Study of the variations in apparent electrical resistivity of activated sludge during the electro-dewatering process.

The high energy consumption of high apparent electrical resistivity (AER) in sludge during the later stages of the electro-dewatering (EDW) process is a difficult problem; however, analysis of sludge AER may contribute to a reduction in energy consumption. In this study, the variations in the AER of activated sludge and potential mechanisms related to sludge properties were systematically examined. First, a sludge cake was divided into four horizontal layers, in order to investigate the sludge AER in each layer. Then, the effects of variations in water distribution, oxidation-reduction potential (ORP), pH, metal ions, sludge conductivity, zeta potential, temperature, and sludge microstructure on the AER in each layer were explored. The results showed that the sludge AER began to increase from the bottom layers to the top layers when the moisture content (MC) was decreased to 60%. The formation of nonionic chemical systems and the gas barrier layer could increase the AER in the top layers, and the increase in sludge AER in the bottom layers was due to the decrease in MC and sludge conductivity. In addition, electrolyte release and electromigration had a significant effect on the sludge AER. This work identifies potential causes for the increase in AER, and provides a reference for solving problems related to high AER in sludge during the later stages of the EDW process.

Effects of sludge characteristics on electrical resistance and energy consumption during electro-dewatering process.

The increase of electrical resistance (ER) and energy consumption (EC) during the later stage of dewatering is a major problem hindering the development of electro-dewatering (EDW) technology. As the variations of sludge characteristics are significant during the EDW process, the relationships between sludge characteristics and ER and EC during EDW remain unclear. In this study, the effects of moisture content (MC), thickness, pH, conductivity, zeta potential, temperature, and gas volume on the ER and EC during the EDW process were statistically investigated using correlation and multiple linear regression analyses. Herein, the results showed that the ER of the sludge near the anode was primarily affected by pH, whereas the sludge near the cathode was primarily affected by the MC and conductivity. Further, sludge temperature and conductivity were the most reliable indicators to predict the EC near the anode and cathode, respectively. The results of this study provide theoretical guidance useful for solving the increase of ER and EC during the later stage of the EDW process.

Investigation on the variations of sludge water holding capacity of electro-dewatering process.

Since the effect of electro-dewatering (EDW) on sludge water holding capacity was unknown, tests were conducted in this study to investigate the water holding capacity of EDW sludge and the potential mechanism related to the sludge physicochemical characteristics, EPS properties and sludge structure. Sludge was dewatered to the average moisture content (AMC) of 80%, 70% and 60% with different applied voltages at 20, 30 and 40V in EDW, respectively. Then the dewatered sludge near the anode and cathode were rewatered. The variation of sludge water holding capacity in EDW process was evaluated in terms of filterability and saturated moisture content (SMC), and the filterability was assessed by the specific resistance to filtration (SRF) of rewatered sludge. The results indicated that SRF of rewatered sludge near the cathode increased greatly. The proteins/polysaccharides (PN/PS) of loosely bound extracellular polymeric substances (LB-EPS) was significantly positively correlated with SRF (r = 0.891, p < 0.01). Moreover, the exposure of hydrophobic sites or groups in PN near the cathode improved the surface hydrophobicity of sludge, which reduced the filterability. In addition, higher voltage could destroy the sludge structure near the anode at the later stage of EDW process, leading to the decrease of SRF and SMC. These results expanded the knowledge about changes in sludge properties and water holding capacity during EDW process.

Effect of B. subtilis in simulated acid red soil on the corrosion behavior of X80 pipeline steel.

The eastern section of China's West-east gas transmission project is laid in acidic red soil. NRB are widespread in soils and play an important role in metal corrosion. In this article, the corrosion failure behavior and mechanism of X80 pipeline steel under the action of NRB in simulated acidic soil were studied. It was found that the biofilm of B. subtilis had significant inhibitory on the overall corrosion of X80 steel. Electrochemical results prove that the corrosion rate of the sterile group after 14 days of immersion was about 4.5 times that of the bacterial group. However, the biofilm promotes the formation of local corrosion pits. Confocal laser scanning microscopy images indicate that that the corrosion pit depth of the bacterial group (46.1 µm) was three times that of the bacterial-free group (15.7 µm) after 14 days. The pH of the acidic environment was slightly improved by B. subtilis. XPS results proved that B. subtilis complicates the corrosion products of X80 steel through its nitrate reduction ability and metabolism.

Investigation on the improvement of activated sludge dewaterability using different iron forms (ZVI vs. Fe(II))/peroxydisulfate combined vertical electro-dewatering processes.

The high moisture content (MC) of activated sludge dewatered by traditional vertical electro-dewatering (VED) is unable to meet the disposal requirements. Therefore, different iron forms (ZVI vs. Fe(II))/peroxydisulfate (PDS) combined VED (ZVI/PDS-VED and Fe(II)/PDS-VED) were employed to enhance the dewaterability of activated sludge. The dewatering behaviors of the two combined dewatering processes and the underlying mechanism related to the sludge characteristics were investigated and compared. Sludge was conditioned using ZVI/PDS and Fe(II)/PDS, respectively, and then dewatered by the VED in the experiment. Experimental results showed that with 0.3 g (g dry solids (DS))-1 of iron activators, 0.583 g (g DS) -1 of PDS, and 30 V of voltage, the MC of sludge after ZVI/PDS-VED and Fe(II)/PDS-VED reached the minimum values of 50.6 ± 1.2% and 32.1 ± 1.5%, respectively. ZVI/PDS and Fe(II)/PDS conditioning reduced the MC difference of sludge between the anode and the cathode during the VED, facilitating the water homogenization in the sludge cake. ZVI/PDS-VED and Fe(II)/PDS-VED could effectively reduce the bound water and the free water. Free water had high correlations with α-helix (r = 0.999, p < 0.05) and CO (r = 0.998, p < 0.05). Compared with the traditional VED and the ZVI/PDS-VED, the Fe(II)/PDS-VED had a greater improvement of sludge dewaterability due to the more efficient degradation of extracellular polymeric substances and the increase of sludge surface hydrophobicity. This study promoted the development of the new sludge deep-dewatering technology.

Effects of whole-body vibration plus hip-knee muscle strengthening training on adult patellofemoral pain syndrome: a randomized controlled trial.

PURPOSE: To investigate whether whole-body vibration (WBV) plus hip-knee muscle strengthening is more efficient in relieving pain and improving function than hip-knee strengthening alone. METHODS: Thirty-six participants with patellofemoral pain syndrome (PFPS) were recruited and randomly allocated to either the (1) hip-knee strengthening only (HK group, n = 18) or (2) WBV plus hip-knee strengthening group (WHK group, n = 18). All participants attended 18 physiotherapy sessions (3 sessions/week, 40 min/session) over 6 weeks. Data on symptoms, function, surface electromyography (sEMG) signals from the vastus medialis and gluteus medius, and quality of life were evaluated at baseline (T0), 6 weeks after (T6), and the 12-week follow-up (T18). RESULTS: Significant group × time interactions were found for the VAS score (p < 0.001) and vastus medialis performance (p ≤ 0.015). The WHK group exhibited a greater pain relief than did the HK group at T18 (p ≤ 0.014). The WHK group exhibited significantly larger improvements in the RMS value than did the HK group at T6 (p ≤ 0.011). CONCLUSIONS: The present study shows that 6 weeks of WBV plus hip-knee strengthening can improve vastus medialis performance and maintain long-term pain relief to a significantly greater extent than can hip-knee strengthening alone.IMPLICATIONS FOR REHABILITATIONThe present study shows that 6 weeks of WBV plus hip-knee strengthening can improve vastus medialis performance and maintain long-term pain relief to a significantly greater extent than can hip-knee strengthening alone.

Wrist-hand extension function recovery in spastic hemiplegia patient by botulinum toxin injection plus surface electromyography biofeedback therapy: A case report.

RATIONALE: Wrist-hand extension function rehabilitation is a vital and difficult part of hand function recovery in spastic stroke patients. Although botulinum toxin type A (BoNTA) injection plus post injection therapy was applied to the wrist-hand rehabilitation in previous reports, conclusion was inconsistent in promoting function. For this phenomenon, proper selection of patients for BoNTA injection and correct choice of post-injection intervention could be the crucial factors for the function recovery. PATIENT CONCERNS: We reported a 46-year-old male suffered a spastic hemiplegia with wrist- hand extension deficit. DIAGNOSES: Computed tomography showed cerebral hemorrhage in the left basal ganglia region. INTERVENTIONS: Four hundred units of BoNTA were injected into the spasticity flexors, and four-week post injection surface electromyography (sEMG) biofeedback therapy was applied to the patient. OUTCOMES: The patient exhibited post-intervention improvement in wrist-hand extensors performance (strength, range of motion, sEMG signals), the flexors spasticity, and upper extremity function. LESSONS: The present case showed that 4-week of BoNTA injection plus sEMG biofeedback exercise improved the performance and function of wrist-hand extensors in the patient for short- and long-term. Proper selection of patients for BoNTA injection and correct choice of post injection exercise could play a vital role in the hand rehabilitation for patient with spastic hemiplegia.