Novel pararosaniline based optical sensor for the determination of sulfite in food extracts.

Sulfite, which is a protective agent in various food industries, also is known as an allergen. Therefore, sulfite content in food must be monitored and controlled. In this context, a novel optical sensor is designed for simple, rapid and sensitive determination of the sulfite content in food samples. Acidified pararosaniline (PRA) hydrochloride reagent in cationic form was immobilized on the surface of the Nafion cation exchanger membrane by electrostatic interactions. In formaldehyde medium, the pale purple PRA-Nafion film was converted to rich purple due to the highly conjugated alkyl amino sulfonic acid formation in the presence of sulfite and the absorbance change at 588 nm was recorded. The proposed optical sensor gave a linear response in a wide concentration range for sulfite. The limit of detection (LOD) and the limit of quantification (LOQ) values obtained for sulfite were 0.084 and 0.280 ppm SO2 equivalent, respectively. The proposed optical sensor was validated in terms of linearity, additivity, precision and recovery parameters. The sulfite contents obtained for real food extracts were found to be comparable to the conventional iodometric titration results (with the exception of highly colored samples containing reducing agents, where iodometry was shown to exhibit a systematic error while the proposed sensor could measure the true value). The proposed optical sensor is insensitive to positive interferences from turbidity and colored components of the sample. Sulfite determination in a complex food matrix can be performed using the rapid, simple and sensitive PRA-based sensor without a need for pre-treatment.

The effects of nutrient limitation (nitrogen and phosphorus) on BOD removal from post-coagulated Pinus radiata sulfite pulp and paper mill wastewater in a baffled aerated stabilisation basin-laboratory pilot scale study.

The use of coagulation and flocculation for tertiary treatment of pulp and paper mill effluent was investigated, where the evaluation was based on the removal of nitrogen (N), phosphorus (P) and BOD from post-coagulated wastewater. The study was undertaken on laboratory scale aerobic stabilisation basins (ASB). Two post coagulated (alum) wastewaters were studied, where the BOD:N:P ratios were 100:1.3:0.06 and 100:1.3:0.3. These wastewaters were treated in two identical concurrent simulations (A & B). The influent ratio for 'A' was selected representing the composition of actual coagulated Pinus radiata sulfite pulp effluent mixed with paper mill effluent. The input composition for 'B' represented a typical P concentration found in existing pulp and paper mill effluents. Unmodified sludge collected from a mill-pond was added at 4% v/v to each simulation replicating the treatment conditions at full-scale. Similar high percentage removals of BOD and COD occurred after 28 days (two HRTs) which were 94 and 67% respectively for 'A', and 98 and 70% respectively for 'B', where both remained at steady state during the third HRT. A statistical analysis of the data revealed that there was no significant difference in the sample variance of the BOD and COD results.

Molasses as an external carbon source for anaerobic treatment of sulphite evaporator condensate.

Failures in stability and COD removal performance often occurred in full-scale anaerobic reactors treating the evaporator condensate from a sulphite pulp mill due to substrate inhibition and occasional contaminations with red liquor (wood cooking liquor). With this work, the beneficial effect provided by the continuous addition of an external carbon source (sugarcane molasses) on the overall performance and stability of the biological process was evaluated. With a moderate addition of molasses the inhibition was mitigated which led to an increase of the COD removal rate from 52% to 77% and a methane production increase from 460 to 1650mld(-1) at an organic loading rate of 2.61g CODl(-1)d(-1). A similar conclusion can be drawn for the case when contamination with red liquor occurs. These results suggest that sugarcane molasses addition may be regarded as a low-cost operational strategy for the anaerobic treatment of sulphite evaporator condensate.