JPS588918B2 - Wastewater treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating waste water, particularly waste water from a wet desulfurization device.

Combustion exhaust gas emitted from thermal power plants contains large amounts of sulfur oxides, which are air pollutants.

Therefore, the same gas is desulfurized through a desulfurization process, typically a wet desulfurization unit, and the absorbed sulfur content is recovered as gypsum and other byproducts in the same process, but the wet desulfurization unit produces a large amount of salt and other It is unavoidable that wastewater containing dithionic acid will be produced.

Since this dithionic acid is a causative agent of water pollutants, particularly COD, it is necessary to remove it from wastewater.

Conventionally, COD removal methods include oxidation treatment using chlorine gas, oxygen gas, etc., activated carbon adsorption, and a combination treatment thereof, but none of these methods are effective in removing dithionic acid.

In some cases, adsorption treatment using anion exchange resin or thermal decomposition treatment under acidic sulfuric acid has been carried out, but even these methods are considered to be sufficiently effective in removing dithionic acid. No, no.

In view of the above points, an object of the present invention is to provide a wastewater treatment method capable of removing dithionic acid at a high removal rate.

That is, this invention was achieved as a result of intensive research on the decomposition properties of dithionic acid by microorganisms, and the invention was achieved by degrading dithionic acid contained in wastewater under anaerobic conditions to pH=
This is a wastewater treatment method characterized by decomposing sludge by microorganisms in the range of 4.5 to 8.5.

As the microorganisms used in this invention, anaerobic microorganisms present in sludge such as sewage and human waste are suitable.

Further, the pH value is preferably in the range of 4.5 to 85, particularly 7.
A neutral region around 0 is optimal.

Example 1 Artificial wastewater A, B, and C containing the components shown in Table 1 were prepared, each wastewater was poured into separate flat culture bottles, sewage sludge was added to each bottle, and the bottles were sealed with water.

In this way, each cell was maintained under anaerobic conditions.

1 The pH of each wastewater was approximately 7.0.

Sampling was performed after a predetermined period of time had elapsed, and the concentration of dithionic acid was measured.

The results are shown in Table 2. As can be seen from Tables 1 and 2,
In both wastewaters, dithionic acid was decomposed and removed at a high removal rate.

The effect was particularly remarkable in wastewater A and wastewater B containing organic nutrients.

Example 2 Acrylic column (diameter 32 mm, height 80 mm) 3
Each book was filled with a silica filler, to which sewage sludge was attached (void volume≈300 ml).

Next, in the waste water A, B and C of Table 1, S20
Drainage water A', B' and C', which were prepared by setting only 6 to 3601 nfl/7 and leaving the other components as they were, were continuously passed through each of the three columns at a flow rate of about 2007 rLll day.

Sampling was performed while water was flowing, and the concentration of dithionic acid was measured.

As a result, in wastewater A' and wastewater B', dithionic acid was completely decomposed and removed after one week.

As for wastewater C', as shown in Table 3, decomposition progressed gradually and was completely decomposed in about 25 days.

Example 3 The influence of pH on the decomposition of dithionic acid was investigated.

First, artificial wastewaters D, E, and F containing the components shown in Table 4 were prepared.

The pH values of these wastewaters are shown in Table 4.

Next, in the same manner as in Example 2, these wastewaters were passed through a column filled with a sewage sludge-adhering filler.

After passing water for 14 days, the dithionic acid concentration of each treated wastewater was measured.

The results are shown in Table 5. As can be seen from Tables 4 and 5,
The optimum pH ranges from 4.5 to 8.5.

Note that the reason why the pH value of the treated effluent is lower than before the treatment is considered to be that S206 is decomposed to generate SO3 or SO4.

As described above, according to the present invention, dithionic acid in waste water can be decomposed and removed at a high removal rate.

Claims (1)

[Claims] 1. Dithionic acid contained in wastewater was adjusted to pH under anaerobic conditions.
A wastewater treatment method characterized by decomposing sludge by microorganisms in the range of = 4.5 to 8.5.