Performance and fouling mechanism of direct contact membrane distillation(DCMD) treating fermentation wastewater with high organic concentrations

In this study,direct contact membrane distillation（DCMD）was used for treating fermentation wastewater with high organic concentrations.DCMD performance characteristics including permeate flux,permeate water quality as well as membrane fouling were investigated systematically.Experimental results showed that,after 12 hr DCMD,the feed wastewater was concentrated by about a factor of 3.7 on a volumetric basis,with the permeate flux decreasing from the initial 8.7 L/m^2/hr to the final 4.3 L/m^2/hr due to membrane fouling;the protein concentration in the feed wastewater was increased by about 3.5 times and achieved a value of 6178 mg/L,which is suitable for reutilization.Although COD and TOC in permeate water increased continuously due to the transfer of volatile components from wastewater,organic rejection of over 95%was achieved in wastewater.GC–MS results suggested that the fermentation wastewater contained 128kinds of organics,in which 14 organics dominated.After 12 hr DCMD,not only volatile organics including trimethyl pyrazine,2-acetyl pyrrole,phenethyl alcohol and phenylacetic acid,but also non-volatile dibutyl phthalate was detected in permeate water due to membrane wetting.FT-IR and SEM–EDS results indicated that the deposits formed on the membrane inner surface mainly consisted of Ca,Mg,and amine,carboxylic acid and aromatic groups.The fouled membrane could be recovered,as most of the deposits could be removed using a HCl/Na OH chemical cleaning method.

Preparation of InYO_3 catalyst and its application in photodegradation of molasses fermentation wastewater

An InYO 3 photocatalyst was prepared through a precipitation method and used for the degradation of molasses fermentation wastewater. The InYO 3 photocatalyst characterized by X-ray diffraction （XRD）, UV-Vis diffuse reflectance spectroscopy, surface area and porosimetry. Energy band structures and density of states were achieved using the Cambridge Serial Total Energy package （CASTEP）. The results indicated that the photodegradation of molasses fermentation wastewater was significantly enhanced in the presence of InYO 3 when compared with PbWO 4 . The calcination temperature was found to have a significant effect on the photocatalytic activity of InYO 3 . Specifically, InYO 3 calcined at 700°C had a considerably larger surface area and lower reflectance intensity and showed higher photocatalytic activity. The mathematical simulation results indicated that InYO 3 is a direct band gap semiconductor, and its conduction band is composed of In 5p and Y 4d orbitals, whereas its valence band is composed of O 2p and In 5s orbitals.

Development of a new cleaner production process for cassava ethanol

A new cleaner production process for cassava ethanol has been developed, in which the thin stillage by-product was treated initially by anaerobic digestion, and the digestate further processed by hydrogen-form cation exchange resin before being recycled as process water to make mash for the next ethanol fermentation batch.Thus wastewater was eliminated and freshwater and energy consumption was significantly reduced. To evaluate the new process, ten consecutive batches of ethanol fermentation and anaerobic digestion at lab scale were carried out. Average ethanol production in the recycling batches was 11.43%(v/v) which was similar to the first batch, where deionized(DI) water was used as process water. The chemical oxygen demand(COD) removal rate reached 98% and the methane yield was 322 ml per gram of COD removed, suggesting an efficient and stable operation of the anaerobic digestion. In conclusion, the application of the new process can contribute to sustainable development of the cassava ethanol industry.