Membrane processes generally refer to a broad range of membrane types: microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO). The first two are simple solids separation techniques, with the latter two providing molecular separation of organics or even salts. A large array of experience exists in applying all of these membrane processes in pressure vessels, as shown in the water reuse campus in Scottsdale, AZ. There, the largest of more than 20 municipal reuse facilities in the US treats up to 10 mgd of raw sewage to potable quality for aquifer recharge trough MF and RO operated in series.
Submerged membranes, driven by basin-head and vacuum pumping downstream, are emerging as an extremely viable treatment process, cutting down on infrastructure cost through reuse of existing basins.
In wastewater, the membrane bioreactor (MBR) process applies micro- or ultrafiltration membranes that are located directly in the aeration tank for the separation of mixed liquor solids from treated effluent. When applied in this manner, membranes replace at least two steps of conventional facilities: final clarifiers and effluent filtration, up to advanced tertiary quality. Depending upon the actual membranes employed, bacteriological control is also achieved, reducing and sometimes eliminating the need for further disinfection.
MBR is becoming more viable as membrane costs continue to decrease, competition develops, and higher discharge quality is imposed. Because it is a compact process occupying as little as 15 to 30 percent of more traditional, comparable processes and requiring minimal plant site and therefore less costly odor control it is a good-neighbor technology. Further, the process can be retrofitted into existing basins, automated quite easily, and is extremely reliable in that its performance is not subject to the more fickle gravity sedimentation techniques commonly used.
Similar arguments push the application of membranes in potable water: reduced footprint, easy automation, high quality of treated water, and operational reliability. And less chemical is required because of the physical barriers of the membranes, resulting in more effective removal of organics as well as microorganisms.
The largest submerged membrane system for drinking water clarification is currently under design in Singapore, where the Choa Chu Kang Waterworks is being upgraded to a capacity close to 100 mgd.
In wastewater, the membrane bioreactor (MBR) process applies micro- or ultrafiltration membranes that are located directly in the aeration tank for the separation of mixed liquor solids from treated effluent. When applied in this manner, membranes replace at least two steps of conventional facilities: final clarifiers and effluent filtration, up to advanced tertiary quality. Depending upon the actual membranes employed, bacteriological control is also achieved, reducing and sometimes eliminating the need for further disinfection.
MBR is becoming more viable as membrane costs continue to decrease, competition develops, and higher discharge quality is imposed. Because it is a compact process occupying as little as 15 to 30 percent of more traditional, comparable processes and requiring minimal plant site and therefore less costly odor control it is a good-neighbor technology. Further, the process can be retrofitted into existing basins, automated quite easily, and is extremely reliable in that its performance is not subject to the more fickle gravity sedimentation techniques commonly used.
Similar arguments push the application of membranes in potable water: reduced footprint, easy automation, high quality of treated water, and operational reliability. And less chemical is required because of the physical barriers of the membranes, resulting in more effective removal of organics as well as microorganisms.
The largest submerged membrane system for drinking water clarification is currently under design in Singapore, where the Choa Chu Kang Waterworks is being upgraded to a capacity close to 100 mgd.
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