Effect of temperature and aeration rate on co-composting of olive mill wastewater with olive stone wooden residues

Co-composting of the solid residues and wastewater from the olive oil production process was examined as a potential bioremediation treatment for these wastes. Experimental results from a semi batch laboratory pilot plant were reported. Composting was performed for 20 days under constant moisture 40% and the temperature ranged from 55 to 72°C and the oxygen partial pressure from 10 to 17%. An operational region of temperature and oxygen partial pressure was defined in order to achieve a ratio of total olive mill wastewater consumption to olive stone wooden residue stabilization equal or greater than 2.5, the typical ratio for an olive mill plant. Another critical parameter for the optimisation of the 20-day co-composting process that was examined was the biological efficiency of the process, as the carbon dioxide produced to the total carbon available to biomass. A strong sigmoid correlation of co-composting efficiency with temperature derived, reaching a maximum plateau of 0.50 at 68°C. The optimum conditions for a 20-day semi batch co-composting proved to be 68°C and 16–17% oxygen partial pressure, indicating that this process could be an integrated treatment scheme for olive mills.     

Respecting Autonomy Over Time: Policy and Empirical Evidence on Re‐Consent in Longitudinal Biomedical Research

Re‐consent in research, the asking for a new consent if there is a change in protocol or to confirm the expectations of participants in case of change, is an under‐explored issue. There is little clarity as to what changes should trigger re‐consent and what impact a re‐consent exercise has on participants and the research project. This article examines applicable policy statements and literature for the prevailing arguments for and against re‐consent in relation to longitudinal cohort studies, tissue banks and biobanks. Examples of re‐consent exercises are presented, triggers and non‐triggers for re‐consent discussed and the conflicting attitudes of commentators, participants and researchers highlighted. We acknowledge current practice and argue for a greater emphasis on ‘responsive autonomy,’ that goes beyond a one‐time consent and encourages greater communication between the parties involved. A balance is needed between respecting participants' wishes on how they want their data and samples used and enabling effective research to proceed.