ENVIRONMENTAL FINAL GOVERNING STANDARDS ITALY

ITALY - 3 Drinking Water
1. Unfiltered Systems
Table 3.1. Surface Water Treatment Requirements
a. Systems which use unfiltered surface water or GWUDISW will analyze the raw water for total
coliforms or fecal coliforms at least weekly and for turbidity at least daily, and must continue as
long as the unfiltered system is in operation. If the total coliforms and/or fecal coliforms exceed
100/100 milliliters (mL) and 20/100 mL, respectively, in excess of 10% of the samples collected in
the previous 6 months, appropriate filtration must be applied. Appropriate filtration must also be
applied if turbidity of the source water immediately prior to the first or only point of disinfectant
application exceeds 1 Nephelometric Turbidity Units (NTU).
b. Disinfection must achieve at least 99.9% (3-log) inactivation of Giardia lamblia cysts and 99.99%
(4-log) inactivation of viruses by meeting applicable CT values, as shown in Tables 3.11. through
3.24.
c. Disinfection systems must have redundant components to ensure uninterrupted disinfection during
operational periods.
d. Disinfectant residual monitoring immediately after disinfection is required once every four hours
that the system is in operation. Disinfectant residual measurements in the distribution system will
be made at the same times as total coliforms are sampled.
e. Disinfectant residual of water entering the distribution system shall be maintained at a minimum of
0.2 mg/L.
f. Water in a distribution system with a heterotrophic bacteria concentration ≤ 500/mL measured as
heterotrophic plate count is considered to have a detectable disinfectant residual for the purpose of
determining compliance with the Surface Water Treatment Requirements.
g. If disinfectant residuals in the distribution system are undetected in more than 5% of monthly
samples for 2 consecutive months, appropriate filtration must be implemented.
2. Filtered Systems
a. Filtered water systems will provide a combination of disinfection and filtration that achieves a total
of 99.9% (3-log) removal of Giardia lamblia cysts and 99.99% (4-log) removal of viruses.
b. The turbidity of filtered water will be monitored at least once every four hours. The turbidity of
filtered water for direct and conventional filtration systems will not exceed 0.5 NTU (1 NTU for
slow sand and diatomaceous earth filters) in 95% of the analyses in a month, with a maximum of 1
NTU.
c. Disinfection must provide the remaining log-removal of Giardia lamblia cysts and viruses not
obtained by the filtration technology applied.*
d. Disinfection residual maintenance and monitoring requirements are the same as those for unfiltered
systems.
*Proper conventional treatment typically removes 2.5-log Giardia/ 2.0-log viruses. Proper direct
filtration and diatomaceous earth filtration remove 2.0-log Giardia/ 1.0-log viruses. Slow sand filtration
removes typically removes 2.0-log Giardia/ 2.0-log viruses. Less log-removal may be assumed if
treatment is not properly applied.
3. SW or GWUDISW systems will provide at least 99% (2-log) removal of Cryptosporidium. A system is
considered to be compliant with the Cryptosporidium removal requirements if:
a. For conventional and direct filtration systems, the turbidity level of the system’s combined filter
effluent water does not exceed 0.3 NTU in at least 95% of the measurements taken each month
and at no time exceeds 1 NTU.
b. For slow sand and diatomaceous earth filtration plants, the turbidity level of the system’s combined
filter effluent water at no time exceeds 1 NTU.
c. For alternative systems, the system demonstrates to the appropriate medical authority that the
alternative filtration technology, in combination with disinfection treatment, consistently achieves
3-log removal and/or inactivation of Giardia lamblia cysts, 4-log removal and/or inactivation of
viruses, and 2-log removal of Cryptosporidium oocysts.
September 2012 Italy FGS 3-13
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