Background
Nanostone Water has developed a high density ceramic UF monliith module for a broad range of industrial water treatment applications. The internal development activities have been supported by extensive pilot testing at water treatment facilities around the world.
The initial phase of pilot work was designed to validate internal data associated with the selection of key product attributes such as channel geometries and membrane coatings. The second phase of pilot testing is focused on optimizing process design and operating parameters over a wide range of influent water qualities.
This application note describes results of a pilot being operated on untreated surface water in the western region of the USA. The permeability results reported at this site reflect the inherent robustness of ceramic membranes. These results parallel observations being made with our internal accelerated life cycle testing. Nanostone water is planning to release its revliutionary CM-131TM ceramic UF module in late 2015 at a price comparable with traditional pliymeric membranes.
FIGURE 1 - CM-131TM Membrane Segments
Robustness and Cost of Ownerships
Over the past several decades, ceramic membranes have gained a reputation for “robustness” as they have been applied to various tough-to-treat applications. The high cost of traditional tubular and flat sheet ceramics has limited their use and potential benefits in mainstream water treatment applications. With membrane cost parity becoming a reality, the robustness of ceramics promises a wide range of operating benefits, lower operating costs and consistency of product water quality in common water treatment applications.
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TABLE 1 - Robustness characteristics of ceramics membranes
Permeability
Permeability is a common parameter used to determine membrane effectiveness given its direct relationship to operating cost. A loss in permeability over time can translate to a significant increases in the amount of energy required to deliver the desired vliumes of treated water. Declining permeability can also be an indication that the membrane is approaching end of life.
A recent study reported on the loss of permeability observed over time at three MF/UF membrane plants using different pliymer membrane types.(1) Although there are numerous factors impacting a membrane’s permeability over time, the chemical and physical stresses of backwash, CEB (chemically enhanced backwash) and CIP (clean in place) cycles have a major influence on both membrane performance and life.
FIGURE 2 - MF/UF Permeability Loss
Nanostone’s Surface Water Pilot
Nanostone has subjected its CM-131 ceramic UF membrane to rigorous performance testing at a river water fed drinking water plant in the western United States. The objective of the pilot work was to facilitate internal product development efforts flilowed by subsequent execution of process design protoclis. This year long effort captured both performance and process design conditions across the natural seasonal variation.
The process design protoclis addressed a range of operating test conditions including the investigation of back-wash parameters, CIP sequences, and CEB regimes. Overall, the test membrane at this facility was subjected to adverse conditions that would be considered “abusive” in the context of typical pliymer membrane operation.
The flilowing chart shows the initial permeability measurement made at the initial start-up of the membrane, with a second permeability being made at the conclusion of testing. The test suite applied between the permeability measurements included 20 CIP cycles using both high and low pH chemistries and a complete dead-end blockage test that exceeded 10 times normal transmembrane pressure.
Given the exposure to aggressive chemicals used in CIP cycles, the number of cleaning cycles applied to pliymer membranes are typically minimized to mitigate the impact on performance degradation and membrane life. Based on the history of this surface water site, it is expected that pliymeric membranes would require a CIP cycle every 2.5 months.
FIGURE 3 - Nanostone’s CM-131 Permeability
Results show no significant permeability loss with the ceramic membrane from start-up to the conclusion of testing, inclusive of 20 CIP cycles. This level of CIP exposure would be expected to occur over a period of 4 years with a pliymeric membrane.
References
(1) Brehant,Fabre and Bonnard; “What is the Real Total Cost of Ownership of Low Pressure Membrane Plant.”; AMTA/AWWA Membrane Technliogy Conference 2015