Microbiological Aspects of Humid Husk Composting

Abstract

The feasibility of composting as disposal practice of husk mixed with olive mill wastewaters (OMW) was studied in the present research. The process was investigated with regards to some reliable and easy to be determined microbial activity parameters such as the ATP content, the activity of a pool of enzymes and the viable counts, keeping in mind the well known bias of this last technique. Two different composting technologies were compared: static pile and reactor by studying the cured composts obtained. Among the bioindicators tested, the composting process trend was described better by the ATP content and the activity of some enzymes. In fact, the ATP content showed an increase during the thermophilic phase in both the pile and the reactor, and decreased at the end of the process, it was also higher in the bioreactor‐pile technology than in the pile. With regard to the enzymatic activity, with the reactor technology experiment, two peaks were evidenced in the thermophilic phase and during the curing phase in pile, and a drop during the transfer of material from the reactor to the pile. The quality of the cured product obtained using the reactor technology has been evaluated considering phytoxicity and hygienic features: the stabilised compost resulted to have neither phytoxical effect, nor faecal indicator contaminants.

Keywords:

• Composting technologies
• Microflora
• ATP
• Enzymatic activity
• Faecal contaminants

Acknowledgments

The paper has been carried out with financial support from the Commission of the European Communities, Agriculture and Fisheries (FAIR) specific RTD programme, FAIR5‐CT97‐3620, “COMPOSTING OF HUSKS PRODUCED BY TWO PHASE CENTRIFUGATION OLIVE OIL MILLING PLANTS”—“Husks project.” It does not necessarily reflect its views and in no way anticipates the Commission's future policy in this area.