Membrane and Desalination Technologies - TCE Moodle Website

138 N.K. Shammas and L.K. Wang
The Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) builds on the
previous surface water treatment rules by requiring additional treatment for those systems
with elevated influent Cryptosporidium levels. The rule identifies a number of “toolbox”
technologies that may be employed to achieve additional Cryptosporidium treatment requirements.
The range of removal or inactivation credits allocated to each of the various toolbox
options under the rule varies based on the capabilities of the particular treatment technology.
Because the various types of membrane filtration processes represent one of these toolbox
alternatives, utilities have the option of using membrane filtration for compliance with the
rule requirements as a distinct technology rather than simply as a general AFT. Consequently,
US EPA has developed specific regulatory requirements and associated guidance, as
contained in the Membrane Filtration Guidance Manual (3), for membrane filtration processes
used for compliance with the LT2ESWTR.
3. LONG TERM 2 ESWTR AND STAGE 2 DBPR REGULATIONS
3.1. Long Term 2 Enhanced Surface Water Treatment Rule
Under the LT2ESWTR, systems that use either a surface water or ground water under the
direct influence of surface water (GWUDI) source (collectively referred to as surface water
systems) are required to conduct source water monitoring to determine average Cryptosporidium
concentrations. Based on the average Cryptosporidium concentration, a system is
classified in one of four possible bins, as shown in Table 4.1. The bin assignment dictates the
supplemental level of Cryptosporidium treatment required in addition to the existing requirements
of the SWTR, IESWTR, and LT1ESWTR. Utilities may comply with additional
treatment requirements by implementing one or more management or treatment techniques
from a toolbox of options that includes membrane filtration. A guidance manual has also been
Table 4.1
LT2ESWTR additional treatment requirements for filtered systems
If source water
Cryptosporidium
concentration for
filtered systems is
in oocyst/L
And if the system uses the following filtration treatments, then additional
treatment requirements are...
Bin
classification
is...
Conventional
Filtration
Treatment