Somatic and F-specific coliphages in New Zealand waste treatment lagoons

Three coliphages (FRNA, FDNA and somatic) and three bacterial indicators (faecal coliforms, Escherichia coli and enterococci) were measured in four waster-treatment lagoons over 10 months. Two of the lagoons treated domestic sewage; the third, meat processing waste and the fourth, meat processing waste with a minor sewage component. In the meat processing lagoons the ratios of FRNA:FDNA were numerically large, due to very low counts of FDNA, and somatic coliphages generally outnumbered FRNA. Many of the FDNA plaques from meat processing lagoons were very small and were not confirmed on the F-plus strain, E. coli C 3000. In sewage lagoons all three coliphages were consistently present and FRNA usually outnumbered both FDNA and somatic coliphages. However, the ratios of FRNA to the other two coliphages were not numerically large. Ratios of coliphages, especially of FRNA:FDNA, seem a promising tool to distinguish between human and animal faecal pollution. Overall, there were no strong correlations between the bacterial indicators and the coliphages.