Case Studies

Case Studies

Nanostone Water’s installed reference cases and multiple pilot studies throughout the world have helped to validate and optimize the performance of our ceramic membranes in a variety of applications highlighted below.


A Membrane System Retrofit-Rapid Valley Sanitary District Case Study

In 2017, the Rapid Valley Sanitary District was not able to reach its goal to deliver three million gallons per day (3 MGD) of drinking water to the community. The root cause was the unreliable and insufficient capacity from the existing polymeric microfiltration systems, which included a system for treatment of backwash from the three other skids. Above and beyond the capacity challenge in the winter, where near-freezing feedwater caused shrinkage in the polymeric membranes, the systems were subject to frequent fiber breakage and irreversible fouling. This problem was particularly exacerbated when the plant experienced turbidity spikes on incoming water quality as high as 15 NTU. Additionally, the constant fiber breakage issue required manual maintenance, creating an untenable situation for the operators. With the number of shutdowns for cleaning and maintenance, in addition to erratic feed water quality fluctuations, increasing along with the corresponding costs of chemicals and labor, the Rapid Valley Sanitary District knew they needed to replace rather than repair – but they didn’t want to replace PUF systems only to have the same problem in the future.

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After a system audit revealed an opportunity for Nanostone to help improve performance and reliability, the district installed its first set of Nanostone CM-151™ ceramic ultrafiltration membrane modules to replace the difficult-to-treat backwash recovery unit. The unique design of the CM-151 ceramic membrane necessitated fewer chemical cleanings, saving the plant 70% on chemical costs, and at the same time, increased the backwash system recovery rate from 80% to 92%, reducing operational headaches and many hours of labor.
Seeing the success of the backwash recovery system, the district retrofitted two out of the three racks of the main processing system with Nanostone CM-151 modules. The unique, patented monolith design of the CM-151 tolerated higher incoming water variability, helping restore Rapid Valley’s output to 3 MGD with only two systems running , as well as enable the plant to consistently and reliably pass its daily integrity test. The systems have also been able to handle feed water turbidity spikes. With the significant increase of the recovery rate of the backwash system, the recovery rate of the overall plant increased from 95% to over 98%.
Since investing in Nanostone’s CM-151™ ceramic UF system, the Rapid Valley operators have a stable, long-term solution for clean water and consistent volume. When the third rack is changed out, the overall capacity will be expanded to 5 MGD with the same footprint, enabling the community to have a resilient water system for current and future capacity needs.

A More Compact, Reliable and Robust UF solution for Xiaojihan Coal Mine Case Study

To meet the new Zero-Liquid Discharge (ZLD) regulations governing wastewater treatment, the Xiaojihan Coal Mine, a member of the China Huadian Group, had to expand the capacity of its wastewater management system.
The mine faced a number of issues with its existing wastewater treatment process, a submerged polymeric ultrafiltration (PUF) membrane system. As is often the case with PUF systems as they age, fouling had become a frequent issue, and the need to perform Clean-In-Place (CIP) had increased to multiple times a week. That, combined with frequent fiber breakage in the PUF membrane and subsequent failure of their downstream RO membrane, resulted in a treatment capacity that was below the plant requirements.

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Nanostone’s CM-151 ceramic ultrafiltration membrane system provided a clear choice to tackle Xiaojihan’s difficult-to-treat wastewater. The outstanding anti-fouling characteristic of the CM-151 ceramic membrane required fewer chemical cleanings. In addition, the unique, patented monolith design of the CM-151 tolerates higher incoming water variability, which optimized the overall process operation by eliminating the pre-filter step (see below). The absence of fibers in the ceramic matrix meant that fiber breakage would no longer be an issue. The CM-151 ceramic system provided more reliable and effective performance which, in turn, stabilized the downstream RO system and allowed Xiaojihan to meet and exceed its increased capacity demand.
The 9.2 MGD ceramic UF system helped the Xiaojihan Coal Mine meet all environmental regulations and optimize the entire treatment process. By investing in Nanostone’s CM-151 ceramic UF system, the mine operators have a robust, reliable long-term solution for consistent efficiency and quality.

Chemical Refinery Waste Water Reuse Case Study

A chemical refinery located in Qinghai China operated a non-biological waste water treatment plant with chemical precipitation followed by clarification, conventional media filtration, and finally with reverse osmosis (RO).

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The RO membranes failed after a short period of time due to high turbidity, high silt density index (SDI), and biological fouling. The more robust and longer lasting Nanostone Ceramic UF membranes were chosen over polymeric UF membranes to improve the system performance. After the Nanostone Ceramic UF membranes were installed, the water quality to the RO membranes was dramatically improved with SDI levels < 3 and turbidity < 0.1 NTU. The Nanostone Ceramic UF membranes operate very stable in dead end mode of operation at a flux rate of 170 LMH (100 GFD).

View the full case study with supportive charts by downloading the PDF.

Coal to Chemical Waste Water Reuse Case Study

Refining coal to other materials is known as CTX, and is a large industry in China. Waste water from the CTX process is difficult to treat industrial waste water. Regular biological treatment is not enough to meet discharge requirements and so the facilities must find ways to reuse this water prior a zero liquid discharge system. Ultrafiltration and RO are the technologies of choice in this application to enable water reuse. A ceramic UF membrane is a promising upgrade for those looking for a more robust UF choice for this type of waste water treatment.

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Refining coal to other materials, such as gas and liquids and gases, is known as CTX, and is a large industry in China. Waste water from the CTX process is difficult to treat industrial waste water. Regular biological treatment is not enough to meet discharge requirements and so the facilities must find ways to reuse this water prior a zero liquid discharge system. Ultrafiltration and RO are the technologies of choice in this environment. Some projects running with polymeric UF membranes are suffering the pain of constant membrane fouling and fiber breakage because of the complicated organic pollutants and high level of variation in water quality. Frequent cleaning of the membranes results in fiber breakage and shortened lifecycle. A ceramic UF membrane is a promising upgrade for those looking for a more robust UF choice for this type of waste water treatment.

View the full case study with supportive charts by downloading the PDF.

Cold Source Water for Industrial Makeup Case Study

Industrial companies require clean water for cooling, boiler makeup, and a variety of manufacturing processes. It is common to use ultrafiltration or microfiltration (UF/MF) membranes to treat the incoming water supply to reduce turbidity and suspended solids of industrial process water directly, or in use as pretreatment to protect the performance of Reverse Osmosis (RO) membranes.

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In many parts of the world, a surface water source will see low temperature periods during the 3-6 months of winter ranging from extremes of 0.3 to 5.0°C (32.5-41°F). For a polymeric MF/UF membrane plant operating in such cold conditions, the typical response is to reduce the flux during the cold periods. Where a plant would be designed for a flux rate of up to 45 GFD (76 LMH) at a temperature of 20°C (68°F), the same design would be reduced to just 28 GFD (48 LMH) if the temperature is reduced to 4°C (39°F), according to the design programs
of most manufacturers. This leaves the designer with two choices: 1) design the plant to reach a design flow rate at the cold condition by adding more membrane area and reducing the flux; or 2) reducing the output of the plant during cold conditions. In most industrial plants, the water demand is constant and so the flux of the polymeric membrane plant must be reduced to be able to keep up during the winter months. Polymeric membrane fibers constrict in extreme cold conditions, reducing the permeability beyond what the water viscosity change alone would predict. In some studies it is shown that there is a permanent permeability reduction from exposure to cold water conditions that never returns even when the water temperature rises. Other changes noted by polymeric membranes in cold conditions include: 1) increased fiber breakage, 2) increased backwash durations, and 3) less effective chemical cleanings.

With ceramic membranes, however, there is a much lower coefficient of expansion due to temperature, and so there is no observed change in permeability beyond the change in water viscosity. This means that a plant can simply size the feed pump to run at a higher pressure during the cold periods without needing to reduce the plant output.

View the full case study with supportive charts by downloading the PDF.

Power Plant Boiler Feed Water Makeup Case Study

Around the world, end users who have had a poor experience with PUF membranes are looking for more robust alternatives for their boiler feed water makeup system. The Nanostone CM-151 CUF membrane has a similar process design to PUF and can directly replace PUF modules with minimal changes to the rest of the system.

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Power producers require clean water for cooling and boiler makeup. Typically, a power plant will use surface water or treated municipal waste water discharge as a water source. The typical approach is to use clarification and filtration to pretreat the water to a quality level appropriate for cooling water makeup. For the boiler feed water
makeup system, it is common to use ultrafiltration or microfiltration (UF/MF) membranes to further treat the clarified water as a pretreatment step to protect the performance of Reverse Osmosis (RO) membranes used in the high purity water treatment system. This case study is just one example of a direct retrofit of PUF membrane
modules to provide the end user with a much more robust and reliable filtration technology than what PUF can accomplish.

View the full case study by downloading the PDF.