|What do we
mean by water quality?
Water quality is
defined in terms of the chemical, physical and biological content of water.
The water quality of rivers and lakes changes with the seasons and
geographic areas, even when there is no pollution present. There is no
single measure that constitutes good water quality. For instance, water
suitable for drinking can be used for irrigation, but water used for
irrigation may not meet drinking water guidelines. The quality of water
appropriate for recreational purposes differs from that used for industrial
the key factors that influence water quality?
affect water quality. The natural water quality of groundwater in aquifers
is related to the quality of recharge water, the mineralogy of soils and
aquifer sediments, the residence time in the ground water flow system, and
the presence of nearby saline water. However, the primary influence on
groundwater quality (as well as surface water quality) is the contamination
brought about by human activity.
agricultural runoff, domestic wastewater, industrial wastewater, and
hydrologic modifications are the major sources of water pollution in
Florida. Other threats include nitrates from dairy and other livestock
operations, fertilizers and pesticides in stormwater runoff, toxic chemicals
in leachate from hazardous waste sites, and erosion from construction sites,
unpaved roads, and farm fields. Septic tank leachate contributes to the
degradation of many water bodies by adding nitrate nitrogen, bacteria,
viruses, and synthetic organics used in household cleaning products and
septic tank cleaners. Industrial activities can increase concentrations of
metals and toxic chemicals, add suspended sediment, increase temperature,
and lower dissolved oxygen in the water. Gasoline storage areas (including
service stations) may have leaks and spills of petroleum products. Roadways
contribute petroleum pollutants leaked from vehicles and metals from exhaust
fumes. Older sanitary landfills, whose leachate may contain many different
chemicals at relatively high concentrations, also pose a threat.
|How do we
measure water quality?
The quality of
water is determined by making measurements in the field or by taking samples
of water, suspended materials, bottom sediment, or biota, and sending them
to a laboratory for physical, chemical and microbiological analyses. For
example, acidity (pH), color and turbidity (a measure of the suspended
particles in the water) are measured in the field. The concentrations of
metals, nutrients, pesticides and other substances are measured in the
Another way to
obtain an indication of the quality of water is biological testing. This
test determines, for example, whether the water or the sediment is toxic to
life forms or if there has been a fluctuation in the numbers and kinds of
plants and animals. Some of these biological tests are done in a laboratory,
while others are carried out at the stream or lake.
good quality drinking water?
drinking water is free from disease-causing organisms, harmful chemical
substances, and radioactive matter. It tastes good, is aesthetically
appealing, and free from objectionable color or odor.
It should be
noted that there is a difference between "pure water" and "safe drinking
water". Pure water, often defined as water containing no minerals or
chemicals, does not exist naturally in the environment. Under ideal
conditions, water may be distilled to produce "pure" water. Safe drinking
water, on the other hand, may retain naturally occurring minerals and
chemicals such as calcium, potassium, sodium or fluoride which are actually
beneficial to human health and may also improve the taste of the water.
Where the minerals or chemicals occur naturally in concentrations that may
be harmful or displeasing, then certain water treatment processes are used
to reduce or remove the substances. In fact, some chemicals are actually
added to produce good drinking water; the best examples of chemical addition
are chlorine used as a disinfectant to destroy microbial contaminants, or
fluoride used to reduce dental cavities.
|How can we
be sure that water is safe to drink?
Since 1974, when
Congress passed the original Safe Drinking Water Act, EPA has set uniform
nationwide minimum standards for drinking water. State public health and
environmental agencies have the primary responsibility for ensuring that
these federal drinking water quality standards, or more stringent ones
required by the state, are met by each public water supplier. Local
governments, public water systems, the states, and EPA work together towards
the goal of ensuring that all public water supplies are safe. For more
information, go to the EPA web site
Water on Tap: What You Need To Know.
For households on
private wells, state and local health departments usually have some
standards for the drinking water, but it is generally up to the homeowner to
maintain the quality of the drinking water. In Florida you can get
information on how to safeguard well water supply from the county extension
office, the county public health department, the Florida Department of
Environmental Protection, and the
Home*A*Syst web site.
|If we could
boil all the water we consume, could we eliminate pollution?
|No. Boiling water kills germs but will not
in the water supply necessary, and could it become a health hazard?
introduced as a disinfectant in water treatment around the turn of the
century. It has since become the predominant method for water disinfection.
Apart from its effectiveness as a germicide, it offers other benefits such
as color removal, taste and odor control, suppression of algal growths, and
precipitation of iron and manganese. In addition, chlorine is easy to apply,
measure and control. It is quite effective and relatively inexpensive.
Chlorine as a
disinfectant in water treatment can be a health hazard if its concentration
or the concentrations of certain by-products (e.g., trihalomethanes, a
chlorinated organic compound) are greater than the allowed by the EPA. If
the maximum acceptable concentrations are exceeded, the authorities
responsible for public health should be consulted for the appropriate
say that you shouldn't pour solvents and other household chemicals down the
drain because they pollute the rivers and lakes. Is that true? How else can
I get rid of them?
household products are generally safe for the uses they are designed for,
some may become harmful to the environment as they accumulate in it. For
this reason you should not put these products down the drain. Most sewage
treatment facilities are not capable of removing such toxic substances.
Anything put into the storm sewers is going directly to the receiving lake
or river completely untreated. So, before you dump anything down the drain,
remember that you or others may be drinking it some day.
Some cities and
communities in Florida sponsor either occasional or permanent hazardous
waste collection program. If your community does not sponsor such a
program, contact the DEP Hazardous Waste Management Section (904/488-0300).
responsible consumer how can I tell if the products I buy are potentially
harmful to the environment?
chemical products and pesticides sold in the United States have warning
labels. These labels tell us whether the product is flammable, poisonous,
corrosive or explosive. The labels usually also give first aid instructions.
Read the label to find out how to use the product safely and what
precautions to take for its disposal.
happens to water that drains out of our home?
the liquid waste and discharge it into lakes, streams or the ocean. Most,
but not all, municipalities treat their sewage using mechanical and/or
biological processes before discharging it. Regardless of the process,
sewage treatment plants concentrate the sewage into a solid called sludge,
which is then utilized on agricultural land, disposed of in a landfill site,
or incinerated. For a detailed description of the wastewater treatment
process, visit the
USGS Water Science for Schools web site.
Residents of rural areas, may have individual septic systems (shown in the
diagram to the left) or have sewage collected by truck.
Eutrophication is a form of pollution. What is a eutrophic lake?
the process of becoming better nourished either naturally or artificially.
In terms of a lake, eutrophication occurs naturally with the gradual input
of nutrients and sediment through erosion and precipitation resulting in a
gradual aging of the lake. Humans speed up this natural process by releasing
nutrients, particularly phosphorus, into rivers and lakes through municipal
and industrial effluent and through increased soil erosion by poor land use
practices. Eventually, a lake has high nutrient concentrations and dense
growths of aquatic weeds and algae. These plants die and decompose causing
depletion of dissolved oxygen in the water. This process often results in
fish kills and changes in a lake's fish species. Ultimately, eutrophication
will fill the lake with sediment and plant material. Lake Apopka, Lake
Okeechobee and the Florida Everglades have suffered from eutrophication.
This resulted from agricultural and urban runoff coupled with the inability
of these waters to flush themselves due to altered drainage.
Algae bloom in Lake Okeechobee
Source: South Florida
Water Management District
irrigation affect water quality?
affects water quality in different ways, depending upon the original water
quality, the type of soil, the underlying geology, the type of irrigation,
the crop grown, and the farming methods used.
Although a large
portion of irrigation water is used by plants or evaporates from the soil
(evapotranspiration), part of it is returned to the source. As is often the
case with water use, when the water returns to the stream or water body, the
quality has been lowered. The water that runs off the fields carries with it
sediments, fertilizers, herbicides, pesticides (if these chemicals are used
on the fields), and natural salts leached from the soil and enters rivers,
lakes and groundwater supplies.
discharge of cooling water from electrical power plants a form of pollution?
Yes, it is called
thermal pollution. Water is used for condenser cooling and then discharged
into nearby rivers, streams, or coastal environments. However, most of these
facilities have controls on the maximum temperature of their discharge
waters, and many of them use cooling ponds or towers.
pollution, when not regulated, can be a problem. Artificially heated water
can promote algae blooms, threatening certain species of fish and otherwise
disturbing the chemistry of the receiving water body and its estuarine life.
When this water is not reused by industries or for heating in nearby
communities, large amounts of energy and potential dollar savings are lost.
is our water?
majority of Florida’s surface waters are of good quality, but problems exist
around densely populated urban areas, primarily in central and southern
Florida. In rivers, nutrient enrichment, low dissolved oxygen, organic
matter, siltation, and habitat alteration degrade water quality. In lakes,
the leading problems result from metals and other toxics, ammonia, and
nutrients. In estuaries, nutrient enrichment, habitat alteration, and
siltation degrade quality. Special state concerns include widespread mercury
contamination in fish, bacterial contamination in the Miami River, and algal
blooms and extensive die-off of mangroves and sea grasses in Florida Bay.
Data from over
1,900 wells in Florida’s ambient monitoring network indicate generally good
water quality, but local ground water contamination problems exist.
Agricultural chemicals, including aldicarb, alachlor, bromacil, simazine,
and ethylene dibromide (EDB) have caused local and regional (in the case of
EDB) problems. The Florida DEP has documented more than 400 instances of
groundwater contamination from leaking gasoline pipes or storage tanks and
found groundwater contamination at 156 hazardous waste sites in the state.