When wastewater is converted into water that can be reused for other purposes, it is referred to as reclaimed water or recycled water. This water can be reused for a multitude of purposes, ranging from as irrigation of gardens or replenishing surface water or groundwater. Treated wastewater can also be used in residences, businesses, and industries for various purposes such as toilet flushing. It can also be treated to meet the drinking water standards which are termed as “direct potable reuse” or “indirect potable reuse”, depending on the approach used.
Types of reclaimed water
The different types of reclaimed water are as follows:
1. Urban reuses: The treated wastewater can be reused for the irrigation of public parks, schoolyards, highway medians, and residential landscapes, as well as for toilet flushing and fire protection.
2. Agricultural reuses: If the reclaimed water is reused for the irrigation in agriculture, the nutrients of the treated wastewater has the benefit of acting as a fertilizer. The irrigation water can be used on different crops in different ways.
3. Environmental reuses: It is nothing but the use of reclaimed water to sustain, enhance, create or augment water bodies including aquatic habitats, or streamflow. For example, constructed wetlands fed by wastewater provide both habitats for flora & fauna and wastewater treatment.
4. Industrial reuses: The use of recycled water to recharge aquifers that are not used as a potable water source.
5. Planned potable reuse: It is publicly acknowledged as an intentional project to recycle water & use it for drinking purpose. The two ways in which potable water can be delivered for reuse is “Indirect Potable Reuse” and “Direct Potable Reuse”.
• Indirect Potable Reuse: It means water is delivered to the customer indirectly. After it is purified, the reused water blends with other supplies and sits a while in some sort of man-made storage or natural storage, before it gets delivered to a pipeline that leads to a water treatment plant or distribution system. That storage can be a surface water reservoir or maybe even groundwater basin.
• Direct Potable Reuse: This means the reused water is put directly into pipelines that go to a water treatment plant or distribution system. DPR may occur with or potentially without “engineered storage” such as above-ground tanks or underground tanks.
New Technologies used in Wastewater Reuse:
1. Membrane Filtration Systems: For wastewater treatment applications, membranes are currently used as a tertiary advanced treatment for the removal of dissolved species, organic compounds, and human pathogens, including bacteria, protozoan cysts, and viruses.
Membrane bioreactors are usually microfiltration or ultrafiltration membranes immersed in aeration tanks or implemented in external pressure-driven membrane units.
2. Nanotechnology: This technology is being investigated for higher-performing membranes with fewer fouling characteristics, improved hydraulic conductivity, and more selective rejection/transport characteristics. Advances in RO technology include improved membranes and configurations, more efficient pumping and energy-recovery systems, and the development of process technology, such as membrane distillation.
3. With microbial fuel cells, a potential breakthrough technology, electrical energy could be extracted directly from organic matter present in the waste stream by using electron transfer to capture the energy produced by micro-organisms for metabolic processes. First, micro-organisms are grown as a biofilm on an electrode; the electron donor is separated from the electron acceptor by a proton exchange membrane, which establishes an electrical current. Electrical energy is then generated through the oxidation of organic matter.
Although this technology is still in the early stages of development and significant advances in process efficiency and economics will be necessary, it has the potential to produce electrical energy directly from organic matter in the waste stream.
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