Shuai-Wen Zou

Electrochemical disinfection for ballast water management: Technology development and risk assessment

Ballast water is essential in maintaining the balance and structural integrity of ships during voyage. However, it has created biological invasion threats to the ocean environment. An innovative electrochemical technology was developed in this study. The microorganisms regulated by the International Maritime Organization (D2) were used as the target organisms. It was found that the required energy to meet the D2 was below 0.006 kWh/m3. The size of disinfector (m3) was about 0.5% of treatment flow rate (m3/h). The complete disappearance of chlorine in seawater was achieved after three days. The ballast tank corrosion was not worsened due to the application of technology. The ecotoxicity studies showed no toxic effect on fish, invertebrate, and algae. Finally, the environmental risk assessment showed the treated water did not pose threats to the environment. It can therefore be concluded that the technology provides a cost-effective and environmental friendly solution to ballast water management.

Uptake of arsenate by an alginate-encapsulated magnetic sorbent: process performance and characterization of adsorption chemistry.

Arsenate removal by a calcium alginate-encapsulated magnetic sorbent was studied. The morphology, microstructure, and composition properties of the sorbent were explored using X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX). The SEM study demonstrates that there are many protuberances and pores on the sorbent surface; the XRD analysis reveals that the sorbent consists of Fe(3)O(4). The EDX analysis indicates that the adsorption on the surfaces of sorbent is highly location dependent. The interaction characteristics between the arsenic and the functional groups on the sorbent were studied by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). These studies indicate that the lattice oxygen in magnetite and the oxygen in hydroxyl of the calcium alginate play important roles in the sorption of arsenate ions onto the sorbent. More importantly, the XPS analysis demonstrates that the arsenate is reduced to arsenite after its adsorption onto the sorbent. It is proposed that divalent iron and the alcoholic group in alginate provide electrons to arsenate. A conceptual model for the adsorption is proposed to illustrate the mechanisms.

Treatment of Food Industry Foods and Wastes by Membrane Filtration

Membrane separation processes are based on the ability of semipermeable membranes of the appropriate physical and chemical nature to discriminate between molecules primarily on the basis of size and to a certain extent, on shape and chemical composition. A membrane’s role is to act as a selective barrier, enriching certain components in a feed-stream, and depleting the others. One of the chief attractions of membrane technology is the low energy requirement compared to other food processing technologies. Since membrane processes are nonthermal and do not involve a change of phases, they are energy-efficient and do not change the nature of the foods during their process operation. This chapter presents the membrane process theory and case histories of various production applications in the food industry. Operational problems and recommended engineering solutions for membrane process optimization are presented and discussed.

Surface and Spray Aeration

urface aeration involves the use of special floating aerators or spray aerators for removing taste/odor-causing substances, carbon dioxide, hydrogen sulfide, methane, volatile organic compounds, etc. from water, and for oxidizing iron and manganese in drinking water. The topics covered in this chapter are: gas solubility, diffusion, equilibrium, mixing, gas transfer, reaeration, instream aeration, surface aeration, spray aeration, and engineering design. Also included are the design examples, and the case histories of hydrogen sulfide removal, deferrization, demanganization, taste and odor removal.