What to do when drinking water is contaminated

Contaminated water leads to the spread of diseases through drinking water that has become a top concern of nations. Human infectious diseases such as typhoid, dysentery, cholera, hepatitis and diarrhea caused by protozoa have been associated with drinking water contaminated by human waste. To learn more about this issue, check out the Bacteria in Drinking Water (Ohio University website) .

Instructions on how to treat contaminated water

Does bacteria in the water affect cattle?

Bacteria in drinking water affect cattle, mature cattle are more resistant to bacteria than small animals . Water used for cleaning cages and cleaning cattle must also be of high quality to prevent contamination and contamination of products.

Table 1: Standard water supply for cattle

How do we detect contaminated water?

Testing to detect disease-causing organisms is expensive and requires a high level of expertise. Moreover, even though the water source has been contaminated, during the sampling days, we may not be able to detect pathogenic microorganisms.

Therefore, to be easier and less expensive, people often take samples to test indicators for pollution caused by human and animal waste, which is coliform. Most non-pathogenic coliforms and some coliforms live in the natural environment, but most live in the digestive tract of humans and animals and we can easily detect them in waste.

If we detect coliform-grade water, we can conclude that the water source has been contaminated by human or animal waste. To be sure that this contamination is caused by human or animal waste, we must conduct further tests, which are tests to detect fecal coliforms (fecal coliforms present only in feces). If fecal coliform is detected, we carry out a third test which is a test to show fecal streptococci to determine whether it is human waste or animal waste. If the fecal coliform / fecal streptococci ratio is close to 4, the water source is polluted by human waste, if this ratio is less than 1, the water source is polluted by animal waste.

Table 2: Specific fecal coliform / fecal streptococci ratio for humans and some cattle

How to collect water samples for bacterial analysis

Open the tap to flow for about 5 minutes. Then open the bottle cap (do not touch the inside of the lid), let the water flow into the bottle. Note that the sample bottle must be disinfected first . Freeze the sample in the icebox and transfer it to the laboratory within 6 hours.

What should you do when your water is contaminated?

The first thing is not to be alarmed, the sources of water contaminated by bacteria are a very common phenomenon. Studies in Ohio state show that 40% of private water resources (drilled wells) are contaminated. Water supply is also polluted at the frequency of 70% of sampling times.

Contamination of wells can be prevented by covering the cement base around the well that has an outward slope.

Must keep the pipeline system clean, any repair of the pump or piping system could lead to the risk of infection. Therefore, after repairing or detecting an infected water we need to clean the pipes and disinfect the chlorine system , this is called " shock chlorination" (SC). The chlorine content used to disinfect 50 - 200 mg / L is 100 - 400 times higher than the normal chlorine content for treating drinking water. This high chlorine content is maintained throughout the water supply system (wells, pipes) within 12-24 hours. Then all the chlorine in the system is discharged and the system is now ready to be used again.

If the SC process is carried out periodically, it will help us eliminate the iron bacteria, the bacteria that make the reddish brown oily membranes in the pipeline, do not cause disease but can reduce pressure. force or pipe blockage.

How to proceed with the SC process

1. Pour a sufficient amount of Javel or chlorine powder (diluted with a little water) into the well.
2. Rinse the upper part of the well with water.
3. Open free-flowing faucets until a strong odor of chlorine is detected. If no chlorine odor is detected, add chlorine to the well.
4. Turn off unused faucets within 12-24 hours.

Note : All water treatment systems such as iron treatment, hard water treatment and sand filtration should also be conducted SC. However, before the process of SC should be considered, will these devices be damaged by using high doses of chlorine? SC procedures should not be used for activated carbon filters because activated carbon will be ineffective due to chlorine adsorption to saturation.

Be careful :

1. When exposed to chlorine, they must be equipped with protective equipment such as rubber gloves, masks .
2. Do not mix chlorine with other cleaners or ammonia because it can produce toxic gases

Note : 1 pint = 0.473 liters (US) or 0.58 liters (UK); 1 quart = 1.14 liters. If your water supply system cannot be completely disinfected by the SC process, you must apply disinfection measures such as boiling, chlorination, UV sterilization, iodine disinfection.

Sterilize by boiling

Boiling is an extremely effective way to disinfect water. Water only needs to boil vigorously within 1 minute to completely kill bacteria, including Giardia eggs. During the boiling process, metals can settle and deposit in the warm bottom. Rinse warm with mild acide solutions such as vinegar or lemon juice to clean these deposits.

Chlorine disinfection

Chlorine kills bacteria (pathogenic bacteria and iron bacteria), but with a chlorine concentration of about 10mg / L for sterilization it cannot kill Giardia eggs.

Chlorine has been used to treat feedwater in the United States since 1908. The effectiveness of chlorine disinfection depends on the chlorine demand of the treated water, the chlorine concentration in the chlorine solution, the contact time between microorganisms. bacteria and chlorine solution, and water quality. These relations can be summarized as follows:

1. The concentration of chlorine increases, the time required for chlorine to be exposed to the bacteria decreases.
2. The treatment of chlorine water has higher efficiency under increasing temperature conditions.
3. Water treatment with chlorine has a gradual reduction in efficiency under increasing pH conditions (alkaline environment).

When chlorine is added to the treated water, some will work with the chemicals in the water (iron, manganese, H2S and NH3) and it will no longer work for sterilization. This amount of chlorine is called the chlorine requirement of water.

To ensure that the water is completely disinfected, chlorine is often used more than the amount of chlorine calculated. This will lead to the creation of excess chlorine in the treatment system and it is found that this excess chlorine by a simple method of introducing appropriate chemicals will detect discolored water.

Table 4: Excess chlorine in case of water treatment at different temperatures, pH and contact times:

To complete the chlorine treatment process, people often pump water into a reservoir, where chlorine is added with an appropriate dose to ensure treatment efficiency. If the water is consumed continuously, the chlorine exposure time in the reservoirs depends on the flow of the pump as follows:

Table 5: Chlorine exposure time according to the pump flow in a 50 gallons tank

Table 6: Exposure time in a 1.25-inch diameter pipe 1000 ft long

Sterilize with UV rays

UV rays have the ability to kill bacteria, viruses and some parasites. However, it cannot destroy Giardia eggs. This method has been used for more than 75 years to disinfect feed water. However, until now people have not designed systems to use for families. Currently, the state of Ohio (USA) has not yet allowed the use of this method to treat feed water.

Under this measure, water is fed through a tank with a quartz lamp installed - mercury emits UV. UV radiation destroys or neutralizes microorganisms almost immediately.

UV is a very effective method to disinfect. However, disinfection only occurs in tanks. Therefore, the possibility of water contamination after leaving the reservoir may occur.

To kill bacteria, UV rays must be exposed to the bacteria, so the light source must always be "clean". The solution of sodium hydrosulfite (0.15%) and citric acid (0.15%) is an effective solution for cleaning up adhesives on light sources (with overnight cleaning time). Dead bacteria can be UV blockers for living bacteria, so the ability to disinfect with UV rays is also limited. The maximum limit for UV treatment is 1000 coliform total / 100mL and 100 fecal coliform / 100 mL.

For effective UV sterilization, sometimes we need to use a pretreatment system to remove color, turbidity and organic particles. Water containing a lot of minerals can deposit on the lamp, so it is necessary to have a hard water treatment system to prevent this.

Disinfection with Iodine

Iodine kills bacteria and pathogenic microorganisms , but it does not kill algae. Iodine has been used to disinfect water since the early 1900s. Iodine is in the form of black crystals, its water solubility depends on temperature.

The simplest method for water treatment is to pump saturated iodine solution into the water supply system. Iodine does not kill bacteria immediately but requires an exposure time of about 20 minutes (depending on the concentration). An excessive amount of iodine from 0.5 to 10 mg / L must be maintained to ensure treatment efficiency, at this concentration iodine does not cause odor and taste to the water. Iodine maintains its ability to kill bacteria in a wide range of pH (loss of effect from pH 10 and above).

Iodine tablets were used during World War II to disinfect military water. Until now, the effects of iodine on human health have not been determined. It is recommended not to use water to treat iodine for a long time.

There are many people who believe that the water supply system is frequent and they have used this water for many years but nothing happened, so worrying about the source of contaminated water is excessive. It is for the following reasons:

1. People use the total coliform index to determine if the water source is contaminated. This indicator indicates that the water source is not hygienic and that the user may suffer from water-related diseases, not to determine that the water contains pathogenic bacteria.
2. Symptoms caused by water-related diseases are sometimes mistaken for symptoms of flu, food poisoning.

Advantages and disadvantages of handling measures