Tag Archives: uv disinfection

Autumn Rainwater System Maintenance

pollenThe dog days of summer in the Seattle area are nearing an end as the cooler, wetter days of Autumn approach.

With Fall rapidly approaching, bringing its gift of rainfall to the Pacific Northwest, rainwater collectors need to prepare for our harvest. Your quality of stored rainwater will be greatly enhanced if your system is ready. Gutters and screens should be cleaned of debris and residue, remembering to divert that water during this part of maintenance of your rainwater collection system. Keep an eye on those gutters during the windy times to be sure that they stay free of accumulation of leaves and needles.

Please remember to be safe with the use of ladders. The goal here is to send the cleanest water we can into our cisterns. You don’t want to send that yuck into your storage; it can decay quickly, cause odor and discoloration of your stored water. While carbon filters will help in the removal of odor, it is not as effective in eliminating discoloration (tannins). It is always a good idea at this time of year, to flush your downspout to storage conveyance lines. If you have clean outs installed, remove them and flush out any accumulation of sediment and/ or debris. If not, a garden hose flushing at each downspout to conveyance line is a good spot to conduct this simple task.

If your system has a sump tank and screen basket, give it the once over. A shop vac with the filter element removed makes this job easy by removing the sediment from the bottom of the sump. A teaspoon of bleach, mixed with about 10 gallons of water for a final rinse will help remove bacteria that may have accumulated during the summer months. Lift your float switch up inside the sump to activate your pump to be sure it is operational. You don’t want to find out that you missed out on collection because of a faulty pump or switch.

Skagit_FiltrationAutumn is also a good time to change your filters and your UV bulb. Most UV bulb manufacturers recommend that the bulb be changed once per year. They do have a life expectancy and begin to lose their intensity, which may result in improper disinfection. Your filters may have sat during vacation without circulation and could have allowed “festering” of the particulate that they have absorbed. Or, because of summer fun, you have not thought about changing them when needed – so it is time. I always shock my system this time of year. With filters removed but UV lamp turned on, add a couple of tablespoons of bleach into the first canister. Replace the canisters without the filters. Open each faucet until you smell a little bleach then close the faucet immediately. Repeat with all faucets in the household. Let the bleach water sit in the plumbing for about half an hour. Then, open all faucets and let run to flush the bleach out of the lines. Replace the filter elements and you’re done.

Good maintenance of your rainwater collection system will ensure the best quality of water available.

Does Rainwater Need Treatment for Drinking?

clear-water-glass_smAlthough it is fairly clean at the outset, when it comes in contact with impure surfaces, rainwater may need some treatment before drinking. A rainwater collection system designed with filtration and disinfection will get the job done.

Harmful bacteria, pathogens, and cysts removal is a must in a potable (drinking) rainwater collection disinfection train. This is typically achieved with a class “A” UV light. Flow rates are calculated to achieve the correct amount of contact time with the UV spectrum for proper disinfection. The correct class of UV for a specific application is required. A class “A” UV must be used for water that is not deemed safe to drink. A class “B” is only used for water that has already been safe to drink.

But there are other considerations for water treatment. The raw water must be relatively free of sediments, turbidity, organics and inorganics before entering the UV chamber. The UV spectrum will not be able to penetrate the water column effectively otherwise. Special consideration of environmental constituents should also be addressed for proper treatment.

Environmental concerns can include location of collection area. Where is the house located? Possible hydrocarbons from a nearby freeway would be a concern. Pesticide use from farming or city landscaping maintenance should be considered. Roof material and manufacturing process could pose a health threat and should be addressed – all of which can be corrected with proper filtration, whether it is accomplished with canister elements or back flush devices.

Rainwater is typically acidic, approximately 5.5 to 6.0 ph; nominal being 7.0 ph. The lower ph levels, while not considered harmful to humans, can have a negative effect on plumbing and fixtures. A more nominal ph level can be achieved with proper treatment.

RainBank Rainwater Systems designs and installs custom treatment systems to meet customers’ specific needs.

This Throwback Thursday post was originally published under the title Considerations for Water Treatment

How to Achieve Potable Harvested Rainwater with UV Disinfection

file0002019685404UV disinfection is the most common method used in residential rainwater collection systems.

UV light is generated by  supplying voltage across a mixture of gas, causing a discharge of photons, disrupting the DNA of microorganisms which prevents them from reproducing.  If the microorganism cannot replicate, it cannot infect, so viruses, bacteria, Cryptosporidium and Giardia cyst threats are effectively reduced.

A residential UV system typically consists of a power supply (ballast), a UV lamp housed in a Quartz sleeve inside a stainless steel chamber. The flow is directed close to the UV light while passing through the chamber. Effects of turbidity or clarity of the water before entering the chamber must be reduced by proper filtration upstream. Sediment and carbon filtration is used to reduce solids and solution contaminants, which can reduce the effects of UV disinfection. Filtration and UV bulb most be routinely changed in order for all to work effectively. It is recommended to follow manufacturer’s instructions closely, and filters should be changed out as needed.

Some UV systems offer an alarm or sensor with solenoid shut down if the UV system is not working properly. A class “A” UV is the only system considered to purify water that has NOT been deemed “safe to drink”, therefore caution is recommended in the use of a class “B” filter which maybe more tempting to use because of price. The difference between the two is the dosage of the UV light; the lower dose is not as effective in disinfecting. If a more advanced filtration system is used prior to disinfection, you can increase the effectiveness of the class “B”, but caution must be taken for proper results.

UV disinfection provides a relatively low cost, dependable, efficient, chemical free method of water purification that the homeowner can operate to disinfect his or her water supply.

With proper design, installation, and maintenance, clean, safe, and dependable potable water can be achieved from UV disinfection and rainwater collection.