12. Water recycling - Introduction

Apart from rainwater harvesting, water recycling is one of the key strategies to conserve water. Water reuse or water recycling is reusing the treated wastewater for beneficial purposes like agriculture and irrigation, industrial processes, potable water supplies, flushing in toilets, environmental restoration and groundwater recharge.

 

Water recycling provides alternatives to the existing water supplies, which enhance water security and sustainability. Sources of water that can be recycled includes:

Wastewater treatment consists of physical, chemical and biological processes that remove the wastewater's solids, organic matter and nutrients.

 

There are \(3\) main stages of wastewater treatment that includes:

In some applications, a more advanced treatment called quaternary water treatment is required. Each stage involves removing different pollutants, with water becoming cleaner as it moves through the successive stages. The different treatment stages are used depending on the quality of water and the required final use.

 

During the primary treatment, wastewater is held temporarily in a settling tank. The heavier solids settle at the bottom of the tank, while lighter solids like oil and grease float over the surface.

 

 

Once the lighter materials are settled, the floating materials are removed. At the same time, the remaining liquid is moved to the secondary phase of wastewater treatment. Primary treatment removes the material that floats or settles readily due to gravity. It includes the physical processes involving screening, comminution, grit removal, and sedimentation.