KR940011522B1 - Method for treatment of waste water using sea water - Google Patents

Abstract

(A) step for separating precipitate that is cohered and precipitated in purification process by using magnesium ion in sea water; (B) step for changing magnesium ion to magnesium hydrogen carbonate by injecting liquidized carbonate gas when coming to pH 9; (C) step for filtering and separating cohered precipitate having magnesium hydrogen carbonate; (D) step for reusing recovered and filtrated solution in purification process.

Description

Regeneration of Coagulant Precipitant for Alkaline Industrial Wastewater Purification Using Seawater

The present invention relates to a method of processing coagulated sediment in industrial wastewater coagulation by seawater or concentrated seawater and reusing it as a coagulant. Particularly, in the industrial wastewater coagulation treatment using Mg ⁺⁺ ions in natural or processed seawater, A method of reusing Mg (OH) ₂ in an aggregate by Mg ⁺⁺ ionization and reusing it as a flocculant in flocculation sedimentation.

As a method for treating alkaline industrial wastewater, there is a method of flocculation using seawater in Korea Patent No. 36186 in the name of the present applicant. This patent method is accomplished by Mg ⁺⁺ ions dissolved in seawater combined with OH ^- ions in an alkaline state to Mg (OH) ₂ to precipitate a solid material and adsorb dissolved organic matter to the formed aggregates. Wastewater treatment method by this method is economically excellent because it does not need a separate chemical required for flocculation by using only seawater, which is an infinite natural material when treating alkaline industrial wastewater.

However, when the alkaline industrial wastewater at the coastal location is treated with the above patent method, it is possible to use the method economically because the seawater is easily supplied, but when the alkaline industrial wastewater is located in the inland region far from the sea. The problem arises that a significant amount of seawater must be exercised and stored.

After all, since the patent method does not use a separate flocculant in terms of using seawater, which is an infinite natural product, it is an excellent method for economically treating alkaline industrial wastewater in a certain region, but this patent method in a place where seawater supply is difficult Silver is not an economically better option than treating industrial wastewater by purchasing a separate flocculant other than seawater.

Therefore, an object of the present invention is to overcome the problems in the prior art of alkaline industrial wastewater treatment using seawater as described above, for processing the flocculation sediment during industrial wastewater coagulation treatment by seawater to reuse as a coagulation flocculator. In providing a method.

The method of the present invention injects carbon gas or liquefied carbon dioxide in circulation into the flocculation sediment, dissolves Mg (OH) ₂ precipitated with the flocculant during seawater treatment, converts it into Mg ⁺⁺ ion, and then dehydrates the gas. The filtrate recovered from the solid components is recovered by reuse of the flocculant in the alkaline industrial wastewater treatment process. The characteristics of the present invention is that insoluble Mg (OH) ₂ precipitated like aggregates in seawater treatment is Mg (HCO ₃ ) ₂ when CO ₂ gas is injected into the water to form Mg ⁺⁺ ions are formed. . Therefore, when reusing Mg (OH) ₂ generated after seawater treatment by the method of the present invention, Mg ⁺⁺ ions can be replenished from aggregates during industrial wastewater treatment with seawater, thereby reducing the amount of seawater required. do.

This makes it possible to treat alkaline industrial wastewater with a small amount of seawater even in inland locations. By using the method of the present invention and the alkaline wastewater treatment method using seawater, it is possible to make the wastewater treatment more economical by flocculating solid matter, dissolved organic matter, color, turbidity, phosphorus and heavy metals in the wastewater, especially when there is a large amount of dissolved organic matter. The use of can reduce the load on subsequent biological treatment facilities, making treatment easier and reducing biological reactors.

Example 1

50 ml (5%, v / v) of seawater was added to 1 L of food wastewater having a pH of 12.6 and flocculated. At this time, the removal efficiency was 98% of the solid component. The flocculated sediment was separated, liquefied carbon dioxide gas and combustion exhaust gas were introduced to pH 8.9, followed by filtration, and the filtrate was entirely administered to alkaline food wastewater to perform agglomeration experiment. Removal efficiency was 95% of the solid component. The precipitated aggregates were separated again, re-dissolved by adding carbon dioxide gas, filtered, and coagulated by filtrating the filtrate into the same food wastewater. At this time, the removal efficiency was 78%. The test was conducted in the same way and the removal efficiency was 68%. This shows that Mg ⁺⁺ ions can be reused several times from flocculated precipitates. However, Mg ⁺⁺ Mg ⁺⁺ ions initially supplied from seawater are lost during the precipitation and filtration processes, and the coagulation efficiency decreases with the number of regeneration. At this time, the addition of a small amount of sea water (1-2%, v / v) increased the aggregation efficiency to 98%.

Example 2

Only 5% of seawater was added to the oxidized paper effluent having a pH of 11.3, and the flocculation experiment was repeated six times. At this time, the solid removal efficiency was 95-97%. The precipitated agglomerates were separated and carbon dioxide gas was added to each so that the respective pHs were 10.1, 9.4, 9.0, 8.5, 8.0 and 7.0. They were separated by filtration and reused the filtrate to coagulate and precipitate the same oxidized paper effluent. Solids removal efficiencies upon reuse by flocculation were 35%, 79%, 91%, 92%, 93% and 93%, respectively. This shows that the amount of carbon dioxide and combustion gas injected during the dissolution of Mg (OH) ₂ can be adjusted to pH, and when the pH is 9 or less, it is determined that almost all of Mg (OH) ₂ becomes Mg ⁺⁺ ions.

The present invention can be treated more economically by using industrial wastewater treatment method using seawater in textile dyeing industry, some food manufacturing industry, petrochemical industry, concrete manufacturing industry, pulp industry and leather industry which generates alkaline industrial wastewater. In addition, by effectively treating the hard-degradable substances and toxic substances in the waste water can protect the state system of rivers and enzymes and prevent eutrophication.

Claims (4)

A method of regenerating the flocculating flocculating agent for the purification of alkaline industrial wastewater, comprising: (a) coagulated precipitate that is precipitated when coagulative sedimentation is used in the purification process of alkaline industrial wastewater or liver water containing a large amount of Mg ⁺⁺ ions; Separating the; (b) converting Mg (HCO ₃ ) ₂ by injecting carbon dioxide gas into the separated flocculated precipitate and removing Mg ⁺⁺ ions from the flocculated precipitate; (c) separating the coagulated sediment from the Mg ⁺⁺ ions converted to Mg (HCO ₃ ) ₂ by filtration; and (d) using the recovered filtrate again for the purification process of alkaline industrial wastewater. The method according to claim 1, wherein the carbon dioxide gas used in step (b) is liquefied carbon dioxide gas or combustion exhaust gas. The method according to claim 1, wherein the carbon dioxide gas is injected until the pH of the flocculating precipitate becomes 9 or less in the step (b). The method according to claim 1, wherein the coagulation efficiency of regenerated flocculents during regeneration over several times is significantly lower than the initial efficiency, so that 1-2% (v / v) of seawater or less brine or concentrated seawater is used. A method of regenerating the flocculating sediment for alkaline industrial wastewater, characterized in that the addition.