Dewatering sludge originating in water treatment works in reed bed systems

摘要

The dewatering process of the liquid water works sludge was examined in a trial with a series of sixntrial beds, each 20 m2n. These were monitored from April 2008 to June 2010. It is possible to get thenvegetation to grow in ferric sludge (∼300,000 mg Fe/kg dry solid, pH 7,7). It has not been necessary tonuse fertilizer. The influence of the loading programs (15–50 kg dry solid/m2n/year) was tested with 1–5ndays of loading and 35–55 days of rest. It is possible to drain and treat ferric sludge. Generally thendewatering profile is a peak with a maximum over 0.015–0.025 L/s/m2n. The times for dewatering ofn6–12 m3nare ∼15 h and over 90% of the load is dewatered in that period. The dry solid (0.16–0.20%)nin the sludge has been concentrated ∼200 times. The dewatering phase results in ferric sludgenwith 30–40% dry solid which cracks up very quickly. The volume reduction is over 99%. The trendnshows that the main volume of reject water has a turbidity level below 5 NTU even in the loadingnperiods.