CLOSING THOUGHTS Tablet Chlorination Richard Weaver and Bruce Lesikar Note: The following is taken from a fact sheet produced by the Texas A&M University System.

Where regulations allow treated becomes hypochlorous acid, the pri- wastewater to be land applied, it first mary disinfectant. must be disinfected to prevent odors Do not use swimming pool chlo- and remove disease-causing microor- rine tablets. They are often made ganisms. Wastewater can be disinfec- from trichloroisocyanuric acid, which ted with chlorine, ozone, and ultravi- is not approved for use in wastewater olet light. For onsite wastewater treatment systems. These tablets treatment systems, the most com- make the chlorine available too slow- mon form of disinfection is tablet ly for it to be effective. If wetted re- chlorination. peatedly, they also can produce ni- Tablet chlorinators generally have trogen chloride, which can explode. four components: Do not combine tablets of liliters. But this does not guarantee • chlorine tablets, trichloroisocyanuric acid with calcium that it is free of disease-causing or- • a tube holding the tablets, hypochlorite, because the combina- ganisms. To reduce the risk of having • a contact device that puts the tion will form the explosive com- any disease-causing organisms, the chlorine tablets into contact with pound nitrogen chloride. Read the wastewater should have at least 0.2 the wastewater, and list of active ingredients on the tablet milliliters of chlorine per liter. • a storage reservoir, usually a pump label to make sure you are using cal- Keep it Working tank, where the wastewater is cium hypochlorite. You can either buy a chlorinator stored before it is distributed. Because chlorine tablets are caus- commercially or have one built by an Before being chlorinated, waste- tic, handle them with care. Wear installer. Please follow the manufac- water from a home is treated by a gloves to protect your skin from direct turer’s recommendations for main- secondary treatment device, usually contact with the tablets. Moist tablets taining the system. in an aerobic treatment unit or sand are the most caustic; handle them • Make sure the chlorinator contains filter. The wastewater moves from the with special care. chlorine tablets at all times. In- treatment device through a pipe to Also, because chlorine gas collects spect it weekly to ensure that the contact device. in the tablet container, open the con- tablets are present and in contact The contact device usually con- tainer in a well-ventilated area. Chlo- with the wastewater. Add chlorine tains a basin where the tube contain- rine gas can escape from the tablets tablets as necessary. Just as cars do ing a stack of chlorine tablets is and container, reducing the effective- not operate without gasoline, placed. The bottom tablet in the ness of the tablets and possibly cor- tablet chlorinators do not operate tube is in contact with the waste- roding metal products stored near without chlorine tablets. water flowing through the basin. As the container. that tablet dissolves and/or erodes, After being chlorinated, the • Tablets can become compacted in the tablet above falls by gravity to re- wastewater enters the pump tank, the tube. To reduce the chances of place it. where the disinfection process is compaction, place two to five A tablet can dissolve quickly or completed. At this point the waste- tablets in the tube at a time. slowly, depending on the amount of water is called reclaimed water. • If the tablets do become compact- wastewater coming into contact with An easy way to determine the ed in the tube, or if a portion of it and the length of time it is in con- chlorine concentration in your re- the bottom tablet has not dis- tact. A balance must be struck re- claimed water is by using chlorine solved and is holding up the rest garding the contact time in the chlo- test kits. They are available in stores of the stack, remove the tube and olume 5, Number 3

V rinator basin: too much contact time that sell swimming pool supplies. wash out the blockage with a causes the wastewater to be over- The most satisfactory kits require stream of water from a garden chlorinated and the tablets to be that you mix a small amount of re- hose. consumed rapidly; too little contact claimed water in a solution and com- • Use only tablets that have been

Summer 2004, time, and the wastewater is not chlo- pare the mixture’s color with those certified for use in domestic waste- , rinated enough. shown in the kit. The kits using paper water systems. State regulations

terly Use only chlorine tablets that are strips may be less satisfactory because do not allow tablets for swimming approved for use in wastewater. They they do not determine the actual con- pools and other applications to be are made of calcium hypochlorite, a centration of chlorine in the water. used to treat wastewater. common household bleach. These Usually, if a test detects any chlo- • Use a chlorine test kit to deter- tablets dissolve in the wastewater, re- rine, the wastewater will contain less mine the chlorine concentration in leasing the hypochlorite, which then than 200 fecal coliforms per 100 mil- the pump. Small Flows Quar

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