Municipal Wastewater Reuse
Municipal wastewater is produced by homes, schools, business and industries from drains such as sinks, showers, laundries, toilets and other drains inside buildings. This wastewater ends up at a wastewater treatment plant (WWTP), also called a sewage treatment plant, which is operated by a municipality. Large volumes of water flow to these plants, with domestic households alone usually producing between 200-300L of wastewater per person per day. The wastewater is typically 99% water, and 1% of contamination which needs to be treated before the water can be reused. The amount of municipal wastewater being reused varies greatly by country, but the percentage is rising due to rising global water scarcity.
The majority of waste water is discharged into waterways following treatment, where it mixes with existing water and returns to the water cycle. Many places in the world treat municipal wastewater to a standard that doesn’t meet drinking water standards, but is approved for uses such as agriculture or irrigation where human contact is limited. An added benefit for use in agriculture or irrigation is a potential reduction in chemical fertiliser use, with a higher amount of nutrients present compared to potable water. Since the agriculture industry is the world’s biggest water consumer, the percentage of water reused is expected to rise with the increase of water stress. Municipalities are also shifting towards potable reuse of wastewater, where their wastewater is treated and used as drinking water.
Municipal wastewater treatment plants are being regulated to meet to meet stringent specifications for discharge in relation to Chemical Oxygen Demand (COD), total nitrogen (TN) and total phosphorus (TP) levels. Meeting these criteria requires the use of advanced biological and membrane processes which can result in much larger plants and increased power requirements for aeration and pumping. These improvements are often difficult to implement and expensive. In colder climates or during winter seasons, the effectiveness of biological treatment can go down substantially, which can also result in the treated effluent exceeding required discharge standards.
Stages of Wastewater Treatment
Wastewater treatment usually occurs in four stages;
Pre Treatment uses bar screens and grit chambers to remove larger objects and sand, which have been wrongly discharged to sewers. These contaminants can’t be removed using chemicals and can potentially damage the pumps used later in the process.
Primary Treatment occurs when the water moves to a primary clarifier, where solids are further removed from the water by settling to the bottom. At the end of this stage, the effluent should be free of larger particles and only contain organic matter.
Secondary Treatment significantly reduce the biological content of the wastewater. In many cases, this starts with the use of aeration basins, where return activated slude (RAS) is used to provide micro-organisms, and air is bubbled through the water to break down remaining biological content.
Teriary Treatment removes nitrogen and phosphorous from the water, which can cause algal blooms in our waterways. These blooms can cause colour changes in water, threaten aquatic life, and may be toxic.
Clean TeQ Water’s CIF® (continuous ionic filtration) technology can provide tertiary treatment of wastewater to reduce the levels of COD, TN and TP for most stringent discharge standards. The process provides continuous physical filtration, along with carefully selected resins to target and remove nitrogen and phosphorous from the water. There is also excellent resistance to fouling, and the process operates with lower energy requirements than other membrane/filtration technologies.
Our BIONEX™ technology uses CIF® to remove nitrogen and phosphorous from the feed water, and then employs our BIOCLENS™ encapsulated bacteria technology to treat them, allowing the brine to be reused.
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Contact us to discuss your water treatment needs.