Thursday, May 8, 2014

E. coli in Your Water What Are Your Options

If your water comes from a well, you need, at a minimum, to test your well each year for bacteria. Even if you have a treatment system in place you need to test to make sure the water you drink, brush your teeth with and cook with is safe.  Though human senses cannot detect many contaminants, if you detect a change in the appearance, taste or smell of your water, test it immediately. If you (or your spouse) become pregnant you should test the water. I you have a new infant in the house you should test the water. A bacteria test is the most basic test to see if your water is potable, if your well tests positive for any bacteria, it is an indication that your well is being impacted by either surface contamination, an animal compost or a failing septic system and you need to do further testing.

Coliform bacteria are not a health threat itself, it is used to indicate other bacteria that may be present and identify that a well is not properly sealed from surface bacteria. The federal standard for coliform bacteria for public drinking water supplies has been recently revised to reflect this, requiring public water suppliers to conduct an assessment to determine if any sanitary defects exist and correct them.  Fecal coliform and E. coli are bacteria whose presence indicates that the water is contaminated with human or animal wastes or as we like to call it in our house, poopy water. Disease-causing microbes (pathogens) in these wastes can cause diarrhea, cramps, nausea, headaches, or other symptoms. These pathogens may pose a special health risk for infants, young children, and those with compromised immune systems. However, people can drink water contaminated with fecal bacteria and not notice.

 If your water is contaminated with coliform but not fecal coliform or E. coli, then you have a nuisance bacteria problem and the source may be infiltration from the surface from rain or snow melt. Typical causes are improperly sealed well cap, failed grouting or surface drainage to the well. Shock chlorinate the well, repack the soil around the well pipe to flow away from the well and replace the well cap. Then after the next big rainstorm retest the well for coliform.  If coliform bacteria are still present then a long-term treatment should be implemented: using UV light, ozonation (less available for home use), or chlorine for continuous disinfection.

If you have fecal coliform in the well or E. coli, your well is being impacted by human or animal waste. If there is not a nearby animal waste composting facility, then you are probably drinking water from a failed septic system- yours or your nearest neighbors. To solve this problem you need to fix or replace the septic system that is causing the contamination, replace the well or implement and properly maintain the right water treatment system. The failing septic systems can often be identified by using tracer dyes. Ideally, you should identify and repair the failing septic system. If it is not your system, you will have to work with the Department of Health and your neighbors to address this problem and it will take time. Even if a failing septic system is repaired, it can take days or years for the contaminated water to dissipate.

In the meantime, you need to treat your water.  Do not be grossed out by the thought of treating and then drinking what is essentially diluted and partially treated waste water. All the water that ever was or will be on earth is here right now. It is not being created or destroyed. The water on earth never rests, it is constantly moving within the hydrologic cycle along various complex pathways and over a wide variety of time scales, days, years, decades, centuries, or more. 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 water. Direct water recycling, using 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 is expanding. Since 1978, the upper Occoquan Sewage Authority has been discharging recycled water into a stream above Occoquan Reservoir that flows right into the reservoir, one of the two potable water supply sources for Fairfax County, Virginia. Recycled water has been part of the Occoquan supply for 34 years and chances are if you lived or worked in Fairfax, parts of Prince William and Loudoun counties you have been regularly drinking recycled water.

While continuous disinfection will work to protect you from fecal bacteria and E. coli, be aware that if your well is being impacted by a septic system, then the well water might also have present traces of all the chemicals and substances that get poured down the drain. In addition, ultra violet or chlorine disinfection does not kill Giardia or Cryptosporidium, two microscopic parasites that can be found in surface water and groundwater that has been impacted by surface water or sewage. Both parasites produce cysts that cause illness and sometimes death. Giardia are often found in human, beaver, muskrat, and dog feces. Cattle feces appear to be the primary source of Cryptosporidium, although these parasites have also been found in humans and other animals. Membrane filtration is the usual treatment for these parasites- a one micron membrane is required and can be accomplished at home with a reverse osmosis system. 

Long term treatment for disinfection, and micro-filtration using reverse osmosis should be implemented to address E coli or fecal coliform contamination:  using UV light, ozonation, or chlorine for continuous disinfection, carbon filtration, and anything that is used for drinking should be further treated with a reverse osmosis systems or micro membrane system that work by using pressure to force water through a semi-permeable membrane. Large quantities of wastewater are produced by reverse osmosis systems and need to bypass the septic system or they will overwhelm that system creating more groundwater problems. Reverse osmosis systems produce water very slowly, a pressurized storage tank and special faucet needs to be installed so that water is available to meet the demand for drinking and cooking.

Nitrate can contaminate well water from fertilizer use and erosion of natural deposits but also is a contaminant from human waste and rising nitrate levels are sometimes seen before E. coli contamination.  The MCL for nitrate is 10 mg/L. Infants below the age of six months who drink water containing nitrate in excess of the MCL could become seriously ill from blue-baby syndrome and, if untreated, may die. Symptoms include shortness of breath and a blue ting to the skin common in blue-baby syndrome. The NO3 dissolves and moves easily through soil which varies seasonally and over time as plants use up the nitrate over the summer. Testing in the spring will usually produce the highest levels. Nitrate is associated with contamination from septic tanks, but do not boil the water- boiling water reduces the water and actually INCREASES the concentration of nitrates. So if your water is being impacted by a septic system, you need to treat the water to remove the nitrate. Disinfection does not treat for nitrate. The appropriate treatment is for nitrate is; distillation, reverse osmosis, or ion exchange. Generally speaking, I would recommend staying away from iron exchange (water softeners) they can create as many problems as they solve and they are very expensive. Though there are situations where softening the water is really necessary do not do it as a default, softened water is believed to shorten the life of septic leach fields and cause the clogging of piping (though only limited research exists).

To properly treat well water that has been impacted by E. coli or fecal contamination, you need to disinfect the water using either a UV light or continuous chlorination. Your choice of systems should be based on personal preference and what other contaminants are present in your water. Both UV light and continuous chlorination do a good job of killing coliform bacteria including fecal coliform and E coli. However, chlorine treatment will control nuisance organisms such as iron, manganese, iron and manganese reducing bacteria and sulfate-reducing bacteria. Chlorine in water at the concentrations used for treatment is not poisonous to humans or animals. However, chlorine can impact the smell and/or taste of water even in very low concentrations. Household chlorination systems often use higher chlorine concentration than the typical 0.3 - 0.5 ppm (parts per million) concentration used for chlorination of public water supplies because the contact time is much shorter in home systems.

The typical home system uses 1-2 ppm. This elevated level of chlorine can result in the swimming pool smell and can impact the taste of food and my beloved cup of coffee. This smell can be removed using an activated carbon or charcoal filter. Trihalomethanes (THMs) are organic chemicals that may form when chlorine is used to treat water supplies that contain humic compounds. This is often the concern in large water systems that use surface water for their supply. Humic compounds form as a part of the decomposition of organic materials such as leaves, grass, wood or animal wastes. Because THMs are very seldom associated with groundwater, they are primarily a concern where surface water supplies are used. THMs can be removed from drinking water through use of an activated carbon filter. 

When installing a continuous chlorination system a chemical feed pump chlorinator is installed before the pressure tank in the basement and wired to water pump pressure switch. A fixed amount of chlorine solution is delivered with each pump discharge stroke. The chlorination system should be tested for free chlorine with test strips to adjust the dose. When the filter is in line the residual free chlorine should be under 1 ppm. You adjust the amount of chlorine by changing the length of the discharge stroke, the speed of the pump, or the running time of the pump to optimize performance of the system. Keeping a supply of good chlorine test strips and monitoring your water will allow you to optimize your system.

A contact tank for additional contact time, and a carbon media filter, for de-chlorination and removal of precipitated contaminants should be installed after the pressure tank. It might be necessary to install a larger pressure tank since to operate optimally a garnet media filter typically requires 50 pounds of pressure and small pressure tanks typically operate in 40-60 pound range. A larger pressure tank might eliminate the need for a contact tank, but be aware that the rubberized bladder can be oxidized by the chlorine over time. If you are removing large quantities of particulates from oxidized iron, manganese and sulfate a media filter that uses a graded from coarse to fine media to trap the suspended particles is necessary followed by activated carbon will deliver the best tasting water. Monitoring chlorine levels in the finished water (at the tap) assures you a supply of disinfected, water free from iron and manganese staining and hydrogen sulfide.

A UV light does not require a contact tank to kill bacteria, but since your water is being contaminated by septic waste, you might want also to have a carbon filtration system or a media filter followed by activated carbon to remove other impurities. The activated carbon filtration system will not remove iron or manganese, but can remove volatile organic chemicals, certain pesticide residues, radon, and odor and taste problems other than hydrogen sulfide (the rotten egg smell). Both disinfections systems require that you have a reverse osmosis system with a one micron membrane for removal of Giardia or Cryptosporidium. Remember that your reverse osmosis system should by-pass the septic system for its waste water discharge. A final note that very hard water will quickly clog the membrane in a reverse osmosis system. Water softeners are often recommended to solve this problem, but more frequent flushing and membrane replacement can also solve the problem. A water softener alone can cost almost $4,000 to install.  

Remember that a water treatment system in the home needs to be maintained and monitored continually. In the March 2012 Good Housekeeping magazine they evaluated home water testing kits. To test the home contaminant-detection kits, the Good Housekeeping Research Institute worked with the Water Sciences Laboratory at the University of Nebraska at Lincoln. Lab researchers spiked water samples with measured concentrations of contaminants the kits claimed to be able to detect, including two herbicides, nitrate, copper, lead, and bacteria. Then after following the kit's instructions, evaluated its performance at detecting the known contaminants. They found the PurTest kit to be the most accurate and easiest to use, but the second ranked First Alert test kit and was also good and significantly cheaper. These kits can be a good way to monitor the effectiveness or your water treatment system on an ongoing basis. 

No comments:

Post a Comment