste disposal with the battery as a whole or
				any unit operated singly. The filter plant shall be provided with means for
				draining all filter units and piping, so that all parts of the system may be
				completely drained to prevent damage from freezing. Pressure tanks should be
				supported by jack legs or other supports to give a free movement of air under
				each tank and to permit access for painting. Where dissimilar metals are used
				in the filters which may set up galvanic electric currents, the filter plant
				design must resist electrolytic corrosion. The filters shall be designed in
				such a manner that they may be easily disassembled with allowances made for
				adequate working space above and around the filter to allow the removal and
				replacement of any part and for other maintenance.
(b)
Filters, sand, conventional
				low-rate.
This chapter shall apply where applicable to either gravity or
				pressure sand filters, designed for a filtration rate not to exceed three (3)
				gallons per square foot per minute. Filter tanks shall be designed with a
				factor of safety of four (4) in relation of working pressure to ultimate
				strength. The filter bed shall consist of suitable grades of filter sand and
				supporting bed of graded gravel or other porous material which shall serve to
				support the filter bed and distribute both filtered and backwash water
				uniformly. The supporting bed shall consist of graded gravel or other material
				and shall support not less than twenty (20) inches of filter media. The filter
				media shall consist of silica sand or other durable, inert material. The filter
				media shall be free of clay and limestone, with effective size between 0.35 and
				0.65 millimeter and uniformity coefficient not exceeding 1.75. The minimum
				freeboard to the draw-off point of backwash water shall be not less than twelve
				(12) inches above the normal level the top of the filter bed. The minimum
				backwash rate shall be not less than twelve (12) gallons per square foot of
				filter bed per minute. Where anthracite coal or other filter media are
				employed, the freeboard shall be adequate to prevent the media being carried
				off to waste when the filter bed is backwashed at a rate adequate to carry off
				foreign material filtered from the water. The freeboard and the rate of
				backwash shall be the subject of individual design, based upon specific gravity
				of the media. The under-drain system shall be constructed of material which is
				corrosion resistant and enduring and the design of the system shall be such
				that uniform collection of the filtered water and distribution of the backwash
				water is effected over the entire filter bed area. Unless other effective means
				are provided of distributing the water entering the unit above the filtering
				media, the filter shall be equipped with a baffle plate for this purpose. Each
				conventional sand and gravel filter unit shall be provided with an access
				opening of not less than a standard eleven (11) x fifteen (15) inch manhole and
				cover.
(c)
Filters, sand,
				pressure high-rate.
High rate pressure sand filters are acceptable
				provided the filter-pump combination is designed and sized to limit the
				filtration rate to a maximum of fifteen (15) gallons per square foot per
				minute. The filter media shall consist of silica sand or other durable, inert
				material, free from clay and limestone and with an effective size between 0.40
				and 0.55 millimeters and a uniformity coefficient not exceeding 1.75. The
				minimum depth for filter sand shall be twenty (20) inches for rapid rate
				filters and twelve (12) inches for high-rate filters.
(d)
Filters, diatomite.
These
				may be of either pressure or vacuum type. The design filter rate shall not
				exceed two and one-half (2-1/2) gallons per minute per square foot of effective
				filter area. If an approved body feed is not used, the rate shall be reduced to
				two (2) gallons per minute per square foot of effective filter area. For pools
				with surface area of sixteen hundred (1600) square feet or more, an approved
				body feed is required. The determination of the filter area shall be made on
				the basis of a true and effective supported septum surface. In the case of
				fabric septums, the area computation will be made on the basis of measurements
				of the septum support in a reasonably constant plane. Area allowances shall not
				be granted for folds in the septum fabric or deviations in the septum surface
				which would easily bridge. The filter cycle of the diatomite filter shall not
				be less than seventy-two (72) hours of continuous operation before cleaning.
				This shall not apply to the initial operation of a pool, but only the operation
				where the pool water at least meets the conditions of water quality given in
				OAC 310: Chapter 320. A precoat of filter aid that evenly covers the filter
				elements must be used before placing the equipment into initial operation and
				after each cleaning. The amount of filter aid shall be selected to provide at
				least the same protection to the filter septum as that given by 0.1 pound of
				diatomaceous earth filter aid per square foot of filter area where body feed is
				employed, or 0.15 pound per square foot where no body feed is used. The
				equipment shall be so arranged that during the precoating the effluent shall be
				refiltered or discharged to an approved waste facility without passing into the
				pool until the effluent is clear of suspended matter. Slurry feeders shall
				include an agitator and positive feed pump. Where provided, the body feeding
				equipment designed for feed of filter aid to the filter influent shall have a
				rate capacity to feed at a reasonably constant rate within a calibrated range.
				The equipment will have capacity to operate at the maximum feed rate of ten
				(10) parts per million at the design filter rate for a period of twenty-four
				(24) hours without refilling. The tank containing the filter elements shall be
				constructed of steel, plastic, or other suitable material which will
				satisfactorily provide resistance to corrosion, with or without coating.
				Pressure filters shall be designed for a working pressure equal to the shutoff
				head of the pump, with a factor of safety of four (4). Vacuum filters shall be
				designed to withstand the pressure developed by the weight of the water
				contained therein and closed vacuum filters shall, in addition, be designed to
				withstand the crushing pressure developed under a vacuum of twenty-five (25)
				inches of mercury, both with a safety factor of three and one-half (3-1/2). The
				septa or elements which support the filter aid shall be of corrosion resistant
				material and shall be provided with openings the minimum dimensions of which
				shall not be greater than 0.005 inches, or as specified in the National
				Sanitation Foundation Standards for Diatomite Filters. The septa shall be
				constructed to be adequately resistant to rupture with the maximum differential
				pressure between influent and effluent of not less than the maximum pressure
				which can be developed by the circulating pump and of adequate strength to
				resist any additional stresses developed by the cleaning operation.
(e)
Surface skimmer filters.
Skimmer filters are acceptable on pools less than sixteen hundred (1600) square
				feet surface area, and on wading pools. The unit shall be designed to filter at
				a rate of two (2) gallons per minute per square foot and shall be equal to the
				design capacity of the skimmer. All requirements in 310:315-7-15 are applicable
				to skimmer filters.
(f)
Cartridge filters.
Cartridge filters are acceptable if they
				conform to the following criteria:
(1) The
				maximum flow through the filter is not greater than 0.375 gpm/square
				foot.
(2) A sump or other means of
				collecting water and wastes drained from the filter, or from the filter
				elements during cleaning, is provided, and discharges into an approved
				wastewater collection system.