Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
2002-09-11
2004-11-02
Nicolas, Wesley A. (Department: 1742)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C204S229200, C205S742000, C205S744000, C205S759000, C205S766000, C205S769000
Reexamination Certificate
active
06811660
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method and an apparatus for cleaning methane fermentation digestion liquids, domestic wastewater, sewage, service water, culture pond water, wastewater produced by an activated sludge method, wastewater from food industries and the like.
BACKGROUND ART
Contamination of water environments is being made more and more serious by developments of industries and economy as well as rising of living levels of human lives. Eutrophication of water areas is made serious by nitrogen, phosphorus and the like which are contained in wastewater produced by agriculture and human lives. Furthermore, health of mankind is threatened by increase of organic matters, organic chlorine compounds, aromatic compounds, environmental hormones and the like contained in industrial wastewater. It is deemed difficult to completely treat such contaminants by a traditional water treating method such as a biological method. Under the present circumstances where legal regulations on environments are being strengthened, on the other hand, it is desired to construct an efficient wastewater treating system in order to maintain a stable ecosystem for a long time and preserve water resources having high safeties. It is therefore attempted to develop a new water treating technique which is to take the place of the biological method and an organic wastewater treatment by an electrochemical technique has been developed in recent years in particular.
A characteristic of the electrochemical treating technique lies in integration of technologies in different domains (for example, electronic engineering, catalytic technology, physical chemistry, microbiology and the like) and fusing techniques in different fields, thereby treating organic wastewater containing contaminants which are deemed hardly decomposable by the biological method.
The electrochemical treating technique is not only capable of removing solid matters and green powder contained in wastewater with a high efficiency without using a flocculant agent and suppressing a running cost at a low level but also produces sludge in an amount smaller than that of sludge produced by the biological treating method and allows the sludge to be reutilized as a fertilizer since the electrochemical technique does not use chemicals.
The electrochemical treatment has a floating function, an agglomerating precipitating function and an oxidizing function. The solid matters and the organic dissolved matters contained in soil water are removed by these three functions. Out of these functions, the oxidizing function is the most important and can be divided into direct oxidation and indirect oxidation. The direct oxidation oxidizes an organic matter directly on a surface of an oxidized metal by a catalytic function of the oxidized metal such as titanium oxide, tin oxide or the like. The indirect oxidation oxidizes with an
−
OH radial generated from water by anode discharge.
A reaction formula is:
H
2
O+M[ ]→M [
−
OH]+H
+
+e
−
(1)
A reaction formula of the organic matter by hydroxyl radicals is:
R+[
−
OH]→M [ ]+RO+H
+
+e
−
(2)
wherein a reference symbol M [ ] represents an active site on the surface of the oxidized metal and a reference symbol R designates the organic matter.
Ozone sending and irradiation with ultrasonic waves or electromagnetic ultrasonic waves are available as methods to generate oxygen radicals and hydroxyl radicals. Furthermore, though there has been developed a method which uses an optical catalytic reaction by titanium oxide, this method generates radicals in an amount small for a high input electric power, decomposes injurious materials with a low efficiency and requires a high cost of an apparatus. Furthermore, ozone is not effective for fresh water though ozone is deemed effective for sea water containing large amounts of bromine and manganese.
Furthermore, attention is paid to use of a transition metal such as cobalt, manganese or the like in combination with hydrogen peroxide. Though it is known the combination of the transient metal and oxygen peroxide generates radicals at an efficiency higher than that of ozone, this method require a delicate technique and final treatment of hydrogen peroxide in an outlet port since hydrogen neroxide has a variability for organisms high enough to be inhibited from being added to food.
It is known that the electrochemical treating method allows oxygen radicals and hydroxyl radicals to be generated with a lifetime of 10 &mgr;s to 100 ms from existing water molecules when electrons enter pores existing in a surface of a material which is composed of fine particles of titanium oxide, tin oxide, ruthenium oxide, platinum or the like (see specification of Japanese Patent Application No. 11-68862). It is known that this radical oxidatively destructs organic substances including carbon sources and nitrogen sources as well as hardly decomposable aromatic substances contained in water.
It is indicated that a specific condition of an electric field to be applied between electrodes exists and it is necessary to prolong a time of contact between wastewater and a surface of a metal oxide for generation of the oxygen radicals and hydroxyl radicals with a high efficiency on the surface of the metal oxide, that it is necessary to clean surfaces of electrodes by transmitting ultrasonic waves when a large amount of floating suspended matters are contained in wastewater, and that a voltage, a current and an electric field frequency are governed by movements of electrons on the surface of the oxidized metal or the surface of the metal.
Since an invention described in the specification of the above mentioned application poses a problem that generation of superoxide radicals is insufficient in a high frequency region and excessive in a low frequency region, a problem that a current is unstable during treatment of wastewater containing a large amount of ions and the like, it is necessary to establish a treating method by combining a low frequency low current with a high frequency slight current and contrive to stabilize voltage pulse application when electric resistance of raw water changes during a treatment.
In order to solve the problems posed by the invention described in the specification of the above mentioned application, the applicant applied “Method and Apparatus for Cleaning Dissolved Organic Matters and Trace Amount of Injurious Materials” (Application 2000-29570 hereinafter referred to as “specification of preceding application”) on February 2, Heisei 12.
An invention described in the specification of the preceding application disclosed a water purifying method characterized by coating a surface of a ceramic having a main body of feldspar or silicon with fine particles of titanium oxide, cobalt oxide, tin oxide, ruthenium oxide, iridium oxide, nickel oxide, iron oxide and vanadium oxide, fine metal particles of titanium, cobalt, nickel, silver and gold or a liquid consisting of a mixture these metals and a solution of the same kinds of metal salts, using as an electrode having a positive polarity the above described metal oxides or metals or the mixture thereof sintered in a temperature region of 800° C. to 1500° C. after a drying treatment and disposing an electrode which has a cathode made of platinum or titanium or stainless steel so as to be opposed to an anode for use of these electrode as a radical generating zone, continuously flowing wastewater between both the electrodes of these electrodes opposed to each other, causing pulse discharge between the electrodes under conditions of a voltage of 0.2 kV/cm to 20 kV/cm, an average current of 1 &mgr;A/cm
2
to 10 mA/cm
2
and a frequency of 5 Hz to 50 MHz, thereby generating radicals by partial decomposition of water and oxidatively-reductively decomposing organic matters and intermediate products thereof dissolved in water.
Furthermore, the invention described in the specifi
Nicolas Wesley A.
Westerman Hattori Daniels & Adrian LLP
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