DEVICE AND METHOD FOR MEASURING SETTLEABILITY OF ACTIVATED SLUDGE IN-SITU

Abstract

A device for in-situ measuring settleability of activated sludge includes a sample chamber, an ultrasonic time domain reflectometer, a magnetic stirrer, an ultrasonic probe, a sample inlet, a sample outlet, and a stagnant zone. The sample chamber is configured to hold an activated sludge sample, and the ultrasonic time domain reflectometer is configured to measure the settling characteristics of the activated sludge. The stagnant zone is disposed in the sample chamber. The sample inlet and the sample outlet communicate with the sample chamber. The stagnant zone includes a top part, a sidewall, and a bottom part. The sample inlet is connected to the top part of the stagnant zone. The sample outlet is connected to the sidewall of the stagnant zone. The magnetic stirrer is disposed at the bottom part of the stagnant zone. The ultrasonic probe is disposed on the top part of the stagnant zone.

Claims

1. A device, comprising: 1) a sample chamber comprising a stagnant zone; 2) an ultrasonic time domain reflectometer; 3) a magnetic stirrer; 4) an ultrasonic probe; 5) a sample inlet; and 6) a sample outlet; wherein: the sample chamber is configured to hold an activated sludge sample, and the ultrasonic time domain reflectometer is configured to measure settling characteristics of the activated sludge sample; the sample inlet and the sample outlet communicate with the sample chamber; the stagnant zone comprises a top part, a sidewall, and a bottom part; the sample inlet is connected to the top part of the stagnant zone; the sample outlet is connected to the sidewall of the stagnant zone; the magnetic stirrer is disposed at the bottom part of the stagnant zone; and the ultrasonic probe is disposed on the top part of the stagnant zone; and the ultrasonic time domain reflectometer is connected to the ultrasonic probe to transmit signals.

2. The device of claim 1, wherein the ultrasonic time domain reflectometer comprises an ultrasonic transmitter and an oscilloscope; the ultrasonic probe further comprises a signal input terminal and a signal output terminal; the ultrasonic transmitter comprises a signal output terminal connected to the signal input terminal of the ultrasonic probe; and the oscilloscope comprises a signal input terminal connected to the signal output terminal of the ultrasonic probe.

3. The device of claim 1, wherein the device further comprises an exhaust pipe comprising a first end and a second end; the first end of the exhaust pipe communicates with the stagnant zone and the second end of the exhaust pipe is extended out of the sample chamber.

4. The device of claim 1, wherein the device further comprises a peristaltic pump and a pipeline; the peristaltic pump is disposed in the sample chamber and used to clear the activated sludge sample; the pipeline is disposed between the sample outlet and the stagnant zone; and the peristaltic pump is disposed on the pipeline.

5. The device of claim 1, wherein the device further comprises a ball valve for controlling a flow velocity of the activated sludge sample at 10-30 mL/min.

6. A method for in-situ measuring settleability of activated sludge using the device of claim 1, the method comprising: 1) collecting an activated sludge sample in a target location using a constant flow peristaltic pump; 2) guiding the activated sludge sample from the sample inlet into the stagnant zone; starting the magnetic stirrer to mix the activated sludge sample where exhaust gas is produced; and removing the exhaust gas out of the stagnant zone through an exhaust pipe communicating with the stagnant zone; 3) stopping the magnetic stirrer; turning on the ultrasonic time domain reflectometer to control the ultrasonic probe to emit an ultrasonic signal to monitor the activated sludge sample in the stagnant zone for 30 minutes; collecting the ultrasonic signal by the oscilloscope and showing an ultrasonic waveform change diagram over time; 4) forming a sludge settling displacement curve according to the ultrasonic waveform change diagram; 5) obtaining a displacement value at 30.sub.th minute according to the sludge settling displacement curve; and calculating a sludge volume index (SVI) according to a fitted equation; and 6) removing the activated sludge sample out of the stagnant zone through a peristaltic pump. The method of claim 6, wherein in 4), the sludge settling displacement curve is formed as follows: obtaining a maximum displacement value at a target peak of the ultrasonic waveform change diagram during each time period; taking a displacement value at 0 minute as a benchmark, calculating a difference between the maximum displacement value during each time period and the benchmark, and drawing the sludge settling displacement curve with time as abscissa and the difference as ordinate.

8. The method of claim 6, wherein in 5), the fitted equation is formed by linear regression of SVI value and displacement value that are respectively derived from a weight subtraction method and an ultrasonic time domain detection; and the fitted equation is expressed as y=4.3x+254.3; where y is the sludge volume index, and x is the displacement at 30.sub.th minute.

9. The method of claim 6, wherein the ultrasonic transmitter is operated at a pulse repetition frequency of 10-20 Hz, a pulse resistance is 10-50 Ω, a pulse voltage is 100-400 V, a gain is 50-60 dB, a high-pass filter is 0.03-0.1 MHz, and a low-pass filter is 1-3 MHz.

10. The method of claim 6, wherein in 3), the oscilloscope collects the ultrasonic signal once every 2-60 seconds.

Description

DETAILED DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 is a perspective view of a device for in-situ measuring settleability of activated sludge according to one example of the disclosure;

[0031] FIG. 2 is a schematic diagram of an ultrasonic wave detected in Example 1 of the disclosure;

[0032] FIG. 3 is a graph showing a sludge settling displacement curve according to Example 1 of the disclosure;

[0033] FIG. 4 is a schematic diagram of an ultrasonic wave detected in Example 2 of the disclosure;

[0034] FIG. 5 is a graph showing a sludge settling displacement curve according to Example 2 of the disclosure;

[0035] FIG. 6 is a schematic diagram of an ultrasonic wave detected in Example 3 of the disclosure; and

[0036] FIG. 7 is a graph showing a sludge settling displacement curve according to Example 3 of the disclosure;

DETAILED DESCRIPTION

[0037] Referring to FIG. 1, a device for in-situ measuring settling characteristics of activated sludge, the device comprising: a sample chamber 1, an ultrasonic time domain reflectometer 10, a sample inlet 2, a sample outlet 5, a magnetic stirrer 7, a stagnant zone 8, an ultrasonic probe 3, a ball valve 13, an exhaust pipe 4, and a peristaltic pump 6, and a pipeline; the sample chamber is configured to hold an activated sludge sample and comprises stainless steel for sound proofing; the stagnant zone 8 is disposed in the sample chamber and has a height of 25 cm and a volume of 500 mL; the stagnant zone is surrounded by glass; the ultrasonic time domain reflectometer is used to monitor the settling characteristics of the activated sludge; the sample inlet 2 and the sample outlet 5 are disposed outside of the sample chamber 1; the sample inlet 2 is in the shape of a funnel for collecting the activated sludge sample; the ball valve is disposed into the sample inlet 2 to control the flow velocity of the activated sludge sample at 10-30 mL/min; the exhaust pipe comprises a first end and a second end; the first end of the exhaust pipe communicates with the stagnant zone and the second end of the exhaust pipe is extended out of the sample chamber for gas removal; the stagnant zone comprises a top part, a sidewall, and a bottom part; the sample inlet is connected to the top part of the stagnant zone; the sample outlet is connected to the sidewall of the stagnant zone; the pipeline is disposed between the sample outlet and the stagnant zone; and the peristaltic pump is disposed on the pipeline; the magnetic stirrer is disposed at the bottom part of the stagnant zone and runs at a speed of 75 rpm for 25 seconds; and the ultrasonic probe is disposed on the top part of the stagnant zone. The ultrasonic time domain reflectometer 10 comprises an ultrasonic transmitter 12 and an oscilloscope 11; the ultrasonic probe comprises a signal input terminal and a signal output terminal; the ultrasonic transmitter comprises a signal output terminal connected to the signal input terminal of the ultrasonic probe;

[0038] and the oscilloscope comprises a signal input terminal connected to the signal output terminal of the ultrasonic probe.

EXAMPLE 1

[0039] A method for monitoring real-time settling characteristics of the sludge that bulks severely in an aerobic tank and cannot meet the Class 1 (A) municipal effluent quality requirements, the method comprising:

[0040] 1. Activated Sludge Sampling

[0041] A target pool was divided into three independent areas; an activated sludge sample was collected at a depth of 0.5 m below the surface of sewage in each area; and three activated sludge samples were mixed together. The specific sampling process was detailed as follows: the activated sludge sample was collected by a peristaltic pump; the peristaltic pump comprised a pump tube provided with a sludge inlet; the sludge inlet was placed in a target location to extract 200 mL of activated sludge as a sample at a flow rate of 10 mL/min; the peristaltic pump was turned on to extract 2 L of sewage in the target location to clean the pump tube before next sludge sampling.

[0042] 2. Sample Processing

[0043] As shown in FIG. 1, the device was placed on flat ground to extract the activated sludge sample via the sample inlet and to transport the activated sludge sample into the stagnant zone; the activated sludge sample was filled up to 2-5 cm below from the top part of the stagnant zone; the magnetic stirrer was turned on to mix the collected activated sludge samples; an exhaust gas flowed out of the stagnant zone through the exhaust pipe; then the stirring stopped, and the ultrasonic transmitter was turned on to control the ultrasonic probe to emit an ultrasonic signal to monitor the activated sludge sample in the stagnant zone for 30 minutes; the oscilloscope collected the ultrasonic signal once every 60 seconds and showed an ultrasonic waveform change diagram over time, as shown in FIG. 2; for the data shown in FIG. 2, the values of time increased from 0 to 30 minutes; the maximum displacement value at a target peak during each time period was obtained; and the displacement value at 0 minute was taken as a benchmark; a difference between the maximum displacement value during each time period and the benchmark was calculated; and a sludge settling displacement curve with time as abscissa and displacement as ordinate was drawn, as shown in FIG. 3. The displacement value increased with time; and the sludge settling curve shown a trend for analyzing the sludge settling rate (SVI) and pollutant removal performance; the ordinate corresponding to abscissa 30.sub.th minute was −7 nanosecond (ns), which was used as index to measure the sludge volume index.

[0044] An equation was formed by linear regression of the displacement value and the SVI data that were respectively derived from the ultrasonic time domain detection and the weight subtraction method; and the equation fitting process comprises:

[0045] 1. a sludge in an aerobic section of a sewage treatment plant was sampled and undergone an SVI measurement to obtain an SVI value; and 1) was repeated three times;

[0046] 2. the same activated sludge sample was analyzed by the device of the disclosure: the activated sludge sample was placed into the sample chamber; the ultrasonic time domain reflectometer was turned on to monitor the activated sludge sample for 30 minutes, so that a displacement value was obtained; and 2) was repeated three times; and

TABLE-US-00001 Sludge volume index Sample (SVI) Displacement 1 −7.2 218.9 2 −22 168.2 3 −14.8 178.2 4 −27.2 157.4 5 −14.2 193.4 6 −43.4 60.0 7 −48.4 43.0

[0047] 3. an equation was formed by linear regression of the SVI value and the displacement value and expressed as y=4.3x+254.3; where y was the sludge volume index, and x was the displacement at 30.sub.th minute.

[0048] The ordinate value -7 ns was substituted into the equation to get an SVI value of 224.2 mL/g, which indicated that severe sludge bulking occurred in the samples of Example 1. The device of the disclosure determined the settling characteristics of the activated sludge within 30 minutes, which was faster than a conventional method consuming 4-5 hours.

EXAMPLE 2

[0049] A method for monitoring real-time settling characteristics of the sludge that bulks severely in an aerobic tank and cannot meet the Class 1 (A) municipal effluent quality requirements, the method comprising:

[0050] 1. Activated Sludge Sampling

[0051] A target pool was divided into three independent areas; an activated sludge sample was collected at a depth of 0.5 m below the surface of sewage in each area; and three activated sludge samples were mixed together. The specific sampling process was detailed as follows: the activated sludge sample was collected by a peristaltic pump; the peristaltic pump comprised a pump tube provided with a sludge inlet; the sludge inlet was placed in a target location to extract 200 mL of activated sludge as a sample at a flow rate of 10 mL/min; the peristaltic pump was turned on to extract 2 L of sewage in the target location to clean the pump tube before next sludge sampling.

[0052] 2. Sample Processing

[0053] As shown in FIG. 1, the device was placed on flat ground to extract the activated sludge sample via the sample inlet and to transport the activated sludge sample into the stagnant zone; the activated sludge sample was filled up to 2-5 cm below from the top part of the stagnant zone; the magnetic stirrer was turned on to mix the collected activated sludge samples; an exhaust gas flowed out of the stagnant zone through the exhaust pipe; then the stirring stopped, and the ultrasonic transmitter was turned on to control the ultrasonic probe to emit an ultrasonic signal to monitor the activated sludge sample in the stagnant zone for 30 minutes; the oscilloscope collected the ultrasonic signal once every 60 seconds and showed an ultrasonic waveform change diagram over time, as shown in FIG. 4. For the data shown in FIG. 4, the values of time increased from 0 to 30 minutes; the maximum displacement value at a target peak during each time period was obtained; and the displacement value at 0 minute was taken as a benchmark; a difference between the maximum displacement value during each time period and the benchmark was calculated; and a sludge settling displacement curve with time as abscissa and displacement as ordinate was drawn, as shown in FIG. 5. For the data shown in FIG. 5, the displacement value increased with time; the ordinate corresponding to abscissa 30.sub.th minute was -22 ns, which was used as index to measure the sludge volume index and substituted into the fitted equation in Example 1 to get an SVI value of 159.7 mL/g, indicating that slight sludge bulking occurred in the samples.

EXAMPLE 3

[0054] A method for monitoring real-time settling characteristics of the sludge that bulks severely in an aerobic tank and cannot meet the Class 1 (A) municipal effluent quality requirements, the method comprising:

[0055] 1. Activated Sludge Sampling

[0056] A target pool was divided into three independent areas; an activated sludge sample was collected at a depth of 0.5 m below the surface of sewage in each area; and three activated sludge samples were mixed together. The specific sampling process was detailed as follows: the activated sludge sample was collected by a peristaltic pump; the peristaltic pump comprised a pump tube provided with a sludge inlet; the sludge inlet was placed in a target location to extract 200 mL of activated sludge as a sample at a flow rate of 10 mL/min; the peristaltic pump was turned on to extract 2 L of sewage in the target location to clean the pump tube before next sludge sampling.

[0057] 2. Sample Processing

[0058] As shown in FIG. 1, the device was placed on flat ground to extract the activated sludge sample via the sample inlet and to transport the activated sludge sample into the stagnant zone; the activated sludge sample was filled up to 2-5 cm below from the top part of the stagnant zone; the magnetic stirrer was turned on to mix the collected activated sludge samples; an exhaust gas flowed out of the stagnant zone through the exhaust pipe; then the stirring stopped, and the ultrasonic transmitter was turned on to control the ultrasonic probe to emit an ultrasonic signal to monitor the activated sludge sample in the stagnant zone for 30 minutes; the oscilloscope collected the ultrasonic signal once every 60 seconds and showed an ultrasonic waveform change diagram over time, as shown in FIG. 6. For the data shown in FIG. 6, the values of time increased from 0 to 30 minutes; the maximum displacement value at a target peak during each time period was obtained; and the displacement value at 0 minute was taken as a benchmark; a difference between the maximum displacement value during each time period and the benchmark was calculated; and a sludge settling displacement curve with time as abscissa and displacement as ordinate was drawn, as shown in FIG. 7. For the data shown in FIG. 7, the displacement value increased with time; the ordinate corresponding to abscissa 30.sub.th minute was −28 ns, which was used as index to measure the sludge volume index and substituted into the fitted equation in Example 1 to get an SVI value of 133.9 mL/g, indicating that slight sludge bulking occurred in the samples.

[0059] It will be obvious to those skilled in the art that changes and modifications may be made, and therefore, the aim in the appended claims is to cover all such changes and modifications.