Pretreatment for the UltraFiltration System HydroCAP 60
Skyworks Solutions, Mexicali branch Internship Summer 2015
"In the Summer of 2015, I was fortunate to given the opportunity to work in one of the biggest semiconductor providers in the world-- Skyworks Solutions, as a Wastewater Treatment Intern with their industrial engineers. Little I knew, Skyworks operated one of the most efficient Wastewater Treatment Systems in the world with leading technology, such as the Reverse Osmosis and the UltraFiltration Systems, both used for water desalination in the drinking industry, all over the world. Apart from learning the team's day to day dynamic, as the only intern in the team, I was given a project by my mentor- to find the most efficient way to prolong the life of the membranes for the UltraFiltration system HydraNautics. With little to no experience in the Wastewater Treatment field, I emerged myself in hours of research, concluding with a 40-page proposal (attached at the bottom of the page) and new solutions and perspective that all my co-workers agreed on. As my mentor said: "We might be in the industry for 20 to 30 years, but we might not see things as clear as someone with a fresh mindset" With these words of encouragement, I embarked to this unknown field and never feared to bring solutions outside of the conventional methods to the table." -Diana Wu Wong |
|
Diana's Work
Abstract
Membrane technology for water filtration has been developing since the 1990’s, and over the past decade it has spread and widely accepted as a feasible alternative to conventional water treatment. This technology is used for a variety of purposes ranging from potable water treatment, pharmaceutical, environmental and in this case semiconductor production between other industry applications. The specific membrane filtration used for drinking water and clean water treatment is the low pressure membranes which includes microfiltration and ultrafiltration systems.
Both technologies provide low carbon foot print, lower cost and better water quality than the conventional system. While the conventional system is highly dependent on the source water quality, the membrane filtration system is able to remove pathogens and other suspended matter independent to the source water conditions. The mechanism for removal of particulate matter in a membrane is a physical sieving process where particulates larger than the pore size of a membrane are physically excluded from the water passing through the membrane surface. This process does not rely on the performance of a reactor, chemical dosing or any alterations for the operation of the membranes. It is flexible to the flow rates, pH levels and temperature fluctuations of the water source. However, there are limitations: the main concern is the membrane fouling, which is described as the accumulation of particles on the surface and inside the pores of the membrane surface. The source of membrane fouling may be silt, bacteria, organic fouling or low feed water quality in general. The effect of membrane fouling on the efficiency of the membrane reduces the water quality and membrane lifetime. Furthermore, it reduces the flux, in which requires the system to increase its pumping intensity to maintain a consistent volume of water being treated, hence increasing energy consumption.
As mentioned before, the goal is to explore different sustainable and affordable pretreatment methods for the pre-existing ultrafiltration system to improve its feed water quality and prolong the lifetime of the membranes. The methods include the following: Coagulation, Biofiltration, Mechanic Filtration and reuse of the old HydraCAP 60 membranes. The specific parameters in which will be used to compare between each method and to assess their feasibilities will be the following: Energy usage, water usage, speculation on membrane performance, efficiency, and water quality. The most appropriate method will be suggested and presented to the company.
The results showed that the most ideal situation would save a total of $422,938 USD, an increase of 44.8% in savings and the least cost saving option would still save up to $287,164 USD, an increase of 10.2%.
Both technologies provide low carbon foot print, lower cost and better water quality than the conventional system. While the conventional system is highly dependent on the source water quality, the membrane filtration system is able to remove pathogens and other suspended matter independent to the source water conditions. The mechanism for removal of particulate matter in a membrane is a physical sieving process where particulates larger than the pore size of a membrane are physically excluded from the water passing through the membrane surface. This process does not rely on the performance of a reactor, chemical dosing or any alterations for the operation of the membranes. It is flexible to the flow rates, pH levels and temperature fluctuations of the water source. However, there are limitations: the main concern is the membrane fouling, which is described as the accumulation of particles on the surface and inside the pores of the membrane surface. The source of membrane fouling may be silt, bacteria, organic fouling or low feed water quality in general. The effect of membrane fouling on the efficiency of the membrane reduces the water quality and membrane lifetime. Furthermore, it reduces the flux, in which requires the system to increase its pumping intensity to maintain a consistent volume of water being treated, hence increasing energy consumption.
As mentioned before, the goal is to explore different sustainable and affordable pretreatment methods for the pre-existing ultrafiltration system to improve its feed water quality and prolong the lifetime of the membranes. The methods include the following: Coagulation, Biofiltration, Mechanic Filtration and reuse of the old HydraCAP 60 membranes. The specific parameters in which will be used to compare between each method and to assess their feasibilities will be the following: Energy usage, water usage, speculation on membrane performance, efficiency, and water quality. The most appropriate method will be suggested and presented to the company.
The results showed that the most ideal situation would save a total of $422,938 USD, an increase of 44.8% in savings and the least cost saving option would still save up to $287,164 USD, an increase of 10.2%.
Result and Analysis
First, the extent of the problem was assessed, How many days did it take to fully exhaust a membrane? What is the turbidity of the feed water and the product water? What do the SDI results show? Having analyzed the current condition of the system, these data will be later used to project a series of scenarios according to each method, as mentioned before: Coagulation, Mechanical Filtration and Pre-UF. These methods are compared with the following parameter: Energy usage, Water usage. Membrane Performance, Water quality and Total Cost. The recommended method is based on the cost saving solution for the current system.
The methods explored are presented below and for the further comparison analysis, please see the document attached at the bottom of the page.
The methods explored are presented below and for the further comparison analysis, please see the document attached at the bottom of the page.
Method 1: Coagulation |
Method 2: Mechanical Filtration |
Method 3: Pre-UF |
The process of Coagulation, often recommended in wastewater treatment, is called flocculation. It refers to the process by which destabilized particles conglomerate into larger aggregates so that they can be separated from the wastewater treatment
Several studies conclude that chemical clarification pretreatment of treat water prior to MicroFiltraion/Reverse Osmosis provides stable operation of high recovery Reverse Osmosis processes. However, the chemical clarification of UF requires design and operation that is outside of normal practice. In other words, they indicate that in order to ensure the decrease of membrane fouling, the feed water needs various chemical tests and constant monitoring, especially under constant change of temperature and conditions. |
Mechanical filtration is a process in which contaminants in a waste stream are filtered or screened out. This method is effective in preventing particles, even very tiny ones like mud and sludge, from moving downstream. Amiad Water Systems has developed a series of self-cleaning mechanical filtration systems intended for the drinking, irrigation and the industry.
The Amiad System offers a relatively inexpensive capital cost of equipment that is 30-50% lower than the conventional systems. Secondly, the water required for backwash is estimated to be less than 1% on the mechanical filters compared to the 5-7% usage by the conventional multimedia system. Furthermore, these filters require a smaller footprint and less complicated valving arrangements nor requiring any chemical flocculation. At last, it is energy cost efficient with only 2-7 psi operating range across a screen filter. |
The UF offers a relatively inexpensive capital cost of equipment that is 30-50% lower than the conventional systems. The water required for backwash is estimated to be less than 1% on the mechanical filters compared to the 5-7% usage by the conventional multimedia system. Furthermore, these filters require a smaller footprint and less complicated valving arrangements nor requiring any chemical flocculation. At last, it is energy cost efficient with only 2-7 psi operating range across a screen filter.
Using exhausted HydraCAP 60 is more efficient on lowering the turbidity of the feed water than any other method suggested above. As opposed to mechanical filtration, the PSD won’t be necessary since the pore size of the membranes will be so small such that it can withhold most particles. However it takes more analysis to observe the cost efficiency using this system over long term. |
Recommendation & Conclusion
It is recommended to perform a Particle Size Distribution Test to assess the particle sizes. The followings are recommendation for three potential test results.
1. If the particles are either mostly bigger than 10 micron (smallest filter size from Amiad SAF 1500) or equally distributed, then it is advised to use the Amiad SAF 1500 as pretreatment. However, the potential risk lies on the consistency of the individual particles. If the particles are soft, regardless of its size, the filter will be less efficient and the rate of membrane fouling will not decrease significantly.
2. If the particles are mostly smaller than 1 micron, it is recommended to use the Pre-UF. Although the Pre-UF system requires a significantly higher energy and water consumption, it is not dependent to the particle sizes and it will effectively retain particles as small as 0.2 microns. However, the potential risk lies on the rate of the membrane saturation.
3. If the particles are equally distributed, it is recommended to use the Amiad SAF 1500 as pretreatment. However, as mentioned before the potential risk lies on the consistency of the individual particles. If the particles are soft, regardless of its size, the filter will be less efficient and the rate of membrane fouling will not decrease significantly.
Complete Report with Data Analysis see below.
1. If the particles are either mostly bigger than 10 micron (smallest filter size from Amiad SAF 1500) or equally distributed, then it is advised to use the Amiad SAF 1500 as pretreatment. However, the potential risk lies on the consistency of the individual particles. If the particles are soft, regardless of its size, the filter will be less efficient and the rate of membrane fouling will not decrease significantly.
2. If the particles are mostly smaller than 1 micron, it is recommended to use the Pre-UF. Although the Pre-UF system requires a significantly higher energy and water consumption, it is not dependent to the particle sizes and it will effectively retain particles as small as 0.2 microns. However, the potential risk lies on the rate of the membrane saturation.
3. If the particles are equally distributed, it is recommended to use the Amiad SAF 1500 as pretreatment. However, as mentioned before the potential risk lies on the consistency of the individual particles. If the particles are soft, regardless of its size, the filter will be less efficient and the rate of membrane fouling will not decrease significantly.
Complete Report with Data Analysis see below.
Formal Proposal |