Long-Term
2 Enhanced Surface Water Treatment Rule
The Long-Term 2
Enhanced Surface Water Treatment Rule (LT2 ESWTR) currently requires public water
supplies that use surface water or groundwater under the direct influence of surface water
and who serve >10,000 people to monitor for Cryptosporidium at least monthly for a 2 year
period.
At
the completion of the 24 month monitoring period, EPA will categorize
systems into risk "bins" based on the concentration of Cryptosporidium detected in their
source water. Any bin classification other than bin 1 will result in the need to implement additional watershed
control measures and/or advanced treatment technologies, which are described in the Microbial
Toolbox. A description of the bin classification system is presented below. For
more information on the
LT2 Rule, follow the link to the EPA
LT2 website.
Engineering
Studies of Advanced Water Treatment Processes
Engineering
opportunities for design and construction of advanced treatment
systems will be available upon completion of the Cryptosporidium monitoring period.
Installation of advanced
water treatment technologies that achieve specified additional log removal
credits (ozone, UV, membranes, bag/cartridge filtration and chlorine dioxide oxidation)
is mandated for systems that are classified in bins 3 or 4, and may be utilized by systems
classified in bin 2. Preliminary testing
of advanced treatment systems at the bench or pilot-scale
level may be performed prior to
full scale implementation.
SMI
supports engineering firms conducting bench and pilot-scale
studies of advanced treatment
technologies. SMI can conduct bench-scale studies in-house, and is capable of supporting
pilot-scale studies at the point of use.
Microbial
Toolbox
The
microbial toolbox consists of 5 major components that utilities
can choose to meet the
additional log removal requirements mandated by their bin
classification. The 5 components are:
- Source
Water
- Pre-Filtraton
- Treatment
Performance
- Additional
Filtration
- Inactivation
_______________________________________________
Source
Water Toolbox Options
Tool
log Credit
1.
Implement a Watershed Control Program
0.5
2.
Utilize Alternative Source or Intake
will be determined from
Cryptosporidium
monitoring data
_______________________________________________
Pre-Filtration
Toolbox Option
Tool
log Credit
1.
Addition of New Presedimentation Basin
0.5
2.
Two Stage Lime Softening
0.5
3.
Addition of New Bank Filtration Process
0.5 for
a 25 foot setback
_______________________________________________
Treatment
Performance Toolbox Options
Tool
log Credit
1.
Combined Filter Performance
0.5 for
combined filter
effluent turbidity
of
<0.15 NTU in 95% of
samples each month
2.
Individual Filter Performance
1.0 for individual filter
effluent turbidity
of
<0.1 NTU in 95% of
daily maximum
samples each month &
no filter >0.3
NTU in 2
consecutive measurements
3.
Demonstration of Performance
State Specifc - based on state
approved protocol
_______________________________________________
Additional
Filtration Toolbox Options
Tool
log Credit
1.
Bag Filters
1log with
demonstration of at
least 2 log removal efficiency
in a challenge test
2.
Cartridge Filters
2 log with demonstration of at
least 3 log removal efficiency
in a challenge test
3.
Membrane Filtration
Log removal
credit up to the
lower value of the removal
efficiency demonstrated
during a challenge test or
verified by a direct integrity
test of the system.
4.
Addition of Separate Second Stage Filtration Process
0.5
5.
Addition of Separate Slow Sand Filter Process
2.5
_______________________________________________
Inactivation
Toolbox Options
Tool
log Credit
1.
Chlorine Dioxide
Based
on demonstration of
compliance with CT
Table
2.
Ozone
Based on demonstration of
compliance with CT
Table
3.
UV
Based on demonstration of
compliance with UV
dose
Table
_______________________________________________
Bin
Classification Criteria
The
log removals listed in the bin classification are in addition
to the existing log removal credit
achieved by the current treatment process. Systems
using direct filtration will be required to
implement an additional 0.5 log removal above the values
listed in bins 2 through 4.
BIN
1: Classification into bin 1, which is assigned
to systems with <0.075 oocysts/L as a running
annual average or 2 year mean if sampling is performed more
often than once per month, will
result in no additional treatment requirements.
BIN
2: Classification into bin 2, which is assigned
to systems with 0.075 to < 1.0 oocysts/L as a
running annual average or 2 year mean if sampling is performed
more often than once per month,
will result in the need to add 1 log additional watershed
control or treatment requirements.
BIN
3: Classification into bin 3, which is assigned
to systems with 1.0 to < 3.0 oocysts/L as a
running
annual average or 2 year mean if sampling is performed more
often than once per month,
will result in the need to add 2 log additional watershed
control and advanced treatment
requirements. At least 1 log of the additional 2 log
treatment must come from treatment using
ozone, chlorine dioxide, UV, membranes, bag/cartridge filters
or in-bank filtration.
BIN
4: Classification into bin 4, which is assigned
to systems with >3.0 oocysts/L as a running annual
average or 2 year mean if sampling is performed more often
than once per month, will result in the need to add 2.5
log additional watershed control and advanced treatment
requirements. At least 1 log of the additional 2 log
treatment must come from treatment using ozone, chlorine
dioxide, UV, membranes, bag/cartridge filters or in-bank
filtration.
For further information about SMI's services, please feel to contact a project manager at (574) 277-4078.
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