Nevada Administrative Code › Chapter 445A - Water Controls › PUBLIC WATER SYSTEMS › Treatment of Water: Generally › Section 445A.533 - Standards for operation of facility for filtration

Current through June 11, 2024
A facility for filtration must be operated in accordance with
				  the following requirements:
1. A plant
				for conventional and direct filtration must be operated at a rate of flow not
				to exceed 3 gallons per minute per square foot for single media filters and 6
				gallons per minute per square foot for deep bed, dual or mixed media filters
				under conditions of gravity flow. For pressure filters, the rates of filtration
				must not exceed 2 gallons per minute per square foot for single media filters
				and 3 gallons per minute per square foot for dual, mixed media or deep bed
				filters.
2. A slow sand filter must
				be operated at a rate of filtration not to exceed 0.1 gallons per minute per
				square foot. The filter bed must not be dewatered except for cleaning and
				maintenance.
3. A diatomaceous
				earth filter must be operated at a rate not to exceed 1 gallon per minute per
				square foot.
4. During normal
				operating conditions, any filter removed from service must be backwashed upon
				start-up.
5. Any membrane
				filtration unit must be subjected to a direct integrity test upon
				start-up.
6. Rates of filtration
				must be increased gradually when placing filters back into service after
				backwashing or any other interruption in the operation of the filter.
7. In a plant using conventional and direct
				filtration, the turbidity of filtered water from any individual filter after
				backwashing or any other interruption must be less than 0.5 units of
				nephelometric turbidity after 4 hours of the initial operation of the filter.
				The level of turbidity must never exceed 1 unit of nephelometric turbidity
				before placing the filter back into operation.
8. A pressure filter must be inspected
				physically and evaluated annually for occurrences such as media condition,
				formation of balls of mud and short circuiting. A written record of the
				inspection must be maintained at the treatment plant.
9. Coagulation and flocculation unit
				processes must be in use at all times when a plant using conventional and
				direct filtration is in operation. The effectiveness and optimization of these
				processes must be demonstrated by jar testing, pilot filter column testing or
				other means acceptable to the Division or the appropriate district board of
				health.
10. The level of turbidity
				of filtered water from each filter unit must be monitored with a continuous
				turbidity meter and recorded at a minimum of every 15 minutes by a sampling
				program approved by the Division or the appropriate district board of health.
				If this monitoring indicates that any filter unit is not performing as required
				by
				40 C.F.R. §
										141.175(b)(4) or
				141.563(c),
				as adopted by reference in NAC 445A.4525, the filter must be inspected to
				determine the cause of its inadequate performance by implementing a composite
				correction program. The Division or the appropriate district board of health
				may require that the filter be taken out of service.
11. To obtain approval for rates higher than
				those specified in subsections 1, 2 and 3, a supplier of water must demonstrate
				to the Division that his or her filters can ensure the same water quality at
				the increased rates of flow.
Added to NAC by Bd. of
				  Health, eff. 11-29-90; A by Environmental Comm'n by R126-05, 10-31-2005;
				  R194-08, 10-27-2009
NRS
					 445A.860