Helsinge sludge reed bed system: reduction of pathogenic microorganisms.
Reduction of pathogenic bacteria: Salmonella, enterococci and Escherichia coli was investigated using the sludge reed bed system. The system at Helsinge was established in 1996 and has a capacity of 630 tonnes dry solids per year and consists of 10 basins. Since 2000 the individual basins have been subjected to an average area-specific loading rate of 46-56 kg dry solids/m2/year. The total sludge residue height in April 2006 was approximately 1.40 m. The sludge (approximately 0.5-0.8% dry solids), with which the individual basins were loaded, contained a large number of bacteria. Salmonella, enterococci and E. coli were found in the sludge in the following quantities: 10-300/100 g (wet weight), 7,000-25,000 CFU/g (wet weight) and 800,000-10,000,000 CFU/100 g (wet weight), respectively. The analysis of the reduction in pathogens in the sludge residue through a period of 3-4 months after the last loading indicated that the pathogen content was reduced down to < 2/100 g (Salmonella), < 10 CFU/g (enterococci) and < 200 number/100 g (E. coli). For enterococci and E. coli the reduction was approximately log 5 and log 6-7, respectively. In the same period the sludge residue achieved a dry solids content of approximately 20-35%.
Nielsen
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S
Orbicon A/S, Ringstedvej 20, DK-4000 Roskilde, Denmark. smn@orbicon.dk
D001673:Biodegradation, Environmental; D016983:Enterococcus / Q000166:cytology / Q000302:isolation & purification; D004926:Escherichia coli / Q000166:cytology / Q000302:isolation & purification; D006801:Humans; D012475:Salmonella / Q000166:cytology / Q000302:isolation & purification; D012722:Sewage / Q000382:microbiology*; D053833:Wetlands