Explain
about Water quality ?
Water quality is
the physical, chemical and biological characteristics of water. It is a
measure of the condition of water relative to the requirements of one or more
biotic species and or to any human need or purpose. It is most frequently used
by reference to a set of standards against which compliance can be assessed.
The most common standards used to assess water quality relate to drinking
water, safety of human contact and for the health of ecosystems.
Standards
In the setting of
standards, agencies make political and technical/scientific decisions about how
the water will be used. In the case of natural water bodies, they also make
some reasonable estimate of pristine conditions. Different uses raise different
concerns and therefore different standards are considered. Natural water bodies
will vary in response to environmental conditions. Environmental scientists
work to understand how these systems function which in turn helps to identify
the sources and fates of contaminants. Environmental lawyers and policy makers
work to define legislation that ensure that water is maintained at an
appropriate quality for its identified use.
The vast majority of
surface water on the planet is neither potable nor toxic. This remains true
even if sea water in the oceans (which is too salty to drink) is not counted.
Another general perception of water quality is that of a simple property
that tells whether water is polluted or not. In fact, water quality is a very
complex subject, in part because water is a complex medium intrinsically tied
to the ecology of the Earth. Industrial pollution is a major cause of water
pollution, as well as runoff from agricultural areas, urban stormwater runoff
and discharge of treated and untreated sewage (especially in developing
countries).
Categories
The parameters for
water quality are determined by the intended use. Work in the area of water
quality tends to be focused on water that is treated for human consumption or
in the environment.
Human consumption
Contaminants that may
be in untreated water include microorganisms such as viruses and bacteria;
inorganic contaminants such as salts and metals; organic chemical contaminants
from industrial processes and petroleum use; pesticides and herbicides; and
radioactive contaminants. Water quality depends on the local geology and
ecosystem, as well as human uses such as sewage dispersion, industrial
pollution, use of water bodies as a heat sink, and overuse (which may lower the
level of the water).
In the United States,
the U.S. Environmental Protection Agency (EPA) limits the amounts of certain
contaminants in tap water provided by public water systems. The Safe Drinking
Water Act authorizes EPA to issue two types of standards: primary standards
regulate substances that potentially affect human health, and secondary
standards prescribe aesthetic qualities, those that affect taste, odor, or
appearance. The U.S. Food and Drug Administration (FDA) regulations establish
limits for contaminants in bottled water that must provide the same protection
for public health. Drinking water, including bottled water, may reasonably be
expected to contain at least small amounts of some contaminants. The presence
of these contaminants does not necessarily indicate that the water poses a
health risk.
Some people use water
purification technology to remove contaminants from the municipal water supply
they get in their homes, or from local pumps or bodies of water. For people who
get water from a local stream, lake, or aquifer (well), their drinking water is
not filtered by the local government.
Environmental
water quality
Environmental water
quality, also called ambient water quality, relates to water bodies such
as lakes, rivers, and oceans. Water quality standards vary significantly due to
different environmental conditions, ecosystems, and intended human uses. Toxic
substances and high populations of certain microorganisms can present a health
hazard for non-drinking purposes such as irrigation, swimming, fishing, rafting,
boating, and industrial uses. These conditions may also affect wildlife which
use the water for drinking or as a habitat. Modern water quality laws general
specify protection of fisheries and recreational use and require as a
minimum,retention of current quality standards.
There is some desire
among the public to return water bodies to pristine, or pre-industrial
conditions. Most current environmental laws focus of the designation of uses.
In some countries these allow for some water contamination as long as the
particular type of contamination is not harmful to the designated uses. Given
the landscape changes in the watersheds of many freshwater bodies, returning to
pristine conditions would be a significant challenge. In these cases,
environmental scientists focus on achieving goals for maintaining healthy
eco-systems and may concentrate on the protection of populations of endangered
species and protecting human health.
Measurement
The complexity of water
quality as a subject is reflected in the many types of measurements of water
quality indicators. Some of the simple measurements listed below can be made on
site-temperature, pH, dissolved oxygen, conductivity, Oxygen Reduction
potential (ORP), turbidity, Secchi disk depth-in direct contact with the water
source in question. More complex measurements that must be made in a lab
setting require a water sample to be collected, preserved, and analyzed at
another location. Making these complex measurements can be expensive. Because
direct measurements of water quality can be expensive, ongoing monitoring
programs are typically conducted by government agencies. However, there are
local volunteer programs and resources available for some general assessment.
Tools available to the general public are on-site test kits commonly used for
home fish tanks and biological assessments.
Testing
in response to natural disasters and other emergencies
Inevitably after events
such as earthquakes and Tsunamis, there is an immediate response by the aid
agencies as relief operations get underway to try and restore basic
infrastructure and provide the basic fundamental items that are necessary for
survival and subsequent recovery. Access to clean drinking water and adequate
sanitation is a priority at times like this. The threat of disease increases
hugely due to the large numbers of people living close together, often in
squalid conditions, and without proper sanitation.
After a natural
disaster, as far as water quality testing is concerned there are widespread
views on the best course of action to take and a variety of methods can be
employed. The key basic water quality parameters that need to be addressed in
an emergency are bacteriological indicators of fecal contamination, Free
Chlorine Residual, pH, turbidity and possibly Conductivity/TDS. There are a
number of portable water test kits on the market widely used by aid and relief
agencies for carrying out such testing.
The following is a list of indicators often measured
by situational category:
Drinking
water
· Alkalinity
· Color
of water
· pH
· Taste
and odor (geosmin, 2-methylisoborneol (MIB), etc)
· Dissolved
metals and salts (sodium, chloride, potassium, calcium, manganese, magnesium)
· Microorganisms
such as fecal coliform bacteria (Escherichia coli), Cryptosporidium, and
Giardia lamblia
· Dissolved
metals and metalloids (lead, mercury, arsenic, etc.)
· Dissolved
organics: colored dissolved organic matter (CDOM), dissolved organic carbon
(DOC)
· Radon
· Heavy
metals
· Pharmaceuticals
· Hormone
analogs
Environmental
Chemical assessment
· (also
see salinity)
· Dissolved
Oxygen (DO)
· nitrate-N
· orthophosphates
· Chemical
oxygen demand (COD)
· Biochemical
oxygen demand (BOD)
· Pesticides
Physical assessment
· pH
· Temperature
· Total
suspended solids (TSS)
· Turbidity
Biological
assessment
Biological
monitoring metrics have been developed in many places, and one widely used
measure is the presence and abundance of members of the insect orders
Ephemeroptera, Plecoptera and Trichoptera. (Common names are, respectively,
Mayfly, Stonefly and Caddisfly.) EPT indexes will naturally vary from region to
region, but generally, within a region, the greater the number of taxa from
these orders, the better the water quality. EPA and other organizations in the
United States offer guidance on developing a monitoring program and identifying
members of these and other aquatic insect orders.
Related Topics
Privacy Policy, Terms and Conditions, DMCA Policy and Compliant
Copyright © 2018-2023 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.