wastes are an important source of fertilisers but are also potential
chemical, microbiological and air pollutants. The presence of
faecal bacteria and the production of malodorous compounds during
storage can be a cause of concern in populated areas.
the last decade, numerous studies have been published on processes
leading to a reduction in pollution from animal wastes. Simple
and complex techniques have been employed: lagooning, anaerobic
digestion with or without energy recovery, aeration, composting,
etc. In the past, some efforts had been made to use an electric
current to treat manure, but they required large amounts of electrical
energy. This means that, in comparison to other treatment (e.g.
aeration) there is no advantage.
it was demonstrated that, under laboratory and practical conditions,
treatment applied during storage with very low currents and copper
electrodes leads to good results for the reduction of odour, better
homogenisation and a reduction of the pathogens in the manure
both during storage and spreading. On the other hand, not all
of the 400 plants currently working are really effective, and
the cause of this erratic behaviour is not known.
overall goal of the investigation is to study the phenomena of
very low electric fields obtained by introducing different electrodes
into stored manure, in order to design a technology for emission
reduction and hygienic control of manure before disposal into
intermediate objectives are:
to study the electro-chemical phenomenon;
to design a technology to reduce ammonia and other noxious gas
emissions, and the deodorisation and hygienic control of manure
to analyse the key factors for process effectiveness;
to set-up new bio-indicator parameters to monitor the electro-chemical
treatment applied to manure, with particular reference to pathogens;
to elucidate the role of the electric effect, metal ions, toxic
compounds etc. on the metabolic activities of microflora related
to odours release;
to assess the technical and economic feasibility of the process.
project will be developed by partners in two geographical areas,
characterised by different climatic conditions (Mediterranean
area and continental area). For the electro project implementation
the following steps are envisaged:
manure characterisation: the most important chemical and microbiological
characteristics will be considered to compare manure of different
origin and to monitor the electrochemical process;
mechanisms of action: in-depth research on the effect of the
electro-chemical process on micro-organism metabolism will be
carried out - the interaction of surviving pathogens with metal-ions,
formation of toxic compounds, etc. will be considered;
bio-monitoring: the new parameters will be compared with those
obtained by traditional biological indicators as microbial counts
and chemical parameters;
monitoring of working parameters, emission and hygienic quality
of the air in laboratory, pilot and medium-scale plants in order
to optimise the process and to prove its effectiveness;
technical and economical feasibility - during the experimentation
the energetic needs will be carefully evaluated.
animal manure-electrochemical treatment-phatogens-emissions-ammonia-odours.
situation/results (first year):
the first year of the project, the tasks concerning the chemical
and microbiological characterisation and the laboratory experiments
have been developed. In particular, the chemical and microbiological
methods have been discussed and defined both for manure characterisation
and for the monitoring of the electrochemical treatment effects;
the laboratories and the experimental equipment have been prepared;
the analyses of microbial metabolism and odour development, effects
on pathogens, biomonitoring parameters and effects on fly development
have been started, and are almost completed.
control units for electrochemical treatment at pilot scale have
been designed and assembled; they are ready to operate.
in order to create a sound background, specific literature researches
have been carried out concerning environmental problems related
to animal manure management, electrochemical treatments and their
chemical and microbiological effects.
manure characterisation methods have been precisely defined and
described. The physical and chemical parameters considered are:
pH, conductivity, total solids, volatile solids, C.O.D., total
nitrogen, ammonia nitrogen, nitrates, nitrites, total phosphorus,
chloride, copper and zinc. The microbiological parameters considered
are: aerobic heterotrophic bacteria, anaerobic heterotrophic bacteria,
anaerobic cellulolytic bacteria, anaerobic proteolytic bacteria,
spore-forming bacteria, anaerobic ammonifying microorganisms,
salmonella, coliform group, total aerobic bacteria, total anaerobic
bacteria, gram-negative, aerobic bacteria, enterococcus spp.,
the first year, several experimental tests have been carried out
at a micro-scale (5 ml electrolytic cells), at a very small-scale
(1 - 5 l electrolytic cells) and at a lab-scale (50 l electrolytic
tanks). Even if several experimental results are still under elaboration,
the following preliminary results can be underlined.
inhibitory effect on E. coli activity in nutrient broth could
be due to the Cu++ ions produced by the electrolytic process.
copper-copper electrode couple, in presence of current intensity
of 20 mA and in nutrient broth, determines the same effects on
the E. coli growth and metabolic activity as the graphite-copper
regards the total electrode weight loss in nutrient broth, the
release of metal ions from the copper-copper electrode couple
was the same percentage as that one from graphite-copper electrodes;
this means that the quantity of copper "loss" in the
nutrient medium from the copper-copper electrode couple in terms
of mg Cu, was about twice that observed of Cu loss in the medium
from the graphite-copper electrodes.
a comparison between treated (electrolysis) and untreated NaCl
medium, no bacterial growth was observed in the treated solution
after three weeks, whereas only a slight decrease in bacterial
concentration occurred in the untreated solution. Analysing these
results together with those observed in a NaCl solution where
a chemical dissolution of CuSO4 occurred, it is possible to hypothesise
that the copper ion lethal effect on E. coli is increased by the
effects of low electric fields.
content and multi-enzymatic activities seem to be equally good
indicators of electrochemical treatment microbial effects.
electrolytic treated tanks a large reduction in fly larvae population
was observed. This reduction could result from two effects. Firstly,
it is assumed that the reduction is caused by the electrical field;
secondly, it could result from the reduction or the absence of
a swimming layer in the electrochemical treated unit.
degli Studi di Udine
delle Scienze 208
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- Claudia SORLINI
Universita' degli Studi di Milano
Via Festa Del Perdono 7
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- Wolfgang MÜLLER
Freie Universität Berlin
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Tel.: +49 30 209 363 24
Fax: +49 30 209 363 23