JPS60251996A - Treatment of waste water - Google Patents

Abstract

PURPOSE:To hold MLSS in a pressure reaction tank to ultra-high oncn., by treating treated water in the pressure reaction tank in a pressurized state by a filter press to separate the same into treated water and conc. sludge while returning the conc. sludge to the pressure reaction tank. CONSTITUTION:Raw water 10 and return sludge 9 are introduced into a pressure reaction tank under pressure by a pressure pump 1 and the oxidation of org. substance in raw water is promoted by the biological reaction with oxygen in air sent in by an air compressor 3. When BOD concn. is reduced to a set value or less, a valve 13 is opened and treated water is sent into a filter press 6 in a pressurized state from a discharge pipe 7. The treated water is separated into clear treated water 11 and conc. sludge by the filter press 6 and excessive sludge 11 is discharged out of the system and the remainder is returned to the pressure reaction tank as return sludge 9.

Description

Detailed Description of the Invention Object of the Invention a) Industrial Application Field The present invention is directed to solid-liquid separation in a pressurized activated sludge method and ML in a reaction tank.
The present invention relates to a method for maintaining SS at an ultra-high concentration.

In other words, the internal pressure of the pressurized activated sludge method is used as the filtration pressure of the filter press, and clear treated water and 30,000 to 200
This wastewater treatment method enables highly efficient purification by separating the sludge into sludge concentrated to 000 mg/l and returning the sludge to a pressurized reaction tank to maintain the MLSS at 20.000 my/l or higher.

b) Prior Art Recently, pressurized aeration methods, pressurized tube type activated sludge methods, fast oxidation methods, deep aeration methods, etc., which are improvements to the standard activated sludge method for the purpose of improving efficiency, have been put into practical use.

These are treatment methods that have high concentration MLSS and a high-speed oxygen transfer function as a means of increasing the reaction rate.

A common drawback of these methods is that the steps of separating sludge and treated water and thickening the sludge are inefficient and unreliable.

The reason for this is that when dissolved gas coexisting with MLSS in a pressurized system is discharged into the atmosphere, it is released in the form of fine bubbles due to a pressure drop. Since these microbubbles adhere to and conjugate with the sludge, the apparent specific gravity of the sludge decreases, and the difference in specific gravity from the liquid phase becomes small, making separation and concentration difficult.

Solutions to this problem include (1) long-term atmospheric pressure aeration-sedimentation separation, (2) vacuum defoaming-sedimentation separation, and (3) flotation separation. Since method (1) requires a large-capacity aeration tank for defoaming, the advantage of high-speed oxidation is diminished. (2)
The construction and operation costs of deaeration equipment are high, and it is difficult to obtain clear treated water. (3) is SS remaining in treated water
In order to obtain clear treated water, tertiary treatments such as coagulation sedimentation and sand filtration are necessary.

(1) In both cases (2X3), the separated sludge concentration is 50
,000my/1 or more is difficult.

Therefore, in terms of the concentration of returned sludge, it is impossible to make the MLSS in the reaction tank more efficient than <20,000 my7.

On the other hand, if MLSS is 20,000 mg/ or more (
Solid-liquid separation is difficult with any of the methods 1), (2), and (3), and a method in which chemicals are applied and then filtered is appropriate.

(c) In order to solve the drawbacks that exceed the problems that the invention aims to solve, it is necessary to reduce the pressure to atmospheric pressure during solid-liquid separation so that the sludge is not trapped in fine bubbles due to the pressure drop. The purpose is to treat the treated water from the pressurized reaction tank and separate it into thickened sludge and clear treated water using a closed pressurized separator such as a pressurized filter press.

In other words, in the pressurized activated sludge method, the treated water in the pressurized reaction tank is treated with a filter press under pressure, separated into treated water and thickened sludge, and the thickened sludge is returned to the pressurized reaction tank. Therefore, this is nothing but a wastewater treatment method characterized by maintaining the MLSS in the tank at 20.00 omg7 or more.

Structure and operation of the invention (a) Means for solving the problem Next, in the present invention, what means was chosen to solve this problem, and its structure and operation. Let's explain based on FIG. 1, which is an example of a flow sheet.

Raw water (a)) and returned sludge (9) are pumped into a pressurized reaction tank using a pressure injection pump (1), and organic substances NH
Proceed with 3rd class oxidation. This tank is pressurized, so MLSS
can be decomposed even at high concentrations. When the BOD concentration falls below the set value, the treated water is sent to the filter press (6) through the discharge pipe (7) by opening the valve (b) and sending it under pressure to the filter press (6).

It is preferable to press the flocculant in the middle of the discharge pipe (7) via the flocculant supply pump (5) to make the sludge suitable for filtration before it reaches the filter press (6). It is. By using the internal pressure in the pressurized system as the driving force for filtration, it is possible to perform good filtration and separation without using a pressure pump or the like.

The filter press (6) separates clear treated water (b) and thickened sludge (fI sludge) (8), the excess sludge (2) is discharged outside the system, and the rest is returned as sludge (9) for pressurized reaction. returned to the tank. The concentration of retransfer sludge is 30,000 to 200,00
o my/L, so even if it is returned to the pressurized reaction tank (2) and mixed with raw water (1), the MLSS in the reaction tank (2)
holds more than 20,000 ■/. Reference number (4) is the exhaust pressure regulating valve.

(b) Example I will show you one example of how BOD etc. can be processed successfully when processed with a high MLSS like this.

・Processing conditions Waste water Human waste + Septic tank sludge processing pressure 3. OJ4/crrt (20°C) Air injection amount: 3Nt/min Tank volume: 20t (processing time: 3 hours batch processing) Filter operation of 52,000mg/MLSS in the tank Addition of 40ppm of Kasubupyrene 202 polymer (cationic polymer flocculant)・What is the processing result? What does MLSS mean in the text? (Mixed Liquo
(Suspended 5 solids) indicates the amount of solids in the tank.

Effects of the invention (1) No need for final sedimentation tank - ensuring clear treated water (2) No worries about bulking due to filamentous bacteria (3) High MLS in reaction tank
Easy to maintain S, easy to disassemble due to pressurized reaction (4) Processing equipment can be downsized - reaction tank can be reduced, etc. (5) Internal pressure within the system can be used for the propulsion force of the filter press

[Brief explanation of the drawing]

Figure 1 shows an example of a flow sheet of the present invention. Explanation of the symbols representing the main parts (1) Raw water/sludge injection pump (2) Pressurized reaction tank (3)
) Air compressor (4) Exhaust pressure regulating valve (5) Coagulant supply pump (6) Filter press (7
) Discharge pipe (8) Thickened sludge (9) Returned sludge ■Raw water (b) Treated water (6) Excess sludge 113) Valve patent applicant Mitsubishi Kakoki Co., Ltd.

Claims (1)

[Claims] In the pressurized activated sludge method, the treated water in the pressurized reaction tank is treated under pressure with a filter press, separated into treated water and thickened sludge, and the thickened sludge is returned to the pressurized reaction tank. , a wastewater treatment method characterized by maintaining MLSS in the tank at 20°000mg/or more.