Water Filtration Recirculation to Prevent TDS Creep
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Solution Overview
Problem
Existing point-of-use water filtration systems experience TDS creep when idle, leading to high TDS concentration in filtered water upon resumption of use, especially when small amounts of water are dispensed, due to the diffusion of impurities across semi-permeable membranes without pressure differential.
Innovation Solution
A point-of-use water filtration system with an idle mode, filtration mode, and recirculation mode, featuring a controller that anticipates water demand based on user habits, recirculates permeate water through the semi-permeable membrane, and adjusts valve positions to prevent TDS creep by maintaining water flow and quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the pump is turned off during idle periods to save energy, then energy consumption is reduced, but TDS concentration in filtered water increases due to TDS creep
Solution Approach 1:
The controller activates the pump in recirculation mode before the anticipated time of next use to preemptively flush TDS from the membrane and permeate line. This preliminary action ensures that when the user actually needs water, high-quality filtered water is immediately available, resolving the contradiction between energy saving during idle periods and maintaining water quality reliability.
Solution Approach 2:
The system uses its own filtered water to flush and clean the membrane and permeate line during recirculation mode, eliminating the need for separate cleaning systems or chemicals. The filtered water circulates through the system to self-cleanse TDS accumulation, maintaining water quality without external intervention while consuming minimal energy compared to continuous operation.
2Reliability
If the system operates continuously to maintain water quality, then TDS concentration remains low, but energy consumption increases
Solution Approach 1:
Instead of continuous operation, the system employs periodic recirculation mode activated by the controller based on learned user patterns and anticipated demand. The pump operates intermittently in recirculation mode to periodically flush TDS, maintaining water quality reliability while significantly reducing energy consumption compared to continuous operation. This periodic action optimizes the balance between water quality and energy usage.
3Reliability
If the system flushes immediately upon entering idle phase to prevent TDS creep, then water quality is maintained, but water waste increases
Solution Approach 1:
The controller activates recirculation mode in advance of the anticipated next use based on learned user habits, performing the flushing action preliminarily rather than immediately upon entering idle phase. This timing optimization maintains water quality by preventing TDS creep before it occurs, while minimizing water waste by avoiding unnecessary flushing during extended idle periods when no water is needed.
Solution Approach 2:
The controller uses feedback from learned user consumption patterns and anticipated demand signals to intelligently control when recirculation mode activates. This feedback mechanism ensures flushing occurs only when necessary to maintain water quality, avoiding wasteful flushing during periods when the system will remain idle for extended times, thus optimizing the balance between water quality and water waste.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system ensures minimal TDS creep during idle periods, maintaining water quality and reducing initial high TDS concentrations upon resumption, providing reliable and optimally filtered water when needed.
Implementation Method 1
The diffusion rate of water across the RO membrane is a function of the osmotic pressure difference between the upstream side and the downstream side of the RO membrane
Implementation Method 2
a pump pressurizes the upstream side of the RO membrane, causing water to diffuse across the RO membrane
Implementation Method 3
The rate at which the TDS diffuse across the RO membrane is a function of the concentration difference in TDS between the upstream side, which has a relatively high TDS concentration, and the downstream side of the RO membrane
Data Source
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AI summary
A point-of-use water filtration system having an idle mode and a filtration mode, the water filtration system including a feed water inlet, a pump in fluid communication with the feed water inlet via a feed water line, and a semi-permeable membrane having an upstream side and a downstream side. A first portion of the upstream side is in fluid communication with a membrane inlet and a second portion of the upstream side is in fluid communication with the concentrate outlet, and the downstream side is in fluid communication with a permeate outlet. The point-of-use water filtration system also includes a permeate line in fluid communication with the permeate outlet and a filtered water outlet, a concentrate line in fluid communication with the concentrate outlet, a flow path configured to selectively connect the permeate line to the feed water line; and a controller configured to anticipate demand for the filtration mode based on operator habit information stored in a memory of the controller when the water filtration system is in the idle mode and to recirculate water in the permeate line through the pump and the semi¬ permeable membrane in response to the anticipated demand for the filtration mode.