Anne-Marie Pourcher1*, Nora Aktouche2, Caroline Côté2, Pierre Rousseau1, Stéphane Godbout2and José Martinez1
1Cemagref, 17 avenue de Cucillé, 35044 Rennes Cedex, France;2IRDA 3300 rue Sicotte Saint-Hyacinthe, J2S 7B8 Québec, Canada.
*Email: anne-marie.pourcher@cemagref.fr
Introduction
In spite of the effectiveness of manure treatments which reduce the transfer of nutrients to the environment, microbiological contamination of manure has become a great concern in Canada and European countries.
There is indeed a sanitary risk related to the use of the effluents from piggeries. Even when healthy, pigs can excrete pathogenic micro-organisms which may be subsequently found in liquid manure. The pathogenic micro-organisms most often isolated from animal manure are Salmonella,Campylobacter,Yersinia, and Cryptosporidium(Guan and Holley, 2003; Heitman et al., 2002).
Biological treatment of manure can reduce both indicators and pathogenic microorganisms (Côté et al., 2006). However, several parameters,
including the composition of liquid manure (Nicholson et al., 2002), the time of storage, the temperature and the level of aeration (Hutchison et al., 2005), influence the effectiveness of liquid manure treatment technology.
The aim of the present study was to compare antimicrobial effectiveness of 5 different proprietary treatments (3 Canadian and 2 French
technologies). Microbiological analyses were carried out on samples of raw and treated manures after biological, chemical or physico-chemical
treatments over periods of 6 to 12 months. The effectiveness of
treatments was evaluated by comparing the extent of E. coli, enterococci, Salmonella and Cryptosporidiumrecovery.
Materials and methods
Five commercial technologies, presented in Table 1, were evaluated in Quebec (Canada) and in France. Samples were taken from the raw
manure and from liquid by-products of the different steps of each process.
Microbial analyses were done within 48 h after sampling. The results were
expressed in terms of the MPN (Most Probable Number) of bacteria
detected per volume of sample. E. coli and enterococci were counted using ColilertTM and EnterolertTM, respectively (IDEXX Laboratory).Salmonella was enumerated using an enrichment broth (Dulcitol-Selenite-Cysteine), followed by inoculation onto XLT4 agar and identification of typical
colonies with API 20E strips (BioMérieux).Cryptosporidium were detected by filtration, immunomagnetic separation of the oocysts from the material captured, and an immunofluorescence assay for determination of oocysts.
Table 1. Description of the treatments.
Technologies Step 1 Step 2 Step 3
separation by centrifugation aerobic digestion decantation Balcopure
(France)
separation by centrifugation limingb separation
a: treatment which allowed the purification of a liquid manure by-product by simultaneous electrocoagulation, electroflotation and electrooxydation.
b: volatilization of ammonia by stripping after addition of lime.
Results and discussion
Independently of the geographic location of the piggeries, variations in concentrations of indicator bacteria were observed in raw manures with mean values ranging between 5 u103 to 105 per g for E. coli and 8 u 102 to 4u 104 for enterococci (Table 2). In contrast, numbers of indicator
organisms in liquid by-products intended for spreading ranged from undetectable to 38 bacteria per mL. As indicated by the high values of standard deviations, variations in numbers of bacteria also occurred within each piggery over the period of the study. However, except for
centrifugation of manure of the two French processes, all steps of each process reduced the survival of both indicators, the concentrations of which decreased by at least 0.7 logarithmic unit after each treatment. The physico-chemical treatments such as polishing, stripping or settling
increased the effectiveness of the processes. It was also clear that enterococci survived better than E. coli regardless the treatment.
Salmonella were detected in all piggeries, but at variable frequency during the present study.
Table 2. Concentrations of bacteria and occurrence of Cryptosporidium in raw manures and in by-products from 5 processes.
Process (sampling period)
Type of manure or treatment
E. colib enterococcib Salmonellab
anumber of samples for each step of the process; bbacterial numbers-MPN/g wet weight ; cpercent of samples positive ;dStandard Deviation ; e floculation / coagulation ;
f Not Determined ; g manure from finish barn ;hnursery pig manure
The concentrations of Salmonella in raw manure varied from 0.2 to 2.9 u 103 MPN g-1. The higher concentration which was observed in manure from nursery barns was also reported by Hutchison et al. (2005).
Regardless of the initial level in manure, the concentration of Salmonella did not exceed 2 bacteria per g in the final liquid by-product. The presence ofCryptosporidium which was detected in the final liquid by-product from 3 of the 5 piggeries confirms the existence of sanitary risk.
Conclusion
The manure treatments studied, initially designed for the removal of nitrogen and phosphorus, make it possible to decrease the level of enteric bacteria from 1 to 4 logarithmic units, but they do not achieve complete sanitisation of the by-products which are intended for spreading on agricultural land.
References
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Guan, T. Y. and Holley, R. A., 2003. Pathogen survival in swine manure
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Heitman, T. L., Frederick, L. M., Viste, J. R., Guselle, N. J., Morgan, U. M., Thompson, R. C. A. and Olson, M. E., 2002. Prevalence of Giardia and Cryptosporidium and characterization of Cryptosporidium spp. isolated from wildlife, human, and agricultural sources in the North Saskatchewan River Basin in Alberta, Canada. Canadian Journal of Microbiology 48 : 530-541.
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