Simulating the impact of piers on hydrodynamics and pollutant transport: A case study in the Middle Yangtze River

It is known that channel engineering, including the construction of piers, will change the river hydrodynamic characteristics, which is a significant factor affecting the transport process of pollutants. With this regard, this study uses the well-validated and tested hydrodynamic module and transport module of MIKE 21 to simulate the hydrodynamics and water quality under various pier densities in the Wuhan reach. Hydrodynamic changes around the piers show spatial differences, which are similar under different discharges. The range and amplitude of hydrodynamic spatial variations increase with the increase in pier density. However, there is a critical value of 1.25 to 2.5 units/km. When the pier density is less than this critical value, this type of cumulative effect is the most significant. Additionally, greater changes can be found in chemical oxygen demand concentrations, which also show spatial and temporal variations. The area with high chemical oxygen demand concentration upstream and downstream from the engineering area exhibits the distribution characteristics of “decrease in the downstream area and increase in the upstream area” and “increase in downstream the area and decrease in the upstream area” respectively. In the reach section of the engineering area, the area with high chemical oxygen demand concentration increases in the front area near the piers and decreases near the shoreline. Furthermore, the concentration shows attenuation actions with a longer residence time owing to the buffering effect of pier groups. These results have significant implications on shoreline planning and utilization. Moreover, they provide scientific guidelines for water management.

Pinch Technology Approach to Freshwater and Wastewater Minimisation in Brewing Operations

The rise in the cost of production of beer due to increasing demand for freshwater and high cost of treating wastewater, motivate research interests in resource management in beer production. This study determines and reduces the concentration of the contaminants in the wastewater samples collected from a brewery in Nigeria, to reduce freshwater demand and to save the cost of operation through wastewater reuse using pinch technology. The wastewater samples were analysed for the concentration of Chemical Oxygen Demand using standard procedures. The Total Dissolved Solids were measured using pH-EC-TDS metre. Water Cascade Analysis was used to evaluate the minimum freshwater demand and wastewater generated to design the maximum wastewater recovery network for minimum freshwater demand in the process. The results showed that for 41.54 t/hr of both the freshwater and wastewater used in the brewery operations, the Chemical Oxygen Demand concentration ranged between 0 – 74,775 ppm and the Total Dissolved Solids concentration ranged from 0 – 2,008 ppm. However, with the application of Water Cascade Analysis, the freshwater and wastewater flow rates reduced to 19.88 t/hr based on Chemical Oxygen Demand concentration and 21.54 t/hr based on Total Dissolved Solids concentration. The freshwater saving per annum based on the concentrations of Chemical Oxygen Demand and Total Dissolved Solids were ₦346,560,000:00 ($962,666.67) and ₦319,840,000:00 ($888,444.44), respectively. The study concluded that the application of Pinch Technology to brewery operation is viable because of its capacity to reduce freshwater demand and wastewater generation.

Enrichment and application of nitrifying activated sludge in membrane bioreactors

In this study, nitrifying bacteria were enriched in a membrane bioreactor (MBR, R1) and their bioaugmentation effectiveness was evaluated in another two MBRs (R2 and R3). Nitrifying activated sludge (NAS) with high nitrification activity of up to 3,000 mg-N/(L·d)−1 was successfully enriched in R1. The results showed that chemical oxygen demand concentration of 100–200 mg/L had no negative effect on NAS enrichment but reduced the ratio of bacterial nitrifiers. Moreover, the cell concentration of nitrifying bacteria in NAS, which was 3.1 × 1011 cells/L, was similar to that of the commercial bacterium agent. For the bioaugmentation test, the reactor inoculated with 14% NAS achieved a 23% higher NH4+-N removal efficiency than that of the uninoculated reactor. Along with the improvement of nitrification performance, the bacterial nitrifiers abundance and microbial richness remarkably increased after bioaugmentation. These results suggested that the MBR system could efficiently enrich nitrifying bacteria using organic carbon containing culture medium, and potentially act as a side-stream reactor to enhance the nitrification function of the wastewater treatment plant.

Experimental Study on the Rapid Start-Up of Two-Phase Anaerobic Reactor Treating Domestic Sewage

An integrated two-phase anaerobic reactor was designed to treat domestic sewage, and the corresponding start-up process was investigated.In this investigation, the volumetric loading rate ( VLR) of the system was raised by basically maintaining the influent COD ( Chemical Oxygen Demand) concentration and gradually decreasing the hydraulic retention time (HRT) at 35°C，and the start-up process was completed only in the 36 days. When the Influent pH was kept in the range of 7.39 ~ 7.67，the acidogenic phase and the methanogenic phaseof integrated two-phase anaerobic reactor were separated only by using the kinetic method. After completing this process, the reactor operated well with VLR at 1.31 kg / ( m3·d) and HRT at about 7h, and a COD removal of more than 80%,a SS removal of about 90% and a gas production rate of about 0.31L/h were respectively achieved.