ABSTRACT
This paper presents the microbial effects of using Ecosan sludge in agriculture. Sludge from KwaZulu Natal in South Africa having a helminth ova content of around 30 HO/gTS, faecal coliforms of 10(6) CFU/gTS, faecal streptococi of 10(6) CFU/gTS and Salmonella spp. of 10(5) CFU/gTS were applied to soils to grow carrots and spinach at different rates. Results showed that helminth ova content in crops was always greater in leaves than in stems, with a content varying from 2 to 15 HO/gTS for spinach and sludge application rates of sludge of 0-37.5 ton/ha and from 2-8 HO/gTS in carrots crops for sludge application rates varying from 0 to35 ton/ha. Health risks resulting from crop consumption were calculated using the beta-poisson and the single-hit exponential models for Salmonella and helminths eggs, respectively. For Salmonella, no risks were found when consuming carrots for all the sludge rates studied while for spinach, risks were high but results were not deemed conclusive due to the technical methods used to measure bacteria. Concerning helminths, it was found that the morbidity rate will increase by 9% for the higher sludge application rates. To increase regional risks by 1% the egg content in crops needs to be less than 0.2 HO/gTS.
Subject(s)
Crops, Agricultural/microbiology , Crops, Agricultural/parasitology , Ecology , Fertilizers , Sanitation , Sewage/adverse effects , Animals , Biodegradation, Environmental , Helminths , Ovum , Risk Factors , Sewage/chemistry , Soil/parasitology , Soil Microbiology , WaterABSTRACT
This paper presents the microbial risks associated with the reuse of Ecosan sludge in agriculture. Sludge from KwaZulu Natal Province in South Africa with a helminth ova content of 30 HO/g TS, faecal coliforms of 10(6) CFU/g TS, faecal streptococci of 10(6) CFU/g TS and Salmonella spp. of 10(5) CFU/g TS was used for this purpose. Applying different rates of sludge to spinach and carrots resulted in an increase in bacterial and helminth ova counts in crops as the quantity of sludge increased. The helminth ova content in crops was always greater in leaves than in stems, with a content varying from 2 to 15 HO/g TS for spinach with sludge application rates of 0-37.5 ton/ha and from 2-8 HO/g TS for carrot crops with sludge application rates varying from 0-35 ton/ha. Nevertheless, viability in crops was 20-25%, reducing the risk of disease. Consequently, the development of an Ecosan sludge revalorisation standard is considered important. Some recommendations are made taking into account the characteristics of the sludge as well as conditions in rural areas.
