Abstract
The influx of toxic pollutants into wastewater treatment plants can negatively affect the quality of the activated sludge (AS). One source is landfill leachate. The identification of microorganisms present in AS is very important, e.g., while improving wastewater treatment technology. Therefore, the aim of the study was to investigate the effect of raw leachate and after purification of Phragmites australis and Ceratophyllum demersum on the composition of the AS bacterial biocenosis. In addition, AS status was assessed by LIVE/DEAD BacLight ™ fluorescent staining. The obtained results showed that the leachate did not significantly affect the cell membranes of AS bacteria, and even a slight improvement was noted. The research carried out using the next-generation sequencing method shows that the origin of the samples (active and closed storage) and the method of processing do not significantly affect the composition of the AS bacterial biocenosis at higher taxonomic levels. However, at the species level, the appearance of bacteria not previously present in AS was observed, namely: Flavobacterium luticocti, Candidimonas nitroreducens and Nitrobacter hamburgensis. The obtained results suggest that the leachate may be a source of microorganisms positively influencing the condition of AS bacteria.
Highlights
The novelty of this study is to investigate the effect of landfill leachate on sludge bacterial biocenosis, which has not been done before
The physicochemical properties of the analysed landfill leachates did not indicate a high degree of contamination; throughout the study period they were characterised by quite high toxicity, which may cause adverse effects on living organisms
The study performed showed that the sources of the samples and the method of treatment (P. australis and C. demersum) did not significantly affect the composition of the bacterial biocenosis of the activated sludge at higher taxonomic levels
Summary
The formation of leachate is one of the many environmental hazards associated with waste disposal [1]. Leachate can be transported to municipal wastewater treatment plants, treated or sub-treated on site or recirculated to a waste heap [4,5]. Biological processes are widely used worldwide for the treatment of raw leachate and/or a mixture of leachate and domestic wastewater [7]. Their particular effectiveness is observed in the treatment of leachate from young landfills containing biodegradable organic matter [7,8]
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