Biodiesel Exhaust Toxicity with and without Diethylene Glycol Dimethyl Ether Fuel Additive in Primary Airway Epithelial Cells Grown at the Air-Liquid Interface.

Biodiesel usage is increasing steadily worldwide as the push for renewable fuel sources increases. The increased oxygen content in biodiesel fuel is believed to cause decreased particulate matter (PM) and increased nitrous oxides within its exhaust. The addition of fuel additives to further increase the oxygen content may contribute to even further benefits in exhaust composition. The aim of this study was to assess the toxicity of 10% (v/v) diethylene glycol dimethyl ether (DGDME) added as a biodiesel fuel additive. Primary human airway epithelial cells were grown at the air-liquid interface and exposed to diluted exhaust from an engine running on either grapeseed, bran, or coconut biodiesel or the same three biodiesels with 10% (v/v) DGDME added to them; mineral diesel and air were used as controls. Exhaust properties, culture permeability, epithelial cell damage, and IL-6 and IL-8 release were measured postexposure. The fuel additive DGDME caused a decrease in PM and nitrous oxide concentrations. However, exhaust exposure with DGDME also caused decreased permeability, increased epithelial cell damage, and increased release of IL-6 and IL-8 (p < 0.05). Despite the fuel additive having beneficial effects on the exhaust properties of the biodiesel, it was found to be more toxic.

Thin-film fixed-bed reactor for solar photocatalytic inactivation of Aeromonas hydrophila: influence of water quality.

BACKGROUND: Controlling fish disease is one of the major concerns in contemporary aquaculture. The use of antibiotics or chemical disinfection cannot provide a healthy aquaculture system without residual effects. Water quality is also important in determining the success or failure of fish production. Several solar photocatalytic reactors have been used to treat drinking water or waste water without leaving chemical residues. This study has investigated the impact of several key aspects of water quality on the inactivation of the pathogenic bacterium Aeromonas hydrophila using a pilot-scale thin-film fixed-bed reactor (TFFBR) system. RESULTS: The level of inactivation of Aeromonas hydrophila ATCC 35654 was determined using a TFFBR with a photocatalytic area of 0.47 m(2) under the influence of various water quality variables (pH, conductivity, turbidity and colour) under high solar irradiance conditions (980-1100 W m(-2)), at a flow rate of 4.8 L h(-1) through the reactor. Bacterial enumeration were obtained through conventional plate count using trypticase soy agar media, cultured in conventional aerobic conditions to detect healthy cells and under ROS-neutralised conditions to detect both healthy and sub-lethally injured (oxygen-sensitive) cells. The results showed that turbidity has a major influence on solar photocatalytic inactivation of A. hydrophila. Humic acids appear to decrease TiO(2) effectiveness under full sunlight and reduce microbial inactivation. pH in the range 7-9 and salinity both have no major effect on the extent of photoinactivation or sub-lethal injury. CONCLUSIONS: This study demonstrates the effectiveness of the TFFBR in the inactivation of Aeromonas hydrophila under the influence of several water quality variables at high solar irradiance, providing an opportunity for the application of solar photocatalysis in aquaculture systems, as long as turbidity remains low.

Thin-film fixed-bed reactor (TFFBR) for solar photocatalytic inactivation of aquaculture pathogen Aeromonas hydrophila.

BACKGROUND: Outbreaks of infectious diseases by microbial pathogens can cause substantial losses of stock in aquaculture systems. There are several ways to eliminate these pathogens including the use of antibiotics, biocides and conventional disinfectants, but these leave undesirable chemical residues. Conversely, using sunlight for disinfection has the advantage of leaving no chemical residue and is particularly suited to countries with sunny climates. Titanium dioxide (TiO2) is a photocatalyst that increases the effectiveness of solar disinfection. In recent years, several different types of solar photocatalytic reactors coated with TiO2 have been developed for waste water and drinking water treatment. In this study a thin-film fixed-bed reactor (TFFBR), designed as a sloping flat plate reactor coated with P25 DEGUSSA TiO2, was used. RESULTS: The level of inactivation of the aquaculture pathogen Aeromonas hydrophila ATCC 35654 was determined after travelling across the TFFBR under various natural sunlight conditions (300-1200 W m(-2)), at 3 different flow rates (4.8, 8.4 and 16.8 L h(-1)). Bacterial numbers were determined by conventional plate counting using selective agar media, cultured (i) under conventional aerobic conditions to detect healthy cells and (ii) under conditions designed to neutralise reactive oxygen species (agar medium supplemented with the peroxide scavenger sodium pyruvate at 0.05% w/v, incubated under anaerobic conditions), to detect both healthy and sub-lethally injured (oxygen-sensitive) cells. The results clearly demonstrate that high sunlight intensities (≥ 600 W m(-2)) and low flow rates (4.8 L h(-1)) provided optimum conditions for inactivation of A. hydrophila ATCC 3564, with greater overall inactivation and fewer sub-lethally injured cells than at low sunlight intensities or high flow rates. Low sunlight intensities resulted in reduced overall inactivation and greater sub-lethal injury at all flow rates. CONCLUSIONS: This is the first demonstration of the effectiveness of the TFFBR in the inactivation of Aeromonas hydrophila at high sunlight intensities, providing proof-of-concept for the application of solar photocatalysis in aquaculture systems.