Optimization of the proportions of four wastewaters in a blend for the cultivation of microalgae using a mixture design.

A 2nd degree mixture design was used to determine the optimal blend prepared from four wastewater streams to produce microalgae-based biomass. The streams consisted of a liquid digestate from an anaerobic digestion process, a landfill leachate, a septic-system sludge treatment plant liquid, and a wastewater treatment plant effluent. The mixture regression analysis indicated that blends with higher proportions of treated effluent and digestate improved cells growth, while the use of leachate was detrimental to the growth. The global solution of the mixture optimization predicted a maximum value of biomass productivity of 22.76 mg L-1 d-1, in a blend consisting of 19% treated effluent, 21% digestate, and 60% water. Proportions of leachate higher than 13.33% were detrimental to the growth. The concentration of ammonia-N in the blends ranged from 0.39 to 150 mg L-1 d-1, and its toxicity effect on the cells diminished with increasing amounts of organic carbon in the cultivation medium.

Physico-chemical changes in tomato with modified atmosphere storage and UV treatment.

Physico-chemical changes in ripe tomato (Lycopersicon esculentum Mill.) were analyzed on day 0 and 2 weeks after ultraviolet-C (UV-C) light treatment or modified atmosphere (MA) storage and combined UV-C + MA storage at 10 °C. Modified atmosphere packaging (MAP) film was used to create MA conditions. The tomatoes were evaluated for surface colour, mass loss, firmness, respiration rate, total soluble solids and antioxidant capacity. The tomatoes treated with UV-C and MA storage underwent least changes in their physico-chemical properties, indicating that combination of UV-C and MA storage was successful in retaining the attributes of the fresh product. The increase in antioxidant capacity of the tomatoes during UV-C treatment suggested that UV treatment during post harvest handling may be successfully combined with MA storage, resulting in a product with better nutritive value.