Recycling Water- Do it Right

The United States still has one of the safest water supplies in the world, but our water treatment and delivery systems are aging increasing the risk for water quality failures. In addition, as the demand for water continues to grow in our cities and for irrigation we are increasingly reusing our waste water for water supply. In the arid west reclaimed or recycled water, is being used to recharge groundwater. In other places waste water treatment plants discharge to rivers that supply drinking water systems. We need to improve our wastewater treatment standards and infrastructure. Water recycling and reuse while increasing supply is potentially introducing a variety of contaminants into our drinking water that many wastewater treatment systems and water regulations were never meant to address.

Under the Safe Drinking Water Act (SDWA), EPA sets standards for approximately 90 contaminants in drinking water including bacteria and disinfection by products. For each of these contaminants, EPA sets a legal limit, called a maximum contaminant level. EPA also sets secondary standards for less hazardous substances based on aesthetic characteristics of taste, smell and appearance, which public water systems and states can choose to adopt or not. Though 90 contaminants is a lot, there are approximately 80,000 chemicals in use in our society and an uncounted number of pathogens.

When EPA looks for emerging contaminants they look at the nation on a statistical basis, so that contaminants emerging from wastewater reuse would be hidden by the vast number regulated water supply companies that are not yet utilizing recycled water; and does not necessarily search for micro traces. EPA requires that all public water supplies be tested for the SDWA list of contaminants on a regular basis and meet these minimum standards, but EPA does not control or regulate the water for the 14% of the population that gets their water from a private well.

As the demand for water grows in our cities and population centers, we are straining to meet the demand. Even in generally water rich areas there are limits to the availability of water and United States has slowly and quietly begun to address the availability of water by recycling the wastewater. In the United States municipal wastewater represents a significant potential source of reclaimed water, an estimated 32 billion gallons of water a day is treated in wastewater treatment plants throughout the country. The National Research Council Water Science & Technology Board estimates that only about 8 % of this municipal waste water is reused, but a third of this water could be reused. (NRC Water Science & Technology Board titled Water Reuse: Potential for Expanding the Nation’s Water Supply Through Reuse of Municipal Wastewater)

Recycled or reclaimed water is former wastewater (sewage) that has been treated to remove solids and certain impurities, and then is used in irrigation, discharged to surface water that is a source of drinking water or injected into the ground to recharge groundwater aquifers. In order to make our river, lake, stream and ocean water safe for fishing and recreation, the Clean Water Act of 1972 mandated elimination of the discharge of untreated waste from municipal and industrial sources. Modern wastewater treatment plants, usually using sand filtration and chlorination or chloramine in addition to primary and secondary treatment, were required to meet certain standards. These standards were not designed to render the waste water potable.

Direct water recycling is reusing treated wastewater for beneficial purposes such as agricultural and landscape irrigation, industrial processes, toilet flushing, and replenishing a ground water basin (referred to as ground water recharge) and less commonly returning the water directly to reservoirs. In some places the treated wastewater is being returned to the drinking water treatment plant, though many of the existing projects that recycle waste water avoid the negative emotional response of drinking water from wastewater treatment plants by either using the water for municipal irrigation or by treatment and then supplementing river flow, reservoirs or groundwater.

Treated wastewater is increasingly being seen and used as a resource. Water reclamation and reuse have taken on increased importance in the water supply of communities in the United States. Increasingly strict effluent discharge limits have resulted in effective and reliable improvements in wastewater treatment technologies. Along with a growing interest in more sustainable water supplies, these improvements have led an ever increasing number of communities (especially in the arid west and urban centers) to use reclaimed water as an alternative source to conventional water supplies for a range of applications.

In some areas of the United States, water reuse and dual water systems for distribution of reclaimed water for non-potable uses have become fully integrated into local water supplies and will expand to become necessary components of sustainable water management. As recycled and reclaimed water is added to the water supply through direct and indirect means, the potential for impacts to the overall water supply increases. Varying amounts of pathogens, pharmaceutical chemicals (e.g., hormones from female hormonal contraception and other pharmaceuticals in common usage) and other trace chemicals are able to pass through the treatment and filtering process, potentially causing danger to humans by their ubiquitous presence in the water supply.

Recognizing the need to provide national guidance on water reuse regulations and program planning, the EPA has updated their comprehensive, water reuse “guidelines” to support regulations and guidelines developed by states, tribes, and other authorities. Water reclamation and reuse standards in the United States are the responsibility of state and local agencies—there are currently no federal regulations for reuse. This may be appropriate since the method of reuse and natural conditions are entirely local. For example depending on the method and purpose of groundwater recharge, most states require either a minimum of secondary treatment with or without additional filtration for groundwater recharge. State Underground Injection Control programs and Sole Source Aquifer Protection are included under Sections 1422 of the SDWA, which provides safeguards so that aquifer recharge wells do not endanger current and future underground sources of drinking water.

There is currently no specific requirement for nutrient removal, but lower effluent nutrient concentrations required for point source discharges could meet strict nutrient groundwater recharge requirements. Nutrient removal at the wastewater plant is also thought to remove N-nitrosodimethylamine (NDMA) precursors, and may remove other contaminants. We must be especially careful of the quality of water used to recharge groundwater. The potential to introduce trace contaminants into our essential groundwater aquifers justifies extra care and expense to ensure water quality. Water technology has improved to the point that a wide range of treatment options are available such that almost any level of water quality can be achieved with reclaimed water.

Inspecting the Septic System Before Buying the House

More than one-third of the homes in the southeastern United States depend on septic systems for their waste water treatment, including more than half a million homes in Virginia and almost half the homes in North Carolina. If you own a home with septic system or plan on buying a home with a septic system you need to understand how they operate and how to maintain them.

Buying a home is probably the biggest purchase you will ever make, so you want to avoid unknowingly buying someone else’s’ problem or at least not knowing that a septic system is not working properly. A septic system has a limited life, is expensive to repair and can cost $15,000-$40,000 to replace so you want it to be in good condition when you buy the home and keep it in good repair as long as possible.

Before you purchase a house you have the system inspected by a licensed septic system service provider. Home inspections do not cover septic and well systems. The average lifespan of a septic system is 15 to 40 years, but it can last longer if properly maintained! A traditional septic system should be inspected every three to five years by a septic system service provider; and an alternative septic system (called an AOSS) must be inspected at least every year in Virginia.

The septic tank in all types of systems should be pumped as recommended by the service provider or as required by your locality. Here in Prince William County it is required to be pumped at least every five years; however every three years is better. Pumping more frequently will extend the life of your system and protect the environment.

A professional septic system inspection should include reviewing :

• Pumping and maintenance records (now available online for registered inspectors from the Virginia Health Department system, VDH); 
• The age of the septic system and general condition of the system and soils. (They typical life of a system is 15-40 years and you want to know how close you might be to needing to replace the system); 
• Sludge levels and scum thickness in the tank; 
• Signs of leakage, such as low water levels in the tank; 
• Signs of backup, such as staining in the tank above the outlet pipe or dark sediment in household toilets; 
• Integrity of the tank, inlet, and outlet pipes; 
• The drainfield, for signs of system failure like standing water or surfacing sewage; (Note that in Fairfax and some other localities it is common to have two drainfields that are rotated every 6 months. Check them both.) 
• The distribution box should be checked to make sure drain lines are receiving equal flow; and 
• Available records at the VDH district office should be checked, to make sure the system complies with local regulations regarding function and location and was certified. 

The following is from the U.S. EPA brochure “New Homeowners Guide to Septic Systems” 

from US EPA

How a septic system works:

1. All water runs out of your house from one main drainage pipe into a septic tank. 
2. The septic tank is a buried, water-tight container. Its job is to hold the wastewater long enough for bacteria to breakdown the solids and for the solid waste to settle to the bottom of the tank as sludge while the fats, oil and grease float to the top as scum. 
3. For conventional septic systems, liquid wastewater exits the tank either by pumping or gravity and is spread evenly throughout the drainfield, usually through a distribution box also called a “zoner.” Systems with more advanced treatment have an additional treatment step like an ATU tank, a peat tank, nitrogen removal system between the septic tank and drainfield. 
4. Once in the drainfield, the wastewater percolates into the soil, which reclaims the water for future reuse by naturally removing harmful bacteria, viruses, and some nutrients. 

These processes may vary based on the site, conditions of the property and design of the septic system installed. In Virginia there are approved septic treatment systems and custom design systems that must meet all the same standards. A DPOR licensed septic system service provider and your septic system’s “as built” drawings will be able to tell you what type of system is on the property. For approved AOSS systems the manual for the system is available online. Read it!

The Proper Way to Build a Well

Location and geology will dictate the type of well that will work and provide an adequate water supply. The most important question is whether you have an aquifer beneath your property and what type of aquifer it might be. Not every location has water, but some locations have several aquifers available. At many locations throughout Prince William County and the country, there are several aquifers that vary with depth from near the ground surface to a thousand feet below the ground surface. The aquifers’ thickness varies from a few feet to hundreds of feet thick and the water quality varies from both natural and man made contaminants.

How you should build a well is determined by type of well (dug or drilled), the local geology (sand, gravel, fractured rock, bed rock, etc.) local precipitation and environmental conditions. So when I get questions on a well the first information I need is how the well is constructed and the geology. There are a number of things that should be true in construction of all wells. The well cap should fit tightly on the top of the well casing, be vented, and have a screen to prevent insects from getting in the well. A sanitary well cap is the best option for protecting your well. The well cap should be at least 12 inches above grade, or higher if in an area that is prone to flooding, to ensure that the well cap is never covered by flood water. The area between the casing and the borehole, called the annulus, should be grouted (filled with bentonite and/or concrete) that will not allow any surface water around the well to go down the well bore or along the casing carrying surface contamination into the groundwater. 

There are three basic styles of modern well construction: Drilled Bedrock Wells or Fractured Rock Wells, Sand and Gravel Wells, Large Diameter Dug and Bored Wells. The drilled bedrock or fractured rock wells are the most basic construction. They have a casing through the overburden or the surface fractured rock to prevent surface runoff from draining into the well. Below the casing these wells are open to the bedrock aquifer. For a properly constructed well in bedrock the casing extends from just above land surface to a short distance into the bedrock where the casing is “seated” into the rock to keep it in place. The borehole continues down into the bedrock aquifer for some distance below the casing. Because bedrock is solid, it acts as the well casing in the lower portion of the well and allows water to enter the well through fractures. The fractures provide water to the well, and the borehole itself stores the water until it is pumped.

from Private Well Class.Org

 A sand and gravel well is finished in a sand and gravel aquifer, which isn’t solid and will cave in if it is not supported. These types of wells need to be completely cased- a casing extends from a foot above the surface to the bottom of the well. However to allow water to enter the well, the lower portion of the casing is a well screen. The well screen is generally made of woven steel wire formed in the shape of a pipe or casing. The screen has openings based on the size of the sand and gravel grains in the aquifer. This way, it keeps the sand out of the well, but water can flow through. 

from Private Well Class. Org

Dug and bored wells are generally around three foot in diameter and are less frequently used today because they are very susceptible to contamination. They were commonly used in unconsolidated finer materials like clay, silt, loess, etc. that may or may not have very thin sand lenses that can move small amounts of water. These wells were built big to provide storage and allow shallow groundwater to slowly seep into them. Old hand dug wells still exist and are in current use, though nearly every state has construction standards for wells that wouldn’t allow a modern well to be built in this way. Today, large diameter wells are constructed by machine and are generally of one of two types; a bored well with concrete collar or a bored well with a buried slab. In the concrete collar construction the casing is generally 4 or 5 foot sections of precast concrete that are placed on top of each other and allows water to seep into the well through the joints between these sections. Because of the possibility of surface infiltration near the well, the upper 10+ feet around the well is grouted with concrete or has a bentonite seal. Bentonite is a very fine clay that expands when wet to create a nearly impermeable layer.

from Illinois Department of Public Health. 

The buried slab construction can look like a drilled well because the upper 10 feet of the well has a standard well casing that has back filled soil or concrete around it. The well casing is fitted into a prefabricated concrete slab that tops the underground portion of the concrete collar lined well.

from  Illinois Department of Public Health.

You need to understand the construction of your well, the geology, and the aquifer to understand your well and make decisions about maintaining and repairing your well. 

Let the Septic System Recover after the Flood

After flood waters recede septic systems should not be used immediately. Drain fields will not work until underground water has receded and the soil has dried out. Whenever the water table is high or your septic drain field has been flooded, there is a risk that sewage will back up into your home. Though septic lines may have broken during the flood it is more likely that the lines were just submerged.

The only way to prevent a flooded system from backing up is to relieve pressure on the system by using it less- so do not allow your tank to pump or drain to the drain field until the soils dry out. Basically, there is nothing you can do but wait, do not use the system if the soil is saturated and flooded. The wastewater will not be treated and will become a source of pollution, if it does not back up into your house, it will bubble up into your yard. Conserve water as much as possible while the system restores itself and the water table fails.

Do not return to your home until flood waters have receded. If there was significant flooding in your yard, water will have flooded into your septic tank through the top. The tops of septic tanks are not water tight. Flood waters entering the septic tank will have lifted the floating crust of fats and grease in the septic tank. Some of this scum may have floated and/or partially plugged the outlet tee. If the septic system backs up into the house check the tank first for outlet blockage. Remember, that septic tanks can be dangerous, methane from the bacterial digestion of waste and lack of oxygen can overwhelm you. Hire someone with the right tools to clear your outlet tee.

Do not pump out the septic tank while the soil is still saturated. Pumping out a tank that is in saturated soil may cause it to “pop out” of the ground. (Likewise, recently installed systems may “pop out” of the ground more readily than older systems because the soil has not had enough time to settle and compact.) Call a septic service company (not just a tank pumping company) and schedule an appointment in a few days. Do not use the septic system for a few days (I know) have the service company clear any outlet blockage, or blockage to the drain field, check pumps and valves and partially pump down the tank if your soils are not dry enough or fully pump the tank if the soil has drained enough. The available volume in the tank will give you several days of plumbing use if you conserve water to allow your drain field to recover. Go easy the septic system operates on the principals of settling, bacterial digestion, and soil filtration all gentle and slow natural processes that have been battered by the storm.

Florence Preparation for Well Owners

Erin Ling with the Virginia Household  Water Quality Program out of Virginia Tech sent out a draft fact sheet from our Extension colleagues at Texas A & M and University of Florida as well as Kelsey Pieper here at Virginia Tech developed during their experiences providing private well outreach and assistance during last year's devastating hurricanes.  

You may find it helpful as Florence approaches this week.

How to prepare your well for flooding: Evacuation Preparations and Return Home

You can take action to better prepare your well for a flood, even as you are making plans to evacuate.  Store adequate bottled water for drinking and cooking because you won’t be able to drink, brush teeth or cook with the well water until it is tested and found suitable. Complete the following during your evacuation planning:

During Potential Evacuation Preparations

1.       Locate a nearby water testing lab to obtain sample collection bottles and instructions. Frequently, the health department can test your water for bacterial contamination. If there is not a health department near you, your county Extension agent can put you in touch with laboratories that test water quality.

2.       Locate the log/well report completed when the well was established and store a copy of it in a safe place that will be accessible if you evacuate.

3.       Locate contact information for licensed well drillers in the area. Contact a driller/s before evacuating if you think your well will need service immediately after the flood. It may be difficult to schedule service after the storm.

4.       Fill up the pressure tank as much as possible.

5.       Turn off the electricity to the well.

6.       If you have an aerobic septic system, turn off the electricity for the system. No special preparations are recommended for conventional septic systems.

7.       If you plan to attempt to disinfect your well yourself upon your return, have these basic shock chlorination materials available before the flood because these supplies may be difficult or time-consuming to acquire following a flood:

a.       Instructions on how to shock chlorinate 

b.      Unscented, liquid bleach

c.       Clean five-gallon bucket and five gallons of uncontaminated water

d.      Garden hose that reaches from an outdoor faucet to the well

e.       Protective goggles and gloves

f.        Wrench for well access

g.       Funnel

h.      Hose

i.         Sample collection bottles from local water testing laboratory.

8.       Learn how to bypass water softeners and household water filters if any are attached to your water system. Read and have manufacturer’s instructions easily available on how to disinfect bypassed water softeners and household water filters. Disconnect water treatment and drain before evacuating.

Upon Return

If you've never disinfected a well, It is strongly recommended that a licensed water well driller be hired to shock chlorinate the well if it has been flooded. A water well driller will have access to more effective products and will have equipment and experience that a typical well owner will not have. However, I know how difficult it is to find a well driller who is available in the middle of an emergency. So, if you plan to attempt to disinfect your well yourself, follow the instructions carefully be methodical and you can do it. Remember you need power to have been restored to disinfect a well.

Using AI to Find the Lead Pipes in Flint

The story of the Water Crisis in Flint Michigan has many facets that began decades earlier with the slow decline of the city. For decades short sighted decisions were made, the city failed to maintain and update their water infrastructure. Then when the city fell towards bankruptcy, Flint decided to switch the City’s water source in a cost saving measure from the old Detroit system to the Flint River as a water source.

The Flint Water Treatment staff and their consultants struggled to meet the Safe Drinking Water Act levels at the water treatment plant. Then residents noticed unpleasant changes in the smell, color, and taste of the water coming out of their taps. Tests showed high levels of bacteria that forced the city to issue boil advisories. In response, the city upped its chlorine levels to kill the pathogens. This created too many disinfectant byproducts, which are carcinogens and corrosive. Then the corrosive water began leaching lead, other metals and whatever else was in the biofilm on the old pipes into the water in the homes.

Flint’s water department might have been able to avert this disaster by having a corrosion management plan and using additives to diminish the corrosiveness of the water at a negligible cost, but there was an underlying problem that effects not only Flint-lead service lines- the lines that connect homes to the city water system.

By 2016 replacing the service lines became a top priority for the City of Flint. Though, technically, these lines are owned by the homeowner, the Michigan state legislature appropriated $27 million towards the expense of replacing these lines and later the U.S. Congress allocated almost another $100 million for Flint.

With money in hand the problems became that the City of Flint did not know how many lead service lines existed and where they were located. Service line information are theoretically documented during original construction or renovation in the building department files, but those records were found to be incomplete or lost.

Because digging up an entire water service line pipe under a resident’s year cost thousands of dollars, unnecessarily digging up a line that turns out not to be a lead service line is wasteful and the city did not have money to waste. Flint believed there might be as many as 50,000 homes potentially needing service line replacements, the city was facing costs up to $250 million.

Google believed data science could expedite the process of identifying specific homes in need of replacement service lines and donated to the University of Michigan and Flint’s Community Foundation. Dr. Jacob Abernethy, then an assistant professor at University of Michigan and now with Georgia Tech, and his Data Science Team of students were called in. With the help of Captricity.com who digitized a set of over 100,000 index cards, water sampling data, and hand-annotated maps digitized by the University of Michigan-Flint GIS Center, Dr. Abernethy and his team were able to analyze the available data to provide statistical and algorithmic support to guide decision making and data gathering. 

Dr. Abernethy and his team developed a machine learning program and statistics to accurately estimate the locations of home needing lead service line replacement as well as those with safe pipes. Their predictive model was found to be empirically accurate for estimating whether a Flint home’s pipes were safe/unsafe with an accuracy rate of 97%. The team estimated that this increase in accuracy would save the City of Flint about $10 million which could be used to replace the pipes at an additional 2,000 homes. This model can be used in other cities to help them identify and replace their lead service lines most cost effectively.

To read the full article:

Jacob Abernethy, Cyrus Anderson, Chengyu Dai, Arya Farahi, Linh Nguyen, AdamRauh, EricSchwartz, WenboShen, GuangshaShi, JonathanStroud,etal. 2018. ActiveRemediation: The Search for Lead Pipes in Flint, Michigan. arXiv:1806.10692v2 [cs.LG] August 2018.

Dead Zone 2018 Smaller than Predicted

This past spring Ecologists from the University of Michigan and the University of Maryland Center for Environmental Science were forecasting that the Chesapeake Bay would have a larger-than-average “dead zone” in 2018, due to increased rainfall in the watershed this spring.

In the Spring the scientists thought that this summer’s dead zone, an area of low to no oxygen that can kill fish and other aquatic life, would be about 1.9 cubic miles, according to their June forecast.

However, when the Maryland Department of Natural Resources actually performed their July measurements they found the opposite. Due to extreme summer weather, dissolved oxygen conditions in Maryland’s portion of the Chesapeake Bay mainstem were the best ever observed in late July, reported the Maryland Department to Natural Resources. The department tracks hypoxia throughout the summer during twice monthly monitoring cruises.

The hypoxic water volume (areas with less than 2 mg/L oxygen) was 0.26 cubic miles a fraction of the June prediction. This good news was likely the result of the massive rainfall in central and northern Maryland and Pennsylvania (and the whole region), which resulted in near maximum monthly water flows throughout the watershed. This wall of freshwater, accompanied by sustained winds of 20 knots before sampling, reduced stratification of the water column and mixed oxygen well into the system. 

Measurements of the Chesapeake Bay’s dead zone go back to 1950, and the 30-year mean maximum dead zone volume is 1.74 cubic miles. Dead zones are a yearly occurrence in the Chesapeake Bay and other estuaries. Dead zones form in summers when higher temperatures reduce the oxygen holding capacity of the water, the air is still and especially in years of heavy rains that carry excess nutrient pollution from cities and farms. The excess nutrient pollution combined with mild weather encourages the explosive growth of phytoplankton, which is a single-celled algae. While the phytoplankton produces oxygen during photosynthesis, when there is excessive growth of algae the light is chocked out and the algae die and fall from the warmer fresh water into the colder sea water. The phytoplankton is decomposed by bacteria, which consumes the already depleted oxygen in the lower salt level, leaving dead oysters, clams, fish and crabs in their wake.

In a wedge estuary such as Chesapeake Bay where the layers of fresh and salt water are not usually well mixed, there are several sources of dissolved oxygen. The most important is the atmosphere. At sea level, air contains about 21% oxygen, while the Bay’s waters contain only a small fraction of a percent. This large difference between the amount of oxygen results in oxygen naturally dissolving into the water. This process is further enhanced by the wind, which mixes the surface of the water. Scientists are still studying the impact of the winds in delivering oxygen to various water layers. The other important sources of oxygen in the water are phytoplankton and aquatic grasses which produce oxygen during photosynthesis, but when they die consume oxygen during decomposition by bacteria. Finally, dissolved oxygen flows into the Bay with the water coming from streams, rivers, and the Atlantic Ocean.

Bottom dissolved oxygen concentrations in the Chesapeake Bay have continued to increase since 2014, and last year we recorded the second-smallest hypoxic volume ever according to the Resource Assessment Service at the Maryland Department of Natural Resources. Great strides have been made in reducing nutrient pollution from point and non-point sources, though more work needs to be done.

The Red Tide in Florida 8 months and counting

A Red Tide, a harmful algal bloom that at high concentrations discolors the water , is currently affecting about 145 miles of the southwest coast of Florida. Karenia brevis the algae that causes red tides produces nuerotoxins that can cause fish kills, respiratory irritation, and mortality of sea turtles, manatees, and dolphins. This has been a particularly long Red Tide. It started in October 2017 and continued through spring of 2018, and by early summer had re-surged and was detected in five southwest Florida counties.

Red Tides form in the Gulf Coast mostly in Florida and Texas. They are caused by the rapid growth of the microscopic algae called Karenia brevi and generally form more than 40 miles from the Florida coast. When large amounts of this algae are present, it can cause a harmful algal bloom that has be seen from space. Karenia brevi at high concentrations discolors water often red, but also light or dark green or even brown. No single factor causes a Red Tide. The algae bloom needs the organism, Karenia brevi, natural or man-made nutrients for growth, the right concentration rain and sunlight and transport from the wind and waves. No single factor causes it.

The Florida Department of Health reports that tests are being conducted to see if coastal nutrients enhance or prolong blooms. However, it seems logical that man-made nutrients do encourage and feed growth. We know that man-made nutrients feed algal blooms elsewhere. Not all algal blooms are harmful. Many ocean algae blooms are beneficial because the algae provide food for ocean animals and essential part of the ocean food web.

A small percentage of algae, however, produce powerful toxins that can kill fish, shellfish, mammals, and birds, and may directly or indirectly cause illness in people. Algae blooms of non-toxic species can have harmful effects on marine ecosystems. For example, the “Dead Zone” in the Chesapeake Bay when masses of algae die and decompose, the decaying process can deplete oxygen in the water, causing the water to become so low in oxygen that animals either leave the area or die.

The Florida Red Tide organism, Karenia brevis, produces potent neurotoxins, called brevetoxins, that can affect the central nervous systems of many animals, causing them to die. That is why Red Tides are often associated with fish kills and the death of other species, including manatees, dolphins, sea turtles, and birds. In the 16th century a Spanish explorer recorded stories by Florida Indians of toxic "red water" and the resulting death of birds and fish.

Wave action near beaches can break open Karenia brevi cells and release the toxins into the air, leading to respiratory irritation. For people with severe or chronic respiratory conditions, such as emphysema or asthma, the Red Tide can cause serious illness. People with respiratory problems should always avoid affected beaches during Red Tides.

The Red Tide toxins can also accumulate in filter-feeder mollusks such as oysters and clams, which can lead to neurotoxic shellfish poisoning in people who consume the contaminated shellfish. Neurotoxic shellfish poisoning is not fatal, but hospitalizations occur. According to the National Institute of Health neurotoxic shellfish poisoning involves a cluster of gastrointestinal and neurological symptoms: nausea and vomiting, paresthesias of the mouth, lips and tongue as well as distal paresthesias, ataxia, slurred speech and dizziness. Neurological symptoms can progress to partial paralysis; respiratory distress has been recorded. In most cases only diarrhea is reported.

Rigorous state monitoring of water and shellfish assures that commercial shellfish is safe, often by closing harvest beds. Commercially available shellfish in restaurants and grocery stores is safe because it comes from water free of Red Tide and is monitored. Recreational harvesters have the greatest risk of neurotoxic shellfish poisoning, often due to a lack of awareness of the problem.

Red Tides are a natural phenomenon that require the right conditions to expand and linger. This Red Tide is unusual but not unprecedented in its duration. In 2005, a Red Tide started off the coast of St. Petersburg, Florida, in January and then spread to Pensacola and Naples by October, persisting for the majority of the year. In the 1994 there was a Red Tide that lasted 2 years. Since the late 1990's Red Tides have occurred each year. The last protracted period of red tides occurred in the 1870's.The duration of a bloom in nearshore Florida waters depends on physical and biological conditions that influence its growth and persistence, including sunlight, nutrients, and salinity, as well as the speed and direction of wind and water currents.

There are currently no means of controlling the occurrence of red tide, research continues in hopes of finding ways to better address the causes and effects of Red Tides and other harmful algal blooms.