JPS5814270B2 - Tambakushitsu Shiboubungan Yuuodakuhaisuino Shiyorihouhou - Google Patents

Description

[Detailed description of the invention] General wastewater from food processing such as dairy products and meat processing contains large amounts of protein and fat, and these wastewaters have a high CO2 content.
Indicates D.

One of the methods for treating these wastewaters is the chemical coagulation sedimentation method.

This treatment method is a treatment method that utilizes the aggregation effect exhibited by the positive charge that hydroxides such as Fe and AI have near neutrality.

Iron salts are generally used as treatment chemicals because they are inexpensive.

This treatment method has the advantage of requiring smaller treatment equipment compared to other treatment methods, such as biological treatment, but the sludge produced by the treatment has poor settling and filterability, making it extremely difficult to separate the sludge. Met.

It is an object of the present invention to provide a method for improving the above-mentioned disadvantages and effectively treating wastewater exhibiting high COD, such as wastewater from food processing such as dairy products and meat processing.

That is, the present invention adds a ferrous salt and an alkaline substance to polluted wastewater exhibiting a high COD, blows in an oxidizing gas to oxidize the ferrous ions, and finally precipitates a ferromagnetic oxide. It is characterized by decomposing and adsorbing and removing pollutants that are a source of high COD.

The precipitate produced in the method of the present invention is a ferromagnetic oxide, which has much better sedimentation properties than the hydroxide precipitate produced by the coagulated precipitation method, and magnetic separation is possible, making solid-liquid separation very easy. becomes easier.

That is, in the method of the present invention, separation and recovery of precipitates is much easier than in the conventional coagulation-sedimentation method, and work efficiency is significantly increased.

Further, the ferromagnetic oxide precipitate produced by carrying out the present invention can be reused as a radio wave absorbing material, a raw material for magnetic fluid, etc., resulting in a closed cycle that is very favorable for the effective use of waste.

Next, the treatment method of the present invention will be explained.
Ferrous salts such as ferrous sulfate are added to waste water cloudy with milk with a concentration of 100 to 3000 ppm.
．． Add an amount equivalent to 5 mol/7, dissolve and stir, and add an alkaline substance such as caustic soda so that the pH becomes 9 to 12. A dark blue-green hydroxide precipitate is formed, and the solution is heated to 40°C or higher. When heated and oxidized by blowing in an oxidizing gas such as air for 10 minutes to 1 hour, a blackish ferromagnetic oxide precipitate is produced.

The supernatant liquid obtained by solid-liquid separation of the treated liquid with a magnet was colorless and transparent, and COD analysis of the liquid by the potassium permanganate method showed that the COD was 20 to 25 ppm or less in all cases.

COD is removed in this way because proteins are decomposed due to the salting-out effect of ferrous salts, alkalis, etc., and at the same time, the oxidation effect during the oxidation reaction of ferrous ions reduces COD.
It is thought that this is because these decomposition products are incorporated into the precipitate at the stage when spinel-type oxide precipitate (black ferromagnetic oxide) is produced, which contributes to the decrease.

Furthermore, the present invention is also capable of treating polluted wastewater that exhibits high COD and is contaminated with heavy metal salts such as potassium dichromate and mercuric chloride, which are often used when conducting analytical research on milk, etc., and under the above treatment conditions. Heavy metals are incorporated into spinel oxides (ferromagnetic oxides) during the process of forming ferromagnetic oxide precipitates, so heavy metals can be removed at the same time as polluted wastewater treatment.The types of heavy metals include cadmium,
These include lead, copper, zinc, manganese, chromium, mercury, iron, nickel, silver, soot, cobalt, titanium, vanadium, aluminum, arsenic, etc., and almost all except alkali metals can be removed.

The amount of ferrous salt used in the treatment of the present invention depends on the COD concentration and heavy metal concentration, but when the ferrous ion concentration is 0. 0
When the amount is less than 0 5 mol/73, it becomes difficult to form a ferromagnetic oxide precipitate.

Furthermore, if the treatment temperature is 40°C or lower, it will be difficult to generate ferromagnetic oxide precipitates, and although treatment can be performed at 40°C or higher,
In consideration of economic efficiency, an oxidation reaction temperature of 40°C to 80°C is preferably suitable.

The alkaline substances used are basic substances such as alkali metals and alkaline earth metals.
H is preferably 9 to 12, and when the pH is 9 or less and p
When H is 12 or more, heavy metals contained in polluted wastewater may not be removed.

In the detailed explanation of the present invention, COD was used as an indicator of the removal rate of pollutants in wastewater, but the method of the present invention uses BOD
, it has the same effect on TOD reduction.

The present invention will be explained in more detail with reference to Examples below.

Example I Cloudy milk bottle wash water 1 showing COD of about 400 ppm
When the Fe2+ concentration is 0. Dissolve ferrous sulfate to a concentration of 0.15 mol/l and add 42% of the IN-NaOH solution.
After adding ml, the temperature was raised to 40° C. and air was blown into the solution for 1 hour to carry out oxidation.

A black ferromagnetic precipitate was obtained after the oxidation reaction.

Magnetized barium ferrite was placed in the solution to separate the precipitate.

The separated liquid was colorless and transparent. After separation, a portion of the liquid was sampled and the remaining metal concentration was examined by atomic absorption spectrophotometry, and the toxic metals, including Fe, were below the detection limit.

Furthermore, COD was 15 ppm and the purification rate was about 96%.

Example 2 Ferrous chloride was dissolved in 1 liter of pale yellow wastewater containing raw beef juice and having a COD of approximately 1000 ppm so that the Fe2+ concentration was 0.05 mol/l, and 12,771 liters of 10N-NaOH solution was added. The temperature was raised to 60° C. and air was blown into the solution for 1 hour to perform oxidation.

After the oxidation reaction, a black ferromagnetic precipitate was obtained.

The liquid obtained by magnetically separating the precipitate was clear and colorless, and when the residual metal concentration was examined by atomic absorption spectrophotometry, the Fe concentration was 0.08p.
pm, and other toxic metals were below detection limits.

Claims (1)

[Claims] 1 Add ferrous salt to polluted wastewater containing protein and fat so that the ferrous ion concentration is 0.005 mol/l or more, dissolve and stir, and add an alkaline substance in an amount greater than the required amount to the anions in the solution. The pH is adjusted to 9 to 12, heated and held at 40°C or above, and oxidized by blowing in oxidizing gas such as air. Finally, a ferromagnetic oxide precipitate (spinel compound) is generated and pollutants in the wastewater are decomposed. A method for treating polluted wastewater containing protein and fat, which is characterized by adsorption and removal.