Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
1999-09-22
2001-11-20
Barry, Chester T. (Department: 1724)
Liquid purification or separation
Processes
Treatment by living organism
C210S150000, C210S620000, C210S758000, C210S739000, C210S220000
Reexamination Certificate
active
06319407
ABSTRACT:
The present invention relates to a system as defined in the preamble of claim
1
. Moreover, the invention relates to a system as defined in the preamble of claim
12
.
In particular, the invention concerns a method and system for the purification of waste water produced by residential areas and industry, e.g. paper and pulp industry, that allow a considerably more effective and cheaper treatment of waste water to remove e.g. organic matter (so-called BOD
7
reduction), nutrient compounds, dyes and organic chlorine compounds dissolved in it than is possible with the methods currently used.
At present, the most commonly used biological process used in waste water treatment is the so-called activated sludge process, of which there are several variants in use. These methods use various expedients to increase the efficiency of the process, e.g. reactor spaces or sub-processes arranged in cascade or separated by partitions, use of pure oxygen, various solid supports, chemicals, etc. If nitrogen or phosphor is to be removed, separate units are often needed. However, almost all variants of the activated sludge process are still based on conventional aeration and separation of solids from water by sedimentation and on sludge return. These processes require large preliminary and final sedimentation plants, and the investment costs for these may amount to as much as one half of the total investment costs of the waste water treatment plant as a whole. Consequently, sewage treatment plants are structurally large, complex and expensive.
The object of the present invention is to eliminate the drawbacks described above and in particular to disclose an efficient and advantageous method and a system that takes up only a small space and obviates the need for preliminary and final sedimentation plants involving high investment costs.
The method of the invention is characterised by what is presented in claim
1
. The system of the invention is characterised by what is presented in claim
12
.
According to the invention, all purification functions, including nitrogen and phosphor removal, are performed in one and the same reactor vessel containing solid support to increase the biomass. In the vessel, oxidation and reduction zones, either predetermined or changing according to a given program, are created in the waste water mass flowing through it by supplying gas mixtures having an optimal oxygen content into the flow at different points in the direction of flux. The solid support and the biomass (microbial mass) adhering to it can be moved automatically e.g. by means of a suitable transfer gear, causing the biomass adhering to the solid support to move rapidly from zone to zone so that it is subjected to abruptly changing conditions. Alternatively, the solid support can be held stationary while periodically alternating oxidation and reduction conditions are created at the same point in the reactor vessel so that the biomass adhering to the solid support is subjected to abruptly changing conditions. In both cases, the phosphor in the biomass is alternately dissolved and bound in biomass growth; nitrogen compounds are oxidised, to be reduced in the next zone into nitride and further into nitrogen gas, which can be recovered or removed into the atmosphere. The amount of solid matter (biomass) in the reactor is regulated by removing activated sludge directly from the reactor basin into sludge treatment via a flotation compaction stage.
A significant advantage in a purification plant constructed according to the invention is that it obviates the need for sludge return and conventional preliminary, intermediate and final sedimentation, with the result that the investment costs are substantially lower, only a fraction of the conventional costs. Also, the size of the treatment plant is substantially smaller than that of a conventional plant. A further advantage of the invention is that the process works with large amounts of biomass, so it is not sensitive to variations in the quality of the incoming waste water. Moreover, control and regulation of the process are easier than in conventional processes.
Other preferred features and embodiments of the method are presented in the sub-claims.
In the system of the invention, the means for carrying out purification operations comprise a reactor vessel in whose interior different alternating oxidation and purification zones are so arranged that all purification operations for waste water treatment take place in one and the same reactor vessel while each purification zone performs a mainly predetermined purification operation and the waste water is subjected to all of the various purification operations as it passes through the reactor vessel. The solid support for increasing biomass and the biomass adhering to it are arranged to be exposed to successive oxidation and reduction operations in oxidation and reduction zones. A gas distributor is arranged to produce in each zone a gas mixture with an optimal oxygen content as needed for the purification operation to be performed in that zone, producing oxygen-rich gas with a 30-50% oxygen content for the oxidation zones and low-oxygen gas with a 0-5% oxygen content for the reduction zones. In a flotation zone, solid matter is brought to the surface by means of a small flotation unit and removed automatically as surface sludge e.g. by means of a floating knife.
The invention has the advantage that, as all the operations and sub-processes associated with waste water purification take place in one and the same reactor space, simultaneously using a solid support at each stage and a suitable gas mixture instead of air or pure oxygen in each sub-process, a particularly efficient purification process and system requiring only a small space is achieved. In the same space, different zones are created in which the various purification operations take place. Since the method does not involve any preliminary, intermediate or final sedimentation, each of which would require a special sedimentation basin and sludge return into the process, the number of parts comprised in the system is significantly reduced and a very advantageous system in respect of costs is achieved.
In an embodiment of the system, the boundary between the conditions in adjacent purification zones is a stepless boundary.
In an embodiment of the system, the purification zones are arranged horizontally one after the other, with the waste water flowing in a horizontal direction in the reactor vessel.
In an embodiment of the system, different conditions in respect of oxygen content are created in the purification zones by using different gas mixtures and/or a flow of gas mixture.
In an embodiment of the system, the gas mixture comprises air, oxygen, nitrogen and/or carbon dioxide or some other suitable gas.
In an embodiment of the system, the reactor vessel comprises partitions provided with flow-through openings.
In an embodiment of the system, biomass containing plenty of bacteria is placed in the reactor vessel.
In an embodiment of the system, the solid support comprises substantially long bristle-like hairs tied in bundles like those in a brush and attached to a device provided with a drive means so that the entire solid support and the biomass adhering to it or desired parts of it are automatically moved from zone to zone in accordance with a predetermined program.
In an embodiment of the system, the solid support comprises substantially large pieces of inert solid material which are buoyant, suspended, stationary e.g. sheets and/or tied to stationary cages or the like.
In an embodiment of the system, the solid support comprises substantially small pieces of solid, porous and/or filamentous structure.
In an embodiment of the system, the solid support comprises fine-grained material particles.
In an embodiment of the system, the system comprises means for generating a pressure and/or vacuum in the interior of the reactor vessel.
In an embodiment of the system, the system comprises means for changing the temperature of the water flowing in the reactor vessel,
M{umlaut over (aa)}ttä Raimo
Viitasaari Matti
Villarreal Antonio
Altera Law Group LLC
Barry Chester T.
Sakkivaline Oy
LandOfFree
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