Alabama Administrative Code › Title 335 - ALABAMA DEPARTMENT OF ENVIRONMENTAL MANAGEMENT › WATER DIVISION - WATER SUPPLY PROGRAM › Chapter 335-7-6 - SURFACE WATER SOURCES AND TREATMENT › Section 335-7-6-.25 - Additional Filtration Toolbox Components

Current through Register Vol. 42, No. 9, June 28, 2024
(1) Bag and cartridge filters. Systems
				receive
Cryptosporidium
treatment credit of up to 2.0-log for
				individual bag or cartridge filters and up to 2.5-log for bag or cartridge
				filters operated in series by meeting the following criteria. To be eligible
				for this credit, systems must report the results of challenge testing that
				meets the requirements of subparagraphs (1)(b) through (i) of this rule to the
				Department. The filters must treat the entire plant flow taken from a surface
				water or ground water under the influence of surface water source.
(a) The
Cryptosporidium
treatment credit awarded to bag or cartridge filters must be based on the
				removal efficiency demonstrated during challenge testing that is conducted
				according to the criteria in subparagraphs (1)(b) through (i) of this rule. A
				factor of safety equal to 1-log for individual bag or cartridge filters and
				0.5-log for bag or cartridge filters in series must be applied to challenge
				testing results to determine removal credit. Systems may use results from
				challenge testing conducted prior to January 5, 2006 if the prior testing was
				consistent with the criteria specified in subparagraphs (1)(b) through (i) of
				this rule.
(b) Challenge testing
				must be performed on full-scale bag or cartridge filters, and the associated
				filter housing or pressure vessel, that are identical in material and
				construction to the filters and housings the system will use for removal of
Cryptosporidium.
Bag or cartridge filters must be challenge
				tested in the same configuration that the system will use, either as individual
				filters or as a series configuration of filters.
(c) Challenge testing must be conducted using
Cryptosporidium
or a surrogate that is removed no more
				efficiently than
Cryptosporidium.
The microorganism or
				surrogate used during challenge testing is referred to as the challenge
				particulate. The concentration of the challenge particulate must be determined
				using a method capable of discreetly quantifying the specific microorganism or
				surrogate used in the test; gross measurements such as turbidity may not be
				used.
(d) The maximum feed water
				concentration that can be used during a challenge test must be based on the
				detection limit of the challenge particulate in the filtrate (i.e., filtrate
				detection limit) and must be calculated using the following equation:
Maximum Feed Concentration = 1 x
				  104 x (Filtrate Detection Limit)
(e) Challenge testing must be conducted at
				the maximum design flow rate for the filter as specified by the
				manufacturer.
(f) Each filter
				evaluated must be tested for a duration sufficient to reach 100 percent of the
				terminal pressure drop, which establishes the maximum pressure drop under which
				the filter may be used to comply with the requirements of this
				subpart.
(g) Removal efficiency of
				a filter must be determined from the results of the challenge test and
				expressed in terms of log removal values using the following equation:
Click to view
				  image
where LRV = log removal value demonstrated during challenge
				  testing; Cf = the feed concentration measured during the challenge test; and Cp
				  = the filtrate concentration measured during the challenge test. In applying
				  this equation, the same units must be used for the feed and filtrate
				  concentrations. If the challenge particulate is not detected in the filtrate,
				  then the term Cp must be set equal to the detection
				  limit.
(h) Each filter
				tested must be challenged with the challenge particulate during three periods
				over the filtration cycle: within two hours of start-up of a new filter; when
				the pressure drop is between 45 and 55 percent of the terminal pressure drop;
				and at the end of the cycle after the pressure drop has reached 100 percent of
				the terminal pressure drop. An LRV must be calculated for each of these
				challenge periods for each filter tested. The LRV for the filter
				(LRVfilter) must be assigned the value of the minimum
				LRV observed during the three challenge periods for that filter.
(i) If fewer than 20 filters are tested, the
				overall removal efficiency for the filter product line must be set equal to the
				lowest LRVfilter among the filters tested. If 20 or more
				filters are tested, the overall removal efficiency for the filter product line
				must be set equal to the 10th percentile of the set of
				LRVfilter values for the various filters tested. The
				percentile is defined by (i/(n+1)) where i is the rank of n individual data
				points ordered lowest to highest. If necessary, the 10th
				  percentile may be calculated using linear
				interpolation.
(j) If a previously
				tested filter is modified in a manner that could change the removal efficiency
				of the filter product line, challenge testing to demonstrate the removal
				efficiency of the modified filter must be conducted and submitted to the
				Department.