JPS59186700A - Water and sewage treating system - Google Patents

Abstract

PURPOSE:To stabilize the electric energy to be generated and to stabilize the utilization of electric power and waste heat on account of such stabilization by controlling the amt. of the activated sludge existing in an activated sludge process in such a way that the electric energy to be generated by gas attains a preset value. CONSTITUTION:A treating system for water and sewage is constituted of an aerating tank 10, an air diffuser 11, a final settling basin 12, a mechanical thickener 13 for excess sludge, an information processing unit 14 for the water treating process, a control device 15 relating to the total amt. of activated sludge, a calculator 16 for information on driving powder, a setter 17 for power generating quantity, a manual setter 18 relating to the total amt. of sludge and a blower 19. The stabilization of the electric energy to be generated by digester gas is accomplished by adjusting the set value for the method of controlling the amt. of the sludge in the activated sludge process according to the difference between the predetermined electric energy to be generated and the present electric energy to be generated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for operating a water treatment and sludge digestion treatment-gas power generation system in a sewage treatment plant or the like.

A conventional operating method of this type is shown in FIG. In the diagram, (1) is a sludge thickening tank, and (2) is ? 7"
+ species, (3) is a heat exchanger that heats the sludge in the digestion tank, (4) is a digester gas generator, (5) is a waste heat boiler, (
6) is a control device, (7a) and (7b) are pumps, (
8a) is a valve, and (9a) and (9b) are measuring devices.

Further, in the figure, dotted line arrows indicate electric signals, dashed-dotted line arrows indicate gas, and solid line arrows indicate 0 flow of sludge or water (hot water).

Next, the operation will be explained. Initial settling sludge and surplus sludge generated in a sewage treatment plant are usually concentrated in a thickening tank (1) and then sent to a digestion tank (2), where they are heated and anaerobically fermented. Digestion gas generated by fermentation is generated by a gas generator (
4) and is burned. The combustion waste gas has a high temperature and is sent to the waste heat boiler (5), and the hot water obtained here is used to heat the sludge in the digester via the heat exchanger (3). The amount of sludge input into the digestion tank is measured by a measuring device (9a), while the generator output is measured by an output meter (9b),
The control device (6) operates the valve (8a) as needed to control the amount of sludge introduced.

Conventional sludge digested gas power generation systems were operated as described above, and the amount of sludge generated itself was not managed. Therefore, depending on the amount of sludge generated and fluctuations in the temperature of the generated sludge, the digested gas power generation system This had the disadvantage of causing fluctuations in power consumption, making the use of electricity and the heat balance for heating the digester tank unstable due to waste heat.

The present invention was made in order to eliminate the disadvantages of the conventional methods as described above, and is a comprehensive method that combines the activated sludge process and the sludge digestion process, which are the core of the water treatment process related to the amount of sludge generated. By managing the amount of sludge and maintaining the appropriate amount of sludge generation, and at the same time considering the main consumption power such as air supply power for the aeration tank, it is possible to stabilize the amount of power generation and thereby improve the effectiveness of electricity use and waste heat utilization. The purpose is to provide an operational system that stabilizes the system and improves energy-saving effects.

An embodiment of the present invention will be described below with reference to the drawings.

In Figure 2, Q(+ aeration tank, 0υ is a diffuser for nuclides, (2) is a final settling tank, 03 is an excess sludge mechanical thickening device, (14) is a water treatment process information processing device, 0
9 is a control device related to the total amount of activated sludge, the head is a power information calculator, Q71 is a power generation amount setting device, α~ is a manual setting device related to the total amount of sludge, and 4 is a blower. .

Figure 3 shows an example of trial calculation evaluation of the effect when implementing the present invention on a scale of sewage treatment amount of 300,000 tons/day, graph (a) shows excess sludge generated dry amount Sw, graph (b) Air supply power of the aeration tank 1) B1 graph (C) shows the surplus power P obtained by subtracting the air supply power from the gas power generation power, and the total amount of activated sludge S.
This is shown for T.

Next, the operation of the present invention will be explained based on examples.

As shown in FIG. 8, the amount of excess sludge Sw has a characteristic that it decreases as the total amount of sludge in the activated sludge process increases. Therefore, by controlling the amount of sludge in the activated sludge process, the amount of excess sludge and, in turn, the amount of gas generated can be stabilized.

In the present invention, the stabilization of the power generated by the digestion gas is achieved by adjusting the set value of the sludge amount management method of the activated sludge process according to the difference between the predetermined amount of generated power and the current generated power tn. This is achieved by

Here, sludge age control, SR'r (Sludge Retenti
Three control methods are shown: on-time control and sludge daily control.

In the case of the sludge daily control method, the set value 8 for the total amount of sludge is adjusted as follows.

S T* “s To” K4 (1 no P
*) ・=・ (1
) Here, P is the measured value of generated power, ■) * is predetermined? The generated power, IL.Sl., is the reference value of the total amount of sludge (amount of power generation * average sludge total amount value that can obtain P as the power), and K1 is the gain.

ST o is the output set by the manual setting device regarding the total amount of activated sludge, and P is the output P of the measuring device (9b), which is obtained as the output of the power generation amount setting device aη.

* The calculation of equation (1) is performed by a calculator QG, and ST is obtained as the output, which serves as a set value input to the control device OQ regarding the total amount of activated sludge.

The control device US regarding the total amount of activated sludge calculates the following equation, operates the valve (8b), and adjusts the amount of excess sludge.

* SW = Sl + 2 (ST ST )
・・・・・・(2) Here, Sw is the target value of surplus sludge amount,
SI is the measured value of the amount of inflow sludge, the measured value of the total amount of ST sludge, and K2 is the gain.

Sl·ST is calculated based on the following equation from each process measurement value inputted to the water treatment process information processing device α, and is obtained as the output of the information processing device a4).

Here, Ccj is the activated sludge concentration, ■ the effective volume of the aeration tank,
γ is the distribution ratio of the amount of self-activated sludge in the aeration tank to the total amount of activated sludge, and n is the number of old plays.

Here, C+j is the inflow SS concentration, and Qij is the inflow water amount.

*Next, in the case of SRT control, the SRT setting value SRT is
Adjust as follows.

SRT-” 5RTo 3 to 10 (P P )
...-(5) Here, 5RTo is SR
The standard value of T (the average SRT value at which P can be obtained with * as the power generation capacity), and H3 is the gain. 5RTo is set by the manual setting device Ql'p regarding the total amount of occupied sludge, and is obtained as the output of the manual setting device 0 piece. The calculation of equation (5) is performed by the calculator OQ, and SRT* is obtained as the output and serves as a set value input to the control device αQ regarding the total amount of activated sludge.

The control device o9 regarding the total amount of activated sludge calculates the following equation, operates the valve (8b), and adjusts the amount of excess sludge.

Sw=S]/SRT*...(6) ST is calculated from each process measurement value input to the water treatment process information processing device q4 using equation (3) as in the case of controlling the total amount of sludge. Calculated, 'clear information processing device α4)
is obtained as the output of

The setting value sA* of the sludge daily age control is adjusted as follows.

* SA = S Ao 10 Kt CP −
P)...=
(6) SA here. is the reference value of the daily sludge age (the average daily sludge value from which P can be obtained as the amount of generated power), and H4 is the gain. SAo is set by the manual setting device α~ regarding the total amount of activated sludge, and is obtained as the output of aa*. The calculation of equation (6) is performed on the performance device 0Q, and δ8
is obtained as this output, and serves as a set value input to the control device 09 regarding the total amount of activated sludge.

The control device 09 regarding the total amount of activated sludge calculates the following formula, operates the valve (8b), and controls the amount of excess sludge.
I'm going to have a good time.

bw −sr (s+*Sx*)
River (7) When Sw<0 5w-0 In equation (7), Sl is the water treatment process information processing device 0 using equation (4) as in the case of controlling the total amount of sludge.
4) is calculated from each process estimated value inputted to 4), and is obtained as an output of the information processing device 04).

The third ward is Q+2aO million m3/' mouth, C+=100
mri/l.

PR and (P
l) This shows the 81 dependence of B). Furthermore, the blower
My friends have demonstrated that the power increases linearly with respect to ST as a result of being dominated by the absorption and absorption storm of activated sludge microorganisms in the air tank.

In addition, the method for determining the set value of the gas emission fkM described in claim 2 can be easily determined using, for example, the following relational expression.

First, the blower power in the activated sludge process can be calculated from the respiration rate of activated sludge microorganisms, the total amount of sludge, the water quality in the tank, and the oxygen dissolution efficiency.

Pa=(a'XJ(1+b')・S[/η8− −=
・(8) Here, Pa + blower power (r< w H
/B)'d; Treated water quality in aeration tank (m9/1)S
l; Amount of sludge in the active process (tons) η□;? 8 hours
The efficiency (-) In addition, the treated water quality l・d in the aeration tank is
D, shown as a function of BOD-8s load calculated from inflow sewage volume.

ld=(Flo, 180) 0840
...Song (9) F2Q1・I-i・10-6/St
・・・・・・aU here TF; BOD-5S load (1/EEI) QI; Inflow sewage amount (m8/day) Ll; Inflow BOD (my/l) On the other hand, the power generation amount of the gas power generation system is calculated by the following formula: It can be found by

p5=ε-HS-Fd/860 --
01) Here, ε, Power generation efficiency (-) H8: Digested residue heat generation ffi (kca17Nm”)
Fd; Digestion gas flea (Nm 7 days) The gas power generation amount is determined by the following formula from the amount of initial settled sludge organic matter and the amount of excess sludge organic matter.

Fd "Yr' So 1 Ya"(11' Sa
``'-'J2 Cocoteyr; Gas generation amount from initial settling sludge (NmV t)Ya-Excess sludge
(Nms//l) α0; Initial settling sludge organic matter ratio (-) αω; Surplus sludge (-) So; Initial settling sludge amount (1/day) Salt Surplus 〃 (17 days) Also, initial settling sludge amount and surplus sludge amount About So”
Qi 'Co-"m" to 'Li...Q3Sω"-(Ci-Qi・10'+Y(J-L
d)・Ql・10'-b-3j)° ωn
・・ σXun here CO+
Initial sedimentation inflow SS Cmy/l) C1; Aeration tank inflow S
S (my/'l)Y; yield (-) b; self-decomposition coefficient (1/day) ωm; solid content recovery rate by electric concentration (-) ωn; machine〃(-) or more (8 to Q4 ) Using the formula, set St so that pa=ps, and calculate the P5 at that time using the formula (8).The generated gas power generation claw can cover the blower power of the activated sludge process. The setting value of is calculated.

Further, each parameter value in equations (8) to αa can be obtained by conducting laboratory-scale experiments or the like.

As an example of the system configuration of the present invention, a thickening tank is provided for initial settling sludge, and a mechanical thickening device is provided for surplus sludge, but this method is not restrictive, and surplus sludge may also be directly put into the thickening tank. .

As described above, according to the present invention, since the amount of surplus sludge generated is managed, it is possible to stably secure the amount of sludge input to the digestion tank, thereby stabilizing the digestion gas power generation and at the same time The blower power of the aeration tank, which accounts for about 30% of the total electricity consumption of a sewage treatment plant and continuously consumes electricity, can be operated on its own at all times.
Comprehensive energy savings can be achieved in water treatment and sludge treatment.

[Brief explanation of the drawing]

Figure 1 shows the conventional sludge digestion gas Q! FIG. 2 is a block diagram showing the system, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a graph showing the effects of the embodiment of the present invention. (1)...Sludge thickening tank, (2)...Digestion tank, (3)
・・・Heat exchanger, (4)・Digestion gas power generation, (5)・・
Waste heat boiler, (6)...Control device, 00...Aeration tank, (6)...Final settling tank, 03...Excess sludge mechanical thickener, a<...Water treatment process information processing device, C.
9: Control device regarding the total amount of activated sludge, OQ: Power information calculator, Auxiliary: Power generation amount setting device, all: Manual setting device regarding the total amount of activated sludge. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Masuo Oiwa Procedural amendment (voluntary) 20 Name of invention Water/sludge treatment system 3 Name of person making the amendment (601) Mitsubishi Electric Corporation Representative Katayuni 8th Department 4 Agent 5 Details subject to amendment claims section of the document. 6. Contents of the amendment (1) The scope of claims in the description will be corrected as shown in the attached sheet. 7 Attachment i: Record I (1) At least one document stating the amended scope of claims
Claims (1) An activated sludge process comprising an aeration tank and a final settling tank, a digestion tank in which excess sludge produced by water treatment in the process is concentrated and then subjected to anaerobic fermentation together with the initial settling sludge; The water/sludge treatment system is mainly composed of a gas power generation engine that uses the digestion gas generated from the digestion tank as fuel.
, so that the gas output of 74 fl becomes a predetermined setting value.
A water/sludge treatment system characterized by controlling the amount of activated sludge present in the activated sludge process. (2) Water and sludge treatment according to broad item 1 of the patent claim, characterized in that the setting value of the gas generator is determined so that the blower power of the aeration tank can be self-sufficient by the power generated from the gas generator. system.

Claims (2)

[Claims] (1) Activated sludge process consisting of an aeration tank and a final settling tank, a digestion tank in which excess sludge produced by water treatment in the process is concentrated and then subjected to anaerobic fermentation, and the digestion gas generated from the digestion tank is used as fuel In a water/sludge treatment system mainly composed of a gas power generation engine, the amount of activated sludge present in the activated sludge process is controlled so that the amount of gas power generation becomes a predetermined set value. water and
Sludge treatment system. (2) The water/sludge treatment system according to claim 1, wherein the set value of the gas power generation amount is determined so that the blower power of the aeration tank can be self-sufficient from the gas power generation power.