Identifying spatiotemporal trends of SARS-CoV-2 RNA in wastewater: from the perspective of upstream and downstream wastewater-based epidemiology (WBE)

Recently, many efforts have been made to address the rapid spread of newly identified COVID-19 virus variants. Wastewater-based epidemiology (WBE) is considered a potential early warning tool for identifying the rapid spread of this virus. This study investigated the occurrence of SARS-CoV-2 in eight wastewater treatment plants (WWTPs) and their sewerage systems which serve most of the population in Taoyuan City, Taiwan. Across the entire study period, the wastewater viral concentrations were correlated with the number of COVID-19 cases in each WWTP (Spearman's r = 0.23-0.76). In addition, it is confirmed that several treatment technologies could effectively eliminate the virus RNA from WWTP influent (> 90%). On the other hand, further results revealed that an inverse distance weighted (IDW) interpolation and hotspot model combined with the geographic information system (GIS) method could be applied to analyze the spatiotemporal variations of SARS-CoV-2 in wastewater from the sewer system. In addition, socio-economic factors, namely, population density, land use, and income tax were successfully identified as the potential drivers which substantially affected the onset of the COVID-19 outbreak in Taiwan. Finally, the data obtained from this study can provide a powerful tool in public health decision-making not only in response to the current epidemic situation but also to other epidemic issues in the future.

The characteristics of stepwise ultrasonic hydrolysates of sludge for enhancing denitrification

The disposal of waste activated sludge (WAS) accounts for approximately 60 % of wastewater treatment plant operating costs. In this study, according to the reaction time and water quality parameters, ultrasonic hydrolysis of WAS is divided into three stages, including floc-disintegration (0-25.2 kJ/g TS), cell-disruption (25.2-36 kJ/g TS), and cell-degradation (over 36 kJ/g TS). The results show that more than 70 % carbon distributes inside the cell, which also contains 63.8 % protein enhancing denitrification capacity. Moreover, cell-degradation hydrolysate has a higher proportion of readily biodegradable COD, indicating that intracellular organic matter is more capable of denitrification than extracellular. Therefore, the optimal ultrasonic operating range is E_s = 36-72 kJ/g TS as carbon source, and obtain the hydrolysate with high ratio of soluble chemical oxygen demand to total nitrogen for denitrification. Furthermore, this study supports the comprehensive interpretation of ultrasonic hydrolyzed WAS and the characteristics of hydrolysate as carbon source for enhancing denitrification.

Electroacoustic analysis, design, and implementation of a small balanced armature speaker

This paper presents a new design and implementation of a balanced armature speaker (BAS), which is composed of permanent magnetic circuits, a moving armature, and a coil. The armature rocks about a pivot with the coil at one end and the permanent magnet on another. A magnetic circuit analysis is conducted for the designed BAS to formulate the force factor, which is required for modeling the coupling between the electrical and mechanical systems. In addition, an electromechanoacoustical analogous circuit is established for the BAS, which bears the same structure as the moving coil loudspeaker, except that the force factor is different. A hybrid model, which combines the lumped parameter model in the electrical and acoustical domains with a finite element model in the mechanical domain, is developed to model the high-frequency response because of the high-order modes of the membrane, the drive rod, and the armature. The electroacoustic analysis is experimentally verified. The results indicate that the sound pressure response that is simulated using the hybrid model is in superior agreement with the measured response to that simulated using the lumped parameter model.