Evaluation of flocculation and dissolved air flotation as an advanced wastewater treatment.
A bench scale study was carried out in order to evaluate the applicability of dissolved air flotation (DAF) as an advanced treatment for effluents from three different domestic wastewater treatment processes, namely: (i) a tertiary activated sludge plant; (ii) an upflow sludge blanket anaerobic reactor (UASB); and (iii) a high-rate stabilization pond.
Particle destabilization for tertiary treatment of municipal wastewater by filtration
Optimization of the chemical pretreatment process prior to tertiary filtration of municipal secondary effluent was studied. Jar tests involving coagulation with alum, flocculation, settling and filtration were conducted on secondary effluent samples and these established the occurrence of two distinct coagulation mechanisms: the mechanism of charge neutralization, and the mechanism of sweep coagulation at different alum dosages and pH conditions. An optimum design region on the alum coagulation diagram also was established where the removals of various wastewater parameters were the highest. This region was bound by alum dosages of 55 to 60 mg/l and pH values of 6 to 6.5. In the above domain, the BOD 5 , TOC, turbidity, total-P, and the orthophosphate levels of the secondary effluent were reduced by 73%, 57%, 98%, and 99% respectively after tertiary filtration. Particle size analysis of the settled and filtered effluent also was conducted in both the charge neutralization and the sweep coagulation zones. A wide difference was observed in particle sizes between the effluents after settling and after filtration in the charge neutralization zone. In comparison, the difference in particle size between the settled and the filtered effluents was smaller in the sweep coagulation zone.
A New Vacuum Pressure Infiltration CFRP Method and Preparation Experimental Study of Composite
In order to prepare a carbon-fiber-reinforced polymer composite (CFRP) with ideal microstructure and properties, a new vacuum pressure infiltration CFRP method is proposed based on an analysis of existing CFRP preparation process methods. Research on composite material preparation systems was carried out by using this new method principle. The system mainly includes a fiber pre-forming module, a vacuum heating infiltration module, a hot-press curing molding module, and a data acquisition control module. Under the conditions of natural curing at 0 MPa + 6 h + 25 °C, vacuum heating curing at –0.05 MPa + 30 min + 80 °C, and hot-press curing at 0.7 MPa + 5 min + 50 °C, a two-dimensional (2D) CFRP with excellent microstructure and properties was successfully prepared. Observing the microstructure of the prepared composite material, it can be found that the inside of the composite material was sufficiently and uniformly infiltrated, and common preparation defects such as holes and delamination were effectively controlled. Through the performance test, the bending strength of the material reached 790 MPa.