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Did
you know?
Reverse osmosis is the finest water filtration method known. This process will
allow the removal of particles as small as ions from a solution. It is used
to purify water and remove salts and other impurities in order to improve the
color, taste or properties of the fluid. R.O. uses a membrane that is semi-permeable,
allowing the fluid that is being purified to pass through it, while rejecting
other ions and contaminants from passing.
This technology uses a process
known as crossflow to allow the r.o. membrane to continually clean itself. This
is the reason of why an r.o. element can last many years before clogging or
need replacement. This
water purification process requires a driving force to push the fluid through
the membrane, and the most common force is household water pressure or pressure
from a booster pump. The higher the pressure, the larger the driving force and
efficiency.
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Toxic
algae? Is it treatable? Details here.
Algae
are vitally important to marine and fresh-water ecosystems, and most species
of algae are not harmful. However, a harmful algal bloom (HAB) can occur
when certain types of microscopic algae grow quickly in water, forming
visible patches that may harm the health of the environment, plants, or
animals. HABs can deplete the oxygen and block the sunlight that other
organisms need to live, and some HAB-causing algae release toxins that
are dangerous to animals and humans. HABs can occur in marine, estuarine,
and fresh waters, and HABs appear to be increasing along the coastlines
and in the surface waters of the United States, according to the National
Oceanic and Atmospheric Administration (NOAA).
Responding
to this suspected increase, the U.S. Congress in 1998 passed a law that
required NOAA to lead an Inter-Agency Task Force on Harmful Algal Blooms
and Hypoxia, and funded research into the origins, types, and possible
human health effects of HABs. Assessing the Impact on Public Health Although
scientists do not yet understand fully how HABs affect human health, authorities
in the United States and abroad are monitoring HABs and developing guidelines
for HAB-related public health action.
The
U.S. Environmental Protection Agency (EPA) has added certain algae associated
with HABs to its Drinking Water Contaminant Candidate List. This list
identifies organisms and toxins that EPA believes are priorities for investigation.
CDC works with public health agencies, universities, and federal partners
to investigate how the following algae, which can cause HABs, may affect
public health: Cyanobacteria, also known as blue-green algae, can produce
toxins that may taint drinking water and recreational water. Humans who
drink or swim in water that contains high concentrations of cyanobacteria
or cyanobacterial toxins may experience gastroenteritis, skin irritation,
allergic responses, or liver damage; Harmful marine algae, such as those
associated with red tides, occur in the ocean and can produce toxins that
may harm or kill fish and marine animals. Humans who eat shellfish containing
toxins produced by these algae may experience neurological symptoms (such
as tingling fingers or toes) and gastrointestinal symptoms. Breathing
air that contains toxins from algae associated with red tide may cause
susceptible individuals to have asthma attacks; Pfiesteria piscicida,
a single-celled organism that lives in estuaries, has been found near
large quantities of dead fish.
Scientists
do not yet know whether P. piscicida affects human health. However, reports
about symptoms such as headache, confusion, skin rash, and eye irritation
in humans exposed to water containing high concentrations of P. piscicida
have prompted public concern; Phytoplankton, or single celled marine plants,
are organisms at the base of the food chain that are the food for many
higher level organisms. Of the thousands of phytoplankton species, less
than hundred or so are considered harmful. Those that produce toxins (poisons)
or cause physical damage with sharp spines are members of groups called
diatoms, dinoflagellates and raphidophytes. In the following sections
we describe which phytoplankton on west coast of North America are harmful
and how they cause harm to fish, marine mammals, and sometimes even humans.
The
detrimental effects of a harmful algal bloom can range from cell and tissue
damage to organism mortality, and can be caused by a number of mechanisms,
including toxin production, predation, particle irritation, induced starvation,
and localized anoxic conditions. As a result, a bloom may affect many
living organisms of the coastal ecosystem, from zooplankton to fish larvae
to people. The toxins produced by HAB. As noted above, only a few HAB
species actually produce toxins that are poisonous to people and marine
animals. The most well known HAB toxins are generically referred to as
ciguatera fish poisoning (CFP), neurotoxic shellfish poisoning NSP), paralytic
shellfish poisoning (PSP), diarrheic shellfish poisoning (DSP), and amnesic
shellfish poisoning (ASP). Pfiesteria piscicida also produces two toxic
fractions, dermonecrotic and neurologic toxins that impact fishes and
humans (Bever et al. 1998, Grattan et al. 1998) (Lowitt and Kauffman 1998)
(Noga et al. 1996).
Cyanobacteria
also produce similar toxins that overlap with several of these general
categories, including neurotoxins and hepatoxins. Symptoms of exposure
to these toxins include gastrointestinal, neurological, cardiovascular,
and hepatological symptoms. The algae that produce these toxins, and the
specific symptoms they cause, are summarized in Appendix A. The terms
"fish" and "shellfish" are associated with these illnesses because the
toxins concentrate in the fish and shellfish that ingest the harmful algae;
people and marine mammals may be poisoned when they consume the affected
seafoods.
Other
harmful algal blooms produce toxins with no identifiable effects on humans
but devastating impacts on coastal living resources. For example, the
flagellate Heterosigma akashiwo is thought to produce an ichthyotoxin
that kills fish (Taylor and Horner 1994), resulting in significant threats
to penned fish in mariculture operations.
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