Rainwater Collection System

Problem Statement

During the rainy season, Nairobi experiences a lot of rain. But too often, in cases of extreme rainfall, the rainwater ends up in the wrong places. Floods, potholes, and deteriorating infrastructure are some of the consequences of poor rainwater management. However, all this rainwater can be used for something good. I plan to build a cheap rainwater collector and filter that collects rainwater directly from the drain pipe, delivering fresh, clean water straight from the sky. This concept has huge potential in growing urban areas that receive a lot of rain. Often, in growing urban areas, water becomes scarce. So, a cheap water collector is needed that can provide more water to a growing city.

Kenya Government Rain Forecast Report 2024

Design Process

Original Concept

This filtration system will work in multiple stages. The most defining characteristic of this system is the inclusion of moringa seed-based water filtration. When mixed with dirty water, the powder coagulates the sediment, making it come together and form lumps of dirt, virtually clearing the turbidity of the water. The next filtration steps are running the water through an activated carbon filter and killing the last remaining pathogens with UV light sterilization.

Order of Filtration

Collection Tank: The water is collected from the source (river, lake, etc.) and stored in a tank.
Coagulation Chamber: The water from the collection tank is passed into a chamber where crushed Moringa seeds are added. The Moringa seeds help coagulate and settle down impurities.
Sedimentation Tank: The water is then directed to a sedimentation tank where the coagulated particles settle at the bottom.
Filtration Unit: After sedimentation, the water is passed through a fine filter (such as sand or activated carbon) to remove remaining particles and impurities.
UV Sterilization Chamber: The filtered water flows into the UV sterilization chamber, where ultraviolet light disinfects and kills any remaining bacteria and viruses.
Storage Tank: The purified water is stored in a clean, covered storage tank.

Collection Tank ---> Coagulation Chamber ---> Sedimentation Tank ---> Filtration Unit ---> UV Chamber ---> Storage Tank

This water filtration system would benefit many communities that struggle with water insecurity, but I realized that it isn't that relevant to Nairobi, where clean drinking water is widely available to buy. Instead, I think it would be better to consider all the wasted rainwater that has not been collected and make a system that collects rainwater rather than filters it. This would also make more sense in an urban environment where non-drinking water is more scarce.

Collector

The Collector is the part of the system that is closest to the drain pipe and contains three components: Debris filter, collector cone, concentric reducer. These three components are responsible from getting the rainwater into the system without sticks, leaves, and other debris.

Flush Diverter

The flush diverter will be used to isolate the initial water from the rainfall that carries dirt, metals, plastic, etc., from the rest of the water. This is to ensure that no contaminated water gets into the tank. The system works by splitting the pipe with a T-Joint, where the initial rainfall keeps going down into an enclosed section of pipe. A bouyant stopper makes sure that when the enclosed pipe section is full, the clean water is diverted to the water tank. The pipe section below the T-joint will be the flush diverter.

Flush Diverter Tutorial

Construction

This is where I wanted the rainwater collection system to be initially. However, due to some complications surrounding the preexisting piping, which I had to remove to install my system, I unfortunately couldn't have it there. In the picture on the right, you can see the new location and the system being installed. I want to thank Farris for helping me throughout the installation process; it would not have been possible without him.

Mounting the system was the trickiest part of this process. I tried different ways but I eventually decided on a system with two sheet metal clips that can be tightened with screws. The two sleeves were then connected with a beam. Initial system on the left, final system on the right.

Final Product

I am very happy that I managed to finish this project. There was a big halt for two months between march and may, but when I finally aquired the materials I needed, I finished very quickly. I would like to have added some polish and some finishing touches like a UV filter. Overall, I am quite happy with the results.

Test and Evaluation

I was surprised by the efficiency of the water collector, specifically of the flush diverter. On the left, you can see the clear water from the tank and the brown water from the flush diverter. These results have been obtained with a critical component of the system missing, the water bottle that blocks the clean rain water from mixing with the flush.

In this image, you can see the debris filter successfully filtering out twigs and other small pieces of debris. The filter itself works extremely well. However, the water tank remains open, so bugs, leaves, or other debris still manage to end up in the water, just not in the system, which is the most important. I would definitely make a lid for the water container to improve the quality of the water.

With the air quality sensor I made last semester, I found that the PM 2.5 and 10 ratings outside of the STEM building were about 30-50mg/m^3, meaning that the rainwater from this area of Nairobi falls slightly above the requirements of the WHO for safe drinking water. Although the water is technically safe, water treatment is still recommended.

One problem I have encountered, although not critical, is the flush diverter cap system. The little black screw cap on the bottom of the flush diverter pipe section. It leaks a bit and makes the tiles outside slippery. A ring-shaped rubber piece would dramatically decrease the amount of leakage, if not stop it completely.

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