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CCAT greenhouse rainwater catchment
Outside CCAT sits a sloping glass greenhouse. Many changes have occurred in and around the structure during its time at the Campus Center for Appropriate Technology including separation from the main building, construction of a new wall using beach grass as insolation, and a floor reconstruction that's occurring concurrently with our project to build a rainwater catchment system for the greenhouse. The water captured from the rain will ensure that the plant life at CCAT will be adequately watered.
The CCAT Greenhouse as of February 21st 2019
The greenhouse at the Campus Center for Appropriate Technology doesn't have a renewable system to ensure the flourishing of the plants inside. The objective of this project is to build a rainwater catchment system for the greenhouse at CCAT to employ the use of our local weather patterns to water the plants within and outside of the greenhouse.
This Literature Review will cover aspects of our greenhouse rainwater catchment at CCAT. Including, the climate for the area, filtration types to use, CCAT background, and overall design of rainwater catchments.
This project takes place at CCAT located on the campus of Humboldt State University in Arcata, Californa. Arcata recieces about 46 inches of annual average rainfall with a annual average temperature of about 53 degrees Fahrenheit. The city recieves its most rain during the months of November,December, January, and February. An average year in Arcata receives 175 days of sun and on average, 77 days of precipitation.
Water Filtration Systems for Purifying Rainwater Catchment Systems
1. To Catch the Rain
Water Filtration is essential to the end use if for human consumption, however, many uses do not require filtration like the first flush or plant use. Filtration concerns
- Unfiltered Rainwater is not to be to be ingested by humans. Different treatment methods effect different pathogens. Many purification treatments are used in combination.
Types of Filtration
Common filtration materials include Canister filters, Activated carbon filters, Ceramic Filters, Hollow fiber membrane filters,Slow-sand filters, Bioremediation, SoDis, Solar pasteurization, Solar distillation, Boiling, Reverse Osmosis, UV, Chorination, and Electrochlorination.
Type 1: Canister Filters
Must contain others filters to work such as: ceramic, activated carbon filters, and typical sedimentation. Although this is one of the more expense filters, they are widely accessible.
Type 2: Activated Carbon Filters Used within a Canister Filter, this filtration method uses chemical absorption to remove contaminants through its surface. Although this system is not effective with removing viruses and bacteria, it does withdraw organic compounds, taste, smell, and chlorine from the rainwater.
Type 3: Ceramic Filters
Based on contaminate size, this filtration method uses microscopic pores to filter the rainwater. Although usually not bacteria removing (if made locally), has a slow flow rate, and is susceptible to clogging, this method is accessible and easily cleaned with a brush.
Type 4: Hallow Fiber Membrane Filter
Often used with a Canister Filter and flushes contaminates depending on size. Although this method can clog easily, the tastes and smells are not fully removed, and can be pricey upfront, small fibers like this can remove bacteria and viruses. Has a high flow rate and lasts a very long time.
Type 5: Slow-Sand Filter
Uses many layers of gravel and sediment in increasing size from bottom to top. Top layer creates biological layer referred to as a Schmutzdecke. Although this method requires large surface area, has slow flow rate, and is less accurate, it is widely accessible and inexpensive.
Type 6: Bioremediation Using biological means, this method can include mycoremediation fungi, or phytoremediation with living plants. Although this tactic is delicate and less exact, this method is reproductive and resilient.
Type 7: SoDis (Solar Water Disinfection)
Plastic water bottles in sunlight disinfects the rain water through UV and heat. Although does not purify or work without sunlight and without low turbidity, this method is easily obtained and inexpensive.
Type 8: Solar Pasteurization
Using sunlight, this method brings the water to a temperature right below boiling for a given time. Although does not purify or work without sunlight and a large area, this is useful because it requires low energy.
Type 9: Solar Distillation
This way harvests the sun’s energy to evaporate the way and collect the condensation on a surface. Although this method can be expensive, needs sunshine, and a a large area, it is not as expensive as other systems and purifies the rain water.
Type 10: Boiling
Using energy, this method boils the rain water to clean it. Although this is time and energy consuming and does not purify the rain water, it is easily accessible.
Type 11: Reverse Osmosis
This method uses pressurized water-permeable membrane to push the rain water through a membrane. Although this method is expensive, delicate, and needs cleaning (brine waste),it is effective against brackish water and produces relatively clean water.
Type 12: UV (ultraviolet radiation)
Using ultraviolet radiation, this way changes the DNA of microorganisms to prevent them from reproducing. Although this method is money and energy intensive and does not work on biological contaminants, the tactic isf good for disinfecting and treats against most water borne illnesses.
Type 13: Chlorination
By killing pathogens, this method uses chlorine to disinfect the rain water. Although this product needs special handling due to potential toxicity and demands chlorine, this is a common filter and disinfects against most water borne illnesses.
Type 14: Electrochlorination
Using an electric current with salt water to produce hypochlorite, this is a good method for large scale rainwater treatment. ALthough this method requires electricity and expertise, it is common, effective, and streams many water borne illnesses. DOes not need chlorine supply.
Designing interpretive materials
According to To Catch the Rain,interpretive materials for rainwater filtration should include a filter, sometimes a structure to hold the filter, and a connecting storage and conveyance point.
2. Rainwater treatment in airports using slow sand filtration followed by chlorination: Efficiency and costs
Rainwater catchment can be highly valuable as for non-potable settings such as airport complexes. Cost efficient, this method is valuable in this setting because of the large catching surfaces. Based out of a mid-sized airport in Brazil, this system studied the performance of slow sand filtration by chlorination and cost effectiveness. Overall, this project resulted in 60% cost efficiency compared to current water supply per cubic meter, ultimately providing chemical and biological-free water.
Not labeled for human consumption
Types of Filtration
Slow Sand filter following Chlorination filtration.
According to the Resources, Conservation, and Recycling book, 70% of the company’s non-potable water can be accounted for by this rainwater catchment and treatment system.
3. Effective removal of microbial contamination from harvested rainwater using a simple point of use filtration and UV-disinfection device
Focusing towards utilizing of harvested rainwater for alternative water source on privately-owned cisterns in Arizona, this treatment uses Point of Use (POU) and UV filtration.
Originally, the untreated water contained levels of lead, Enterococci and E. coli, POC filtration sufficiently cleaned the rainwater of most contaminates.
Rainwater Catchment Design
Rainwater design has been worked with for millennia. Ancient civilizations in modern day India and Israel are recorded using catchment methods as early as 3000 BC and later on the Romans developed vast systems of aqueducts, gardens, and pools all fed by rainwater. Since then rainwater catchment has gone into and out of style many times as other technologies developed, but it remains the most reliable and renewable way of attaining access to water.
There is no one way to catch rainwater and design varies depending on many different variables including location, weather patterns, end usage, community utilization, etc.
Catchment design can be broadly categorized into active and passive systems, where active is a system that is built and maintained through human activity and passive is a system mostly in place in the environment that is initially worked on and then maintained by humans. We'll focus on active systems as the project we are working on will fall into that category. In active systems there are some fundamental components.
1. Catchment Surface - Where the rain is falling
2. Conveyance - Transports water from catchment surface to end use
3. Screens - Filters out debris
4. First Flush - Diverts initial most dirty water
5. Storage - Holds water til later use
6. Purification - Cleans water for desired use
7. End Use - Gives the system purpose!
For each of these components there are different materials and technologies you can use.
The main parameters for these systems are rainfall, catchment area, collection efficiency, tank volume and water demand. Systems should be tailored specifically to the community they're serving, so a good place to start you design process is on the ground with the people who will be using it.
Kinkade-Levario, Heather Design for Water: Rainwater Harvesting, Stormwater Catchment, and Alternate Water Reuse New Society Publishers, Jun 1, 2007
Grafman, Lonny To Catch The Rain Arcata. Humboldt State University Press, 2017
Mun, J.S. "Design and operational parameters of a rooftop rainwater harvesting system: Definition, sensitivity and verification" Eleviser Volume 93, Issue 1 (2012)