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In the rush to move away from the use of gaseous chlorine for disinfection, many industrial users have run to sodium hypochlorite. Bleach, the common name for sodium hypochlorite, is not the be-all-end-all to replace gas. Nevertheless, with growing concerns over gas leaks, operator safety and the well-being of those within the kill zones of gas cylinders, sodium hypochlorite may be the safest solution to meet water treatment professionals’ disinfection needs.
The use of bleach has taught industrial users several things.
First, even if delivered to the site, bleach is very difficult to handle. It is not an easy chemical to have on site because it is very corrosive, highly toxic and potentially hazardous to personnel. Bleach, at its best, is toxic and must be labeled as a hazardous chemical.
Second, bleach wreaks havoc on pumps and nearby electrical panels and clogs valves regularly. Chlorine-feed buildings with corroded doors barely hanging on their hinges and green panels give evidence of bleach use. Even pumps are continuously redesigned to overcome the inherent weaknesses of bleach.
Finally, we should keep in mind the propensity of bleach to degrade rapidly. When affected by time and temperature, bleach degrades quickly, leaving the majority of disinfectant liquid useless. As a result, the treated water may not be appropriately disinfected. Although bleach or sodium hypochlorite has a lower price point, it often does not deliver the needed results.
Considering the inherent weaknesses of bleach, the question is: Is there a safe alternative? And the answer is yes, absolutely. When asked, “Which disinfectant do you believe to be the safest: bleach, chlorine gas or solid chlorine tablets?” most water treatment professionals would agree that chlorine tablets, although still a form of chlorine, are the safest type of chlorine available. The substantiation for this revolves around the fact that as tablets, the chlorine is in a solid form, and it remains that way until dissolved in liquid.
There is a vast difference between a chlorine gas leak, a bleach spill and knocking over a bucket of tablets. A chlorine gas leak has potentially deadly consequences. A bleach spill requires a hazmat response team. A spill of chlorine tablets requires an operator with gloves, a dust mask and goggles to pick up the tablets and place them back into the bucket. Therefore, the question of safety in response to a spill leaves one leaning toward the use of chlorine in solid form; however, the major question now becomes: Can tablets go into a solution safely and then be fed back into the process accurately? Again, the answer is yes.
Similar to other technologies, tablet chlorinators have continually evolved. This evolution has been enhanced by the need to find safe alternatives to gas and bleach.
Tablet chlorinators started out as nothing more than a bucket with water running over the tablets. This leaves much to be desired when trying to make consistent solution strength and feed it accurately. Tablet technology today can be just as accurate as traditional gas feeders. The goal is to find a system that makes solution on demand and uses some type of positive displacement metering pump. There are several systems on the market that make batches of chlorine solution on demand and then feed the solution via a variable speed metering pump.
Anything other than a positive displacement metering pump on a tablet system may lead to accuracy problems. It is unlikely that an industrial user would choose a centrifugal pump over a metering pump to inject a chlorine solution. Centrifugal pumps are not intended for use in precise applications requiring accurate solution injection. When it comes to something as critical as disinfecting water, precise volumetric accuracy is a must.
In addition, spare parts must be taken into consideration. Because disinfecting water is a critical application, it should not be overlooked that at some point the equipment in use may fail. Ask the manufacturer or representative for a spare parts list and then stock up on the critical parts that will keep the system running. When considering the evolution of tablet feeders and the safety of water treatment operators and nearby neighbors, tablet chlorination is a safe and wise alternative to gas and bleach.