| In the Caribbean harvesting of rainwater is a | | | | a submerged lamp. It is regularly used to disinfect |
| common way of obtaining water for a variety of | | | | water for drinking and wastewater discharge. It is |
| uses because fresh water is a scarce resource. In | | | | effective against a wide range of pathogens and |
| the continental US, the harvesting of rainwater is | | | | does not require the storage or addition of any |
| becoming more important in areas with drought | | | | chemicals. One disadvantage of UV is that it cannot |
| conditions or because of an increasing interest in | | | | project its disinfecting power to the tank or the |
| environmental damage that can be caused by storm | | | | distribution system. Only water that passes by the |
| water run off. In cities, where open ground is limited, | | | | UV lamp is disinfected. If microorganisms are living up |
| rainwater is simply flushed to the storm sewers | | | | or down stream of the lamp they will be unaffected. |
| where it enters rivers and lakes carrying the oils, | | | | The other green disinfection option is ozone. Ozone |
| debris and bacteria from the city. Using rainwater | | | | also does not require the addition or storage of any |
| means that the equivalent volume of water does not | | | | chemicals. The ozone is produced from the oxygen |
| have to be take from surface or ground sources and | | | | found in air. Ozone is a strong disinfectant and works |
| treated. This saves money and energy. | | | | against a wide range of pathogens likely to be found |
| Green building standards encourage the use of | | | | in rain water. Unlike UV, ozone maintains a residual in |
| rainwater harvesting and more buildings are trying to | | | | water. So it not only disinfects the water that passes |
| capture and use rainwater. Typical uses of rainwater | | | | through the injection system, but it also maintains its |
| include toilet flushing and landscape irrigation. The | | | | disinfecting power in the storage tank. This is |
| collected water is normally not used directly, but is | | | | beneficial since bacteria or other microorganisms |
| treated to make it safer and aesthetically appealing | | | | might adhere to the tank walls providing a continuous |
| to the building occupants. Water collected from a | | | | source of pathogens in the water. Besides being a |
| roof, for example, can contain dirt, bird droppings and | | | | safety threat, these organisms could create odor in |
| roofing materials. This can contaminate the water | | | | the tank that might be unpleasant for the building |
| with pathogens and organic compounds that might | | | | occupants and neighbors. |
| make the water unsafe, color the water or create | | | | Another advantage of ozone is that it can remove |
| unpleasant odors. Even an application such as | | | | color and odor from the water. In some applications |
| landscape irrigation can create an aerosol of water | | | | like toilet flushing, building occupants may not |
| that could spread pathogens. Legionnaires disease can | | | | appreciate the water having a tint or discoloration. |
| be caused by water spray coming off building cooling | | | | While the water might be safe, it may give the |
| towers. So proper treatment of rainwater is a | | | | occupants the feeling the water is not clean. Ozone |
| prudent approach to using this resource while keeping | | | | would eliminate this problem. |
| building occupants and neighbors safe and happy. | | | | It is possible to combine ozone and UV for rainwater |
| A rainwater treatment system should have at least | | | | treatment. In this approach you use ozone to make |
| two components: filtration and disinfection. Filtration is | | | | sure nothing grows in the tank and to remove color |
| the simplest and least expensive portion of the | | | | and potential odor problems with the rainwater. The |
| system. The filtration system should contain a | | | | UV treats the water prior to entering the distribution |
| strainer to prevent large objects from the collection | | | | system or application. Using both systems provides |
| surface from entering the storage tank. A finer filter | | | | two levels of protection. The Thursgood Marshall |
| can be added to remove particulates of dirt from the | | | | Federal Building in NYC is being built with an ozone/UV |
| water. Cartridge or bags filters would be good | | | | rainwater harvesting system to provide this higher |
| options for the fine filter application. | | | | level of protection. |
| While there are a variety of disinfection options | | | | Rain water harvesting is good for the environment |
| available, two green options are UV and ozone. | | | | and can also save money, but it needs to be done in |
| UV involves exposing the water to UV radiation from | | | | a safe and effective manner. |