Membrane technology application: flexible and economical water treatment techniques
Membrane technology is a new technology that can be used flexibly. This article introduces two application cases of membrane technology in practical engineering. The water supply department of Carmichael City, California adopted the MEMCOR® continuous microfiltration system to treat backwash wastewater, which on the one hand increased the water recovery rate, and on the other hand reduced the final wastewater discharge; Oconee County Sewage Treatment Plant in Georgia introduced MemJet membrane-bioreactor Greatly improve its processing capacity.
Many communities now mostly rely on membrane filtration water treatment systems to solve current water treatment problems. The following discussion is the application of this flexible new technology-membrane technology.
The first case is in Carmichael, California. The local water supply management department uses the MEMCOR® microfiltration system to treat river water and backwash wastewater to increase water recovery and reduce wastewater discharge.
The second case is in Oconee County, Georgia. The county’s sewage treatment plant used MemJetTM membrane-bioreactor as the core unit in water treatment to treat wastewater during its expansion.
Case 1 California’s strict standards
The Water Supply Department of Carmichael City (California State) is a government-owned and operated agency responsible for providing domestic water for approximately 39,000 residents in the suburbs of Sacramento County. Approximately 75% of the influent of the water supply plant comes from the American River, and the shortfall is supplemented by groundwater.
However, the California state government ordered the department to strengthen its treatment process for the inflow of the American River. To this end, the local water supply department needs to find a comprehensive treatment method. On the one hand, it must meet the strict standards of public health and safety, and on the other hand, it must ensure a good environmental condition of the riverbed near the river. In addition, the proposal for a solution must also be approved by the public.
With the assistance of the local design and engineering consulting company Montgomery Watson Harza and the public advisory team, the water supply department evaluated many traditional and non-traditional filtration methods, and finally selected membrane treatment technology, which was installed and implemented in the BajamontWay water treatment plant.
This decision is based on the following factors:
The pilot test results of MEMCOR® microfiltration technology are good. The MEMCOR® system has the ability to test the overall adhesion. USFilter, the supplier of MEMCOR®, has extremely competitive equipment prices. USFilter has practical engineering experience in sewage treatment plants
After being collected by the man-made Ranney well, the raw water of the American River flows through the pipeline buried under the river bed under the action of gravity to enter the membrane treatment plant, and then enters the membrane treatment system through the inlet water distribution box. The MEMCOR® continuous microfiltration system is installed in a single-story residential building. The building covers an area of 1.6 acres, and its architectural style is consistent with the surrounding community. The site was previously used to place maintenance equipment for water supply facilities.
There are 12 sets of microfiltration modules in the entire filtration system, and each microfiltration module contains 90 membrane modules. The average flow rate of the whole set of equipment during operation is 9 million gallons/day (about 34065 cubic meters/day), and the peak flow rate reaches 17 million gallons/day (about 64345 cubic meters/day). In order to maintain a stable water flow, the system runs a total of 11 microfiltration modules online at the same time, and the remaining 1 module is chemically cleaned.
The backwash wastewater of the microfiltration system is processed by another set of secondary microfiltration system. The system contains 2 sets of microfiltration modules and a total of 96 membrane modules, which can treat and recover 90% of the backwash water, with a total of about 600,000 gallons/day. Under the action of the primary and secondary microfiltration system, the plant can treat 99% of the incoming water into potable purified water.
According to the California State Health Service Department’s regulations, the filtered water from the secondary treatment must be returned to the source of the water plant for reprocessing.
In late 2002, the newly added three-stage treatment system-including 2 continuous microfiltration modules and a total of 12 membrane modules-was used to treat the backwash water of the secondary microfiltration. Since then, the water recovery rate of the entire water plant has increased to 99.96%.
The application of membrane technology has achieved good results
After the MEMCOR® continuous microfiltration system was installed in the BajamontWay sewage treatment plant, the effluent quality has been greatly improved. The turbidity of the effluent of the water plant has been below 0.05NTU; in addition, the operator uses a fully automatic and sensitive integrated test system to verify that the reduction of pathogenic microorganisms reaches 4 logarithmic orders (4-log). This makes it easy for the system to meet current and future drinking water supply standards.
After the continuous microfiltration system was installed in Carmichael City, it not only improved the water quality of the water supply, but also reduced wastewater discharge to a minimum through the backwash water recovery system. This measure protects the appearance, biological and environmental quality of the American River.
Since the installation of the new treatment system, the sediment discharge of the system has been reduced by 80%. The online monitoring function of the overall tightness of the system and the lower maintenance costs of the machinery have greatly reduced the operating costs and wages of the system.
Case 2 Membrane system used in sewage plant expansion
The service area of CallsCreek sewage treatment plant includes remote areas in Watkinsville, Georgia and Oconee County. In order to protect water resources to meet commercial needs, the area has long had a policy restricting the use of treated wastewater for residents’ lives.
The wastewater treatment plant used USFilter’s EnvirexOrbalTM biological treatment process before. The core of this process is a three-channel circulating activated sludge treatment system. During the pilot test, USFilter combined the MemJetTM membrane-bioreactor as a tertiary treatment process with the previous OrbalTM treatment facility.
After the successful pilot test, USFilter installed a MemJetTM membrane-bioreactor with an output of 1 million gallons/day to achieve a higher level of biological treatment. At the same time, the treatment capacity of the UV system was improved due to the increase in water transmittance. The plant is also equipped with two ultra-fine screens with an average pore size of 250 microns. All the influent water from the OrbalTM treatment system and the return water between the membrane system need to pass through this screen to remove inert solids in the water. Only then can it enter the membrane system. In addition, USFilter has also installed an edge flow processor in the micron ultrafine screen collection sump to further remove inert sediments.
The final step of biological treatment is the biological reduction of sludge in the Ultrair digester. This process can remove garbage and other inert substances in the activated sludge mixed liquid, so the processing capacity of the membrane-bioreactor can be improved.
After the expansion, the processing capacity of the CallsCreek sewage treatment plant will increase from 400,000 gallons/day (approximately 1,514 cubic meters/day) to more than 670,000 gallons/day (approximately 2536 cubic meters/day). With the economic development, the factory can install another set of membrane treatment system to increase the processing capacity to 1 million gallons/day to meet future demand, and even serve other regions.
With the installation of micron ultra-fine screens, sediment edge flow processors, and Ultrair bioreactors, the production of biological sludge has been reduced by more than half, and the final sludge discharge of the factory has also been greatly reduced.
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