EMERGENCY DISINFECTION OF DRINKING WATER
USE ONLY WATER THAT HAS BEEN PROPERLY DISINFECTED FOR DRINKING, COOKING, MAKING ANY PREPARED DRINK, OR FOR BRUSHING TEETH
1. Use bottled water that has not been exposed to flood waters if it is available.
2. If you don’t have bottled water, you should boil water to make it safe. Boiling water will kill most types of disease-causing organisms that may be present. If the water is cloudy, filter it through clean cloths or allow it to settle, and draw off the clear water for boiling. Boil the water for one minute, let it cool, and store it in clean containers with covers.
3. If you can’t boil water, you can disinfect it using household bleach. Bleach will kill some, but not all, types of disease-causing organisms that may be in the water. If the water is cloudy, filter it through clean cloths or allow it to settle, and draw off the clear water for disinfection. Add 1/8 teaspoon (or 8 drops) of regular, unscented, liquid household bleach for each gallon of water, stir it well and let it stand for 30 minutes before you use it. Store disinfected water in clean containers with covers.
4. If you have a well that has been flooded, the water should be tested and disinfected after flood waters recede. If you suspect that your well may be contaminated, contact your local or state health department or agriculture extension agent for specific advice.
(U.S. federal agencies and the Red Cross recommend these same four steps to disinfect drinking water in an emergency. Please, read the text below for important details about disinfection.)
More information about disinfection
In times of crisis, follow advice from local officials. Local health departments or public water systems may urge consumers to use more caution or to follow additional measures than the information provided here.
Look for other sources of potable water in and around your home. When your home water supply is interrupted by natural or other forms of disaster, you can obtain limited amounts of water by draining your hot water tank or melting ice cubes. In most cases, well water is the preferred source of drinking water. If it is not available and river or lake water must be used, avoid sources containing floating material and water with a dark color or an odor. Generally, flowing water is better quality than stagnant water.
Examine the physical condition of the water. When emergency disinfection is necessary, disinfectants are less effective in cloudy, murky or colored water. Filter murky or colored water through clean cloths or allow it to settle. It is better to both settle and filter. After filtering until it is clear, or allowing all dirt and other particles to settle, draw off the clean and clear water for disinfection. Water prepared for disinfection should be stored only in clean, tightly covered, containers, not subject to corrosion.
Choose a disinfection method. Boiling and chemical treatment are two general methods used to effectively disinfect small quantities of filtered and settled water.
Boiling is the surest method to make water safe to drink and kill disease-causing microorganisms like Giardia lamblia and Cryptosporidium, which are frequently found in rivers and lakes. These disease-causing organisms are less likely to occur in well water (as long as it has not been affected by flood waters). If not treated properly and neutralized, Giardia may cause diarrhea, fatigue, and cramps after ingestion. Cryptosporidium is highly resistant to disinfection. It may cause diarrhea, nausea and/or stomach cramps. People with severely weakened immune systems are likely to have more severe and more persistent symptoms than healthy individuals. Boil filtered and settled water vigorously for one minute (at altitudes above one mile, boil for three minutes). To improve the flat taste of boiled water, aerate it by pouring it back and forth from one container to another and allow it to stand for a few hours, or add a pinch of salt for each quart or liter of water boiled.
If boiling is not possible, chemical disinfection of filtered and settled water collected from a well, spring, river, or other surface water body will still provide some health benefits and is better than no treatment at all.
When boiling is not practical, certain chemicals will kill most harmful or disease-causing organisms. For chemical disinfection to
be effective, the water must be filtered and settled first. Chlorine and iodine are the two chemicals commonly used to treat water. They are somewhat effective in protecting against exposure to Giardia, but may not
be effective in controlling more resistant organisms like Cryptosporidium.
Chlorine is generally more effective than iodine in controlling Giardia, and both disinfectants work much better in warm water.
· You can use a non-scented, household chlorine bleach that contains a chlorine compound to disinfect water. Do not use non-chlorine bleach to disinfect water. Typically, household chlorine bleaches will be 5.25% available chlorine. Follow the procedure written on the label. When the necessary procedure is not given, find the percentage of available chlorine on the label and use the information in the following table as a guide. (Remember, 1/8 teaspoon and 8 drops are about the same quantity.)
Available Drops per Quart/Gallon of Clear Water Drops per Liter of Clear
Chlorine Water
1% 10 per Quart -- 40 per Gallon 10 per Liter
4-6% 2 per Quart -- 8 per Gallon (1/8 teaspoon) 2 per Liter
7-10% 1 per Quart -- 4 per Gallon 1 per Liter
(If the strength of the bleach is unknown, add ten drops per quart or liter of filtered and settled water. Double the amount of chlorine for cloudy, murky or colored water or water that is extremely cold.)
Mix the treated water thoroughly and allow it to stand, preferably covered, for 30 minutes. The water should have a slight chlorine odor. If not, repeat the dosage and allow the water to stand for an additional 15 minutes. If the treated water has too strong a chlorine taste, allow the water to stand exposed to the air for a few hours or pour it from one clean container to another several times.
• You can use granular calcium hypochlorite to disinfect water. Add and dissolve one heaping teaspoon of high-test granular calcium hypochlorite (approximately ¼ ounce) for each two gallons of water, or 5 milliliters (approximately 7 grams) per 7.5 liters of water. The mixture will produce a stock chlorine solution of approximately 500 milligrams per liter, since the calcium hypochlorite has available chlorine equal to 70 percent of its weight. To disinfect water, add the chlorine solution in the ratio of one part of chlorine solution to each 100 parts of water to be treated. This is roughly equal to adding 1 pint (16 ounces) of stock chlorine to each 12.5 gallons of water or (approximately ½ liter to 50 liters of water) to be disinfected. To remove any objectionable chlorine odor, aerate the disinfected water by pouring it back and forth from one clean container to another.
• You can use chlorine tablets to disinfect filtered and settled water. Chlorine tablets containing the necessary dosage for drinking water disinfection can be purchased in a commercially prepared form. These tablets are available from drug and sporting goods stores and should be used as stated in the instructions. When instructions are not available, use one tablet for each quart or liter of water to be purified.
• You can use tincture of iodine to disinfect filtered and settled water. Common household iodine from the medicine chest or first aid kit may be used to disinfect water. Add five drops of
2 percent U.S. or your country’s approved Pharmacopeia tincture of iodine to each quart or liter of clear water.
For cloudy water add ten drops and let the solution stand for at least 30 minutes.
• You can use iodine tablets to disinfect filtered and settled water. Purchase commercially prepared iodine tablets containing the necessary dosage for drinking water disinfection at drug and sporting goods stores. Use as stated in instructions. When instructions are not available, use one tablet for each quart or liter of filtered and settled water to be purified.
ONLY USE WATER THAT HAS BEEN PROPERLY DISINFECTED FOR DRINKING, COOKING, MAKING ANY PREPARED DRINK, OR FOR BRUSHING TEETH
Summary of Key Points:
· Filter murky or colored water through clean cloths or allow it to settle. It is better to both settle and filter.
· Boiling is the surest method to make water safe to drink and kill disease-causing microorganisms like Giardia lamblia and Cryptosporidium, which are frequently found in rivers and lakes.
· To improve the flat taste of boiled water, aerate it by pouring it back and forth from one container to another and allow it to stand for a few hours, or add a pinch of salt for each quart or liter of water boiled.
· When boiling is not practical, certain chemicals will kill most harmful or disease-causing organisms. Chlorine (in the form of unscented bleach) and iodine are the two chemicals commonly used to treat water.
· You can use a non-scented, household chlorine bleach that contains a chlorine compound to disinfect water. (Remember, 1/8 teaspoon and 8 drops are about the same quantity.)
· You can use tincture of iodine to disinfect filtered and settled water. Common household iodine from the medicine chest or first aid kit may be used to disinfect water.
· Tincture of iodine. For cloudy water add ten drops and let the solution stand for at least 30 minutes.
Office of Water 4606-M EPA 816-F-06-027 August 2006 www.epa.gov/safewater
*************************************************************************
Water Filtration Terminologies and Specifications:
Common pathogen sizes and size ranges are typically described in Microns:
A Micron is one-millionth of a meter It’s unit symbol μm, or can be written as um.
Cysts range in size from 4 to 14 microns
Protozoa range in size from 2 to 200 microns
Bacteria range in size from 0.1 to 15 microns
Viruses range in size from 0.02 to 0.4 microns
Information regarding water filtration will likely refer to these measurements and specifications, and may also reference Log reduction values.
The term "log," as in log removal or inactivation (reduction) refers to an order of magnitude of change.
For example, if a given volume of water containing 1,000,000 (one million) organisms is treated so that it now
only contains 1,000 organisms, this is a 3-log reduction. If the one million were reduced to 10 (ten), this would be a 5-log reduction. And if it's treated so that only one remains, this is 6-log reduction.
If the original water only contains 100 organisms, and is treated to the point where it contains only one,
this is 2-log reduction.
If the contamination is a concentration of one million organisms per a given volume of water a 7-log reduction would be zero, and if the concentration were one hundred a 3-log reduction would be zero.
Microns Nanometers and Log specifications:
A Micron is one-millionth of a meter It’s unit symbol μm, or can be written as um.
A Nanometer is one-billionth of a meter it’s unit symbol mµ, or can be written as nm.
Measuring specifications: Microns to Nanometers
1 Micron = 1000 Nanometers
0.5 Microns = 500 Nanometers
0.1 Microns = 100 Nanometers
0.05 Microns = 50 Nanometers
0.02 Microns = 20 Nanometers
0.001 Microns = 1 Nanometer
Log specification: Log reduction is the measured reduction of a known concentration.
Another way to state Log Reduction specification would be:
90% = 1 log
99% = 2 log
99.9 % = 3 log
99.99% = 4 log
99.999% = 5 log
99.9999 %= 6 log
99.99999%= 7 log.
Current water filter technologies offer Ceramic filters that can remove Cysts, Protozoa, Bacteria, and large Viruses. Micron Membrane and Hollow Fiber technologies can even remove small Viruses.
Absolute filtration rating
The absolute rating, of cut-off point, of a filter refers to the diameter of the largest spherical glass particle, normally expressed in micrometers (microns), which will pass through the filter under laboratory conditions.
It represents the pore opening size of the filter medium. Filter media with an exact and consistent pore size or opening thus, theoretically at least, have an exact absolute rating.
It represents the pore opening size of the filter medium. Filter media with an exact and consistent pore size or opening thus, theoretically at least, have an exact absolute rating.
Nominal filtration rating
The nominal rating refers to a filter capable of cutting off a nominated minimum percentage by weight of solid particles of a specific contaminant greater than a stated micron size, normally expressed in micrometers (microns) 90% of a 10 micron particle. It also represents a nominal efficiency figure, or more correctly, a degree of filtration. Process conditions such as operating pressure, concentration of contaminant etc, have a significant effect on the retention of the filters. Many filter manufacturers use similar tests but, due to the lack of uniformity and reproducibility of the basic method, the use of nominal ratings has fallen into disfavor.
Mean filtration rating
The mean filter rating refers to the measurement of the average pore size of a filter element. It establishes the particle size above which the filter starts to be effective. It is determined by the bubble point test and it is more meaningful than a nominal rating, and in the case of filter elements with varying pore size, more realistic than an absolute rating.
Source: 'Filters and Filtration Handbook', T Christopher Dickenson, Elsevier, January 1, 1997
Chemical Dilution Specifications:
Working with Chemical water treatment and disinfection you may see specifications in milligrams per liter
or parts per million. ( mg/L – Ppm )
Dilutions rated in milligrams per liter and parts per million are essentially equal ratios, as one liter of water
weighs one million milligrams.
Milligrams per liter (mg/L) = parts per million (ppm) ( 4 mg/L = 4 ppm ) ( 0.2 mg/L = 0.2 ppm )
If you choose to treat with chlorine you can also use test strips to verify the amount and level of chlorination.
****************************************************
Chlorine Residual Testing Fact Sheet, CDC SWS Project, 3-16-2005
When chlorine is added to water, some of the chlorine reacts first with organic materials and metals in the water and is not available for disinfection (this is called the chlorine demand of the water).
The remaining chlorine concentration after the chlorine demand is accounted for is called total chlorine. Total chlorine is further divided into: 1) the amount of chlorine that has reacted with nitrates and is unavailable for disinfection which is called combined chlorine and, 2) the free chlorine, which is the chlorine available to inactivate disease-causing organisms, and thus a measure to determine the pot ability of water.
For example, if using completely clean water the chlorine demand will be zero, and there will be no nitrates present, so no combined chlorine will be present. Thus, the free chlorine concentration will be equal to the concentration of chlorine initially added.
In natural waters, especially surface water supplies such as rivers, organic material will exert a chlorine demand, and nitrates will form combined chlorine. Thus, the free chlorine concentration will be less than the concentration of chlorine initially added.
The goal of dosage testing is to determine how much chlorine (sodium hypochlorite) solution to add to water that will be used for drinking to maintain free chlorine residual in the water for the average storage time in a household system (typically 4-24 hours).
This goal differs from the goal of infrastructure-based (piped) water treatment systems, whose aim is effective disinfection at the endpoints (i.e., water taps) of the system: defined by the WHO (1993) as: “a residual concentration of free chlorine of greater than or equal to 0.5 mg/litre after at least 30 minutes contact time at pH less than 8.0.” This definition is only appropriate when users drink water directly from the flowing tap.
A free chlorine level of 0.5 mg/Liter of free chlorine will be enough residual to maintain the quality of water through the distribution network, but is most likely not adequate to maintain the quality of the water when this water is stored in the home in a bucket or jerry can for 24 hours.
Thus, the SWS program recommends in our dosage testing that:
1. At 30 minutes after the addition of sodium hypochlorite there should be no more
than 2.0 mg/L of free chlorine residual present (this ensures the water does not have an unpleasant taste or odor).
2. At 24 hours after the addition of sodium hypochlorite to containers that are used by families to store water there should be a minimum of 0.2 mg/L of free chlorine residual present (this ensures microbiologically clean water).
The SWS project methodology leads to chlorine residual levels that are significantly lower than
the WHO guideline value for free chlorine residual in drinking water, which is 5 mg/L value.
************************************************
Sample of Bacteria, Fungi and Viruses, Sizes and Significance Measurements are in Microns
Organism
|
Microbial Group
|
Rod Length µm
|
Rod or Coccus Diameter µm
|
Source
|
Significance
|
Absidia corymbifera
|
Fungi
|
3.8
|
Environmental
|
Zygomycosis
| |
Acetobacter Melanogenus
|
Bacteria
|
1.0-2.0
|
0.4-0.8
|
Strong beer/vinegar bacterium.
| |
Acinetobacter
|
Bacteria
|
1.3
|
Environmental
|
Opportunistic infections
| |
Acremonium spp.
|
Fungi
|
2.5
|
Environmental
|
Extrinsic Allergic Aveons
| |
Actinomyces israelii
|
Bacteria
|
1.0
|
Humans
|
Antinomycosis
| |
Adenovirus
|
Virus
|
0.08
|
Humans
|
Colds
| |
Alcaligenes Viscolactis
|
Bacteria
|
0.8-2.6
|
0.6-1.0
|
Causes ropiness in milk.
| |
Alkaligenes
|
Bacteria
|
0.75
|
Humans
|
Opportunistic infections
| |
Alternaria alternata
|
Fungi
|
14.4
|
Environmental
|
Mycotoxicosis
| |
Arenavirus
|
Virus
|
0.18
|
Rodents
|
Hemorrhagic fever
| |
Aspergillis spp.
|
Fungi
|
3.5
|
Environmental
|
Aspergillosis, Volatile Organic Compound
| |
Aureobasidium pullulans
|
Fungi
|
5
|
Environmental
|
Chromomycosis
| |
Bacillus anthracis
|
Bacteria
|
3.0-10.0
|
1.0-1.3
(1.1 average)
|
Environmental
|
Causes anthrax in mammals
|
Bacillus Stearothermophilus
|
Bacteria
|
2.0-5.0
|
0.6-1.0
|
Biological indicator for steam sterilization
| |
Bacillus subtilis
|
Bacteria
|
2.0-3.0
|
0.7-0.8
|
Biological indicator for ethylene oxide sterilization
| |
Blastomyces dermatiitidis
|
Fungi
|
14
|
Environmental
|
Blastomycosis
| |
Bordetella pertussis
|
Bacteria
|
0.25
|
Humans
|
Whooping cough
| |
Botrytis cinera
|
Fungi
|
7
|
Environmental
|
Extrinsic Allergic Aveons
| |
Cardiobacterium
|
Bacteria
|
0.63
|
Humans
|
Opportunistic infections
| |
Chaetomium globosum
|
Fungi
|
5.5
|
Environmental
|
Chromomycosis, Volatile Organic Compound
| |
Chiamydia psittaci
|
Bacteria
|
0.3
|
Birds
|
Psittacosis
| |
Chlamydia pneumoiae
|
Virus
|
0.3
|
Humans
|
Pneumonia
| |
Cladosporium spp.
|
Fungi
|
9
|
Environmental
|
Chromblastomycosis
| |
Clostridium botulinum (B)
|
Bacteria
|
3.0-8.0
|
0.5-0.8
|
Produces exotin causes botulism
| |
Clostridium Perinngens
|
Bacteria
|
4.0-8.0
|
1.0-1.5
|
Produces toxin causing food poisoning
| |
Clostridium tetani
|
Bacteria
|
4.0-8.0
|
0.4-0.6
|
Produces exotoxin causing tetanus
| |
Coccidioides immitis
|
Fungi
|
4
|
Environmental
|
Coccidiodomycosis
| |
Coronavirus
|
Virus
|
0.11
|
Humans
|
Colds
| |
Corynebacteria diphtheria
|
Bacteria
|
1.0
|
Humans
|
Diphtheria
| |
Coxiella burnetii
|
Bacteria
|
0.5
|
Cattle, sheep
|
Q fever
| |
Coxsackievirus
|
Virus
|
0.027
|
Humans
|
Colds
| |
Cryptococcus neoformans
|
Fungi
|
5.5
|
Environmental
|
Cryptococcosis
| |
Diplococcus Pneumoniae
|
Bacteria
|
0.5-1.25
|
Causes lobar pneumonia
| ||
Echovirus
|
Virus
|
0.028
|
Humans
|
Colds
| |
Emericella nidulans
|
Fungi
|
3.3
|
Environmental
|
Mycotoxicosis, Volatile Organic Compound
| |
Epicoccum nigrum
|
Fungi
|
20
|
Environmental
|
Extrinsic Allergic Aveons
| |
Erwina aroideae
|
Bacteria
|
2.0-3.0
|
0.5
|
Causes soft rot in vegetables.
| |
Escherichia Coli
(E Coli) |
Bacteria
|
1.0-3.0
|
0.5
|
Indicator of fecal contamination in water.
| |
Eurotium spp.
|
Fungi
|
5.8
|
Environmental
|
Extrinsic Allergic Aveons
| |
Exophiala jeanselmei
|
Fungi
|
2
|
Environmental
|
Chromomycosis
| |
Francisella tularensis
|
Bacteria
|
0.2
|
Wild animals
|
Tularemia
| |
Geomyces pannorum
|
Fungi
|
3
|
Environmental
|
Extrinsic Allergic Aveons
| |
Haemophilus influenzae
|
Bacteria
|
0.5-2.0
|
0.2-0.3
|
Causes influenza and acute respiratory infections
| |
Haemophilus influenzae
|
Bacteria
|
0.43
|
Humans
|
Meningitis, pneumonia
| |
Haemophilus parainfluenzae
|
Bacteria
|
1
|
Humans
|
Opportunistic infections
| |
Hantavirus
|
Virus
|
0.07
|
Rodents
|
Hantavirus
| |
Helminthosporium
|
Fungi
|
12.5
|
Environmental
|
Extrinsic Allergic Aveons
| |
Histoplasma capsulatum
|
Fungi
|
3
|
Environmental
|
Histoplasmosis
| |
Influenza
|
Virus
|
0.1
|
Humans, birds
|
Flu
| |
Klebsielia pneumoniae
|
Bacteria
|
5
|
0.4-0.5
|
Environmental
|
Opportunistic infections, causes pneumonia and other respiratory inflammation
|
Lactobacillus Delbrueckil
|
Bacteria
|
2.0-9.0
|
0.5-0.8
|
Causes souring of grain-mashes
| |
Legionella pneumophia
|
Bacteria
|
0.6
|
Environmental
|
Pontiac fever
| |
Micromonospora faeni
|
Actinomycetes
|
1
|
Agricultural
|
Farmers" lung, Hypersensitivity Pneumonitis
| |
Micropolyspora faeni
|
Actinomycetes
|
0.69
|
Agricultural
|
Farmers" lung, Hypersensitivity Pneumonitis
| |
Moraxella catarrhalis
|
Bacteria
|
1.3
|
Humans
|
Opportunistic infections
| |
Moraxella lacunata
|
Bacteria
|
1
|
Humans
|
Opportunistic infections
| |
Morbillvirus
|
Virus
|
0.12
|
Humans
|
Measles (rubeola)
| |
Mucor plumbeus
|
Fungi
|
7.5
|
Environmental
|
Mucormycosis
| |
Mycobacterium avium
|
Bacteria
|
1.2
|
Environmental
|
Cavitary pulmonary disorder
| |
Mycobacterium intracellulare
|
Bacteria
|
1.2
|
Environmental
|
Cavitary pulmonary disorder
| |
Mycobacterium kansasli
|
Bacteria
|
0.86
|
Unknown
|
Cavitary pulmonary disorder
| |
Mycobacterium Tuberculosis
|
Bacteria
|
1.0-4.0
|
0.2-0.5
(0.86 average)
|
Humans
|
Hard swelling of body tissues. TB
|
Mycoplasma pneumoniae
|
Bacteria
|
0.25
|
Humans
|
Pneumonia
| |
Mycoplasma pneumoniae (PPLO)
|
Bacteria
|
0.3-0.5
|
Smallest known free-living organism
| ||
Neisseria meningitidis
|
Bacteria
|
0.8
|
Humans
|
Meningitis
| |
Nocardia Brasilensis
|
Actinomycetes
|
1.5
|
Environmental
|
Pulmonary mycetoma
| |
Nocardiaasteroides
|
Actinomycetes
|
1.1
|
Environmental
|
Nocardiosis
| |
Paecilomyces variotii
|
Fungi
|
3
|
Environmental
|
Mucormycosis
| |
Paracoccidioides brasilensis
|
Fungi
|
23
|
Environmental
|
Paracoccidioidomycosis
| |
Parainfluenza
|
Virus
|
0.22
|
Humans
|
Flu
| |
Paramyxovirus
|
Virus
|
0.23
|
Humans
|
Mumps
| |
Parvovirus B19
|
Virus
|
0.022
|
Humans
|
Filth disease, anemia
| |
Pediococcus acidilactci
|
Bacteria
|
0.6-1.0
|
Causes mash spoilage in brewing
| ||
Pediococcus Cerevisiae
|
Bacteria
|
1.0-1.3
|
Causes deterioration in beer
| ||
Penicillium spp.
|
Fungi
|
3.3
|
Environmental
|
Mycotoxicosis, Volatile Organic Compound
| |
Phialophora spp.
|
Fungi
|
1.5
|
Environmental
|
Chromomycosis
| |
Phoma spp
|
Fungi
|
3.3
|
Environmental
|
Mucormycosis
| |
Pneumocystis carinii
|
Bacteria
|
2
|
Environmental
|
Pneumocystosis
| |
Poxvirus - Vaccinia
|
Virus
|
0.23
|
Agricultural
|
Cowpox
| |
Pseudomonas aeruginosa
|
Bacteria
|
0.57
|
Environmental
|
Opportunistic infections
| |
Pseudomonas mallei
|
Bacteria
|
0.77
|
Environmental
|
Opportunistic infections
| |
Pseudomonas pseudomallei
|
Bacteria
|
0.57
|
Environmental
|
Opportunistic infections
| |
Pseudormonas diminuta
|
Bacteria
|
1.0 0.3
|
Test organism for retention 0.2 µm membranes
| ||
Rhinorvirus
|
Virus
|
0.023
|
Humans
|
Colds
| |
Rhizopus stolonifer
|
Fungi
|
8
|
Environmental
|
Zygomycosis
| |
Rhodoturula spp.
|
Fungi
|
14
|
Environmental
|
Extrinsic Allergic Aveons
| |
Salmonella enteritidis
|
Bacteria
|
2.0-3.0
|
0.6-0.7
|
Causes food poisoning
| |
Salmonella enteritidis
|
Bacteria
|
2.0-3.0
|
0.6-0.7
|
Causes food poisoning
| |
Salmonella hirschefeldii
|
Bacteria
|
1.0-2.5
|
0.3-0.5
|
Causes enteric fever
| |
Salmonella typhimurium
|
Bacteria
|
1.0-1.5 0.5
|
Causes food poisoning in man
| ||
Salmonella typhosa
|
Bacteria
|
2.0-3.0
|
0.6-0.7
|
Causes typhoid fever
| |
Sarcina maxima
|
Bacteria
|
4.0-4.5
|
Isolated from fermenting malt mash
| ||
Scopulariopsis spp.
|
Fungi
|
6
|
Environmental
|
Onychomycosis
| |
Serratia marcescens
|
Bacteria
|
0.5-1.0
|
0.5
|
Test organism for retention of 0.45 µm membranes
| |
Serratia marcescens
|
Bacteria
|
1.3
|
Environmental
|
Opportunistic infections
| |
Shigella dysenteriae
|
Bacteria
|
1.0-3.0
|
0.4-0.6
|
Causes dysentery in man
| |
Sporothrix schenckii
|
Fungi
|
6.5
|
Environmental
|
Sporotrichosis
| |
Stachybotrys spp.
|
Fungi
|
5.7
|
Environmental
|
Stachybotryotoxicosis
| |
Staphylococcus Aureus
|
Bacteria
|
0.8-1.0
|
Humans
|
Causes pus forming infections, opportunistic infections
| |
Streptoccous lactis
|
Bacteria
|
0.5-1.0
|
Contaminant in milk
| ||
Streptococcus pneumoniae
|
Bacteria
|
0.9
|
Humans
|
Pneumonia, otitis media
| |
Streptococcus pyogenes
|
Bacteria
|
0.6-1.0
(0.9 average)
|
Humans
|
Causes pus forming infections, scarlet fever, pharyngitis
| |
Thermoactinomyces sacchari
|
Actinomycetes
|
0.86
|
Agricultural
|
Bagassosis
| |
Thermoactinomyces vulgaris
|
Actinomycetes
|
1
|
Agricultural
|
Farmers" lung, Hypersensitivity Pneumonitis
| |
Thermomonspora viridis
|
Actinomycetes
|
0.6
|
Agricultural
|
Farmers" lung, Hypersensitivity Pneumonitis
| |
Togavirus
|
Virus
|
0.063
|
Humans
|
Rubella (german measles)
| |
Trichoderma spp.
|
Fungi
|
4.1
|
Environmental
|
Mycotoxicosis, Volatile Organic Compound
| |
Ulociadium spp.
|
Fungi
|
15
|
Environmental
|
Extrinsic Allergic Aveons
| |
Varicella-zoster
|
Virus
|
0.3
|
Humans
|
Chickenpox
| |
Wallemia sebi
|
Fungi
|
3
|
Environmental
|
Extrinsic Allergic Aveons
| |
Yersinia pestis
|
Virus
|
0.75
|
Humans
|
Pheumonic plague
|
**************************************************************
How many different ways will you want for getting or making clean drinking water?
******************************
************************************
Information - Education Links:
Rainwater Collection – Water Storage:
Water Filters:
Chemical Treatment:
Iodine Crystals
Chlorine Dioxide
Chlor-Floc
UV
High Test Calcium Hypochlorite
Chlorine Testing-Test Strips:
How many different ways will you want for getting or making clean drinking water?
******************************
Construction and maintenance of rainwater harvesting tanks
Construction and maintenance of roof water
harvesting system
Date 22 January 2011
Project Water harvesting at Good Times Infants School Ngalamye,
Uganda
Reference 62-1
More information http://www.samsamwater.com/projectdata.php?projectid=62
From Sander de Haas
Email sanderdehaas@samsamwater.com
Introduction
Drinking water can be harvested using rainwater, collected from rooftops. The rainwater can be
guided by gutters to the tank. These systems are elaborately discussed in reports (Roofwater
Harvesting by T.H. Thomas and D.B. Martinson, Rainwater harvesting for domestic use by Janette
Worm and Tim van Hattum, Water from roofs by E. Nissen-Petersen and M. Lee). These reports deal
with design, construction and maintenance. These reports can be found online in the SamSamWater
library.
Sizing the system
The average rainfall in the area is about 1300 mm
(http://www.samsamwater.com/climate/climatedata.php?lat=0.48503&lng=32.63919&alt=1143&loc=
Kampala%2C+Uganda).
Figure 1 Rainfall and potential evapotranspiration per month
The total size of the roofs of the classrooms is 383 m2.
There will be around 365 children using the system.
Using a runoff coefficient of 0.9 (galvanised iron roofs) a total amount of 441 m3 (441.000 l) can be
collected yearly.
With two tanks of 10 m3 (10.000 l) each and the rainfall distribution as displayed in figure 1, it is
possible to provide 3 litre per child per day, all year round. This amount is enough to provide
drinking water and water for sanitation purposes (washing hands) for the students.
Westzijderveld 101 R
1507 AA Zaandam
The Netherlands
www.SamSamWater.com
Construction and maintenance of rainwater harvesting tanks 2
Construction of the roof water harvesting system
A shortlist of important points for the design and construction are given below:
· The water will be collected by a gutter. The gutter runs the water to the tank. The gutter has to
be cleaned regularly!
· To prevent large pieces of dirt, sticks etc to flow into the tank a mesh wire is placed at the end of
the gutter. This mesh-wire filter has to be cleaned regularly!
· A first flush diverter will be installed. The primary purpose of a first-flush diverter is to take the
first flow of rainwater from the roof and divert it away from your storage reservoir. The bottom
of the downpipe has a small hole so the water drains out slowly. So the downpipe is empty
before the next rain starts.
· Users have to be informed about the usage of this first-flush system.
· The tank has to be closed completely. No light and small animals are allowed to enter the tank
since this could decrease the water quality.
· Water can be obtained from the tank from a small tap.
· The tank has to have a hatch. From this the tank can be entered for maintenance. The tank has
to be cleaned at the start of each rainy season.
· An overflow has to be constructed into the tank.
· Users have to be informed about maintenance. The next pages can be used as a maintenance
manual.
downpipe
Construction and maintenance of rainwater harvesting tanks 3
Maintenance rainwater harvesting system
The rainwater tank can provide clean and safe drinking water, but only
when the following activities are carried out thoroughly each season!
To do before the rainy season: • Clean the tank
• Clean the roof
• Clean the gutters
• Clean the mesh filters
• Clean the downpipe
The rainy season starts
The first minutes of each rain rains will wash away any remaining dirt on the roof
and gutter. This dirty water fills the downpipe. Once the downpipe is full the clean
water will flow into the tank.
The rains continue
The water in the downpipe will slowly drain out through the small hole. This
ensures that the dirty ‘first flush’ water of each rain doesn’t enter the tank.
To do regularly during the rainy season: • Empty downpipe after each rain
• Check and clean roof
• Check and clean gutters
• Check and clean mesh filters
• Check and clean the downpipe
It’s the end of the rainy season (or your tank is full)
Preparations have to be made to make sure you can have safe and clean drinking
water during the next months
To do at the end of the rainy season • Make sure the hatch is closed properly
or when the tank is full: • Make sure no animals, mosquitoes or
light can enter the tank (this can
decrease the water quality!)
Construction and maintenance of rainwater harvesting tanks 4
Rainwater harvesting system
Cleaning the gutter
gutter
tank
tap
mesh
filter
downpipeConstruction and maintenance of rainwater harvesting tanks 1
Construction and maintenance of roof water
harvesting system
Date 22 January 2011
Project Water harvesting at Good Times Infants School Ngalamye,
Uganda
Reference 62-1
More information http://www.samsamwater.com/projectdata.php?projectid=62
From Sander de Haas
Email sanderdehaas@samsamwater.com
Introduction
Drinking water can be harvested using rainwater, collected from rooftops. The rainwater can be
guided by gutters to the tank. These systems are elaborately discussed in reports (Roofwater
Harvesting by T.H. Thomas and D.B. Martinson, Rainwater harvesting for domestic use by Janette
Worm and Tim van Hattum, Water from roofs by E. Nissen-Petersen and M. Lee). These reports deal
with design, construction and maintenance. These reports can be found online in the SamSamWater
library.
Sizing the system
The average rainfall in the area is about 1300 mm
(http://www.samsamwater.com/climate/climatedata.php?lat=0.48503&lng=32.63919&alt=1143&loc=
Kampala%2C+Uganda).
Figure 1 Rainfall and potential evapotranspiration per month
The total size of the roofs of the classrooms is 383 m2.
There will be around 365 children using the system.
Using a runoff coefficient of 0.9 (galvanised iron roofs) a total amount of 441 m3 (441.000 l) can be
collected yearly.
With two tanks of 10 m3 (10.000 l) each and the rainfall distribution as displayed in figure 1, it is
possible to provide 3 litre per child per day, all year round. This amount is enough to provide
drinking water and water for sanitation purposes (washing hands) for the students.
Westzijderveld 101 R
1507 AA Zaandam
The Netherlands
www.SamSamWater.com
Construction and maintenance of rainwater harvesting tanks 2
Construction of the roof water harvesting system
A shortlist of important points for the design and construction are given below:
· The water will be collected by a gutter. The gutter runs the water to the tank. The gutter has to
be cleaned regularly!
· To prevent large pieces of dirt, sticks etc to flow into the tank a mesh wire is placed at the end of
the gutter. This mesh-wire filter has to be cleaned regularly!
· A first flush diverter will be installed. The primary purpose of a first-flush diverter is to take the
first flow of rainwater from the roof and divert it away from your storage reservoir. The bottom
of the downpipe has a small hole so the water drains out slowly. So the downpipe is empty
before the next rain starts.
· Users have to be informed about the usage of this first-flush system.
· The tank has to be closed completely. No light and small animals are allowed to enter the tank
since this could decrease the water quality.
· Water can be obtained from the tank from a small tap.
· The tank has to have a hatch. From this the tank can be entered for maintenance. The tank has
to be cleaned at the start of each rainy season.
· An overflow has to be constructed into the tank.
· Users have to be informed about maintenance. The next pages can be used as a maintenance
manual.
downpipe
Construction and maintenance of rainwater harvesting tanks 3
Maintenance rainwater harvesting system
The rainwater tank can provide clean and safe drinking water, but only
when the following activities are carried out thoroughly each season!
To do before the rainy season: • Clean the tank
• Clean the roof
• Clean the gutters
• Clean the mesh filters
• Clean the downpipe
The rainy season starts
The first minutes of each rain rains will wash away any remaining dirt on the roof
and gutter. This dirty water fills the downpipe. Once the downpipe is full the clean
water will flow into the tank.
The rains continue
The water in the downpipe will slowly drain out through the small hole. This
ensures that the dirty ‘first flush’ water of each rain doesn’t enter the tank.
To do regularly during the rainy season: • Empty downpipe after each rain
• Check and clean roof
• Check and clean gutters
• Check and clean mesh filters
• Check and clean the downpipe
It’s the end of the rainy season (or your tank is full)
Preparations have to be made to make sure you can have safe and clean drinking
water during the next months
To do at the end of the rainy season • Make sure the hatch is closed properly
or when the tank is full: • Make sure no animals, mosquitoes or
light can enter the tank (this can
decrease the water quality!)
Construction and maintenance of rainwater harvesting tanks 4
Rainwater harvesting system
Cleaning the gutter
gutter
tank
tap
mesh
filter
downpipe
***********************************
The most important variables in the effectiveness of chlorine disinfection of drinking water are the chlorine dose, demand, residual concentration, and contact time after the demand has been exceeded.
The chlorine dose is the amount of chlorine added per unit volume of water and is usually expressed in ppm or its equivalent mg/L.
The chlorine demand is the amount of chlorine per liter of water that reacts with inorganic and organic matter, including microorganisms, and is no longer available for disinfection.
After the demand is completely satisfied, any remaining chlorine will be free chlorine that is available (FAC) to be measured as a residual. The residual chlorine will react with contaminants
that subsequently get into the water as well as prevent re-growth of bacteria in any storage and distribution system that may be in use.
The effectiveness of chlorine disinfection is influenced by:
The type and density of organisms present (viruses, bacteria, protozoa, helminthes, or others) and their resistance to chlorine. Vegetative bacteria and viruses are the most susceptible to chlorine disinfection, whereas the cysts or oocysts of the protozoa Entamoeba histolytica, Giardia lamblia, and Cryptosporidium parvum are the most resistant.
(ii) The concentrations of chemical compounds containing oxidizable substances, ammonia, or organic matter that exert a chlorine demand.
(iii) The suspended solids concentration (measured as turbidity). In addition to exerting their own chlorine demand, suspended solids can surround microorganisms and protect them from contact
with the chlorine.
(d) The effectiveness of chlorine disinfection can also be influenced by variables that include:
(i) Mixing.
Adequate mixing of the chlorine into the water is needed to ensure direct contact with the target microorganisms. The chlorine must be well dispersed and thoroughly mixed to ensure that all of the disease-producing organisms come in contact with the chlorine for the required contact time.
(ii) Contact time.
It takes time for the chlorine to react with and inactivate pathogenic microorganisms. Lower (FAC) Free Available Chlorine or residual concentrations require longer contact times to achieve the same level of disinfection. For a given FAC residual, an increase in contact time will improve the level of disinfection.
(iii) Water pH.
As the pH of the water increases from 5 to 9, the form of the FAC residual changes from hypochlorous acid (HOCl − the most effective form) to the hypochlorite ion (OCl- − the less effective form). The most effective chlorine disinfection occurs when the pH is between 5.5 and 6.5. The typical pH of treated water is usually in the range of 5.5, which is the most effective pH for chlorine disinfection.
Water temperature.
At lower temperatures, microorganism inactivation tends to be slower. To obtain the same level of disinfection at low temperatures as at higher temperatures, higher chlorine residuals or longer contact times are required.
(2) Chlorine residual requirements.
Drinking water treated by other methods. PM personnel should evaluate the system capabilities and operating procedures for drinking water treated by any method other than Reverse Osmosis, and recommend a suitable FAC residual and contact time. If the treatment system will remove turbidity, cysts, and spores, and the treated water can meet the Short Term Potable and Long Term Potable standards for the initial and long-term operating periods, respectively, providing 2 mg/L FAC with a 30-min contact time is acceptable.
If the treatment system or operating procedures will not effectively remove cysts and spores, the chlorine dosage should achieve the equivalent of 5.0 mg/L FAC residual after a 30-min contact time.
(iii) Shower water. Water intended for human use other than drinking, cooking, or brushing teeth, such as shower water, must have a minimum FAC residual of 1.0
If the volume and/or concentration you are working with are not in the tables above, use the following equations to calculate the volume of required bleach, HTH, or concentrated calcium hypochlorite solution in mL; then use table 2–8 to convert that volume to enable using the best measuring device you have available.
(i) General equations:
grams HTH = desired mg/L chlorine x gallons to be treated x 3.785 L/gal
1,000 mg/g x (% available chlorine in HTH/100) mL HTH = grams HTH.
HTH density in mg/L (typical density is 2.35 g/mL)
mL liquid bleach = desired mg/L chlorine x gallons to be treated x 3.785 L/gal
1,000 mg/mL x (% chlorine in bleach/100)
For liquid bleach (~ 5 percent available chlorine):
mL required = desired mg/L chlorine x number of gallons to be treated x 13.2
(iii) For HTH (~70 percent available chlorine):
mL required = desired mg/L chlorine x number of gallons to be treated x 434.6
(iv) For a calcium hypochlorite solution made from adding 1 level tsp HTH to half a canteen cup of water: mL required = desired concentration in mg/L x number of gallons to be treated x 6.04
For example: chlorinating 10 gallons of water with a dose of 5 mg/L chlorine would require the following:
5 x 10 = 3.8 mL of 5% bleach
13.2
5 x 10 = 0.115 mL of 70% HTH, or
434.6
5 x 10 = 8.3 mL of hypochlorite solution made from 1 level tsp HTH in half a canteen cup
6.04 (1 ½ cups) of water.
(b) If your measuring device is not as precise as the number you come up with, it is generally advisable to round the calculated number up to ensure you get at least the dose you intended to provide. For water destined for drinking, it is particularly important to provide a 30-min contact time after adding the chlorine and mixing, then to test the water to ensure the desired FAC residual has been achieved.
In summary: current military chlorination standards are 0.2 mg/L-ppm residual after filtering and contact time of field produced transported and stored water.
A residual or free available chlorine level of 2.0 mg/L-ppm after 30 minute contact time for established fresh water sources when filtering is not available.
And a 5.0 mg/L-ppm residual after a 30 minute contact time for emergency use of natural surface waters.
Note: Where Cryptosporidium parvum is suspected to be present in untreated water, boiling is the recommended emergency water treatment method because of the relative ineffectiveness of chlorine and iodine against that organism.
Current municipal water treatment facilities recommend “residual or free chlorine” levels below 4ppm - mg/L
“safe for sustained use”, and advise against continuous or extended intake of chlorine above those levels.
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