Helsinge Sludge Reed Bed Systems

Nielsen, S.1, and Willoughby, N.,2
1Orbicon A/S (Former Hedeselskabet, Environment and Energy A/S), 2ARM Ltd


The Helsinge Sludge Reed Bed System was established and planted with reeds in October 1996. The Reed Bed System has
a capacity of 630 TDS per year and consists of 10 basins, each having an area of 1,050 m2 at the filter surface and a
maximum area loading rate of 60 kg DS/m2/year. Sludge production from the Helsinge Wastewater Treatment Plant consists
of activated sludge direct from the activated sludge plant and activated sludge from final settling tanks. The production
constitutes approximately 50% of the loading of the sludge reed bed system. The remaining 50% of the sludge production
consists of concentrated activated sludge from four smaller wastewater treatment plants. The two sludge types are mixed
before being added to the Reed Bed System.

Annual sludge production amounts to approximately 550 - 600 TDS. The loading regime of the system consists of applications
of approximately 130-150m3 of sludge being applied once or twice daily, the feed concentration being approximately 0.5-0.8
% DS. During commissioning (1996-1998), the quota was increased from approximately 200 to 1,000m3. From 2000, each
basin was subjected to a loading quota of 1,500m3 over a period of approximately 7-8 days. Loading was followed by 55-65
days of rest. The loading quota changed by a factor of 10 during the 10 year period of operation. Since 1998, individual basins
were subjected to an average loading rate of approximately 55 TDS per year after commissioning, resulting in an average
area-specific loading rate of 52.4kg DS/m2/year. The sludge residue height increased between 1998 and 2001 by 0.68 m, and
the total sludge residue height by June 2004 was 1.10m.

The plan is to empty the Helsinge sludge reed bed system over a 5-year period with 2 out of 10 basins selected for emptying
per year. Capacity during the emptying period (5 years) will be maintained at 630 tonnes of dry solids per year despite the
reduction of the number of basins during the emptying period from 10 to 8.
According to the plan, emptying will commence in 2005, therefore, the emptying of all 10 basins will be complete within 5
years. The two basins selected for emptying are excluded from the loading plan approximately ½-1 year before emptying.
This period of time that will be sufficient to reduce the pathogenic micro-organisms in the top layer of the sludge residue.

Advanced treated, Biosolids, Enhanced treated, Sludge dewatering, Sludge drying, Reed beds, Loading cycles, Pathogen
removal, Emptying, Quality of sludge residue.

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