Chemistry: electrical and wave energy – Processes and products – Electrostatic field or electrical discharge
Patent
1994-02-25
1995-08-01
Niebling, John
Chemistry: electrical and wave energy
Processes and products
Electrostatic field or electrical discharge
204152, 204130, C02F 1461
Patent
active
054377765
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for reducing the phosphorus content of waste water, which is conducted in a purification cycle through individual treatment tanks, such as preliminary treatment tanks, activation tanks, final sedimentation tanks, or the like.
The phosphorus and nitrogen content of the waste water supplies the nutrient basis for an often uncontrolled algal bloom, so that in any waste water treatment great attention has to be paid to reducing the phosphorus content, since precipitation of the phosphorus from the waste water provides a practical possibility to influence the formation of algae in the natural water bodies. So far, phosphorus and phosphates have been precipitated from the waste water by addition of chemical precipitating agents, such as iron salts or lime, this process however on the one hand causes high costs for the chemicals and on the other hand additionally pollutes the water with the chemicals.
Therefore it is the objective of the invention to remove these shortcomings and to provide a process of the kind mentioned above, which in an economical and also especially effective way allows a decisive reduction of the phosphorus content of the waste water, rendering superfluous to a great extent the addition of chemicals for phosphorus precipitation.
The invention achieves this objective by subjecting the waste water in one of the treatment tanks, preferably in the activation tank, to electrolysis, by means of metal electrodes and an electric direct voltage. The building up of an electric field in the waste water leads to chemical changes due to the electrode reactions and ion migration, which involve a surprisingly strong phosphorus precipitation, the phosphorus being enriched in the sludge and then withdrawn with the excess sludge from the purification cycle. The remaining residual part of the phosphorus is decomposed preferably biologically by microorganisms in the activation tank, so that a reduction of the phosphorus content of the waste water to a desired extent in a non-polluting way, without addition of chemicals, can be guaranteed.
Thus for example, in a sewage treatment plant for about 10,000 population equivalences, electrolysis was performed in the activation tank by means of two tubular electrodes of stainless steel (V4A) connected to a 24 V direct current supplying terminal, which have a length of about 180 cm and a diameter of about 15 cm and which immerse into the waste water with a mutual distance of about 50 cm, providing an approximately 90-95% reduction of the phosphorus content to a level clearly below the legally established limits without addition of precipitating agents, the electrodes having to be replaced after an endurance of some weeks.
FIG. 1 is a block diagram illustrating an embodiment of the invention.
In FIG. 1 an embodiment of the invention is illustrated in more detail.
In a sewage treatment plant 1, the waste water is subjected to a purification cycle, being conducted through an admission 2, a rain tank 3, an admission spiral pump 4, a raking and sandcatching device 5, a preliminary sedimentation tank 6, an activation tank 7 and a final sedimentation tank 8. A return sludge spiral pump 9 returns the sludge from the final sedimentation tank 8 partially before and partially after the preliminary sedimentation tank 6 back to the purification cycle, and the treated water flows from the final sedimentation tank 8 through the discharge 10 into a draining ditch 11. In the activation tank 7, metal electrodes 12, which are connected to a direct current supply terminal 13, immerse into the waste water, allowing an electric field to build up.
The waste water fed into the sewage treatment plant 1 reaches, after the mecanical purification by a raking and sandcatching device 5, the preliminary sedimentation tank 6, where denitrification takes place and most of the suspended matter settles. This primary sludge is withdrawn together with the excess sludge returned to the cycle from the final sedimentation tank 8, from the preliminary sedimentation tank 6 and
REFERENCES:
patent: 3971707 (1976-07-01), Deshpande
patent: 4204925 (1980-05-01), Coll-Palagos
English Language Dialog Abstract of JP 63-137795 Nov. 1986.
English Language Dialog Abstract of JP 52-109757 Sep. 1977.
English Language Dialog Abstract of JP 57-107289 Jul. 1982.
Lumetzberger Rudolf
Schwabegger Johann
Niebling John
Phasge Arun S,.
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