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"DO-IT-YOURSELF" LIQUID CHLORINE BLEACH FOR RURAL SANITATION
by: G.J. Grott, Superior Salt, Inc, Twentynine Palms, CA. 92277 Presented at the Symposium on Rural Small Drinking Water and Wastewater Systems April 2001, Washington, D.C. Sponsored by NSF Int., WHO, PAHO
"Do-It-Yourself" liquid chlorine bleach for sanitizing and/or protecting drinking water is made using salt, cells costing about $20.00 in US. and 12 Volt DC electric power from a car battery. Recharging may be by a battery charger, or solar cells, or a car alternator belt-driven by a bicycle wheel. 'Field Partners" working in Rural Communities are solicited to teach by demonstrating the equipment and practices through their own use when in rural areas. 'Home Partners' are invited to aid by 'Spreading the Word" among Charitable Persons and Organizations, NGO's, and Governmental Aid Organizations. Design and operating information, feedback from the field, and recognition of contributions from Field Partners and Home Partners are all presented using a web site to be named www.waterpot.org. This activity is not-for-profit.
Problem Definition
Much of the world's population depends on boiling to produce safe drinking water but the first utensil dipped into the cooled water may re-contaminate it, and the water will no longer be "safe to drink". Solar heat and other practices may also be used for killing parasites and germs but the problem of recontamination remains. Chlorine is the only practical means for extending the period of safety of the drinking water.
Many plants and vegetables must be cooked to prevent illness when they could be made safe to eat simply by washing with chlorinated water. Just like the drinking water, cooked foods, after cooling, can be re-contaminated by use of serving utensils that were not sanitized.
The accompanying photos show conditions in a farm area in Kenya. Except for a few trees left for shade, the plains and hills have been stripped of trees and shrubs and wood must be carried for long distances.
Liquid Chlorine Bleach
Chlorine is a common agent for sanitizing water and residual chlorine adds a measure of lasting protection to the treated water. (note of caution: chlorine does not kill parasites). Liquid chlorine bleach, sodium hypochlorite, is one material common in home use for supplying active chlorine.
Handling dilute bleach, even with chlorine concentrations below 1%. requires caution, eye protection is advised, and drinking the bleach itself is very dangerous. Use of bleach in sanitizing water containing organic materials is reported to increase the risk of cancer in humans by up to 10 chances per million.
* Presented at the Third NSF International Symposium on Small Drinking Water and Wastewater Systems, April 22-25, 2001, Washington DC. USA.
Electric Power Sources
The objective is to have equipment and operations requiring skills comparable with those of bicycle and auto mechanics, and to use commonly available materials to the full extent possible. Cell dimensions were matched to the capabilities of a 12-volt car battery. Sodium hypochlorite forms when salt water is electrolyzed using Direct Current (DC). The theoretical voltage drop across a single cell is below 3 volts but in operation it is about 3.3 to 4.0 volts depending on resistance losses in the wires and electrodes, the salt concentration and temperature of the solution, and the spacing of the electrodes. The 10-12 volt drop for a 3-cell electrolysis unit fits well with the 1 2 volt D.C. battery typically used in cars.
Car batteries are charged (recharged) using a source of DC power at about 14 volts. Battery chargers converting AC to DC are common, and there are also solar cell chargers. For a true '"do-it-yourself" power unit we chose to use a car alternator, or generator, and to drive it by a Vee belt using the driving wheel on a bicycle. The rate of rotation of the bicycle wheel is matched to the characteristics of a particular alternator or generator. A typical alternator from a mid-sized American car will produce about 7 amperes at 1500 revolutions per minute (rpm) and the power output increases as the rpm are increased. The size of the pulley used on the alternator is chosen to meet the preference of the bicyclist to produce the necessary 1500-2000 rpm. Charging to maintain battery capacity is usually carried out during the bleach making so as to avoid drawing the battery down below the full 12 volts operating capability.
Alternators require voltage regulation. They may have a built-in voltage regulator or they may require a separate one and it is necessary to know which design of alternator is being used. Generators require a separate voltage regulator. We find that producing the 7-10 amps at 14 volts common for battery' chargers is well within the comfort range for even lightly built teenagers. They report that producing a charger output of 7-10 amperes feels comparable to pumping a bicycle on level pavement at about 12-15 miles per hour. Geared bicycle drives allow adjusting the pedaling rpm to an individuals comfort range.
In the USA the cost for all components, including, a rebuilt alternator, and a voltage regulator Vee belt, and used bicycle components is on the order of $ 100-150 per charging unit.
The First Generation Electrolysis Cell
This "first generation" cell will serve to get the program started. Ingenuity and feed back from practitioners and interested volunteers will bring forth improvements and adaptations to better fit various local conditions. Full success of the program depends on these ideas from the field.
Graphite and/or titanium were chosen for the electrodes because of their known properties. availability, and acceptable costs. Commercial electrolysis units commonly use plated titanium to allow long use before maintenance or replacement is required. This extra expense for coating is not cost effective where labor costs are low and there is a need to minimize the cost of imports.
An assembly of four electrodes is clamped with the faces parallel. Plastic strips that do not conduct electricity, and about 2.5 wide x 7.5 cm long x 6 mm thick, are placed at the top of the electrode assembly to provide a 6-mm spacing between electrodes. A 3-cell unit with a voltage drop of 10-12 volts is formed by clamping 4 electrodes with faces parallel, and with a 6 mm spacing between the faces, as shown in the photo. Power is supplied only to the outside electrodes with the two inner electrodes providing two working surfaces each. If a coating forms on the electrodes, reversing the wires cleans the electrodes. Electrode dimensions of 7.5 cm x 15 cm were chosen to fit the power output ranges of different size batteries. For this assembly the depth of immersion of the electrodes can adjust the amperage required by the cell. Immersion to 7.5 cm. in a 1% salt solution typically draws 9-11 amperes. Of course changing the salt content of the solution also changes the electric characteristics of the system.
The container can be any glass or plastic. A 2-liter plastic soft drink bottle works well. A working capacity of about 1.5 liters is available when the bottle top is cut off just above the label. Active chlorine produced depends on the power source, the strength of the salt solution and the electrode area submerged as well as the length of the time period during which power is applied to the cell.
The hourly chlorine production can be varied within the range of 600 parts per million, (PPM) to 6000 PPM. Even the lower concentration is enough to sanitize and protect several hundred liters of drinking water.
Experience with this simple unit has demonstrated that making usable solutions of bleach is well within the capability of persons having commonly available skills.
"Using the Bleach
In the USA, household bleach is sold and used at strength of 5.5% chlorine. A great many people of all educational levels, in large quantities use it, and one rarely hears of accidents damaging to users or their children. The bleach generated in the cells described herein is usually only a tenth to a hundredth of this strength.
For use in sanitizing water, instrumentation for testing for residual chlorine is of great help. In the absence of such instrumentation and skills, another way is available. The US Navy' has used bleach on ships for many years and much information is available on the Internet. For water sanitation, one typically adds so many drops of bleach to a gallon of water, waits 30 minutes, and smells the water. If the bleach is detectable by smell then there is enough residual chlorine that bacteria in the water were killed, (but not parasites which must be filtered out or killed by pasteurization or boiling.) If the smell is too strong, dilute the treated water by a measured amount, mix. Wait 30 minutes. and try the smell again. If there is no chlorine smell add another measured amount of the bleach, mix. Wait another 30 minutes, and smell again.
This trial procedure establishes a safe level by experience without the use of instrumentation or test kits, and even when the initial strength if the bleach is not known. It is tedious and boring at any time and can be very' irritating if one is thirsty', but it works. When, after that 30-minute wait period, the residual chlorine is detected by smell, then there is enough residual chlorine to give all of the benefits possible.
For removal of parasites, building and using slow sand filtration units is well within the skills of at least some inhabitants of most villages. Demonstrating and teaching slow sand filtration presents a further opportunity for "teaching a person to fish".
Nothing Succeeds Like Success
The first field unit is now being demonstrated in Kenya by Mr. Thomas Opande, MSc Chemistry, Stockholm University. Lecturer at Kisumu Polytechhic, and a consultant in the water and sanitation sector. Mr. Thomas recently completed a study of the drinking water quality' of 280 rural families for Swedish International Development Agency (SIDA) and contacted us by email after learning of our efforts through an Internet forum on water.
Mr. Thomas reports that SIDA, upon learning of the cell, paid for his travel to the October 2000, Kenya Rainwater Harvesting festival in Nairobi, Kenya, where he exhibited the unit. Attendees ranging in professions from poor farmers to members of SIDA and high government officials were amazed that sodium hypochlorite could be made so easily. Women were particularly interested.
"Do-It-Yourself" bleach making offers an opportunity to persons who want to have more control over their health. Success with increasing the safety of their drinking water will give them an accomplishment of which they can be proud and the success will increase their desire and skills for learning more about how to help themselves.
Spreading the Word
The National Grange is an organization of small farmers and their business associates and friends. The California Grange volunteered to be the primary organization for assisting in 'spreading the word'. At the Annual Convention of the California State Grange, October 2000, a resolution was passed whereby the California State Grange (22,000 members) will cooperate in "Spreading the Word" about the availability of this information to be distributed on a non-profit basis. A group of Grangers is preparing a pilot program for adopting a village and assisting and following developments. At the option of local chapters of the Grange, non-members may join an Adopting Group without joining the Grange. It is hoped that the many other Organizations will follow this example and adopt one or more villages or schools, and seek Field Partners to assist in propagating this self-help program.
YOUR advice and assistance, and that of YOUR organization, in "spreading the word, in teaching, and in demonstrating the bleach making is earnestly requested.
* Personal communication, Mr. Thomas Opande
Notes For Emergencies
A rounded teaspoon of table salt weighs about 10 grams. Dissolve this amount in a liter of water to make an (approximately) 1% salt solution.
Seawater contains about 2.75%. by weight of sodium chloride, plus other salts. Seawater may be used directly but dilution of seawater with twice its volume of fresh water makes a solution much like the 1% salt solution. This works well for sanitation of glass, plastic, metal surfaces, and clothing and bedding, but caution is advised when considering continuous use in drinking water.
Cholera - Emergency Saline Solution. Diarrhea causes massive loss of fluids and salts. Drinking one to two liters, per person, of a saline solution containing about 0.9% sodium chloride is often used in replacement of these losses. While standard saline solutions contain ingredients in addition to salt, in an emergency, plain salt water is better than nothing at all.
Two liters of a 0.9 to 1% salt solution made with filtered water may be sanitized in a minute or less by using the cell. Remember to "smell test" the solution just like drinking water.
Wait the full 30 minutes for the chlorine to act and see if the chlorine smell persists. If there is no smell, treat it more, and repeat the smell testing.
If the smell and taste are too strong, dilute with more of the solution, mix, wait 30 minutes, and smell again.
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