Ultrasonic conditioning sludge test
Under the condition of ultrasonic frequency of 20 Hz, power of 60 W and treatment volume of 200 mL, the effect of ultrasonic action time on sludge dewatering was investigated.
The results are shown in Figure 1 and Figure 2.
Figure 1 Effect of ultrasonic action time on sludge
Fig. 2 Effect of ultrasonic action time on sludge moisture content
It can be seen from Fig. 1 and Fig. 2 that as the ultrasonic action time increases, the CST decreases first and then increases, and the centrifugal moisture content of the sludge decreases first, then increases and then decreases.
When the ultrasonic action time was 20 s, the CST and sludge centrifugal moisture content were the smallest, 354 s and 86.23%, respectively.
This is because the short-time ultrasonic action destroys the floc structure of the sludge, so that the water in the sludge is easily released, which is convenient for dehydration, resulting in low centrifugal water content of CST and sludge;
The long-term ultrasonic action, due to the cavitation and mechanical effects of the ultrasonic wave, makes the sludge particles too small to facilitate dehydration, and the CST and sludge centrifugal moisture content increases.
This test determined that the action time of the ultrasonic conditioning sludge was 20 s.
1.3.2 Ultrasonic and CGG combined conditioning sludge
Ultrasonic and CGG are combined to firstly use ultrasonic conditioning sludge, and then CGG for sludge conditioning.
Effect of combined action on sludge CST
The test compares the changes of sludge CST after adding different amounts of CGG conditioning sludge in two cases with and without ultrasonic pretreatment. The results are shown in Fig. 3.
Figure 3 Effect of CGG dosage on sludge CST
It can be seen from Fig. 3 that the CST of the sludge is reduced to some extent than the original sludge in both cases, and both decrease with the increase of the CGG dosage.Among them, the ultra-pretreated sludge CST is lower overall than when it is not subjected to ultrasonic pretreatment.
The CST without ultrasonic wave was the lowest when the dosage of CGG was 900 mg/L, which was 154 s. After the ultrasonic treatment, when the dosage of CGG was >540 mg/L, the CST was between 65 and 95 s. Between, the change is small.
The CST value of the untreated ultrasonic sludge at the CGG dosage of 900 mg/L is equivalent to the CST value of the ultrasonically treated sludge at a CGG dosage of 540 mg/L, indicating that the ultrasonic wave and CGG are The combined action can save the amount of CGG.
Effect of combined action on centrifugal moisture content of sludge
The test compares the changes of the centrifuge water content of the sludge after adding different amounts of CGG conditioning sludge in the presence and absence of ultrasonic pretreatment. The results are shown in Table 1.
It can be seen from Table 1 that after the ultrasonic pretreated sludge is further treated with a certain amount of CGG, the sludge has a centrifugal moisture content lower than that of the CGG-treated sludge which has not been subjected to ultrasonic treatment.
The centrifuged water content of the ultrasonic pretreated sludge decreased with the increase of CGG dosage. When the CGG dosage was >720 mg/L, the centrifugal moisture content of the sludge tends to be gentle.
It is indicated that after a certain amount of CGG dosage is reached, the effect of further increasing the dosage of CGG on the centrifugal moisture content of the sludge is reduced.
1.3.4 Ultrasonic combined with composite flocculant (CGG+PAM) to condition sludge
PAM has good flocculation property and is one of the commonly used high-molecular flocculants. In the sludge treatment, it mainly achieves the effect of flocculation and sedimentation by adsorption bridging.
The experiment investigated the effect of ultrasonic combined with CGG+PAM on sludge dewatering. In the test, the sludge was first subjected to ultrasonic pretreatment, and then CGG and PAM were sequentially added. The combination of the dosages of the two agents and the test results are shown in Table 2.
It can be seen from Table 2 that under the action of composite flocculant, the ultrasonic pretreated sludge CST is lower than that without ultrasonic treatment. Except for the first group, the ultrasonically treated sludge CST is lower than 50. s, the dehydration effect is very good.
The sludge CST without ultrasonic treatment will also have a significant decrease after the dosage of the drug reaches a certain level, but it is much higher than the CST of the sludge with the same amount of ultrasonic pretreatment.
This is because the large sludge particles are broken into small particles by ultrasonic treatment, and the small granular sludge can be more fully contacted with the flocculant, thereby better exerting the flocculation effect of the flocculant and improving the dewatering effect of the sludge.
Considering the combination, the test results of the fourth group of pharmaceutical dosages are better, and the CST is 18 s. When the sludge is not treated with ultrasonic waves and only different flocculation agents are added, The centrifugal water content of the sludge is higher than 70%, and the centrifugal water content of the sludge is greatly reduced when subjected to ultrasonic pretreatment and flocculation treatment.
Especially when the dosage of CGG and PAM is 300 and 120 mg/L, respectively, the centrifuge water content of the sludge is reduced to 58.8%.It shows that the combined treatment of ultrasonic and composite flocculant (CGG+PAM) greatly improves the dewatering of sludge and reduces the amount of flocculant added.http://www.hy-sewagetreatment.com/