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===Storage Unit===
===Storage Unit===
For the storage unit in our system we are using a Tinaco. Tinacos are commonly used throughout the Dominican Republic to provide municipal water when power shortages occur. Tinaco's are located on the rooftops of houses to provided water pressure when needed for sinks, faucets, and toilets.  By raising the tinaco in our system onto cinder blocks weighed down by cement bags, we have created more head for our system to ensure that there is enough pressure to push the water from the storage unit through the filtration process. It is vital that water storage units attain an overflow so that pressure does not build up and cause damage to the rest of the system. At the desired level, water must be able to easily leave the storage unit through the overflow. However, the overflow and the lid of the system must be sealed so outside objects, pollutants, and mosquito larva are unable to enter into the storage unit. Sealing the storage unit also prevents exposure to sunlight within the tank, which in turn reduces algae growth. It is important that the storage unit remains protected because it is the most difficult part of the system to clean and maintain.  
For the storage unit in our system we are using a Tinaco. Tinacos are commonly used throughout the Dominican Republic to provide municipal water when power shortages occur. Tinaco's are located on the rooftops of houses to provided water pressure when needed for sinks, faucets, and toilets.  By raising the tinaco in our system onto cinder blocks weighed down by cement bags, we have created more head for our system to ensure that there is enough pressure to push the water from the storage unit through the filtration process. It is vital that water storage units attain an overflow so that pressure does not build up and cause damage to the rest of the system. At the desired level, water must be able to easily leave the storage unit through the overflow. However, the overflow and the lid of the system must be sealed so outside objects, pollutants, and mosquito larva are unable to enter into the storage unit. Sealing the storage unit also prevents exposure to sunlight within the tank, which in turn reduces algae growth. It is important that the storage unit remains protected because it is the most difficult part of the system to clean and maintain.


===Cost===


==Climate in The Dominican Republic==
==Climate in The Dominican Republic==

Revision as of 19:06, 27 June 2012

Background

The Humboldt State University Dominicana Program for, summer of 2012, has partnered with Universidad Iberoamericana, RevArt, and community members of La Yuca to improve the rainwater catchment system that was built during the 2011 Humboldt State Dominicana Program. The program takes place in Santo Domingo, 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.

Problem Definition

The objective of this project is to provide inexpensive potable water and cleaning water for the local school in La Yuca, Santo Domingo. Replacing purchased water with captured water will allow funds to be allocated for other important services.

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
Community School where the rainwater catchment system was built


Literature Review

First Flush

A roof can be a natural collector of dust, plant debris, insects, animal feces, and other airborne residues. Rainwater that contacts a dirty roof must not be stored. A first flush is used to divert contaminated water away from the storage tank. Contaminated water is 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 the length of time in which the event. 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 [1] 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

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 [2].

Chlorination

The process of adding chlorine oxidizes the cell membranes of microbes destroying the possibility of contamination. When adding chlorine, 2 fluid ounces (1/4 cup) must be added per 1,000 gallons of rainwater.[3]

Alternative Disinfection Methods

  • Chlorination
  • Monochloramine
  • Chlorine Dioxide
  • Iodine
  • Ozone
  • Ultraviolet Irradiation
  • Slow Sand Filtration
  • Ion Exchange
  • Reverse Osmosis
  • Distillation
  • Microporous Basic Filtration
  • Ultra Filtration


Components of The System

The Roof

For our roof we are using a steel roof galvanized in zinc. The catchment area of our system is approximately 175ft^2, or 16m^2. The area of catchment for a system is directly related to the amount of water that is going to be harvested, the size of the site your system is going to be constructedon, and the size of the system’s storage tank. The use of a metal roof is better than one that is textured such as tile because a metal roof attains a smooth surface that allows debris build up and other pollutants such as dust to easily slide off of the roof during rain. The ability of metal to conduct heat from the sun allows a metal roof to partially kill some bacteria and other pathogens on the roof during full sun. When considering what material may be best for your system it is important to consider that certain metals leach toxic chemicals into water. Avoid using bitumen, this metal is directly associated with adverse health affects and leaves an undesirable flavor in potable water after treatment. The seepage of Aluminum into water is linked with potentially being a cause of Alzheimer’s disease. Aluminum is commonly used as the material that makes up the roof of a catchment system, but is often questioned due to the health risks that are associated with the use of this material. Galvanizing metals helps to reduce the amount of seepage that may occur. While zinc is known to undergo the seepage of toxins into a system, the amount of zinc present in a steal roof galvanized in zinc is not enough to pose a health threat. By using a steal roof galvanized in zinc the amount of rust that forms on the roof and enters the system is efficiently reduced. It is vital to consider what metals experience fewer problems with rust. Reducing the amount of rust that may exist on the catchment roof will improve the quality of the water and save money on materials and maintenance. Metals that experience issues with rust earlier will negatively impact your system and prolong the system’s buy back time.

The Gutter

For the gutter we are using a 3”inch PVC pipe cut down the middle. We attached the system using wire to the side of the roof runoff. At the end of the gutter we have placed a 90degree 3” inch pvc piece to ensure that the water from the gutter flows directly through the primary screening and into the first flush. The gutter’s efficiency of collecting runoff from the roof is dependent on the slop of the gutter. If the gutter’s slope is too steep, not all of the runoff water will flow into the gutter. If the gutter’s slope is leveled, stagnate water will become trapped in the middle of the gutter. Stagnate water in the system increases the risk of algae growth and production of Mosquito larva. It is a useful precaution to place an end cap on the gutter so that rodents and other small animals are unable to enter the system. Seamless aluminum gutters are sustainable for the system. However, these gutters are not cost efficient for the system, they usually require professional installation at expensive rates. Lead gutters are never good for rainwater harvesting. The acidic levels present in rain are strong enough to deteriorate lead gutters over time and cause seepage of lead into the system, contaminating the entire water supply.

Primary Screening

Debris such as leaves, trash, gum, glass, cigarette filters, branches, and many other undesirable objects often collect on catchment roofs in between rainstorms. To prevent these objects from entering the system we are using primary screening. Primary screening is used to filter out large objects before runoff water enters the first flush. To construct our primary treatment we used a 5-galloon jug commonly known as a botellon. We turned the container upside down and cut the base of the botellon at an angle so that more surface area would be provided for the screen. We then attached chicken wire over the base, for the screen. We did this by making wholes near the base and using wire to attach the chicken wire. We placed a stainless steel sink drain filter at the entrance.

Storage Unit

For the storage unit in our system we are using a Tinaco. Tinacos are commonly used throughout the Dominican Republic to provide municipal water when power shortages occur. Tinaco's are located on the rooftops of houses to provided water pressure when needed for sinks, faucets, and toilets. By raising the tinaco in our system onto cinder blocks weighed down by cement bags, we have created more head for our system to ensure that there is enough pressure to push the water from the storage unit through the filtration process. It is vital that water storage units attain an overflow so that pressure does not build up and cause damage to the rest of the system. At the desired level, water must be able to easily leave the storage unit through the overflow. However, the overflow and the lid of the system must be sealed so outside objects, pollutants, and mosquito larva are unable to enter into the storage unit. Sealing the storage unit also prevents exposure to sunlight within the tank, which in turn reduces algae growth. It is important that the storage unit remains protected because it is the most difficult part of the system to clean and maintain.

Cost

Climate in The Dominican Republic

Temperature

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.[4]

Hurricanes

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. [5]

Rainfall

The average annual rainfall for the Dominican Republic is 150cm[6]

Las cifras indican que en 50 años la ponderación de la intensidad de lluvia máxima para el diseño de las obras hidráulicas en el país se ha incrementado en un 40%”, expresan los técnicos.[7] {Rainfall intensity has increased by 40% within the last 50 years.}

Project Timeline

June 9, 2012

  1. Started Project
  2. Measured all pipe lengths, diameters, and calculate the volumes of the first flush and container.
  3. Tested flow rate of the filtered water out of the slow sand filter.

June 10, 2012

  1. Set Criteria.

June 11, 2012

  1. Formulated plans.
  2. Generated alternative designs.

June 13, 2012

  1. Discussed plans with a community member (Oswaldo)
  2. Looked at gutter systems nearby especially ones with sediment traps.

June 16, 2012

  1. Experimented with first flush containers that could be the correct size.

June 18, 2012

  1. Search for student participation in water testing.

June 19, 2012

  1. Plan filter installation.

How to build your own

File: LaYucaRainwater2012-escuela.jpg
How to build a rainwater catchment system

References

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