Biocide Dosing via Feed Stream Segmentation for Membrane Biofouling Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Membrane separation processes, particularly in water purification, face challenges with biofouling, which can lead to reduced water quality and flow rates due to the growth of microbes on membrane surfaces, and existing methods for controlling biocides at low concentrations are inaccurate and difficult to maintain.
Innovation Solution
A system that separates the feed stream into a primary and a secondary stream, allowing for the controlled addition of biocides to the secondary stream at higher concentrations, which are then diluted to achieve the desired low concentrations in the overall feed stream, using a sensor to monitor and adjust the biocide addition based on the secondary stream's concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If biocide is added directly to the feed stream at low concentrations, then the desired low biocide concentration (less than 1 ppm) is achieved, but sensor accuracy drift causes gross changes in biocide addition rate
Solution Approach 1:
The feed stream is divided into a primary feed stream and a secondary feed stream. Biocide is added to the secondary feed stream at a higher concentration than the target concentration in the combined feed stream. The secondary stream then mixes with the primary stream to achieve the desired low concentration in the overall feed stream. This segmentation allows the sensor to measure at higher concentrations where accuracy drift has less impact on the final low concentration achieved in the feed stream.
Solution Approach 2:
The invention changes the concentration parameter of biocide in the secondary feed stream to be higher than the target concentration in the combined feed stream. By operating the sensor and biocide addition system at higher concentrations in the secondary stream, the system achieves better measurement precision and control stability, which then translates to accurate low concentration delivery when diluted with the primary stream.
2Measurement precision
If sensor calibration frequency is increased to maintain measurement accuracy, then measurement precision improves, but system complexity and operational burden increase
Solution Approach 1:
By segmenting the feed stream into primary and secondary streams, the system allows the sensor to operate in the secondary stream at higher biocide concentrations. This concentration amplification effect means that sensor accuracy drift has proportionally less impact on the final low concentration in the combined feed stream, thereby reducing the frequency of calibration needed and simplifying operational requirements.
3Quantity of substance
If biocide concentration in feed stream is kept very low (less than 0.01 ppm), then effective biofouling control is achieved, but sensor measurement accuracy becomes insufficient
Solution Approach 1:
The feed stream is segmented into primary and secondary streams, allowing biocide to be added to the secondary stream at concentrations that are higher than the target concentration in the combined feed stream. This enables the sensor to measure at concentrations within its accurate measurement range, while the final mixed feed stream still achieves the desired very low biocide concentration for effective biofouling control.
Solution Approach 2:
The secondary feed stream acts as an intermediary medium that enables concentration amplification. By adding biocide to the secondary stream at higher concentrations and then mixing it with the primary stream, the system achieves accurate sensor measurement in the intermediary secondary stream while delivering the required low concentration in the final combined feed stream for biofouling control.
Data Source
AI summary
Biocide can be controllably added to a feed stream for a membrane. In some examples, the feed stream is separated into a primary feed stream and a secondary feed stream, for example, with the secondary feed stream having a lower flow rate than the primary feed stream. The secondary feed stream may be used to monitor and control the addition of the biocide, which is then diluted when the secondary feed stream is combined with the primary feed stream to form a combined stream for delivery to the membrane.