How to improve water circularity?

In recent years, a lot of emphasis is being placed on smart water usage, with special consideration being given to ZLD (Zero Liquid Discharge) concept. Many countries like India are working on policies to make it compulsory for industries and large housing societies to incorporate the ZLD concept making water reclamation a necessity for them.

What is water recycling/reuse or reclamation?  

Water recycling (also known as water reuse or water reclamation) reclaims water from a variety of sources then treats and reuses it for beneficial purposes such as agriculture and irrigation, potable water supplies, groundwater replenishment, industrial processes, and environmental restoration. Water reclamation or recycling primarily makes non-potable wastewater useful, thus saving the economic and environmental costs related to establishing new water supplies.

All the water that is present on Earth has been recycled multiple times. Nature’s water cycle is essentially a vast water recycling system. But here we are talking about a man-made water recycling system that can be planned as well as unplanned. 

Unplanned water reuse refers to situations in which a source of water is substantially composed of previously-used water. For an example of unplanned water, reuse occurs when communities draw their water supplies from aquifers that receive reclaimed water from the water harvesting system.

Planned water reuse refers to water systems designed to beneficially reuse a recycled water supply. Often, communities will seek to optimize their overall water use by reusing water to the extent possible within the community, before the water is reintroduced to the environment. Examples of planned reuse include agricultural and landscape irrigation, industrial process water, potable water supplies, and groundwater supply management.

Sources of reusable wastewater:

Sources of water for potential reuse can include municipal wastewater, industrial process, and cooling water, stormwater, agriculture runoff, and return flows and produced water from natural resource extraction activities. Currently, most recycled water comes from treated municipal wastewater, sewage, or greywater. Since most of the industries recycle/ reuse the wastewater generated by them within their own industrial complex, it’s the municipal wastewater and domestic greywater that need to be focused on by authorities. Approximately 50-70% of the water used in your house results in greywater generation but in developing countries like India, not even 5% of this is recycled in the urban household. Most of the greywater generated can be easily utilized in-situ after undergoing basic and cheap treatment as a result it is safe to say that there is immense scope and needs to recycle greywater.

Benefits of recycling water:

Recycling water acts as an alternative water source and can provide significant economic, social, and environmental benefits. Not only does recycling water, provide us with an alternate water resource in the water-scarce area, but it also prevents the over-exploitation of groundwater. As per the UN, the benefits of recycled water can be divided into 2 categories;

Environmental Benefits

  • By reusing wastewater, instead of discharging it into the environment reduces the environmental pollution as well as over-exploitation of other water resources
  • Saves energy otherwise required to extract or transport freshwater to the area.
  • Recharges groundwater, avoiding freshwater resource degradation and salinization
  • Irrigating the crops with treated wastewater may contribute to improve production yields, reduce the ecological footprint and promote socioeconomic benefits. It may also lead to the reduced application of fertilizers (i.e. conservation of nutrients and reducing the need for artificial fertilizer (e.g. soil nutrition by the nutrients existing in the treated effluents).
  • Recycled water can be used to revive old water bodies like ponds and lakes that have dried up, and turn them into wetlands.

Socioeconomic Benefits

  • Increases water availability for potential water-stressed or arid areas.
  • Provides an easily accessible water source to economic sectors such as industry and agriculture, promoting economic development and food production.
  • Improves the quality of agriculture through the use of valuable nutrients extracted from the wastewater.
  • Diversifies water sources, which increases climate resilience.

Challenges in Reusing water:

  • Foul smell: if the water treatment is system is not properly designed, it may lead to a foul smell in the entire neighborhood.
  • Health risk: recycled water, has a certain degree of treatment for a specific purpose if a person consumes water that is not treated for drinking purposes, they may get sick.
  • Social unacceptance: Today, the technology is there to recycle wastewater into drinking water. But most people still find it taboo or have that sense of uneasiness in using recycled water for drinking purpose
  • Improper reuse of water in the household can lead to various health hazards.

Uses of Recycle water:

With the right amount of treatment recycled water can be made fit for even drinking purposes. But currently due to various socio-economic constraints, recycled water is mainly used for:

  • Irrigation of fields, parks, gardens, etc.
  • Washing and spraying of roads
  • Reviving wetlands, lakes, ponds, etc.
  • Flushing
  • Washing of vehicles
  • Recharging aquifers

How to reuse water?

Water recycling is beneficial, but how can we recycle the water? Do we need special treatment devices or methods or is it simple? The answer to that question depends on how we plan to use that water. Water reusing can be as simple as reusing waste RO water for watering plants or can be as complex as reusing wastewater for drinking purposes. Hence we can divide the methods to recycle water into 2 broad categories i.e. 1) recycling of water on a large scale and 2) domestic recycling of water. Below is a list of various methods we can use to recycle/ reuse water. 

Recycling water on a large scale

The large-scale recycling of water requires the setting up of a collection system and well-designed water treatment plants. The plants are designed to obtain the desired quality of water to make it fit for specific use. The cost and type of treatment are largely based on the input quality of water and the desired output quality of water. A particular treatment plant can consist of one or more treatment methods. These treatment methods can be further classified as Primary, Secondary, and Tertiary treatments. A few of the most common treatment methods used are:

  • Primary treatments: Primary treatment processes are the first step in all water recycling plants. These treatments include various physical processes like screening, grit removal, sedimentation, and clarification. Primary treatment targets heavy matter and scum that floats to the surface
  • Secondary treatment: Secondary treatment processes are employed to remove total suspended solids, dissolved organic matter. These processes usually consist of aerated activated sludge basins with return activated sludge or fixed-media filters with recycling flow. 
  • Tertiary treatment: Tertiary treatment processes are only employed in cases where a very high quality of water is desired. It includes processes like filtration, ion exchange, activated carbon adsorption, electrodialysis, RO, FO, etc. 

Domestic recycling of water:

While domestic sewage water usually requires some level of treatment and hence needs to be treated in water recycling plants. On average we waste around 80% of good quality water that can easily be reused without any treatment. Below are few simple methods by which we can reuse water in our household.

  • Rainwater collection: Rainwater is one of the freshest forms of water available. By preventing the rainwater from running down the drain and collecting it, we can reuse it for almost any purpose.  
  • Reusing the RO reject water: RO filtration system wastes almost 80% of water as RO reject. This water can be easily collected and used for the purposes like washing utensils, floor flushing or if mixed with tap water, it can even be used for watering plants
  • Save Kitchen water: cooking generates a lot of wastewater, be it during washing vegetables or boiling pulses. This water once cooled makes up for excellent food for plants.
  • Installing a greywater collection system: Greywater refers to wastewater generated in-household, which does not contain fecal or other biological contaminants. The greywater can be reused for flushing purposes. It can be easily done by installing a greywater collection system that collects the greywater and redirects it to flushing devices

These are just a few of the basic methods. The potential to reuse water within our households is enormous and if we carefully look around us, we can easily find many more areas from which we can collect and reuse the water.