Emergency Well Disinfection for Rural Water Systems: A Step-by-Step Guide

In rural areas, small utility operators and technical assistance providers shoulder the responsibility to ensure safe drinking water from private and community wells. Well disinfection procedures using bleach are a crucial tool, but sometimes they can feel like high-stakes chemistry experiments. Careful calculations are needed to balance eliminating pathogens with avoiding excessive chlorine levels that could cause health risks or make the water smell like a high school swimming pool; you’ll also want a keen grasp on well characteristics like depth, diameter and the reason for disinfection. 

Too little chlorine leaves harmful bacteria and viruses behind, while too much can pose health risks and create unpleasant odors and tastes that could make customers consider switching to bottled water. Furthermore, operators must navigate various challenges, such as fluctuating water levels, changes in water demand, and unexpected contamination events – the kind that leave you dreaming of a long vacation far from the nearest well. Successfully managing these factors requires detailed well mechanics knowledge, and the ability to adapt bleach calculations quickly and accurately. 

Agencies like the Environmental Protection Agency (EPA) provide regulatory guidance on emergency well disinfections, but applying these guidelines requires a nuanced understanding of individual well systems. To ensure drinking water safety in rural communities, operators and technical assistance providers need reliable information for accurate well disinfection calculations. 

So let’s delve deeper into the specifics of bleach calculations for well disinfection! By blending technical guidance with practical insights, we can empower water leaders and TAPs to make informed decisions and safeguard the health of the communities they serve. 

Situations Warranting Emergency Well Disinfection 

Small utility operators and technical assistance providers must initiate emergency well disinfection procedures under several key circumstances. These include: 

• Loss of Water Pressure: A drop in pressure compromises your well’s defenses against invaders—think equipment failures, pipe breaks, or your less-than-considerate neighbor’s epic backyard water slide party. 

• Maintenance or Repairs: Anytime maintenance or repairs open up your well system, consider disinfection as a preventative health checkup as it helps keep out unwanted bacterial guests. 

• Cross-Connection Events: A cross-connection, where contaminated water or other questionable substances backtrack into the well, poses a serious health hazard. Backflow problems, plumbing mishaps, or the neighbor who accidentally hooked up their compost tea sprayer to your water supply – these can all send questionable substances into your well. Time for a serious disinfecting cleanse! 

• Coliform Bacteria Contamination: Coliform bacteria are the flashing red lights of possible fecal contamination. While not all coliform bacteria are harmful, their presence is a cause for concern – like finding that neighbor’s shorts floating in your pool. Urgent disinfection is necessary to eliminate potential pathogens and protect public health. 

Notify Your Customers First 

Before you start pouring bleach into the well, give your customers a heads-up! Water with high chlorine levels can be harmful to individuals with certain medical conditions, such as kidney dialysis patients. Maintaining a list of these customers allows for timely notification prior to disinfection. And let’s not forget the fish enthusiasts – those with aquariums or ponds need to know about chlorination procedures to protect their aquatic friends.

Disinfecting a Well* 

1. Calculate Water Volume: Consult Table 1 to determine the water volume in your well. You’ll need the total well depth and the static water level (when the pump is off). The difference between these two measurements tells you how much water is in the well – and how much chlorine you might need to bring. 
2. Determine Chlorine Dosage: Refer to Table 2 to calculate the correct amount of chlorine for your well. Remember, getting this measurement right is crucial – too little chlorine won’t properly disinfect the water and too much will leave everyone dreaming of bottled water. 
3. Prepare the Solution: Add the required amount of bleach to a 5-gallon bucket of water. Carefully pour this chlorine solution down the inside of the well as you silently hope it doesn’t splash back at you. 
4. Circulate the Water: Attach a clean garden hose to the nearest outdoor faucet and run the water back into the well, ensuring the chlorine is mixed thoroughly and distributed throughout the water column. 
5. Rinse the Well Casing: Once you detect the smell of chlorine in the water coming out of the hose, use it to rinse the upper part of the well casing with disinfectant. 
6. Allow to Rest: Let the chlorine remain in the water system for at least 6 hours for thorough disinfection. 
7. Flush the System: Use faucets, blowoffs, or hydrants to draw the chlorinated water out of the system. Flush thoroughly until you can no longer detect a chlorine odor. 
8. Test Chlorine Residual: Take a free chlorine residual reading to ensure the water is safe for consumption. 

Table 1: Calculating well volume 

Table 2: Chlorine bleach needed for well disinfection 

*ADAPTED FROM: Washington State Department of Health, “Emergency Disinfection of Small Water Systems” (April 2016, revised), DOH 331-242.