Design of a pilot plant for treatment of an industrial leachate

Abstract

During last decades, various types of treatment systems have been used in purification of
household and municipal wastewaters, leachate from municipal or industrial landfills and
wastewater from industrial processes. However, the suitability of a treatment system should be
tested in each individual case due to different composition of polluted water, climatic and
geological conditions, economic sources and limit values for effluents. The technology and
operational parameters must be confirmed through several development steps on different scales:
batch, column and pilot tests.
A filter bed technique has been selected as a treatment method for purification of a leachate from
an industrial landfill. The landfill contains residues from the recycling industry, residues from car
wrecking and discarded electrical and electronic equipment (cable scrap, rubber, foam, plastics,
textiles, etc). A pilot-scale experiment was conducted in Halmstad, Sweden. The pilot plant
consisted of three treatment steps: aeration, sedimentation and filtration. The leachate was
collected to the retention pond and pumped into the aeration tanks and then led to sedimentation
stage. Finally, the leachate was distributed over the surface of two geo-filters (I m3 each), one
located indoors and the other outdoors. The mixture of peat and carbon-rich ash, previously
investigated in the batch and column experiments, was used for filling the filter-bed tanks.
Determination of heavy metals, nitrogen, TOC, DOC and phenolic compounds in the influent and
the effluent of the pilot plant were made. The results showed that a significant reduction of the
pollutants in the leachate was achieved in the pilot plant. It is important to conduct the pilot plant
experiment in order to obtain valuable information of the design, the operational parameters, the
scale effects, climatic effects, system maintenance requirements and the lifetime of the filterbeds. Experience from the pilot-scale experiment gave valuable information for a construction
and optimization of a full scale treatment plant.