Electrolysis: processes – compositions used therein – and methods – Electrolytic synthesis – Preparing nonmetal element
Patent
1998-08-17
2000-07-04
Phasge, Arun S
Electrolysis: processes, compositions used therein, and methods
Electrolytic synthesis
Preparing nonmetal element
205688, 205742, 205743, 205745, 205761, C02F 1461
Patent
active
060833777
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the treatment of polluted or contaminated water by electrochemical treatment (which includes both galvanic and electrolytic treatment). The invention is intended to be applied to waters contaminated by dissolved nitrogenous compounds.
In conventional cases where electrolysis has been used for treating contaminated water, the reactions that have been utilised have been those, for example, which take metals out of solution by cathode deposition.
Work has been done on the use of electrolysis for treating effluent from manufacturing establishments, where the water is polluted with a specific pollutant. But those systems were special in that the effluent water was already contained, and the research effort was directed to cleaning up or recovering specific contaminants, at known concentrations, and in a system that was designed to cater for the pollutant when the factory was built.
Ammonium (NH.sub.4.sup.+) in sewage water can be broken down by bacterial action. Much consideration and effort has been applied over many years to engineering the ammonium breakdown reaction on a large scale, in the context of municipal sewage water treatment. Generally, bacteria promote oxidation of the ammonium into nitrate; other bacteria then promote denitrification or reduction of the nitrate to nitrogen gas. The reaction has been engineered by providing an environment in which bacteria can effect the oxidation and reduction.
Some shortcomings of this conventional procedure will now be discussed. The biological oxidation of ammonium to nitrate and the subsequent reduction of the nitrate to nitrogen gas, has undesirable side-effects. Other compounds of nitrogen are formed, such as nitric oxide (NO), nitrous oxide (N.sub.2 O), and nitrogen dioxide (NO.sub.2), which are considered to be either directly toxic to humans and other animals, or harmful to the ozone layer or other aspects of the environment.
One problem is that the conversion of ammonium to nitrogen, via nitrate, done microbiologically, as in the conventional systems, has been far from complete. Significant quantities of the nitrogen oxides can be released, as gases, during the reactions, in addition to the nitrogen gas. When, as in the conventional systems, the oxidation of ammonium /ammonia occurred biologically (nitrification), the reaction pathway may be described as: O).fwdarw.NO.sub.3.spsb.- atmosphere.
Also, the nitrate produced by the ammonium breakdown cannot be left in the water. And nitrate itself, for example from agricultural run-off, may be present as a nitrogenous contaminant per se, in groundwater.
When the reduction of nitrate occurred biologically (denitrification), the reaction pathway may be described as: O.fwdarw.N.sub.2
Another point that should be noted is that the efficiency of the conventional biochemical nitrification and denitrification reactions is affected by cold weather, whereby it is found that the gases released to the atmosphere in the winter contain an even larger proportion of N.sub.2 O and NO.sub.x gases. This is a marked disadvantage of the conventional systems. In some cases, also, the temperature can be so low that biological reactions substantially do not take place at all, and breakdown of the contaminants has to await warmer weather.
It is recognised that the electrochemical reactions as described herein have the potential to proceed at lower temperatures than the conventional biological processes. They may therefore be suitable for cold-climate applications, where biological remediation is ineffective for most of the year.
GENERAL FEATURES OF THE INVENTION
It is recognised in the invention that, in order to remove nitrogenous contamination, the nitrogenous contaminants can be transformed, by engineered electrochemical processes, directly into nitrogen gas. (Nitrogen gas of course already comprises 4/5 of the atmosphere, and its release is not harmful.)
It is also recognised that inorganic electrochemical reactions can be used to drive both kinds of breakdown reaction, i.e the oxidation of e.g ammon
REFERENCES:
patent: 5565107 (1996-10-01), Campen et al.
patent: 5614078 (1997-03-01), Lubin et al.
Chesworth Ward
Lin Mei
Shelp Gene S
ENPAR Technologies Inc.
Phasge Arun S
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