JPH0218905B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to sewage treatment, and particularly to a method for solubilizing suspended organic substances in low-concentration organic wastewater such as sewage or building wastewater flowing into a sewage treatment plant using an enzyme. [Conventional technology] As rivers and lakes become eutrophic and it becomes difficult to secure water sources, there is a social demand for the development of highly efficient sewage treatment technology. As part of this effort, it is hoped that nitrogen will be removed from sewage. There are two types of nitrogen removal methods: physicochemical methods and biological methods.The former can only remove ammonia nitrogen, while the latter can also remove organic nitrogen, so it can be Biological methods are considered suitable for treating wastewater containing organic nitrogen. The biological nitrogen removal method consists of a nitrification process and a denitrification process, and it is a rational process because BOD in sewage is consumed as an organic carbon source necessary for the denitrification process. [Problems to be solved by the invention] By the way, the organic carbon source necessary for the denitrification process in biological treatment is theoretically nitrate nitrogen.
This is more than 2.86 times, but in the future, with the transition to improved and faster processing of treated water, it will become an organic carbon source.
There are concerns about a lack of BOD, and BOD replenishment will be necessary. As a method of supplying this BOD source from within the system,
One possibility is to solubilize suspended organic matter in sewage to replenish organic carbon sources. Possible solubilization methods include (1) heat treatment, (2) acid and alkali treatment, (3) combination of heat and acid or alkali treatment, and (4) enzyme treatment. Various studies have been conducted on (1) to (3), and several reports have been made, but they tend to degrade even those that are difficult to biologically treat. On the other hand, enzyme treatment (4) is expected to gently decompose to the extent that it can be easily biotreated, but there are no examples of its application yet. Therefore, it is an object of the present invention to provide an enzyme treatment method capable of eliminating the drawbacks of the prior art and capable of decomposing and solubilizing organic suspended substances in sewage to the extent that they can be easily biooxidized. [Means for Solving the Problems] The present invention solves the above problems by adding enzymes in a particular order. That is, the present invention relates to a method for enzymatically treating organic suspended solids in sewage, which is characterized in that the order of addition of enzymes is first a starch degrading enzyme, then a protease degrading enzyme, and then other organic matter degrading enzymes. Even if two or more enzymes are added to sewage at the same time, the suspended organic matter in the sewage will be degraded at the same rate or less than when the enzymes are added individually.
According to the present invention, organic substances are efficiently decomposed by first adding a starch-degrading enzyme, then a protease, and then adding the remaining enzymes. The third enzyme added is cellulolytic enzyme,
There are lipolytic enzymes, cell wall degrading enzymes, etc., but no matter what order these are added, the effect will not be affected. Starch degrading enzymes are α- and β-amylases, and are present or produced in pancreatic juice and saliva of animals, molds, bacteria, and the like. Examples of proteases include pepsin, trypsin, chymotrypsin, and fungal, yeast, or bacterial proteases. Lipolytic enzymes include lipase, which exists in pancreatic or gastric juice of animals, or in castor seeds, rapeseed seeds, molds, yeasts, and bacteria, and is produced by these. Cellulose-degrading enzymes are cellulases, which exist and are produced by molds, bacteria, protozoa, plants, and the like. Furthermore,
Lysozyme is an example of a cell wall degrading enzyme. Lysozyme, obtained from egg whites and fig milk, is an enzyme that catalyzes the hydrolysis of mucopolysaccharides in bacterial cell walls. The reaction conditions for adding and reacting each enzyme vary depending on the type of enzyme and its origin, but those skilled in the art can appropriately select the optimal reaction conditions for each enzyme. Organic matter solubilized by enzyme treatment is
It can be measured as an increase in TOC. [Examples] Next, the present invention will be described in detail based on Examples.
The present invention is not limited to this. Reference example 1 Sewage flowing into a separate type K treatment plant is collected, and α
- amylase (origin: Bacillus subtilis), neutral protease (origin: actinobacteria), lipase (arachnoid fungus),
Cellulase (origin: filamentous fungi) and egg white lysozyme were each used alone for treatment. The processing conditions at that time are as follows:

[Table] Table 1 shows the processing results. Table 1 Enzyme name TOC increase rate (%) α-amylase 26 Neutral protease 9 Lipase 11 Cellulase 8 Lysozyme 7 The enzyme with the highest TOC increase rate was α-amylase. Example 1 The same sewage as described in Reference Example 1 was collected and first treated with α-amylase under the same conditions as described in Reference Example 1, and then treated individually with the remaining enzymes. , the results shown in Table 2 were obtained.

[Table] Among these, the one with the highest TOC increase rate was
This was the case when neutral protease was added, and almost no difference was observed in other cases. Next, after first treating with α-amylase and then with neutral protease, the results of treating each with lipase, cellulase, or lysozyme alone were compared with the third treatment.
Shown in the table. As is clear from Table 3, the TOC increment showed almost no difference depending on the type of enzyme added third.

〔Effect of the invention〕

According to the invention, first the amylolytic enzyme, then the
By treating with proteolytic enzymes and then with other enzymes, the enzymatic treatment of organic suspended solids in sewage can proceed efficiently, and the organic suspended solids can be solubilized to the extent that they can be easily processed biologically. can.

Claims (1)

[Claims] 1. A sewage system characterized in that when enzymes are added to sewage to solubilize suspended organic matter, the enzymes are added in the order of starch-degrading enzymes, then proteolytic enzymes, and then other organic matter-degrading enzymes. Enzyme treatment method for organic suspended solids inside.