Optics: measuring and testing – For light transmission or absorption – Of fluent material
Reexamination Certificate
1999-11-19
2001-10-23
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
For light transmission or absorption
Of fluent material
C356S339000
Reexamination Certificate
active
06307630
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to turbidimeters and their use in monitoring the turbidity of water (e.g. drinking water). More particularly, this invention relates to the use of a turbidimeter to monitor the effluent from membrane filters.
BACKGROUND OF THE INVENTION
Many water plants which are used to produce drinking water utilize membrane filters (e.g. micro-filtration, ultra-filtration, and nano-filtration). Typical ultra-filtration membranes have an effective pore size of less than 0.1 micron which means that not only do they completely remove most bacteriological pathogens, but they also have the capability to filter out most viruses. The California Department of Health and other state and federal agencies are considering means by which they can offer virus removal credit to water plants which adopt ultra-filtration technology. If adopted, water plants will be able to save very significant amounts of money by avoiding the costs associated with chemical disinfection of drinking water.
A serious disadvantage associated with the use of filtration membranes is the periodic failure or rupture of a membrane. Typically there are thousands of relatively small diameter elongated membrane fibers contained in a parallel arrangement in a single cartridge, with numerous cartridges (e.g. 1000 or more in racks of 20 to 50) being used simultaneously in a single water plant. Presently, the operator of the plant periodically (e.g. every four hours or so) takes each rack off-line and passes air through one end while the other end is submerged in water. Below a certain air pressure, air should not be able to pass through a membrane, unless the membrane has been punctured or has ruptured. If the membrane has ruptured or been punctured, a stream of bubbles will be detected from that membrane at the submerged end. The failed membrane can then be identified and mechanically plugged, after which the cartridge can be put back into service. The main problem with this approach is that it allows for a four to six hour period during which undesirable material could pass through the cartridge and enter into the effluent water.
Although manufacturers have provided turbidimeters and particle counters for on-line monitoring of water quality, those instruments generally lack sensitivity to sub-micron particles. Furthermore, a full scale water plant would require several hundred membrane cartridges, and the instrumentation costs for monitoring the effluent of each membrane would be prohibitive.
There has not heretofore been provided a system for accurately and efficiently monitoring the effluent of multiple membranes used for ultra-filtration of water.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a turbidimeter system for efficiently monitoring the effluent of a plurality of membrane cartridges comprising a membrane filtration plant.
It is another object of this invention to provide a turbidimeter system in which a plurality of sample chambers are used.
It is a further object of this invention to provide a turbidimeter system with an array of sample chambers and in which a common light source and a common detector are shared for turbidity testing of separate liquid samples contained in the separate chambers.
To accomplish the foregoing and other objects, the present invention provides a turbidimeter array system comprising a plurality of sample chambers for containing a liquid sample to be tested, and wherein the system includes a common light source and a common detector means. In other words, the system includes a plurality of sample chambers which share a common light source and a common detector when a turbidity measurement is made of the liquid in a particular chamber.
In one embodiment, a single light source is adapted to sequentially direct a light beam into each of the sample chambers, and the detector means is adapted to detect light which is scattered by the liquid sample in each of the sample chambers. In another embodiment, a single light source is adapted to direct a light beam to all of the separate sample chambers simultaneously, and a detector is adapted to sequentially detect scattered light from each of the sample chambers. For example, a shutter at each chamber can be moved from a closed position to an open position to allow the light beam to pass into one chamber at a time, and scattered light from that particular chamber is detected by the sole detector. In yet another embodiment, a separate light source is used for each chamber, and a common detector is used to sequentially measure scattered light from the different chambers.
The system of this invention enables efficient monitoring of the turbidity of a plurality of liquid samples contained in a plurality of separate chambers, without requiring a separate light source and separate detector for each sample chamber. Rather, in a preferred embodiment the system utilizes a common light source, detector means, associated control electronics, display, etc.
Other advantages and features of the turbidimeter array system of the invention will be apparent from the following detailed description and the accompanying drawings.
REFERENCES:
patent: 4534651 (1985-08-01), Minikane
patent: 4549809 (1985-10-01), Minekane et al.
patent: 4639137 (1987-01-01), Hazan et al.
patent: 4826319 (1989-05-01), Namba et al.
patent: 4888484 (1989-12-01), Harvey
patent: 6134000 (2000-10-01), Schmid et al.
Edmundson Dean P.
Hach Company
Pham Hoa Q.
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