Comparing extraction buffers to identify optimal method to extract somatic coliphages from sewage sludges.

Somatic coliphages are present in high numbers in sewage sludge. Since they are conservative indicators of viruses during wastewater treatment processes, they are being used to evaluate the effectiveness of sludge treatment processes. However, efficient methods to extract them from sludge are lacking. The objective was to compare different virus extraction procedures and develop a method to extract coliphages from sewage sludge. Twelve different extraction buffers and procedures varying in composition, pH, and sonication were compared in their ability to recover indigenous phages from sludges. The 3% buffered beef extract (BBE) (pH 9.0), the 10% BBE (pH 9.0), and the 10% BBE (pH 7.0) with sonication were short-listed and their recovery efficiency was determined using coliphage-spiked samples. The highest recovery was 16% for the extraction that involved 10% BBE at pH 9.0. There is a need to develop methods to extract somatic phages from sludges for monitoring sludge treatment processes.