Even though the earth is composed of 70 per cent water, most of it is saline or underground; less than 1 per cent of freshwater is accessible for human use. Large areas in developing countries do not have access to safe drinking water because of water shortages from poor infrastructure and drought.
As the global population increases and climate change contributes to extreme weather conditions, finding enough water to meet everyday needs, grows more complicated. Increasing the use of recycled wastewater conserves freshwater resources.
The term ‘wastewater’ does not have an appealing connotation to some, and its use may be culturally or politically unacceptable to others. However, with growing scarcity comes the need to adapt. Even if it is perceived to be unsafe and unclean, many people are recycling water to help ease demand from town water supply and harvested freshwater.
There are three processes in water recycling that depend on water application and how pure it needs to be.
The first step in wastewater treatment uses simple mechanical and physical processes to eliminate suspended contaminants. Incoming raw industrial wastewater or sewage is fed through mechanical bar screens to remove large solids from the wastewater stream. The captured materials are then deposited into a dumpster using a conveyor and sent to a sanitary landfill, or are dewatered and composted. Primary clarifiers may also be used so that a further reduction of solids can occur. Clarifiers can take the form of DAF or Dissolved Air Flotation or more conventional Lamella type clarifiers.
This next step, which is also known as ‘biological oxidation; uses biological processes to eliminate most of the organic contaminants that remain. In this process, oxygen is introduced into aeration basins or tanks. Bacterial microorganisms then consume the organic material as part of the oxidation, or digestion, process. The resultant product is known as activated sludge, and clean water is separated in final clarifiers, or settling tanks, resulting in wastewater biosolids. Biosolids are organic matter that has been recycled from sewage. The removed biosolids are then digested, dewatered and used for purposes such as soil composting and conditioning. In processes such as MBR (Membrane Bio Reactor) and MBBR (Moving Bed Biofilm Reactor), the same clean water outcome is achieved via a different methodology but with the same digestion principles. With MBBR, the oxidation of organic is achieved by biofilm that grows on suspended plastic media spheres; with MBR, the activated sludge is filtered with a membrane placed within the activated sludge tank.
All remaining solids and pathogenic organisms are filtered and removed using sand filtration or ultrafiltration. The clear water enters a chlorine contact chamber for chemical disinfection. Other chemicals can be used depending on the application. Reverse osmosis desalination can be used to ensure the water has a low level of minerals for final use. The water is now adequately treated, recycled and ready for release.
When wastewater isn’t treated or recycled, the raw source pollutes waterways and land, causing environmental damage. Recycled water provides a safe, environmentally responsible and economically viable option to reduce water shortages. Today, technical advances mean that recycled water can reduce the costs of the mains supply by half. If recycled wastewater replaces mains water, the expense and environmental impact of thirsty processes such as boilers and cooling towers reduces.
Waterform is a family-owned and managed company that provides advanced water and wastewater treatment solutions. They offer tailored solutions to suit your water intensive business and solve the toughest water scarcity and compliance challenges. We source innovative technologies from all over the world to make sure we remain at the forefront of water treatment innovation. To learn more about us, visit our website at www.waterform.com.au.