(a)(1) Systems receive the treatment credits listed in the table in paragraph (b) of this section by meeting the conditions for microbial toolbox options described in Sec. Sec. 141.716 through 141.720. Systems apply these treatment credits to meet the treatment requirements in Sec. 141.711 or Sec. 141.712, as applicable.
(1) Systems receive the treatment credits listed in the table in paragraph (b) of this section by meeting the conditions for microbial toolbox options described in Sec. Sec. 141.716 through 141.720. Systems apply these treatment credits to meet the treatment requirements in Sec. 141.711 or Sec. 141.712, as applicable.
(2) Unfiltered systems are eligible for treatment credits for the microbial toolbox options described in Sec. 141.720 only.
(b) The following table summarizes options in the microbial toolbox: Microbial Toolbox Summary Table: Options, Treatment Credits and Criteria------------------------------------------------------------------------
Cryptosporidium treatment credit with
Toolbox Option design and implementation criteria------------------------------------------------------------------------
(1) Watershed control program 0.5-log credit for State-approved program
comprising required elements, annual
program status report to State, and
regular watershed survey. Unfiltered
systems are not eligible for credit.
Specific criteria are in Sec.
141.716(a).(2) Alternative source/intake No prescribed credit. Systems may conduct
management. simultaneous monitoring for treatment
bin classification at alternative intake
locations or under alternative intake
management strategies. Specific criteria
are in Sec. 141.716(b).------------------------------------------------------------------------
Pre Filtration Toolbox Options------------------------------------------------------------------------(3) Presedimentation basin 0.5-log credit during any month that
with coagulation. presedimentation basins achieve a
monthly mean reduction of 0.5-log or
greater in turbidity or alternative
State-approved performance criteria. To
be eligible, basins must be operated
continuously with coagulant addition and
all plant flow must pass through basins.
Specific criteria are in Sec.
141.717(a).(4) Two-stage lime softening. 0.5-log credit for two-stage softening
where chemical addition and hardness
precipitation occur in both stages. All
plant flow must pass through both
stages. Single-stage softening is
credited as equivalent to conventional
treatment. Specific criteria are in Sec.
141.717(b).(5) Bank filtration.......... 0.5-log credit for 25-foot setback; 1.0-
log credit for 50-foot setback; aquifer
must be unconsolidated sand containing
at least 10 percent fines; average
turbidity in wells must be less than 1
NTU. Systems using wells followed by
filtration when conducting source water
monitoring must sample the well to
determine bin classification and are not
eligible for additional credit. Specific
criteria are in Sec. 141.717(c).------------------------------------------------------------------------
Treatment Performance Toolbox Options------------------------------------------------------------------------(6) Combined filter 0.5-log credit for combined filter
performance. effluent turbidity less than or equal to
0.15 NTU in at least 95 percent of
measurements each month. Specific
criteria are in Sec. 141.718(a).(7) Individual filter 0.5-log credit (in addition to 0.5-log
performance. combined filter performance credit) if
individual filter effluent turbidity is
less than or equal to 0.15 NTU in at
least 95 percent of samples each month
in each filter and is never greater than
0.3 NTU in two consecutive measurements
in any filter. Specific criteria are in
Sec. 141.718(b).(8) Demonstration of Credit awarded to unit process or
performance. treatment train based on a demonstration
to the State with a State- approved
protocol. Specific criteria are in Sec.
141.718(c).------------------------------------------------------------------------
Additional Filtration Toolbox Options------------------------------------------------------------------------(9) Bag or cartridge filters Up to 2-log credit based on the removal
(individual filters). efficiency demonstrated during challenge
testing with a 1.0-log factor of safety.
Specific criteria are in Sec.
141.719(a).(10) Bag or cartridge filters Up to 2.5-log credit based on the removal
(in series). efficiency demonstrated during challenge
testing with a 0.5-log factor of safety.
Specific criteria are in Sec.
141.719(a).(11) Membrane filtration..... Log credit equivalent to removal
efficiency demonstrated in challenge
test for device if supported by direct
integrity testing. Specific criteria are
in Sec. 141.719(b).(12) Second stage filtration. 0.5-log credit for second separate
granular media filtration stage if
treatment train includes coagulation
prior to first filter. Specific criteria
are in Sec. 141.719(c)(13) Slow sand filters....... 2.5-log credit as a secondary filtration
step; 3.0-log credit as a primary
filtration process. No prior
chlorination for either option. Specific
criteria are in Sec. 141.719(d).------------------------------------------------------------------------
Inactivation Toolbox Options------------------------------------------------------------------------(14) Chlorine dioxide........ Log credit based on measured CT in
relation to CT table. Specific criteria
in Sec. 141.720(b)(15) Ozone................... Log credit based on measured CT in
relation to CT table. Specific criteria
in Sec. 141.720(b).(16) UV...................... Log credit based on validated UV dose in
relation to UV dose table; reactor
validation testing required to establish
UV dose and associated operating
conditions. Specific criteria in Sec.
141.720(d).------------------------------------------------------------------------