Reverse Osmosis Pump Cycling and TDS Creep Control
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Solution Overview
Problem
Double-pass reverse osmosis systems face issues with excessive pump cycling, TDS creep, and water hammering, leading to mechanical damage, significant power consumption, and reduced water quality due to inadequate water management and pressure control.
Innovation Solution
A system with a central control unit, adjustable fresh water flow valve, and valves for diverting purified and waste water flow to maintain processing water levels, reducing pump cycling and TDS creep, and alleviating water hammer by controlling fresh water flow and pressure within the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pump operates in a double-pass reverse osmosis system to produce purified water, then water purification is achieved, but excessive pump cycling occurs leading to mechanical damage and high power consumption
Solution Approach 1:
The system pre-fills the processing reservoir to a predetermined level before pump operation begins. This preliminary action ensures that sufficient feed water is available when the pump starts, preventing immediate cycling and allowing the pump to operate continuously for longer periods, thereby improving reliability and reducing cycling frequency.
Solution Approach 2:
The processing reservoir acts as an intermediary between the feed water source and the reverse osmosis system. It buffers water supply fluctuations and maintains a stable water level, preventing direct pump cycling caused by intermittent feed water availability. This intermediary function decouples the pump operation from feed water variability.
2Reliability
If the pump runs continuously to avoid cycling, then pump durability improves, but TDS creep occurs due to inadequate water flow through the membrane
Solution Approach 1:
The system incorporates a water level sensor that continuously monitors the processing reservoir level and provides feedback to the control circuit. When the level drops below a threshold, the control circuit activates the pump. When the level reaches the predetermined high level, the pump shuts off. This feedback mechanism ensures the pump operates only when needed, maintaining both operational stability and adequate water flow for quality purification.
Solution Approach 2:
The system dynamically adjusts pump operation based on real-time water level conditions. Rather than running continuously or cycling frequently, the pump operates in adaptive intervals that respond to the actual state of the processing reservoir. This dynamic control maintains stable operation while ensuring sufficient flow through the membrane to prevent TDS creep.
3Productivity
If high pressure is applied to force water through the membrane, then purification efficiency improves, but water hammering occurs causing mechanical damage
Solution Approach 1:
The system pre-fills the processing reservoir before pump operation, creating a cushion of water that absorbs pressure surges. This preliminary water inventory acts as a buffer that prevents sudden pressure changes and water hammering when the pump starts or stops, while still allowing high pressure to be applied during pump operation to maintain efficient purification rates.
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 effectively reduces pump cycling and TDS creep, minimizes mechanical damage and power consumption, and prevents water hammering, ensuring continuous and uninterrupted operation while maintaining water quality by managing water levels and pressure.
Implementation Method 1
Reverse osmosis is a process for removing dissolved mineral salts, organic molecules and certain other impurities by forcing water under pressure to pass through a semi-permeable membrane. The reverse osmosis process reverses the natural osmotic effect in which fluids with a low concentration of dissolved solids pass through a membrane into an area of higher concentration. With reverse osmosis, water is made to pass from a state of high concentration to a state of low concentration.
Implementation Method 2
Pumps must be sized to meet the required operating pressure and flow rate of the reverse osmosis system and they constitute the largest energy consuming component in a reverse osmosis system. To force water through a semi-permeable membrane, pressure must be applied to overcome the water's osmotic back pressure and permeate back pressure.
Implementation Method 3
TDS creep occurs when the amount of processing water in the processing reservoir is insufficient to maintain continuous operation. The control system monitors and maintains water levels to prevent the concentrated water on the feed side of the membrane from equilibrating with low mineral content water on the permeate side through natural osmosis when no pressure is applied.
Data Source
AI summary
A system for reducing water pump cycling and TDS creep when producing purified water is disclosed. The system includes a central control unit for receiving signals from a processing reservoir water level sensor and controlling a purified water valve and a waste water valve. The purified water valve is configured to divert at least a purified water flow through a purified water conduit to the processing reservoir and the waste water valve is configured to divert waste water flow through a waste water conduit to the processing reservoir to maintain the pump in a pumping condition such that the amount of processing water is at least as great as a processing water threshold thereby reducing cycling of the pump and TDS creep.