For turbidity, color and microbiological control

AN OVERVIEW OF WATER AND WASTEWATER TREATMENT 9
uniform. Small systems are the most frequent violators of federal regulations.
Microbiological violations account for the vast majority of cases, with failure to
monitor and report. Among others, violations exceeding SDWA maximum
contaminant levels (MCLs) are quite common. Bringing small water systems into
compliance requires applicable technologies, operator ability, financial resources,
and institutional arrangements. The 1986 SDWA amendments authorized USEPA
to set the best available technology (BAT) that can be incorporated in the design for
the purposes of complying with the National Primary Drinking Water Regulations
(NPDWR). Current BAT to maintain standards are as follows:
For turbidity, color and microbiological control in surface water treatment:
filtration. Common variations of filtration are conventional, direct, slow sand,
diatomaceous earth, and membranes.
For inactivation of microorganisms: disinfection. Typical disinfectants are
chlorine, chlorine dioxide, chloramines, and ozone.
For organic contaminant removal from surface water: packed-tower aeration,
granular activated carbon (GAC), powdered activated carbon (PAC), diffused
aeration, advanced oxidation processes, and reverse osmosis (RO).
For inorganic contaminants removal: membranes, ion exchange, activated
alumina, and GAC.

10 WATER AND WASTEWATER TREATMENT TECHNOLOGIES
For corrosion control: typically, pH adjustment or corrosion inhibitors. The
implications of the 1986 amendments to the SDWA and new regulations have
resulted in rapid development and introduction of new technologies and equipment
for water treatment and monitoring over the last two decades. Biological processes
in particular have proven effective in removing biodegradable organic carbon that
may sustain the regrowth of potentially harmful microorganisms in the distribution
system, effective taste and odor control, and reduction in chlorine demand and DBP
formation potential. Both biologically-active sand or carbon filters provide cost
effective treatment of micro-contaminants than do physicochernical processes in
many cases. Pertinent to the subject matter cover in this volume, membrane
technology has been applied in drinking water treatment, partly because of
affordable membranes and demand to removal of many contaminants.
Microfiltration, ultrafiltration, nanofiltration and others have become common
names in the water industry. Membrane technology is experimented with for the
removal of microbes, such as Giardia and Cryptosporidium and for selective
removal of nitrate. In other instances, membrane technology is applied for removal
of DBP precursors, VOCs, and others.
Other treatment technologies that have potential for full-scale adoption are
photochemical oxidation using ozone and UV radiation or hydrogen peroxide for
destruction of refractory organic compounds. One example of a technology that
was developed outside North America and later emerged in the U.S. is the Haberer
process. This process combines contact flocculation, filtration, and powdered
activated carbon adsorption to meet a wide range of requirements for surface water
and groundwater purification.
Utilities are seeking not only to improve treatment, but also to monitor their
supplies for microbiological contaminants more effectively. Electro-optical sensors
are used to allow early detection of algal blooms in a reservoir and allow for
diagnosis of problems and guidance in operational changes. Gene probe technology
was first developed in response to the need for improved identification of microbes
in the field of clinical microbiology. Attempts are now being made by radiolabeled
and nonradioactive gene-probe assays with traditional detection methods for enteric
viruses and protozoan parasites, such as Giardia and Cryptosporidium. This
technique has the potential for monitoring water supplies for increasingly complex
groups of microbes.
In spite of the multitudinous regulations and standards that an existing public water
system must comply with, the principles of conventional water treatment process
have not changed significantly over half a century. Whether a filter contains sand,
anthracite, or both, slow or rapid rate, constant or declining rate, filtration is still
filtration, sedimentation is still sedimentation, and disinfection is still disinfection.
What has changed, however, are many tools that we now have in our engineering
arsenal. For example,, a supervisory control and data acquisition (SCADA) system
can provide operators and managers with accurate process control variables and
operation and maintenance records. In addition to being able to look at the various

AN OVERVIEW OF WATER AND WASTEWATER TREATMENT 11
options on the computer screen, engineers can conduct pilot plant studies of the
multiple variables inherent in water treatment plant design. Likewise, operators and
managers can utilize an ongoing pilot plant facility to optimize chemical feed and
develop important information needed for future expansion and upgrading.
Technology and ultimately equipment selection depends on the standards set by the
regulations. Drinking water standards are regulations that EPA sets to control the
level of contaminants in the nation's drinking water. These standards are part of the
Safe Drinking Water Act's "multiple barrier" approach to drinking water
protection, which includes assessing and protecting drinking water sources;
protecting wells and collection systems; making sure water is treated by qualified
operators; ensuring the integrity of distribution systems; and making information
available to the public on the quality of their drinking water. With the involvement
of EPA, states, tribes, drinking water utilities, communities and citizens, these
multiple barriers ensure that tap water in the U.S. and territories is safe to drink.
In most cases, EPA delegates responsibility for implementing drinking water
standards to states and tribes. There are two categories of drinking water standards:
* A National Primary Drinking Water Regulation (NPDWR or primary
standard) is a legally-enforceable standard that applies to public water
systems. Primary standards protect drinking water quality by limiting the
levels of specific contaminants that can adversely affect public health and
are known or anticipated to occur in water. They take the form of
Maximum Contaminant Levels (MCL) or Treatment Techniques (TT).
9 A National Secondary Drinking Water Regulation (NSDWR or secondary
standard) is a non-enforceable guideline regarding contaminants that may
cause cosmetic effects (such as skin or tooth discoloration) or aesthetic
effects (such as taste, odor, or color) in drinking water. EPA recommends
secondary standards to water systems but does not require systems to
comply. However, states may choose to adopt them as enforceable
standards. This information focuses on national primary standards.
Drinking water standards apply to public water systems (PWSs), which provide
water for human consumption through at least 15 service connections, or regularly
serve at least 25 individuals. Public water systems include municipal water
companies, homeowner associations, schools, businesses, campgrounds and
shopping malls. EPA considers input from many individuals and groups throughout
the rule-making process. One of the formal means by which EPA solicits the
assistance of its stakeholders is the National Drinking Water Advisory Council
(NDWAC). The 15-member committee was created by the Safe Drinking Water
Act. It is comprised of five members of the general public, five representatives of
state and local agencies concerned with water hygiene and public water supply, and
five representations of private organizations and groups demonstrating an active
interest in water hygiene and public water supply, including two members who are
associated with small rural public water systems.

12 WATERA ND WASTEWATER TREATMENT TECHNOLOGIES
NDWAC advises EPA's Administrator on all of the agency's activities relating to
drinking water. In addition to the NDWAC, representatives from water utilities,
environmental groups, public interest groups, states, tribes and the general public
are encouraged to take an active role in shaping the regulations, by participating in
public meetings and commenting on proposed rules. Special meetings are also held
to obtain input from minority and low-income communities, as well as
representatives of small businesses.
The 1996 Amendments to Safe Drinking Water Act require EPA to go through
several steps to determine, first, whether setting a standard is appropriate for a
particular contaminant, and if so, what the standard should be. Peer-reviewed
science and data support an intensive technological evaluation, which includes many
factors: occurrence in the environment; human exposure and risks of adverse health
effects in the general population and sensitive subpopulations; analytical methods
of detection; technical feasibility; and impacts of regulation on water systems, the
economy and public health. Considering public input throughout the process, EPA
must (1) identify drinking water problems; (2) establish priorities; and (3) set
standards.
EPA must first make determinations about which contaminants to regulate. These
determinations are based on health risks and the likelihood that the contaminant
occurs in public water systems at levels of concern. The National Drinking Water
Contaminant Candidate List (CCL), published March 2, 1998, lists contaminants
that (1) are not already regulated under SDWA; (2) may have adverse health
effects; (3) are known or anticipated to occur in public water systems; and (4) may
require regulations under SDWA. Contaminants on the CCL are divided into
priorities for regulation, health research and occurrence data collection.
In August 2001, EPA selected five contaminants from the regulatory priorities on
the CCL and determined whether to regulate them. To support these decisions, the
Agency determined that regulating the contaminants presents a meaningful
opportunity to reduce health risk. If the EPA determines regulations are necessary,
the Agency must propose them by August 2003, and finalize them by February
2005. In addition, the Agency will also select up to 30 unregulated contaminants
from the CCL for monitoring by public water systems serving at least 100,000
people. Currently, most of the unregulated contaminants with potential of occurring
in drinking water are pesticides and microbes. Every five years, EPA will repeat
the cycle of revising the CCL, making regulatory determinations for five
contaminants and identifying up to 30 contaminants for unregulated monitoring. In
addition, every six years, EPA will re-evaluate existing regulations to determine if
modifications are necessary. Beginning in August 1999, a new National
Contaminant Occurrence Database was developed to store data on regulated and
unregulated chemical, radiological, microbial and physical contaminants, and other
such contaminants likely to occur in finished, raw and source waters of public water
systems.

AN OVERVIEW OF WATER AND WASTEWATER TREATMENT 13
After reviewing health effects studies, EPA sets a Maximum Contaminant Level
Goal (MCLG), the maximum level of a contaminant in drinking water at which no
known or anticipated adverse effect on the health of persons would occur, and
which allows an adequate margin of safety. MCLGs are non-enforceable public
health goals. Since MCLGs consider only public health and not the limits of
detection and treatment technology, sometimes they are set at a level which water
systems cannot meet. When determining an MCLG, EPA considers the risk to
sensitive subpopulations (infants, children, the elderly, and those with compromised
immune systems) of experiencing a variety of adverse health effects.
Non-Carcinogens (excluding microbial contaminants): For chemicals that can
cause adverse non-cancer health effects, the MCLG is based on the reference dose.
A reference dose (RFD) is an estimate of the amount of a chemical that a person
can be exposed to on a daily basis that is not anticipated to cause adverse health
effects over a person's lifetime. In RFD calculations, sensitive subgroups are
included, and uncertainty may span an order of magnitude. The RFD is multiplied
by typical adult body weight (70 kg) and divided by daily water consumption (2
liters) to provide a Drinking Water Equivalent Level (DWEL). Note that the
DWEL is multiplied by a percentage of the total daily exposure contributed by

14 WATERA ND WASTEWATER TREATMENT TECHNOLOGIES
drinking water to determine the MCLG. This empirical factor is usually 20 percent,
but can be a higher value.
Chemical Contaminants (Carcinogens): If there is evidence that a chemical may
cause cancer, and there is no dose below which the chemical is considered safe, the
MCLG is set at zero. If a chemical is carcinogenic and a safe dose can be deter
mined, the MCLG is set at a level above zero that is safe.
Microbial Contaminants: For microbial contaminants that may present public
health risk, the MCLG is set at zero because ingesting one protozoa, virus, or
bacterium may cause adverse health effects. EPA is conducting studies to determine
whether there is a safe level above zero for some microbial contaminants. So far,
however, this has not been established.
Once the MCLG is determined, EPA sets an enforceable standard. In most cases,
the standard is a Maximum Contaminant Level (MCL), the maximum permissible
level of a contaminant in water which is delivered to any user of a public water
system. The MCL is set as close to the MCLG as feasible, which the Safe Drinking
Water Act defines as the level that may be achieved with the use of the best
available technology, treatment techniques, and other means which EPA finds are
available(after examination for efficiency under field conditions and not solely
under laboratory conditions) are available, taking cost into consideration. When
there is no reliable method that is economically and technically feasible to measure
a contaminant at particularly low concentrations, a Treatment Technique (TT) is
set rather than an MCL. A treatment technique (TT) is an enforceable procedure
or level of technological performance which public water systems must follow to
ensure control of a contaminant. Examples of Treatment Technique rules are the
Surface Water Treatment Rule (disinfection and filtration) and the Lead and Copper
Rule (optimized corrosion control). After determining a MCL or TT based on
affordable technology for large systems, EPA must complete an economic analysis
to determine whether the benefits of that standard justify the costs. If not, EPA may
adjust the MCL for a particular class or group of systems to a level that "maximizes
health risk reduction benefits at a cost that is justified by the benefits."
WHAT THE CURRENT DRINKING WATER STANDARDS ARE
The following matrices provide you with a summary of the NPDWRs or primary
standards. You should visit the EPA Web site (www.epa.gov) and become familiar
with the various documents that are publically available. You will not only find
these regulations there, but detailed information that explains the reasoning behind
each MCLG. You will also find the entire legislation on this site and can become
familiar with all of the subtleties of this piece of complex environmental legislation.
Tables 1 through 5 are derived from EPA Web site- www.epa.gov/safewater.

AN OVERVIEW OF WATER AND WASTEWATER TREATMENT 15
Table 1. NPDW Regulations for Microorganisms.
Microorganisms MCLG 1
(mg/L) z
: Cryptosporidium
I
Giardia lamblia
Heterotrophic n/a
l MCL or Potential Health Effects Sources of [
TT 1 from Ingestion of Water Contaminant in
. (mg/L) z . . Drinking Water .
as of Gastrointestinal illness Human and
(e.g., diarrhea, vomiting, animal fecal wastel
cramps) I
9 . !
01/01/02:
TT 3
TT 3
TT 3
Gastrointestinal illness
(e.g., diarrhea, vomiting,
cramps)
Human and
animal fecal waste l
HPC has no health effects, HPC measures a
plate count but can indicate how
effective treatment is at
controlling
microorganisms.
Legionella
Total Coliforms
(including fecal
coliform and E.
Coli)
TT 3
5.0% 4
Legionnaire's Disease,
commonly known as
.pneumonia
Used as an indicator that
other potentially harmful
bacteria may be present s
range of bacteria
that are naturally
present in the
environment
Found naturally in
water; multiplies
]in heating systems
Coliforms are
naturally present
in the
environment;
fecal coliforms
and E. coli come
from human and
animal fecal
waste.
Turbidity n/a TT 3 Turbidity, a measure of
water cloudiness, is used
to indicate water quality
and filtration effectiveness
(e.g., whether diseasejcausing
organisms are
ipresent). Higher turbidity
!is associated with higher J
levels of microorganisms
such as viruses, parasites
and some bacteria. These
organisms can cause
symptoms such as nausea,
cramps, diarrhea, and
associated headaches.
Soil runoff
Viruses (enteric)
i
TT s Gastrointestinal illness
(e.g.~ diarrhea/vomiting)
Human and
animal fecal waste l