United States
Environmental Protection
Agency
Office of Water
4601
EPA 570/9-91-300
January 1995
EPA Surface Water Treatment Rule
"Surface
water systems
must filter
and disinfect
the water
supply."
Table 1. Standards
Contaminant
MCLG
Giardia lamblia 0
Viruses 0
Legionella 0
Turbidity non-turbid
HPC none
The Surface Water Treatment Rule (SWTR) was published in the Federal
Register on June 29, 1989. It became effective on December 31, 1990. This rule
requires water treatment in lieu of water testing because it regulates contami-
nants which are difficult to detect and pose acute health risks.
Under this rule, disinfection is required for surface water systems and for
groundwater systems under the direct influence (UDI) of surface water. These
systems must also install filtration if the microbiological, turbidity and other
criteria for avoiding filtration in this rule are not met. All surface water
systems must disinfect.
Water Quality Standards
Maximum Contaminant Level Goals (MCLGs): Zero
Water systems should try to produce water which is free of the microbial
contaminants given in Table 1. These are non-enforceable goals.
Maximum Contaminant Levels (MCLs): Treatment Required
Specific enforceable MCL standards for these microbial contaminants are
not established in this rule. Instead, treatment is required for surface
water systems and groundwater systems under the direct influence of
surface water.
Water Treatment Requirements
Criteria to be met by systems seeking to avoid filtration
Table 2. Unfiltered System Criteria
Criterion
Standard
Source water quality
Coli forms
Turbidity
Disinfection
Giardia
Viruses
Residual
Coliform Sampling
25-501 persons served
501-3300
3301-10,000
10,001-25,000
More than 25,000
acceptable
<5NTU
99.9% effective
99.99% effective
0.2 mg/1 at entry
I/week
2/week
3/week
4/week
5/week
Although all systems are required to filter their water,
unfiltered systems may avoid this requirement as long as
they meet certain source water quality and system operation
criteria. These criteria are given in Table 2. The water supply
source must not exceed bacterial and other standards before
the water is treated. The effectiveness of disinfection will be
demonstrated in part by the amount of disinfectant in
treated water and the length of time it is in contact with the
water before reaching the first customer.
The water system must also operate in a way which mini-
mizes the risk that the supply will be susceptible to microbio-
logical contamination:
• System must maintain a watershed control program.
• System must have no more than 2 monthly total coliform
MCL violations in any consecutive 12 month period.
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System must have no history of waterborne disease outbreaks.
Systems serving 10,000 or more people must be in compliance
with Total Trihalomethane requirements.
Criteria for filtered systems Turbidity
Systems which filter their water must ensure that the overall filtra-
tion and disinfection process they use is performing effectively as
demonstrated by turbidity and disinfection criteria. These criteria are n- • f
given in Table 3. As with unfiltered systems, effectiveness will be "ismrection
demonstrated in part by the amount of disinfectant and the length of Giardia
time it is in contact with the water before reaching the first customer. Viruses
Residual
Table 3. Filtered System Criteria
Criterion Standard
<5 NTU at all times
<0.5 NTU in 95% of
all samples
99.9% effective
99.99% effective
0.2 mg/1 at entry
Compliance
Systems were given time to comply with the water quality standards and
treatment requirements of this rule. Specific dates are given in Table 4.
Surface water (SW) systems
• Unfiltered systems had to meet monitoring requirements
within 18 months after the rule was promulgated.
• Unfiltered systems had to meet criteria to avoid filtration
within 30 months after the rule was promulgated.
• Beginning 30 months after the rule was promulgated,
unfiltered systems which failed to meet any criteria to avoid
filtration were required to install filtration within 18 months
of such failure.
• Filtered systems had to meet monitoring and treatment per-
formance requirements beginning 48 months after the rule
was promulgated.
Ground water systems under direct influence of surface water
(GW-UDI)
• States had to determine which Community Water Systems are under
direct influence of surface water within 5 years of promulgating the rule
and which Non-Community Systems are under direct influence of surface
water within 10 years of promulgating the rule.
Variances and Exemptions
Filtration
• Variances are not allowed since systems may avoid filtration by meeting
the criteria given above.
• Exemptions are allowed under some conditions as long as an unreasonable
risk to health does not exist.
Disinfection
Because of the acute and serious health effects associated with poor disinfec-
tion of surface waters
• Surface water systems must disinfect (no variances or exemptions).
• Exemptions allowed only for the level of disinfection required.
Table 4. Compliance Dates
System
Type
SW-UF i
SW-UF
SW-UF
SW-F |
GW-UDI;
Requirement
Begin monitoring
Meet all criteria
to avoid nitration
Install filtration
if required to filter
Performance and
monitoring
State must notify
system that it is UDI
Date
12/31790
12/31/91
6/29/93
6/29/93
6/29/94
For More Information
Call the Safe Drinking
Water Hotline at
1-800-426-4791
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