Liquid purification or separation – Processes – Chemical treatment
Patent
1987-01-07
1988-10-25
Sever, Frank
Liquid purification or separation
Processes
Chemical treatment
210150, 2102212, 261128, 261 76, E01F 304
Patent
active
047802170
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for introducing oxygen into water, especially naturally and artifically laid-out surface water, whereby the natural stratification of the water is maintained; and to an apparatus for implementing the said method.
The simplest way of enriching with oxygen bodies of water suffering from a lack of oxygen is to inject compressed air thereinto. For instance, perforated hoses are laid on the bottom, at particularly deep locations, and compressed air is fed into the hoses by a compressor. In this case, however, ascending air-bubbles transport water vertically, according to the principle of the air-lift pump, and this gradually breaks down the temperature-dependent water-stratification. If this process is carried out in lakes which are already largely eutrophied and, as a result of longterm anaerobiosis, possess, in the contact zone between sludge and water, an extensive layer of sludge along the bottom, there is a danger of nutrients (especially phosphates), released with the deep water carried to the surface, being transported to the trophogenic zone. This may lead to additional and even more extensive bioproduction in the upper layer of water, especially if, as a result of the aeration measures, the watertemperature of the lake is the same at all depth during the summertime, so that most of the deep water carried to the surface remains there. This produces exactly the opposite of the desired effect, bioproduction is stimulated in the body of water.
In addition to this, and especially in small lakes, transporting water low in oxygen to the surface results in fish living in the water suddenly finding water low in oxygen at all depths and thus dying from lack of oxygen. This occurs mainly when the oxygen added to the water carried to the surface is not enough for adequate oxygen enrichment within the available contact-time. Under no circumstances, therefore, should compressed air be merely introduced into highly eutrophied bodies of water.
For the purpose of overcoming these problems, an aerating device has been developed in which there is no vertical mixing of the layers of water. In this case compressed air rises, through candle-filters, in a riser-pipe. The water carried along has intensive contact with the ascending air-bubbles. Located at the top of the riser-pipe is a degasifying chamber. From here, the oxygen-enriched water is returned through a downpipe arranged concentrically around the riser-pipe and distributorpipes radiating therefrom, into the lake. The process usually takes place in the hypolimnion. Leading to the surface is only a degasifying line through which air can escape from the degasifying chamber.
The disadvantage of this method is that it must be supplied with compressed air and therefore requires a compressor. But all compressors operate very inefficiently. In addition to this, the power required to drive the air down to deep water all goes to waste. Compressors also require considerable maintenance, especially when supplying compressed air without oil, they are subject to wear, and they contribute to environmental pollution by their noise. For economic reasons, therefore, it ist often impossible to use the known method.
It is the purpose of the invention to provide a method, and an apparatus for the implementation thereof, which overcomes the problems and drawbacks of the already known methods.
According to the invention, this purpose is accomplished in that a pump draws deep water in and forces it through an injector which, in turn, draws in air from the atmosphere, mixes it with water, and then injects the mixture of water and air into a riser-pipe in which the ascending air-bubbles produce an upwardly directed vertical flow. Through the lower opening in the riser-pipe, which descends into deep water (the hypolimnion), additional deep water is drawn in and is brought, on its way upwards, into contact with the air-bubbles. The residual air, which has reached the top, can escape into the atmosphere, after releasing part of the oxygen which it contains, fr
REFERENCES:
patent: 3956124 (1976-05-01), Fast et al.
patent: 4107240 (1978-08-01), Verner et al.
patent: 4347143 (1982-08-01), Righetti
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