Watsa Khongnakorn

Performance evaluation of novel PVDF–Cloisite 15A hollow fiber composite membranes for treatment of effluents containing dyes and salts using membrane distillation

The present study reports the performance of a novel PVDF–Cloisite 15A hollow fiber composite membrane for the treatment of effluents containing dyes and salts through a direct contact membrane distillation (DCMD) process. The performance of the membrane was evaluated by varying several important parameters during the DCMD process which included feed properties (type of dyes, dye and salt concentration) and process conditions (feed temperature and flow rate). The experimental results showed that the in-house made membrane was able to achieve stable fluxes and excellent dye rejections (>97%) when tested with feed solutions containing dyes of different classes and molecular weights (MW), except crystal violet (CV) dye. The lower rejection resulting from a CV-containing feed is likely due to its small MW coupled with its high diffusion rate in aqueous solution. With respect to feed concentration, it is found that an increase in salt concentration in the feed solution had a negligible effect on the membrane separation performance. Increasing the dye concentration in the feed however led to lower membrane water flux owing to the deposition of dye particles on the membrane surface which resulted in severe fouling. Meanwhile, increasing the feed temperature and its flow rate could improve the membrane flux without affecting the permeate quality. When tested using a dyeing solution containing 50 ppm acid red and 1.0 M NaCl, the membrane flux was reported to enhance by 200% and 25% on increasing the feed temperature from 50 to 90 °C and the flow rate from 0.010 to 0.023 m s−1, respectively.

Production of Sludge in a Submerged Membrane Bioreactor and Dewatering Aspects

In wastewater treatment, the membrane bioreactor (MBR) holds the potential to become one of the new generation processes, ensuring effluent quality and disinfection of sufficiently high levels to allow water reuse and recycle. Furthermore, the possibility to operate with high biomass concentrations (2 to 5 times higher than in conventional activated sludge process, CAS) allows to impose high solid retention times(SRT) that can be beneficial to a sludge production reduction and so to a reduction of disposal costs. These non-conventional operating conditions (high SRT) can also induce different sludge characteristics and dewatering aptitude, which are essential parameters for the optimization of the sludge post-treatment, like mechanical dewatering. The objective of this work was to study the performances of a complete sludge retention membrane bioreactor, in terms of organic removal efficiency, sludge production and sludge dewaterability. The adaptability of Activated Sludge Model 3 (ASM3) to provide good prediction results of high SRT-MBR was studied. Typical parameters adopted to describe sludge dewaterability were quantified and compared with the conventional activated sludge process (CAS).

Applications and characterization of silicalite-1/polydimethylsiloxane composite membranes for the pervaporation of a model solution and fermentation broth

Abstract Ethanol recovery via pervaporation is greatly influenced by membrane separation performance, which can be enhanced by adding hydrophobic fillers such as silicalite-1. Silicalite-1 was prepared by controlling the gel molar composition in hydrothermal synthesis, and it was incorporated into a polydimethylsiloxane (PDMS) membrane on Teflon. The silicalite-1 Si-O-Si structures interacted with the -Si(CH3)2-O- backbone of the PDMS chain. The thermal gravimetric analysis results showed that the silicalite-1 improved the thermal stability and raised the initial decomposition temperature from 405°C to 450–470°C. Increasing silicalite-1 content from 5 to 20 wt% enhanced the relative ethanol/water swelling from 1.33% to 1.52% and advanced the contact angle from 112.6° to 138.6°. Addition of 20 wt% silicalite-1 improved the separation factor in broth from 2.55 to 5.56. When using 20 wt% silicalite-1/PDMS membrane and replacing the ethanol solution with broth, fouling reduced the flux from 597 to 482 g m−2 h−1, but the broth composite increased the separation factor from 3.14 to 5.56. The overall pervaporation separation index with a santol broth of the 20 wt% silicalite-1/PDMS and commercial PDMS membranes were 2199 and 2110. The prepared membranes had similar overall performance as a commercial membrane.

Energy Consumption for Brine Solution Recovery in Direct Contact Membrane Distillation

Direct contact membrane distillation (DCMD) process was applied for brine solution recovery. The energy consumption of the process was evaluated as varying feed temperature and cross flow velocity (CFV). The evaporation efficiency and energy consumption were also studied. The experiments was carried out using a hollow fiber PVDF membrane with pore size of 0.1 μm and NaCl 3.5 %wt as feed solution. The operating feed temperature and CFV were in range of 40 °C-70 °C and 0.14-0.42 m/s (laminar and transition flow region), respectively. The temperature and CFV of permeate were fixed at 20 °C and 1.97 m/s respectively. It was found that the flux rate was in function with the temperature, CFV and temperature polarization coefficient (TPC). The best result in terms of energy consumption and evaporation efficiency were obtained at CFV and temperature of 0.28 m/s and 70 °C about 188.6 W and 41.1 %, respectively.