Wastewater Ratio
What Does the Wastewater Ratio Mean?
The wastewater ratio, also known as the recovery rate, is a unique performance parameter for reverse osmosis (RO) water purifiers.
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Definition: It refers to the volume ratio between the "pure water" produced by the purifier and the "wastewater," also called "concentrated water."
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Expression: It is typically represented as a ratio of numbers.
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For example, 1:1**: This means that for every 1 cup of pure water produced, 1 cup of wastewater is generated.
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For example, 2:1**: This means that for every 2 cups of pure water produced, 1 cup of wastewater is generated (indicating more water-saving).
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For example, 3:1**: This means that for every 3 cups of pure water produced, 1 cup of wastewater is generated (indicating more water-saving).
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Calculation Formula:
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Wastewater Ratio = Pure Water Output : Wastewater Output
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Another Related Concept: Recovery Rate
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Recovery Rate (%) = (Pure Water Output / Total Incoming Water) × 100%
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A 1:1 wastewater ratio corresponds to a 50% recovery rate (1 part of pure water / (1 pure + 1 waste) = 50%).
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A 2:1 wastewater ratio corresponds to a 66% recovery rate (2 parts of pure water / (2 pure + 1 waste) ≈ 66%).
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A 3:1 wastewater ratio corresponds to a 75% recovery rate (3 parts of pure water / (3 pure + 1 waste) = 75%).
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In simple terms: The higher the wastewater ratio (the smaller the second number), the more water-efficient the purifier is.
Why Does Wastewater Occur?
To understand why the wastewater ratio matters, it's crucial to first understand the inevitability of wastewater production.
RO membranes have extremely tiny pores (0.0001 microns), and a high pressure from a pump is required to push water molecules through. In this process:
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Washing Effect: Some of the water flow (pure water) passes through the membrane, while the other part (wastewater) is swept away at high speed along the surface of the membrane. This flow is crucial as it helps remove salt, bacteria, heavy metals, and other concentrated impurities trapped on the membrane surface.
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Prevention of Scaling: Without this wastewater continuously flushing the membrane, pollutants would quickly accumulate, causing scaling on the membrane surface, similar to limescale in a kettle. This would block the pores, leading to a **sharp drop in water production, a decrease in desalination performance (TDS value increase), and a significant reduction in the RO membrane's lifespan**.
Conclusion: The generation of wastewater is a necessary condition for RO water purification technology to work properly and ensure the long-term use of the RO membrane. The so-called “zero wastewater” RO machine is technically contradictory and typically only recycles wastewater back to the incoming water, which can actually worsen membrane contamination.
Why Should We Pay Attention to the Wastewater Ratio? (User Benefits)
Focusing on the wastewater ratio means paying attention to the following three core aspects:
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Usage Costs (Saving Money)
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Water Bills: Wastewater is directly discharged into the sewer, consuming tap water. The higher the wastewater ratio (e.g., 1:1), the more water is wasted, and the monthly water bills will increase accordingly. A machine with a 2:1 wastewater ratio will save about 33% on water bills compared to a 1:1 machine.
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Filter Life Costs: As mentioned above, sufficient wastewater flow is crucial for protecting the RO membrane and extending its lifespan. Excessively high wastewater ratios (e.g., 4:1 or higher) often come at the cost of the RO membrane's lifespan. Since RO membranes are the most expensive consumables in a water purifier, saving a bit on water bills might result in having to replace an RO membrane worth hundreds of dollars months earlier than expected, which is certainly not worth it.
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Environmental Benefits (Saving Resources)
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For environmentally conscious consumers, a lower wastewater ratio means less water resource waste and a smaller environmental burden, which becomes an important purchasing decision factor.
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Performance and Lifespan Balance (Peace of Mind)
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A good water purifier strikes the best balance between water conservation (high wastewater ratio) and **protecting the RO membrane (ensuring sufficient wastewater flow)**.
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A reasonable wastewater ratio (e.g., 2:1 or 3:1) is the optimal solution derived from extensive testing by engineers, balancing water-saving needs and ensuring enough water flow to wash the RO membrane, guaranteeing its proper functioning and long lifespan. Blindly pursuing an excessively high wastewater ratio may lead to unstable performance and higher long-term maintenance costs.
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“RO water purification technology generates concentrated water for flushing to ensure the filter’s long lifespan and pure water output. Purifighter optimizes water flow design through innovative technology, improving water-saving efficiency by about 33%.”
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