THE AGRICULTURAL REUSE OF RECLAIMED WASTE-WATERS SLUDGES
The wide-spread technologies currently applied to the treatment of
municipal waste waters involve high energetic consumptions and produce a
huge quantity of sludges containing heavy metals, organic compounds,
pathogenous agents as well as appreciable amount of nutrients such as
nitrogen, phosphorous and potassium.
The EU directives, namely EC 91/271/EEC, do not permit the spreading of
waste waters sludges on the ground, whereas the disposal by thermal
incineration has appreciable costs. An interesting alternative may be
represented by their use in agriculture after the removal of toxic
components either inorganic or organic by an adequate treatment.
The project " A new integrated bioleaching process for agricultural
applications of waste-waters sludges", developed in the frame of the UE
Programme INCO-Copernicus, concerns the development of bacterial-assisted
leaching of heavy metals contained in the sludges and the contemporary
utilization of the fly ash as a stabilizing agents.
The chemical dissolution of heavy metals has some disadvantages concerning
plant design and environmental issues. As an alternative the bioleaching
has shown to be technically feasible, environmentally friendly and
economically suitable.
The process of stabilization/pasteurisation of sludges has been developed
by using coal fly ash previously mechanically activated.
The IGAG participates to the project as operative unit in cooperation with
other partners: ECOMETAL Company (Brescia,Italy); Austrian Research
Center of Seibersdorf (Vienna, Austria); Moscow State Institute of Steel &
Alloys (Mosca, Russia); Dumansky Institute of the Ukrainian Academy of
Sciences (Kiev, Ukraine) and the National Academy of Sciences of Armenia
(Yerevan, Armenia).
The main objectives of the project are the following:
1) the technical and economical comparison of the different
technologies;
2) the development of a straight and low energetic cost process for
the treatment of waste waters;
3) the contaminants control for the use of sludges in agriculture in
Russia, Ukraine and Armenia;
4) the evaluation of dangerous effects on vegetable cultivation,
agricultural products, soil microorganisms and hydrological properties of
ground;
5) the optimisation of an integrated flowsheet in relation to the
pedologic and agricultural aspect of terrains.
The overall results and products to be expected, and already partly
achieved, are the following:
1) an efficient bioleaching process;
2) a literature survey on the heavy metals removal;
3) a stabilization/pasteurisation process of the waste-waters sludges;
4) a technical evaluation of agricultural soils after the treatment
with the reclaimed sludges;
5) the prototype design of a commercial plant.
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