Samples of sewage sludges, taken over a 12-month period from 9 Scottish sewage works, contained on average 0.24 cysts of Globodera spp. (potato cyst-nematodes) of which 11% were viable. Exposure of cysts in sludge to mesophilic anaerobic digestion, cold anaerobic digestion, pasteurisation and aerobic thermophilic digestion reduced viability of eggs within the cysts by almost 100%. Sludges so treated can therefore be considered to be free from infection risk to potato crops, although the non-infective cysts may still be recovered. Treatment with lime at pH 11.5 by aerobic stabilisation in an oxidation ditch and by activated-sludge treatment did not reduced viability acceptably. Accelerated cold digestion did not reduce viability sufficiently after the usual 15 weeks but rendered eggs completely non-viable after 21 weeks. The results show that even sludge treated to destroy viable cysts should not be applied to land used for growing seed potatoes and subject to testing for freedom from infestation. Additional aspects of the study are discussed.
|Number of pages
|Water Science and Technology
|8 -9 pt 3
|Print publication - 1 Dec 1989
|Proceedings of the Fourteenth Biennial Conference of the International Association on Water Pollution Research and Control. Part 2 - Brighton, Engl
Duration: 18 Jul 1988 → 21 Jul 1988