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===First Flush=== | ===First Flush=== | ||
A roof can be a natural collector of dust, plant debris, insects, animal feces, and other airborne residues. The first flush is for the first catchment of rain that comes off of the roof that is contaminated to be diverted away from the storage tank and rerouted in a length of pipe that is capped at the end. There are varying opinions on the amount of volume of rainwater to divert. Varying opinions occur because there are many variables to consider such as; the slope and smoothness of the collection surface, the intensity of the rain and how the length of time the event happens. When the pipe is filled with water, a ball shuts off the top of the pipe so additional rainfall flows directly into the rainwater storage tank. | A roof can be a natural collector of dust, plant debris, insects, animal feces, and other airborne residues. The first flush is for the first catchment of rain that comes off of the roof that is contaminated to be diverted away from the storage tank and rerouted in a length of pipe that is capped at the end. There are varying opinions on the amount of volume of rainwater to divert. Varying opinions occur because there are many variables to consider such as; the slope and smoothness of the collection surface, the intensity of the rain and how the length of time the event happens. When the pipe is filled with water, a ball shuts off the top of the pipe so additional rainfall flows directly into the rainwater storage tank. | ||
"In order to effectively wash a collection surface, a rain intensity of one-tenth of an inch of rain per hour is needed to wash a sloped roof. A flat or near-flat collection surface requires 0.18 inches of rain per hour for an effective washing of the surface. | |||
The recommended diversion of first flush ranges from one to two gallons of first-flush diversion for each 100 square feet of collection area." | |||
===Granular Filtration=== | ===Granular Filtration=== | ||
Revision as of 18:57, 25 June 2012
Background
The Humboldt State University Dominicana Program for summer of 2012 has partnered with students from Universidad Iberoamericana and community members of La Yuca to improve the rainwater catchment system that was built during the 2011 Humboldt State Dominicana Program, in The Dominican Republic. The rainwater catchment system of 2011, produced water that is frequently used in La Yuca for cleaning. However, the system had problems producing drinkable water. Our group’s goal was to improve the quality of water filtration so that rainwater catchment may be used to supply drinkable water for the grammar school in La Yuca. This will save the school an average of RD$300 a week. The system was also simplified and made more accessible for maintenance and repair. The involvement of La Yuca community members and Universidad Iberamericana students ensued that the system would be maintained well after the program’s end and also lead us to make the project more efficient based on the wants and needs of the community.
- "The northern areas of the Dominican Republic tend to see the greatest amount of rainfall whereas the southern areas of the Dominican Republic tend to be very hot and dry."[1]
- "Hurricanes pose a great threat to the island. Routes and patterns of the hurricanes are unpredictable, but the greatest danger comes in August and September, when hurricanes can last two weeks."[2]
- "The average annual rainfall for the Dominican Republic is 150 cm."[3]
Problem Definition
The objective of this project is to provide inexpensive potable water and cleaning water for the local school in La Yucca, Santo Domingo. Replacing the cost of water bought will allow funds to be allocated for other important services, which the school could provide the children.
Criteria
Criteria is a compilation of goals that are necessary to reach a final design. These criteria are designed to ensure that the project meets what the community of La Yuca wants.
| Criteria | Weight | Constraints |
|---|---|---|
| Aesthetics | 3 | Must be acceptable to the client |
| Ease of maintenance | 8 | Maintenance must be simple, quick and understandable |
| Safety | 10 | Must be safe for children to play around. Water must be potable. |
| Reproducibility | 9 | Must be replicable in similar situations with minor modifications |
| Adaptability | 8 | Must be flexible to changes desired by the user |
| Reproduction cost | 9 | Must be less than $1000 US |
| R&D cost | 3 | Must be less than $1000 US |
| O&M cost | 10 | Must be less than purchasing the same amount of potable water |
| Educational Value | 9 | Can be used for lessons by teachers |
| Durability | 9 | Must withstand strong tropical storms |
Literature Review
First Flush
A roof can be a natural collector of dust, plant debris, insects, animal feces, and other airborne residues. The first flush is for the first catchment of rain that comes off of the roof that is contaminated to be diverted away from the storage tank and rerouted in a length of pipe that is capped at the end. There are varying opinions on the amount of volume of rainwater to divert. Varying opinions occur because there are many variables to consider such as; the slope and smoothness of the collection surface, the intensity of the rain and how the length of time the event happens. When the pipe is filled with water, a ball shuts off the top of the pipe so additional rainfall flows directly into the rainwater storage tank. "In order to effectively wash a collection surface, a rain intensity of one-tenth of an inch of rain per hour is needed to wash a sloped roof. A flat or near-flat collection surface requires 0.18 inches of rain per hour for an effective washing of the surface. The recommended diversion of first flush ranges from one to two gallons of first-flush diversion for each 100 square feet of collection area."
Granular Filtration
Turbidity at certain level can interfere with subsequent disinfection processes [4] In order to reduce turbidity in the collected water, a granular, slow-sand filter will be used. Typically, the granular filtration media (e.g. anthracite, garnet, sand) is placed on top of support media and a water collection system (i.e. gravel).
Slow sand filters tend to not use the entire filter depth as much as other granular filter types such as rapid sand, or multimedia high-rate filters. Slow sand filters accumulate water constituents on the very top level of the filter, which is referred to as the schmutzdecke. The schmutzdecke is periodically removed since it causes large amounts of headloss.
Disinfection
The effluent of the slow sand filter will be disinfected and further cleaned by an impregnated silver activated carbon filter. Activated carbon has a very high surface area and is ideal for constituent removal by adsorption. Activated carbon is known to remove taste and odor-causing compounds effectively as well as some trace organics [5].
Chlorination
The process of adding chlorine oxidizes the cell membranes of microbes destroying the possibility of contamination. When adding chlorine use 2 fluid ounces (¼ cup) must be added per 1,000 gallons of rainwater. [6].
Timeline
References
- ↑ http://dominican.peacecorps.gov/pcdr.php
- ↑ http://www.peacecorps.gov/wws/publications/insights/pdf/InsightsBackground.pdf
- ↑ http://www.nrel.gov/docs/fy02osti/27602.pdf
- ↑ Davis, M. (2010). Water and wastewater engineering : design principles and practice.
- ↑ Ireland EPA WATER TREATMENT MANUALS FILTRATION
- ↑ The Texas Manual for Rainwater Catchment