How to ensure the quality of harvested rainwater?
Rainwater harvesting techniques are the best alternative to attain a balance between increasing water requirements and limited or no water supply. Nowadays people are installing a rainwater harvesting system in their home as an additional source of water.
What is Rainwater Harvesting?
Rainwater harvesting is collection, purification and storage of rainwater from rooftops, courtyards, paved and unpaved areas before it runoff. The scarcity of ground water is increasing day by day. More and more people are harvesting rainwater to meet their needs of water, as this technique is cost effective.
Rainwater Harvesting System
The basic components of a rainwater harvesting system are:
Catchment: Catchment is the area on which rain falls directly. It is the area which contributes water to harvesting system. Rooftops, sloppy roof, courtyards, paved and unpaved areas are catchment areas.
Transportation pipes: Transportation pipes transport rainwater from catchment to storage system. They include down water pipes and drains.
First flush: First flush is a device to flush off the first shower of rain. It is important to flush off this water as it contains all contaminants and bacterias from catchment and atmosphere.
Filters: Filtering of rainwater is important before its storage and usage.
Following filters are used to make the water fit for potable use:
- Gutter screens
- In tank filters
- Sand filters
- Cartridge filters
Storage tank: The tank that stores rainwater after its purification is called a storage tank.
Tips to ensure the quality of harvested Rainwater:
Rainwater is one of the most pure form of water. It is a high quality soft water, so it requires less amount of detergent and soap for washing clothes and body. It can be used for multi purpose i.e drinking, watering plants, toilet, laundry.
However, while collecting and storing, rainwater gets contaminated. So, to ensure the quality of rainwater, a properly designed and operated rainwater harvesting system is required.
System design
- The catchment should be made of nontoxic materials. There should be no lead based paints on catchment areas.
- Drains, pipes and gutters should be made of UV resistant materials.
- There should be a micro wire mesh at the mouth of each pipe or drain to prevent floating materials from passing through these pipes. All tank inlets should be properly covered.
- To separate the first flush of water from roof and gutters, first flush diverter should be installed. It prevents first flush from going into a storage tank.
- To avoid blockage due to debris, leaves, sand etc. filters should be regularly cleared.
- The storage tank should be light proof and covered. There should be in tank filters where the water enters the tank from drains, pipes and other inlets.
Rainwater quality standards
Maintenance and Treatments
Maintaining cleanliness and hygiene of the rainwater harvesting system is very important to avoid contamination of water.
- Catchment area should always be clean so that there is no debris, leaves and moss to contaminate rainwater.
- Gutters, pipes, tank inlets, filters and screens should be cleaned at regular intervals.
- Inspecting tanks at least once a year, disinfecting water and cleaning tank, whenever necessary.
- The water in the storage tank should be checked regularly for any change in its physical qualities e.g. color and smell.
There are few treatments to ensure that the quality of stored rainwater is maintained and it does not get contaminated. Following are the treatments:
Chlorination: Chlorination is most commonly used for treatment of stored rainwater. If the stored water is smelling or colored you can go for chlorination. It kills all types of bacterias and make water safe for drinking.
Boiling: boiling is a simple and effective method to remove all biological contaminants from water and make it pure and safe for drinking and potable use.
