A Case for Water Reuse

In recent years, the increased recycling process of water has evolved exponentially in its practices and concepts. Several elements such as diminishing water resources, severe famines, saltwater interference, residents increase in intensity, and others have produced a necessity for municipalities and industries to discover alternative possibilities for an uninterrupted water supply. Fortunately, there are now various alternative solutions such as RO – membrane systems, that can improve capabilities of exploring reliable water recycle treatment techniques.

Water reuse applications include:

• Direct Potable Reuse (DPR), in this method, water is purified precisely into a drinkable water supply distribution system.
• Indirect Potable Reuse (IPR) is used for environment lakes or groundwater before potable treatment.
• Non-potable applications are used for recreational purposes at parks or golf courses, industrial processes, and agriculture purposes.

How Filtration Treatment Options Can be Used for Water Reuse:

Among reuse applications of water treatment, membrane technology is a widely accepted method that results in producing consistent, stable, high-quality water secures for individual consumption. Membrane technology not only removes salts in water but also removes pathogens, which is considered as a primary in the treatment of water. Membrane technology requires less treatment process compared to the other methods and it can be used daily.

Usually, we use packaged ultrafiltration system as it is a fully performed, self-controlled unit that includes all the elements and controls which are necessary for the treatment of water.

Microfiltration (MF) and ultrafiltration (UF) membranes will remove turbid particles, suspended solid matter, bacteria, and viruses from secondary treated wastewater or industrially processed water. Microfiltration/ultrafiltration acts as a barrier that has hollow fibres with nominal pore sizes from 0.01 to 0.1micron which removes all contaminants present in water. Hollow fibres connected are called  modules, which are integrated to function fully in household water treatments.

Low-pressure filtration systems are generally used in the household treatment of water, as it is required by individuals daily. Advanced treatment methods such as Nanofiltration (NF) and Reverse Osmosis (RO) are used to treat hardness and dissolved solids present in water. Usually, in RO treatment, high pressure is utilized to neutralize natural osmotic pressure and remove the dissolved pollutants present in water.

Nanofiltration (NF) and Reverse Osmosis (RO) are used in advanced water reuse applications where high-quality permeate is required with low levels of dissolved solids and hardness. For the RO process, high pressure is used to counter natural osmotic pressure and the dissolved contaminants are rejected, like ultrafiltration. The Reverse osmosis elements require various operating systems to remove salts and dissolved contaminants.

Reverse osmosis is carried out in the household treatment of water in which a sheet is wound over a centre tube through which membrane water is allowed to filter so that it removes hardness or excess salts present in water along with concentrated salts. It can also remove dissolved pollutants or contaminants. This kind of process can be carried for households mainly without going outside or using any other problematic water treatment process. Microfiltration, ultrafiltration, and reverse osmosis play a vital role in emerging water reuse best methods and preserving this limited source.

Why is RO Wastewater produced?

All of us are concerned about the quality of water distributed through municipal and borewell techniques. This concern is due to the increasing pollutants in borewell systems leading to water-borne diseases if water is not treated properly. Due to this reason, people use more RO purifiers to get clean potable, and palatable water. There are a few things that we should know about the treatment process.

• Additional water is required in RO membrane technology to remove impurities.
• The use of additional water leads to the wastage of water.
• From few research studies, it has been found that RO filters three times extra water than what is filtered, which means 80% of water gets wasted.

What is the Danger of using RO Reject Water?

As per research made by water experts, the wastewater from RO filters is a no-go-zone for it contains high total dissolved solids (TDS) which makes water unfit for drinking and unsuitable for daily usage. Additionally, the amount of mineral salt and organic substance in this wastewater discharge is extremely high Due to which filtered water is not suitable for usage. As this water has a high level of TDS, it leads to foul odour and taste. It leads to severe health issues such as reproduction failure and stunted growth.

Reverse Osmosis Water Waste: How to Reduce, Recycle and Reuse RO Wastewater:

There is a lot of evidence that the RO system will purify water, but there is a disadvantage, i.e., rejected water creates issues in the household system. Roughly 80% of input water will be purified by the RO system. As we know that water is one of the vital natural resources required for human survival. The disadvantage in RO treatment is wastewater comes out from RO purifiers. There are a lot of ways to tackle this problem. Let us see how to cut down wastewater in the RO purifier system.

7 Easy and Tested Ways to Reuse RO Wastewater:

If there is a RO set up at home or office, we need to have a discharge bucket to store water. And then we can use it for various purposes which reduces the wastage of water.

1. Mopping
   We can use RO rejected water in household tasks like mopping and cleaning floors. We need to ensure that it can be mixed with fresh water to reduce high TDS and salts present in it, as it may leave stains and make the floor sticky or greasy.
2. Car Wash
   As we all know we require around 14 litres of water for car washing substituting this with RO wastewater can save freshwater.
3. Water your Garden
   The most appropriate and efficient application of the rejected RO water can be used for gardening. Recently the new concept of vertical gardening is in trend these times. We can use our terrace or patio wall to cultivate plants. The high-level minerals and nutrients present in RO expelled water can improve the growth of plants and bloom. Even Though, this is desirable for metropolitan areas only wherever the municipal water TDS concentrations are usually lower.
4. Dish Washing
   Most of us fix the RO filters in the kitchen. Normally 2gallons/minute of water is used for dishwashing. Hence RO wastewater can act as the perfect choice to decrease this amount of water. We can pre-soak or wash utensils once after each meal. Soaking will also help to eliminate crumbs and food caught on the plates.
5. Toilet Flushing
   Though we cannot use RO wastewater for bathing, we can use it for cleaning and toilet flushing. Flushing requires around 6 to 7 litres of water which immediately goes to the drain. Instead of using freshwater, we can replace it with RO expelled water.
6. Bathing Pets
   We can use RO wastewater for bathing pets instead of discarding, however, few pets are sensitive to hard water then we can dilute it with ordinary tap water.
7. Pre-Rinsing Laundry
   Laundry cleaning normally requires a large quantity of water which gets wasted. As an alternative, we can use RO discharge wastewater for pre-rinsing. Dissolved salts in RO expelled water also removes stubborn stains.

 

Prof. Asha Rani N.R.
Assistant Professor
Department of Civil Engineering
Alliance College of Engineering and Design