Rainwater Harvesting

Rainwater harvesting is the process of collecting and storing rainwater for later use. This practice has been used for thousands of years in various parts of the world to provide a source of water for drinking, irrigation, and other purposes. In recent years, rainwater harvesting has increased in popularity due to its environmental and economic benefits. This is an overview of the concept of rainwater harvesting, its benefits, the types of systems used for harvesting rainwater, and treatment options for the rainwater.

Rainwater harvesting involves the collection of rainwater from rooftops and other surfaces, filtration of the water collected, and using it for various purposes. Collected rainwater can be used for irrigation, water closet flushing, laundry, and other non-potable purposes. Rainwater can also be filtered and disinfected to make it pure enough for potable purposes.

Rainwater harvesting has many environmental and economic benefits. Some of these include:

1. Reduced Water Demand: rainwater harvesting reduces the demand for municipal water supply, thereby conserving water resources.
2. Reduced Energy Usage: depending on the final intended use, rainwater harvesting reduces the need for energy intensive water treatment and municipal distribution systems, which in turn reduces energy use and associated greenhouse gas emissions.
3. Reduced Flooding and Erosion: rainwater harvesting helps to reduce flooding and erosion by capturing and storing rainwater, which would otherwise runoff, causing soil erosion and increasing flooding potential.
4. Monetary Savings: harvesting rainwater can provide significant cost savings over time by reducing the need for municipal water supply and associated water utility bills.

There are several types of rainwater harvesting systems used for collecting and storing rainwater for later use. The three main types are:

• Aboveground Tank Systems
  Aboveground tank systems are the most common type of rainwater harvesting system. These types of systems involve collecting rainwater from rooftops and storing it in a tank above ground. Absent of any water treatment, these types of systems are relatively simple to install and maintain.

• Underground Tank Systems
  Underground tank systems involve collecting rainwater from rooftops and/or the ground and storing it in a tank located underground. These types of systems are ideal for sites with limited space or where aesthetic considerations are important. Typically, the underground tank system will require a pump to deliver the stored rainwater to the intended location of use.

• In-Ground Systems
  An in-ground system involves the collection of rainwater from a permeable ground surface such as a lawn or garden bed and storing it in a trench or reservoir located below ground. These systems are ideal for large-scale non-potable applications such as irrigation.

Rainwater Treatment

The quality of rainwater depends on many various factors, including the source of the water, the location of collection, and the season of the year. Pollutants such as bird droppings, dust, leaves, and other debris can accumulate on rooftops and other collection surfaces, leading to contamination of collected rainwater. The presence of bacteria, viruses, and other microorganisms can also be a concern, especially in areas where there is a high level of animal or aviary activity.

To ensure the safe use of rainwater for drinking and other potable purposes, treatment is required. Rainwater treatment involves a series of processes that remove contaminants and microorganisms from the collected water. The treatment process may include filtration, disinfection, and pH adjustment.

1. Filtration is the first step in the rainwater treatment process. Filtration removes large scale debris and sediment from the collected water. This is achieved through using a variety of filters, mesh screens, sand filters, and sediment tanks. Filtration will reduce the load on the subsequent treatment processes and increase the overall efficiency of the water treatment process.
2. Disinfection is the next step in the treatment process and involves the removal of microorganisms and bacteria from the collected water. There are several methods for disinfection including chlorination, ultraviolet (UV) treatment, and ozonation.
   1. Chlorination involves the addition of chlorine into the water to kill bacteria and viruses.
   2. UV treatment uses ultraviolet light to destroy the DNA of microorganisms.
   3. Ozonation uses ozone gas to oxidize and kill microorganisms.

Any of the disinfection methods listed above can be used singularly or in conjunction with one another to purify rainwater to potable standards.

The adjustment of water pH is the final step of the treatment process. The pH of rainwater can be affected by the presence of pollutants and contaminants, which can make the water acidic or alkaline. Adjusting the pH to an appropriate level helps to improve the taste and quality of the water.

Rainwater harvesting is a sustainable and cost-effective way of providing a reliable source of water for non-potable use. Rainwater harvesting has numerous environmental and economic benefits and is gaining in popularity in the United States. However, if rainwater collected is to be used for potable purposes, treatment is required to ensure its safe use, thereby increasing cost of operation, and contributing to increased maintenance obligations. Proper treatment of rainwater for its intended end-use is essential in ensuring its safety and efficiency as a water source.