La Yuca rainwater catchment 2014

Literature Review

For The Practivistas Dominicana program in 2014, rain water catchment will be specific to the Santo Domingo area. Humboldt State University has teamed up with UNIBE in Santo Domingo to design and implement sustainable solutions to a variety of issues; whereas, rainwater catchment is a huge issue in local communities. Rainwater catchment usually refers to the harvesting, filtering, transferring, storing, and using of collected rainwater. However, these topics differ for each geographic location. This page will discuss these topics specific to the La Yuca community in Santo Domingo.

Rain Catchment

Rain Water harvesting consists of catching, redirecting, and storing rainwater for domestic use. (Agrilife Extension, 2014)

In order to improve water quality, sedimentation should be prohibited from entering system, this is accomplished through the use of filters and separators at the inlet and outlet. (Hattum, 2006) Position of the tap on storage tank is also important, it should be placed 15 cm above the tank bottom and 50 cm for drinking water. (Hattum, 2006)

^[1]

Cleaning

Maintenance required for rain water catchment system is minimal, only obligations are annual inspection of gutters, roof, and screening for mosquitos and sediment, such as leaves and dirt. Cleaning of the harvesting tank is also essential. In order to prevent mosquito breeding and infestation it is crucial to ensure that any opening in the tank are entirely screened. (Hattum, 2006)

During the dry season, when surfaces have the potential to become dirty, it is advised to clean and sweep all parts of harvesting system such as roof, gutters, and tank in order to avoid contamination of rain water during the first flush. (Hattum, 2006)

The tank should be checked for damage and leaks, regularly. (Hattum, 2006)

^[2]

A table describing the frequency adviced for maintainace of the different components of a rainwater harvesting system provided by the EPA.

^[3]

Storage

Storage can be either underground or above ground, including cisterns, tanks, and barrels. Container materials include clay, plastic, and galvanized steel. To avoid algae growth tank should be stored away from direct sunlight and should not be transparent. Placement of tank is also important, in order to take advantage of gravitational flow, it should be placed at an elevated area. In order to reduce the distance that needs to be traveled by water, and therefore avoid contamination, tanks should be placed close to area of use. (City of San Diego , 2007) ^[4]

Materials utilized for water storage can be plastic, fiberglass, or concrete; interior should also be lined in order to make sure that the storage tank is watertight.

^[5]

Filtration

Types of Filters

This section discusses the different filters used to clean water and the possible treatments we will consider in our examination of La Yuca. The information on the various filters were found using the following reference ^[6]

Carbon/Activated Carbon: Activated carbon chemically bonds with and removes some contaminants in water filtered through it. Carbon filters vary greatly in effectiveness: Some just remove chlorine and improve taste and odor, while others remove a wide range of contaminants including asbestos, lead, mercury and volatile organic compounds (VOCs). However, activated carbon cannot effectively remove common “inorganic” pollutants such as arsenic, fluoride, hexavalent chromium, nitrate and perchlorate. Generally, carbon filters come in two forms, carbon block and granulated activated carbon.

Carbon Block: Carbon block filters contain pulverized activated carbon that is shaped into blocks under high pressure. They are typically more effective than granulated activated carbon filters because they have more surface area. Their effectiveness depends in part on how quickly water flows through.

Granulated Activated Carbon: These filters contain fine grains of activated carbon. They are typically less effective than carbon block filters because they have a smaller surface area of activated carbon. Their effectiveness also depends on how quickly water flows through.

Ceramic: Ceramic filters have very small holes throughout the material that block solid contaminants such as cysts and sediments. They do not remove chemical contaminants.

Deionization: These filters use an ion exchange process that removes mineral salts and other electrically charged molecules (ions) from water. The process cannot remove non-ionic contaminants (including trihalomethanes and other common volatile organic compounds) or microorganisms. EWG’s water filter guide does not include any filters based on this technology.

Distillation: This technology heats water enough to vaporize it and then condenses the steam back into water. The process removes minerals, many bacteria and viruses and chemicals that have a higher boiling point than water. It cannot remove chlorine, trihalomethanes or volatile organic chemicals (VOCs). EWG’s water filter guide does not include any filters based on this technology.

Ion Exchange: This technology passes water over a resin that replaces undesirable ions with others that are more desirable. One common application is water softening, which replaces calcium and magnesium with sodium. The resin must be periodically “recharged” with replacement ions.

Mechanical Filters: Like ceramic filters, these filters are riddled with small holes that remove contaminants such as cysts and sediments. They are often used in conjunction with other kinds of technologies, but sometimes are used alone. They cannot remove chemical contaminants.

Ozone: Ozone kills bacteria and other microorganisms and is often used in conjunction with other filtering technologies. It is not effective in removing chemical contaminants. EWG’s water filter guide does not include any filters based on this technology.

Reverse Osmosis: This process pushes water through a semi-permeable membrane that blocks particles larger than water molecules. Reverse osmosis can remove many contaminants not removed by activated carbon, including arsenic, fluoride, hexavalent chromium, nitrates and perchlorate. However, reverse osmosis does not remove chlorine, trihalomethanes or volatile organic chemicals (VOCs). Many reverse osmosis systems include an activated carbon component than can remove these other contaminants. Quality can vary tremendously in both the membrane system and the carbon filter typically used with it. Consumers should also be aware that reverse osmosis filters use 3-to-20 times more water than they produce. Because they waste quite a bit of water, they are best used for drinking and cooking water only.

UV (ultraviolet): These systems use ultraviolet light to kill bacteria and other microorganisms. They cannot remove chemical contaminants. EWG’s water filter guide does not include any filters based on this technology.

Cisterns

• • Used for rainwater collection and for later consumption.
  • Rooftops are ideal for collection location.
  • Should have overflow pipe in case of overflow.
  • Should contain a lining on inside of cistern.
  • A pump is occasionally required to deliver the captured water.
  • Ideally, rooftop should be of galvanized steel/aluminum. This prevents buildup of organic solids.
  • Same materials should be used for gutters and downspouts as above.
  • Should have a first flush mechanism and a filter before cistern entrance.

 This information was gathered from the New York University of Environmental Science and Forestry [7]

Piping/Friction

“velocity (so called; more accurately it would be called speed) is usually considered to be uniform over the cross section of flow. In reality, it is not. The fluid in contact with the conduit wall must be at zero velocity, and velocity ordinarily increases toward the center. The assumption of uniform velocity immensely simplifies fluid flow calculations. There is an inaccuracy introduced by this assumption, but, fortunately, it usually does not affect the confidence level of fluid flow computations." ^[8] Furthermore, friction could be simply described as the following: "Friction is proportional to the load or the normal force. Depends on the nature of the surfaces. Does not depend on the apparent area of contact of the surfaces. Friction is independent of velocity." ^[9] It is interesting to note, "The friction loss of the PVC pipe was found to be approximately 2/3 of that of a galvanized steel pipe."^[10]. Furthermore, "using plastic piping over other piping materials such as metal can “reduce friction factor by more than 40%".” ^[11] Cost-wise, "PVC and CPVC pipes are cheaper piping materials than most other metals and other materials at 2 inches in diameter for 400 ft." ^[12]

Piping can really depend on the amount of use in the home. This table illustrates average home use. Reference for table- ^[13]

Rate	Time
Lowest Rate	"11:30 pm to 5:00 am"
Moderate Rate	"noon to 5:00 pm (lull around 3:00 pm)"
Sharp rise in rate	"5:00 am to noon (peak hourly use from 7:00 am to 8:00 am)"
Increasing evening use	"5:00 pm to 11:00 pm (second minor peak, 6:00 pm to 8:00 pm)"

Roofing Basics

"Rainwater collected from a rooftop rainwater harvesting (RWH) system is typically not considered suitable for potable uses, primarily because of poor microbial quality. The quality of stored rainwater, however, can be improved through basic design and maintenance practices during the construction and operation of an RWH system. This paper presents the microbial analysis of rainwater in two RWH systems installed at the Seoul National University Campus in South Korea. Rainwater samples were collected at different locations within each system and analyzed for total and fecal coliforms, Escherichia coli, and heterotrophic plate count bacteria. Within their storage tanks, water quality improved horizontally from inlet to outlet points, and higher quality was observed at the supply point (located about 0.5 m from the base of the tank) than at the surface or bottom of the tank. First-flush rainwater was found to be highly contaminated but rainwater quality improved following about 1 mm of precipitation. The catchment surface also had a significant effect on the quality of rainwater; samples collected from a rooftop exhibited better microbial quality than from a terrace catchment. Better water quality in underground tanks (dark storage conditions) compared to open weirs/ filters (exposed to natural light) demonstrated the importance of storage conditions. Water quality also improved with longer storage, and a decrease of 70% to 90% in microbial concentrations was observed after about 1 week of storage time. The findings of this study demonstrate that the microbial quality of harvested rainwater can be improved significantly by the adoption of proper design and maintenance guidelines." ^{[14] [15]}

Reference for table- ^[16]

Topic	Description
Catchment Surface	"rooftop or other raised solid surface. The best catchment systems have hard, smooth surfaces such as metal roofs or concrete areas. The amount of water harvested depends on the quantity of rainfall, and the size of the surface and the slope of the catchment area."
Gutters and downspouts	"also known as distribution systems that channel the water from the catchment area to a holding container such as a barrel, cistern, planted area, etc."
Leaf screens	"a screen that removes or catches debris."
Roof Washers	"a device that diverts the "first flush" of rain before it enters the storage tank. Most rainwater suppliers recommend that the "first flush" of water is diverted to an outside area of the storage system, since the catchment surface may accumulate bird droppings, debris and other pollution."
Storage Tanks	"In general, the storage tank is the most expensive component of a rainwater harvesting system. There are numerous types and styles of storage tanks available. Storage can be above-ground or underground. Storage containers can be made from galvanized steel, wood, concrete, clay, plastic, fiberglass, polyethylene, masonry, etc. Examples of above-ground storage include; cisterns, barrels, tanks, garbage cans, above ground swimming pools, etc. Storage tank prices vary based on different variables such as size, material and complexity. To inhibit the growth of algae, storage tanks should be opaque and preferably placed away from direct sunlight. The tanks should also be placed close to the areas of use and supply line to reduce the distance over which the water is delivered. Also consider placing the storage at an elevated area to take advantage of gravity flow. The tank should always be placed on a stable and level area to prevent it from leaning and possibly collapsing."
Delivery System	"Gravity-fed or pumped to the landscape or other end use areas."
Purification	"needed for potable systems to make the water safe for human consumption. Please check with your local health department for information on filtration systems and certification requirements."

Weather

The climate of Santo Domingo is always changing, yet remains a tropical climate year round with consistent rainfall. This year, the average rainfall was about 4.5 inches per month, but that number obviously increases during the rainy months (May-October) and decreases during the dry months. The temperature of each day on average stays within 80-88 degrees Fahrenheit during the day and doesn’t usually drop below 70 degrees fahrenheit at night. ^[17]

References

Template:Reflist