The synergistic effect of chemical oxidation and microbial activity on improving volatile fatty acids (VFAs) production during the animal wastewater anaerobic digestion process treated with persulfate/biochar.

Improving volatile fatty acid (VFA) production, rather than producing methane from the anaerobic digestion (AD) of waste, has become a new strategy of resource utilization. In regard to animal wastewater, the effectiveness of persulfate/biochar (potassium peroxodisulfate, PDS/BC) on the hydrolysis and acidogenesis stages and the reaction mechanisms are still unclear. In this study, the AD process on cow wastewater was controlled at the hydrolysis and acidification stages by setting the hydraulic retention time (HRT) at 25 days. The results showed that the contents of total solids (TS) and volatile solids (VS) were further reduced by PDS/BC treatment with 0.15 gPDS/gTS of PDS added. The VFAs production increased by 12.4 % from day 0 to 25 compared to the blank set. Based on our molecular analysis, the rate of increase for the dissolved organic matter with low molecular weight (0-10 kDa) was 699.5 mg/(L·d) in the first 10 days. The change rate increased nearly 2.1 times, leading to higher VFAs yield. Moreover, the activities of fermentative bacteria were enhanced and Anaerocella was determined to be the specific and critical genus. However, excessive PDS (0.3 gPDS/gTS) prolonged the acidification period and caused the inactivation of fermentative bacteria. Structural equation modeling demonstrated that PDS can directly affect VFAs yield and also had an indirect effect by influencing the decomposition of particulate matter and microbial activities. Therefore, the enhancement of VFAs production using the PDS/BC method could be due to synergistic chemical and microbial effects. Findings from this study can provide a practical strategy to enhance the VFAs production of AD technology for livestock wastewater and help reveal the reaction mechanism of PDS/BC treatment.

The relationship between the molecular composition of dissolved organic matter and bioavailability of digestate during anaerobic digestion process: Characteristics, transformation and the key molecular interval.

In this study, swine wastewater (SW) and cow wastewater (CW) were used for anaerobic digestion (AD). We found the bioavailability of dissolved organic matter (DOM) was affected by the molecular weight ranges and molecular composition during the AD process. The organic substance in the small molecular range (0-5 kDa) accumulated due to a larger molecular fraction (>10 kDa) degradation, which enhanced the bioavailability of the DOM. Moreover, based on the excitation emission matrix-parallel factor (EEM-PARAFAC) analysis, the protein-like component in 0-5 kDa molecular size and humic-like component over 5 kDa are significantly positively correlated with DOM bioavailability. This study indicated that increasing the hydrolysis of larger organic matter and humification degree of molecular weights>5 kDa are critical solutions to improving the bioavailability of DOM. These conclusions can help explain the molecular mechanisms of DOM transformation and the AD process of livestock wastewater.

Relationships of Blood Pressure Circadian Rhythm and Brain Natriuretic Peptide with Left Ventricular Hypertrophy in the Patients with Primary Hypertension.

Objective To investigate the relationships of blood pressure circadian rhythm and brain natriuretic peptide (BNP) with left ventricular hypertrophy (LVH) in patients with primary hypertension. Methods Totally 349 patients (74 with LVH and 275 without LVH) with primary hypertension were enrolled in this study.Echocardiography was performed to determine left ventricular mass index (LVMI) using the Devereux formula. The nocturnal blood pressure decline rate,24-hour blood pressure (24 h PP; especially 24 h mean systolic blood pressure,24 h SBP) and blood pressure index (PPI) were determined by 24 h-ambulatory blood pressure monitoring. These 349 hypertensive patients were divided into four groups including supper-dipper group (defined as≥;20%, n=7),dipper group (defined as 10%- 20%, n=77),non-dipper group (defined as 0- 10%, n=173),and anti-dipper group (defined as<0, n=92). The baseline demographic characteristics of patients were collected. Fasting blood sugar,blood lipids,blood urea nitrogen,serum cretinine,cystatin C,uric acid,and plasma BNP level were measured. Results The patients with LVH (n=74) had significantly higher percentage of grade 3 hypertension (85.1% vs. 46.9%;χ2=34.428,P<0.001),24 h SBP (134 mmHg vs. 129 mmHg; t=3.175,P=0.002)(1 mmHg=0.133 kPa),daytime-mean SBP (134 mmHg vs. 130 mmHg; t=2.197,P=0.029),night-mean SBP(132 mmHg vs. 121 mmHg; t=4.763,P<0.001),and 24 h PP(57 mmHg vs. 52 mmHg; t=4.120,P<0.001) and PPI (0.43 vs. 0.41; t=3.335,P=0.001) and lower nocturnal blood pressure decline rate [(1.30±8.02)% vs. (5.68±7.25)%; t=-4.510,P<0.001] than the non-LVH patients (n=275). The LVH hypertensive group had significantly higher BNP level (87.8 pg/ml vs. 28.8 pg/ml; t=2.170,P=0.034) and LVMI (135.1 g/m2 vs. 88.7 g/m2; t=15.285,P<0.001) than the control group. No significant difference was observed in the BNP level among supper-dipper,dipper,non-dipper and anti-dipper groups (P=0.137).However,the difference was statistically significant in the LVMI (P=0.001). Additionally,patients in the anti-dipper group had significantly higher LVMI than those in the dipper patients (100.3 g/m2 vs. 86.3 g/m2; t=4.335,P<0.001) and non-dipper (100.3 g/m2 vs.93.7 g/m2; t=1.987,P=0.048). Patients in the non-dipper group had significantly higher LVMI than those in the dipper group (93.7 g/m2 vs. 86.3 g/m2; t=2.693,P=0.008). The multivariate linear correation analysis and logistic regressions analysis suggested a significant correlation of LVMI with BNP and the grade of hypertension. Conclusion With the increasing of plasma BNP level,the left ventricular hypertrophy is closely related to abnormal blood pressure circadian rhythm and the grade of hypertension in primary hypertensive patients.