JPS58109189A - Treatment for waste water of emulsified oil - Google Patents

Abstract

PURPOSE:To treat waste liquid relatively easily by adding an excess amt. of a polyaluminum chloride soln. which does not settle by the effect of the pH of the waste liquid itself, filtering out the formed precipitate, adding NaOH to the filtrate thereof, and settling the polyaluminum chloride dissolved as an excessive component. CONSTITUTION:About 10W/V% polyaluminum chloride soln. in terms of Al2O3 is added to waste liquid of emulsified oil in an excess amt. at which the polyaluminum chloride does not settle by the effect of the pH of the waste liquid itself. The liquid is stirred and the flocculated matter of oil formed by the Al(OH)3 formed by the pH of the soln. is filtered out. About 10W/V% NaOH is added into the filtrate and the excess polyaluminum chloride is settled as Al(OH)2.

Description

[Detailed description of the invention] The present invention relates to a method for treating emulsified oil wastewater.

Conventional methods for treating emulsified oil wastewater, in which the solution contains stabilizers such as surfactants and stabilizes fine oil particles, include the addition of Ca-based chemicals or the application of an electric field to create oil droplets. The current charge is neutralized.

However, even if the emulsification can be destroyed and the oil content in the wastewater can be removed as described above, surfactants and other soluble organic substances still remain in the wastewater, so activated carbon is used as the next step of treatment. Adsorption methods, photo-oxidation methods, biological treatment methods, etc. are commonly used, and the treatments are extremely complex.

The present invention makes it possible to relatively easily treat emulsified oil wastewater, which has conventionally been very complicated, and will be described below.

Emulsified oil wastewater, which contains stabilizers such as surfactants in the solution and has stable oil particles, has a high COD concentration and oil concentration, as shown in Table 1, so it cannot be discharged as is. Can not.

Therefore, an excess amount of polyaluminum chloride (approximately 10 W/V% in terms of At203, hereinafter referred to as PAC), which is an inorganic polymer flocculant, is added to the emulsified oil wastewater as shown in Table 1 above.

The amount of PAC added varies depending on the oil concentration in the emulsified oil wastewater, but is determined by the relational expression 1 in FIG. 2 based on the experimental example described later.

Moreover, the excessive amount is an amount that, when the pH value of the emulsified oil wastewater is 4.2 or less, does not cause PAC to precipitate any more and becomes soluble At3+.

Furthermore, the reason for using PAC as a flocculant is that PAC
This is because they have high cohesive strength and toxicity for various industrial wastewaters, including water and sewerage systems, and are cheaper than organic polymer flocculants.

As mentioned above, the excessive amount of PAC added to the emulsified oil wastewater generates At(OH)3 depending on the PH value of the emulsified oil wastewater itself, and the generated At(OH)a coagulates most of the oil. The flocculated precipitate is removed by filtration.

The filtrate from which the coagulated precipitate was removed has a low pH value (PH 4, 2) due to the excessive addition of PAC as described above.

In this filtrate with a low pH value, the amount of N determined by the relational expression 2 in Fig. 3 based on the experimental example described later.
a0H (10 W/V%) was added to bring the filtrate OPH value back to 5-7, thereby reducing the soluble At3+ in the filtrate.
The existing PAC was converted into At(OH)3,
At(OH) removes oil, surfactant, etc. remaining in the filtrate.
)3, and by removing this coagulated precipitate by filtration, the oil concentration in the filtrate was reduced to 11.
It is possible to reduce the power to 0PP or less.

Note that neutralizing agents include ammonia, sodium carbonate, etc., but ammonia forms a complex with At3+, and sodium carbonate generates carbon dioxide gas on the acidic side. NaOH was used because it is safe and inexpensive.

Experimental Example Sample A-3 shown in Table 1 was collected in a 300 mt beaker, and while stirring, the power was approximately 10 W/ in terms of A L 203.
After adding 9 mt of PAC having a concentration of v % and stirring thoroughly, the solution is allowed to stand, and the oil in the sample is aggregated by At (OH) 3 generated by the pH value of the solution.

Next, after removing the aggregates by filtration, 1.5 mA of IOW/V% NaOH was added to the filtrate while stirring, and the excess P was removed by further stirring.
When AC was precipitated as At(OH)3 and the oil concentration in the solution was measured, the results were as shown in Figure 1 (,,lQPP
m or less.

Note that the P'H value of the liquid in this case was 5.6.

Figure 2 shows oil concentration and PA based on the experimental results (Figure 1).
This is a graph showing the relationship between the amount of C added, and FIG. 3 is a graph showing the relationship between the oil concentration and PAC/NaOH.

In addition, relational expression 1 in Fig. 2 (here) and relational expression 2 in Fig. 3 were created based on the above experimental results, and relational expression i (here, By pre-drying an oil concentration of 1 ogy, it is possible to calculate the appropriate amount of PAC addition/strengthening for the emulsified oil wastewater.

In Relational Expression 2, the amount of NaOH added is calculated to neutralize the excess amount PAC, and the oil concentration and PAC addition amount in Relational Expression 1 may be substituted into Relational Expression 2.

As described above, according to the present invention, the treatment of emulsified oil wastewater, which has conventionally been very complicated, can be performed relatively easily.

[Brief explanation of drawings]

Figure 1 shows the oil concentration and PA in emulsified oil wastewater to be treated.
FIG. 2 is a graph showing the relationship between oil concentration and PAC addition amount. FIG. 3 is a graph showing the relationship between oil concentration and PAC/NaOH. Disgrace Irikawa, is Saki Steel Co., Ltd. Ichiban-4- a connoisseur? IPAC: In addition to P^CΔνp (ml) Figure 2, Figure 3.

Claims (1)

[Claims] An excess amount of polyaluminum chloride solution that does not precipitate depending on the pH value of the wastewater itself is added to emulsified oil wastewater, and the resulting precipitate is removed by filtration, and then NaOH is added to the filtrate. A method for treating emulsified oil wastewater, characterized by reprecipitating polyaluminum chloride dissolved in excess.