Evaluation of Lyophilization Effects on Operational Parameters and Characteristics of Activated Sludge

Advances in microbial and biotechnology have given great impetus to the filed of pollution control. In some countries efforts are being focused on the application of biotechnology for wastewater treatment. Occurrence of microbial growth inhibitors in the biological reactor will affect their activity, which this in turn will lead to reduced performance of the system in pollutants removal. Restart up of the system, especially in the biological treatment of industrial wastewater, will require abundance time and cost. An effective solution to reduce these problems is to prepare and store dried concentrated sludge bearing the needed microorganisms to be used later. The most effective technique to produce such concentrated sludge is lyophilization in which a stabilized biological solid is produced through rapid freezing and then drying under high vacuum conditions. This study was carried out to investigate the lyophilization effect on the microbial quality of the activated sludge. In this regard, operational characteristics including OUR, SVI, soluble COD removal efficiency and predominant microorganisms species before and after lyophilization in a lab-scale experiment were used. The results showed that sludge lyophilization had no influence on microorganisms' performance and operational characteristics of the activated sludge. In addition, there was not a significant change in the sludge properties before and after lyophilization. Sludge microorganisms were viable after lyophilization. So, lyophilization was concluded to be a suitable technology for preparation and preservation of cells in activated sludge because of preserving viability, ease of handling and simplicity.